present day kinematics of the mediterranean a comprehensive overview of gps results i combine recently published gps results to derive a geodetic horizontal velocity field consistent at the scale of the mediterranean and the surrounding alpine belts the velocity field is then used to discuss the boundary conditions around each major deforming area in the mediterranean to describe the main patterns of motion and deformation to critically review the existing kinematics models and to finally point out the main unresolved kinematics questions strain rate in europe north of the alpines belt is dominated by the signature of the glacial isostatic adjustment and tectonic strain remains below the current accuracy of gps results in the western mediterranean deformation is restricted to the betics the alboran and the morrocan rif with west to southwestward motion with respect to iberia which is part of stable europe shortening consistent with the relative nubia eurasia plate motion is found throughout the maghrebides but the distribution of deformation in northern africa remains largely unknown the central mediterranean is dominated by the counter clockwise rotation of the adriatic the junction between the southern adriatic domain and nubia has yet to be firmly established the deformation over a wide area east of the maghrebides in tunisia and the gulf of sirte in libya still remains to be quantified in the eastern mediterranean the velocity field is dominated by a general anti clockwise rotation and a general trend towards the hellenic trench with velocity magnitude increasing with decreasing distances from the trench this trend is observed not only in the aegean and anatolia but also in the southern balkans geodetic results emphasize that the convergence of the nubia and arabia plates towards eurasia directly controls the deformation across only very few segments along the plate boundary zone additional processes are therefore required to explain the observed velocity field and deformation pattern

hypocentre determination offshore of eastern taiwan using the maximum intersection method summary the maximum intersection maxi method which derives from the master station method msm determines within a 3 d velocity model the absolute hypocentral location based on observed arrival times first the spatial node that better satisfies the arrival time differences computed at all station pairs plus or minus an error tolerance value in seconds is defined as the preliminary hypocentral solution pred second because pred depends neither on the estimate of origin time nor on the residual root mean square rms residual outliers are objectively detected and cleaned out from the original data set without any iterative process or weighting third a statistical minimization residual rms is conducted in a small domain around the pred node which results in a unique final solution the maxi method is applied to the determination of earthquake hypocentres with the proper station correction terms in the southernmost extremity of the ryukyu subduction zone where several dense seismic clusters occur near the seismogenic plate interface the location of earthquakes recorded at both the taiwanese and japanese networks is obtained for about a thousand events between 1992 and 1997 the process uses a detailed 3 d velocity model based on multiple geophysical data sources obtained in the junction area between subduction and collision east of taiwan the earthquake clustering and the significant drop in residual statistics 1 20 0 80 and 0 35 s for taiwanese catalogue msm and maxim solutions respectively indicate the accuracy of the method which can be used to routinely determine absolute hypocentre location based on observed arrival times

the stubenberg meteorite an ll6 chondrite fragmental breccia recovered soon after precise prediction of the strewn field on march 6 2016 at 21 36 51 ut extended areas of upper austria bavaria germany and the southwestern part of the czech republic were illuminated by a very bright bolide this bolide was recorded by instruments in the czech part of the european fireball network and it enabled complex and precise description of this event including prediction of the impact area so far six meteorites totaling 1473 g have been found in the predicted area the first pieces were recovered on march 12 2016 on a field close to the village of stubenberg bavaria stubenberg is a weakly shocked s3 fragmental breccia consisting of abundant highly recrystallized rock fragments embedded in a clastic matrix the texture the large grain size of plagioclase and the homogeneous compositions of olivine fa31 4 and pyroxene fs25 4 clearly indicate that stubenberg is an ll6 chondrite breccia this is consistent with the data on o ti and cr isotopes stubenberg does not contain solar wind implanted noble gases data on the bulk chemistry ir spectroscopy cosmogenic nuclides and organic components also indicate similarities to other metamorphosed ll chondrites noble gas studies reveal that the meteorite has a cosmic ray exposure cre age of 36 3 ma and that most of the cosmogenic gases were produced in a meteoroid with a radius of at least 35 cm this is larger than the size of the meteoroid which entered the earth s atmosphere which is constrained to 20 cm from short lived radionuclide data in combination this might suggest a complex exposure history for stubenberg

source parameters of the 1992 melilla spain mw 4 8 1994 alhoceima morocco mw 5 8 and 1994 mascara algeria mw 5 7 earthquakes and seismotectonic implications source mechanisms of the melilla alhoceima and mascara earthquakes including fault plane solutions waveform modeling and spectral analysis are presented strike slip solutions have been obtained for the melilla and alhoceima earthquakes and reverse faulting for mascara teleseismic p wave inversion using broadband data show a complex mechanism for the alhoceima earthquake formed by two subevents at very shallow depth 7 and 8 km and scalar seismic moments of 1 1 10e 17 n m and 4 8 10e 17 n m the mascara earthquake was a single event with a shallow depth 4 5 km and a scalar seismic moment of 3 3 10e 17 n m results of the alhoceima melilla and mascara earthquakes together with 53 focal mechanisms in the region show a regional stress regime that corresponds to horizontal compression in a nw se direction associated with the convergence between eurasia and africa a change of the stress regime in the plate boundary of the ibero maghrebian region has been found

the temporal distribution of aftershock sequences in the subduction zones of the pacific summary the temporal behaviour of 146 aftershock sequences distributed on the subduction zones in the circum pacific belt is examined almost all of the sequences were modelled well by omori s relation the well known parameter p or p value is the expression of the aftershock decay with time mean p values are estimated for the east and west parts of the circum pacific belt the different p values estimated for these areas are statistically tested and an interpretation regarding the tectonics is given

oxygen isotope studies of carbonaceous chondrites abstract the carbonaceous chondrites display the widest range of oxygen isotopic composition of any meteorite group as a consequence of the interaction of primordial isotopic reservoirs in the solar nebula these isotopic variations can be used to identify the reservoirs and to determine conditions and loci of their interactions we present a comprehensive set of whole rock analyses of cv co ck cm cr ch and ci chondrites as well as selected components of some of these meteorites a simple model is developed which describes the isotopic behavior during parent body aqueous alteration processes the process of thermal dehydration also produces a recognizable effect in the oxygen isotopic composition

nature of the lithosphere across the variscan orogen of sw iberia dense wide angle seismic reflection data 1 two wide angle seismic transects have been acquired across the sw iberian massif they crossed three major geological zones south portuguese zone ossa morena zone and central iberian zone with their tectonic contacts and the pyrite belt being of greatest interest a total of 690 digital seismic recording instruments 650 texans and 40 reftek 3 component units from the iris passcal instrument pool were used the transects a and b are each approximately 300 km long and consist of 3 and 6 shot points respectively with an approximately 60 km shot point interval the charge sizes range from 1000 kg at the edges to 500 kg at the center these recently acquired experiments were designed to provide velocity constraints on the lithosphere and to complement the previously acquired normal incidence seismic profile iberseis both data sets are part of the sw iberia project which was developed within the europrobe program and designed to address fundamental questions about the nature and dynamics of the variscan lithosphere the acquisition parameters provide closely spaced wide angle seismic images of the lithosphere beneath sw iberia in transect a the station spacing was on average 400 m while along transect b the receiver spacing was approximately 150 m because of this close trace spacing the lateral continuity of the seismic arrivals is greatly improved frequency analysis revealed that the recorded events feature relatively low frequencies 6 25 hz after processing the shot records show high amplitude and well defined arrivals the interpreted pmp arrival located at approximately 11 s normal incidence traveltime is characterized by high amplitude and relatively low frequency 6 12 hz a well defined pn arrival appears at offsets beyond 120 km at far offsets greater than 180 km an upper mantle reflection is observed furthermore within the upper crust the shots records feature a relatively high velocity arrival located at 4 5 s normal incidence traveltime the analysis of this arrival indicates that it probably corresponds to the top of the iberian reflective body identified in the iberseis deep seismic profile the velocity models obtained by forward modeling show a complex crust especially in the middle crust the velocity models are the most detailed ones that have been produced in the area and contain a large amount of new features that are relevant to the understanding of the composition of the crust and upper mantle beneath the zone the velocity depth functions derived from the velocity models have higher middle crustal velocities than the average in other continental areas a comparison between laboratory seismic velocity measurements and the velocities of the models was carried out in order to estimate the crustal and the upper mantle composition results indicate that the high middle crust velocities correspond to rocks of a mafic composition the combined data set reveals new aspects related to the lithospheric evolution of this transpressive orogen and allows us to attempt an interpretative cross section of the upper lithosphere in sw iberia

oxygen isotope studies of achondrites abstract oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites among the differentiated achondrites three isotopic groups are recognized l snc mars 2 earth and moon and 3 hed howardites eucrites diogenites the hed group also contains the mesosiderites main group pallasites and silicates from iiiab irons the angrites may be marginally resolvable from the hed group within each of these groups internal geologic processes give rise to isotopic variations along a slope 1 2 fractionation line as is well known for terrestrial materials variations of 17o from one planet to another are inherited from the inhomogeneities in the solar nebula as illustrated by the isotopic compositions of chondrites and their constituents among the undifferentiated achondrites five isotopic groups are found 1 aubrites 2 winonaites and iab iiicd irons 3 brachinites 4 acapulcoites and lodranites and 5 ureilites the isotopic compositions of aubrites coincide with the earth and moon and also with the enstatite chondrites these bodies apparently were derived from a common reservoir the isotopic composition of which was established at the chondrule scale by nebular processes isotopic similarities between chondrites and achondrites are seen only for the following instances 1 enstatite chondrites and aubrites 2 h chondrites and he irons and 3 l or ll chondrites and iva irons the isotopic data also support the following genetic associations 1 winonaites and iab iiicd irons 2 acapulcoites and lodranites and 3 ureilites and dark inclusions of c3 chondrites an attempt to reconcile the whole planet isotopic compositions of earth mars and the eucrite parent body with mixing models of their chemical compositions failed it is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive solar system components

peak metamorphic temperatures in type 6 ordinary chondrites an evaluation of pyroxene and plagioclase geothermometry quantifying the peak temperatures achieved during metamorphism is critical for understanding the thermal histories of ordinary chondrite parent bodies various geothermometers have been used to estimate equilibration temperatures for chondrites of the highest metamorphic grade type 6 but results are inconsistent and span hundreds of degrees because different geothermometers and calibration models were used with different meteorites it is unclear whether variations in peak temperatures represent actual ranges of metamorphic conditions within type 6 chondrites or differences in model calibrations we addressed this problem by performing twopyroxene geothermometry using quilf95 on the same type 6 chondrites for which peak temperatures were estimated using the plagioclase geothermometer nakamuta and motomura 1999 we also calculated temperatures for published pyroxene analyses from other type 6 h l and ll chondrites to determine the most representative peak metamorphic temperatures for ordinary chondrites pyroxenes record a narrow overlapping range of temperatures in h6 865 926 c l6 812 934 c and ll6 874 945 c chondrites plagioclase temperature estimates are 96 179 c lower than pyroxenes in the same type 6 meteorites plagioclase estimates may not reflect peak metamorphic temperatures because chondrule glass probably recrystallized to plagioclase prior to reaching the metamorphic peak the average temperature for h l and ll chondrites 900 c which agrees with previously published oxygen isotope geothermometry is at least 50 c lower than the peak temperatures used in current asteroid thermal evolution models this difference may require minor adjustments to thermal model calculations

kinematics of the western africa eurasia plate boundary from focal mechanisms and gps data summary the western mediterranean displays a complex pattern of crustal deformation distributed along tectonically active belts developed in the framework of slow oblique plate convergence we used earthquake and global positioning system gps data to study the present day kinematics and tectonics of the africa eurasia plate boundary in this region crustal seismicity and focal mechanisms analysed in terms of seismic moment release and seismic deformation outline the geometry of major seismic belts and characterize their tectonics and kinematics continuous gps data have been analysed to determine euler vectors for the nubian and eurasian plates and to provide the global frame for a new mediterranean gps velocity field obtained by merging continuous and campaign observations collected in the 1991 2005 time span gps velocities and displacements predicted by the nubia eurasia rotation pole provide estimates of the deformation accommodated across the tectonically active belts the rather simple deformation occurring in the atlantic region characterized by extension about perpendicular to the middle atlantic and terceira ridges and right lateral motion along the gloria transform fault turns into a complex pattern of deformation occurring along broader seismic belts where continental lithosphere is involved our analysis reveals a more complex fragmentation of the plate boundary than previously proposed the roughly e w trending mainly compressive segments i e southwestern iberia northern algeria and southern tyrrhenian where plate convergence is largely accomodated across rather localized deformation zones and partially transferred northward to the adjacent domains i e the algero balearic and tyrrhenian basins are interrupted by regions of more distributed deformation i e the rif alboran betics tunisia libya and eastern sicily or limited seismicity i e the strait of sicily which are characterized by less homogeneous tectonics regimes mainly transcurrent to extensional in correspondence of the observed breaks tectonic structures with different orientation interfere and we find belts with only limited deformation i e the high and middle atlas the tunisian atlas and the offshore tunisia libya belt that extends from the plate boundary into the nubian plate along pre existing tectonic lineaments our analysis suggest that the sicilian pelagian domain is moving independently from nubia according to the presence of a right lateral and extensional decoupling zone corresponding to the tunisia libya and strait of sicily deformation zone despite the space variability of active tectonic regimes plate convergence still governs most of the seismotectonic and kinematic setting up to the central aeolian region in general local complexities derive from pre existing structural features inherited from the tectonic evolution of the mediterranean region on the contrary along calabria and the apennines the contribution of the subducted ionian oceanic lithosphere and the occurrence of microplates i e adria appear to substantially modify both tectonics and kinematics finally gps data across the gibraltar arc and the tyrrhenian calabria domain support the hypothesis that slab rollback in these regions is mostly slowed down or stopped

early stages of core segregation recorded by fe isotopes in an asteroidal mantle ureilites displays 56 fe values higher than average chondrite 29 segregation of fe sulfide melts explains the high 56 fe values in ureilites 30 formation of a core can begin at very low degrees of melting through the circulation of a fe s melt 31 through a silicate mantle 32 33 earth and planetary science letters in press 11 3 15 34 2 35 abstract 36 37 ureilite meteorites are achondrites that are debris of the mantle of a now disrupted 38 differentiated asteroid rich in carbon they provide a unique opportunity to study the differentiation 39 processes of such a body we analyzed the iron isotopic compositions of 30 samples from the ureilite 40 parent body upb including 29 unbrecciated ureilites and one ureilitic trachyandesite alm a 41 which is at present the sole large crustal sample of the upb the 56 fe of the whole rocks fall within a 42 restricted range from 0 01 to 0 11 with an average of 0 056 0 008 which is significantly 43 higher than that of chondrites we show that this difference can be ascribed to the segregation of s 44 rich metallic melts at low degrees of melting at a temperature close to the fe fes eutectic and 45 certainly before the onset of the melting of the silicates 1100 c in agreement with the marked s 46 depletions and the siderophile element abundances of the ureilites these results point to an efficient 47 segregation of s rich metallic melts during the differentiation of small terrestrial bodies 48 49

the proto earth as a significant source of lunar material geochemical evidence continues to challenge giant impact models which predict that the moon formed from both proto earth and impactor material analyses of lunar samples reveal isotopic homogeneity in titanium a highly refractory element suggesting lunar material was derived predominantly from the mantle of the proto earth

heat flow anomalies in the gulf of cadiz and off cape san vincente portugal heat flow anomalies provide critical information in active tectonic environments the gulf of cadiz and adjacent areas are affected by the plate convergence between africa and europe causing widespread deformation and faulting active thrust faults cause lateral movement and advection of heat that produces systematic variations in surface heat flow in december 2003 new heat flow data were collected during the research vessel sonne cruise so175 in the gulf of cadiz over two sites of recent focused research activity i the gulf of cadiz sedimentary prism and ii the marques de pombal escarpment both features have also been discussed as potential source areas of the great lisbon earthquake and tsunami of 1755 background heat flow at the eastern terminus of the horseshoe abyssal plain is about 52 59 mw m2 over the gulf of cadiz prism heat flow decreases from 57 mw m2 to unusually low values of 45 mw m2 roughly 120 km eastward such low values and the heat flow trend are typical for active thrusting supporting the idea of an east dipping thrust fault slip rates are 10 5 mm per year assuming that the fault dips at 2 a fault dipping at 5 however would result into slip rates of 1 5 5 mm per year suggesting that subduction has largely ceased based on seismic data the marques de pombal fault is interpreted as part of an active fault system located 100 km westward of cape san vincente heat flow over the fault is affected by refraction of heat caused by the 1 km high escarpment thermal models suggest that the slip rate along the fault must either be small or shear stresses acting on the fault are rather high with respect to other fault zones however it is reasonable to assume that the fault s slip rate is small

source analysis of the february 12th 2007 mw 6 0 horseshoe earthquake implications for the 1755 lisbon earthquake 1 while very large earthquakes are generally confined to subduction zones the sw iberian margin setting of the famous mw 8 5 8 7 1755 lisbon tsunami earthquake may be an exception to this rule evidence for active subduction is not conclusive here but instead plate convergence in old oceanic lithosphere with large brittle layer thickness can account for the occurrence of great earthquakes along moderate length faults we estimate the source parameters of the february 12th 2007 horseshoe earthquake regional moment tensor inversion yields an mw 6 0 reverse to strike slip faulting source in the upper mantle modelling teleseismic surface reflected body waves pp pwp sp indicates a source depth of 40 km beneath the seafloor analysing apparent source time functions allows identifying the preferred fault plane strike n245 e dip 55 rake 50 and estimating rupture area 53 km2 and average slip 0 27 m scaling the source characteristics to the size of the 1755 earthquake suggests a fault length of 230 315 km being compatible with the length of mapped faults in the area

the quest for the africa eurasia plate boundary west of the strait of gibraltar the missing link in the plate boundary between eurasia and africa in the central atlantic is presented and discussed a set of almost linear and sub parallel dextral strike slip faults the swim1 faults that form a narrow band of deformation over a length of 600 km coincident with a small circle centred on the pole of rotation of africa with respect to eurasia was mapped using a new swath bathymetry compilation available in the area offshore sw portugal these faults connect the gloria fault to the rif tell fault zone two segments of the plate boundary between africa and eurasia the swim faults cut across the gulf of cadiz in the atlantic ocean where the 1755 great lisbon earthquake m 8 5 8 7 and tsunami were generated providing a new insight on its source location

reclassification of villalbeto de la pena occurrence of a winonaite related fragment in a hydrothermally metamorphosed polymict l chondritic breccia na meteorite clearly bears consequences for the previous classification of the rock the oxygen isotope data clearly show that an exotic eye catching black and plagioclase maskelynite rich clast is not of l chondrite heritage villalbeto de la pe is consequently reclassified as a polymict chondritic breccia the oxygen isotope data of the clast are more closely related to data for the winonaite tierra blanca and the anomalous silicate bearing iron meteorite lew 86211 than to the ordinary chondrite groups the ree pattern of the bulk inclusion indicates genetic similarities to those of differentiated rocks and their minerals e g lunar anorthosites eucritic and winonaitic plagioclases and points to an igneous origin the an content of the plagioclase within the inclusion is increasing from the fragment host meteorite boundary approximately an10 toward the interior of the clast approximately an52 this is accompanied by a successive compositionally controlled transformation of plagioclase into maskelynite by shock as found for plagioclase compositions of individual spinels enclosed in plagioclase maskelynite also vary from the border toward the interior of the inclusion in addition huge variations in oxygen isotope composition were found correlating with distance into the object the chemical and isotopical profiles observed in the fragment indicate postaccretionary metamorphism under the presence of a volatile phase

brecciation among 2280 ordinary chondrites constraints on the evolution of their parent bodies abstract after accretion of meteorite parent bodies larger and smaller collisions have led to significant modifications of these bodies involved processes include excavation of material thermal metamorphism melting mixing of different materials re accretion and re lithification all these processes can be repeated several times in this study polished thin sections pts of 2280 chondrites 1193 h 947 l and 140 ll chondrites were investigated in order to obtain the abundance of brecciated rocks among the ordinary chondrites in addition we have determined the abundance and characteristics of shock vein bearing h l and ll chondrites and of impact melt rock clasts we also recognized xenolithic components based on o isotope studies noble gas data were considered in order to detect regolith breccias and to discuss late impact histories the investigation of 2280 samples shows that 23 276 of 1193 of the h chondrites 23 220 of 947 of the l chondrites and 79 110 of 140 of the ll chondrites are brecciated considering the heavily brecciated ll chondrites in 63 of the 140 chondrites 45 shock veins were clearly detected 57 of these 63 chondrites are brecciated rocks the investigation of the h and l chondrites has shown that about 26 310 of 1193 of the h chondrites and 40 379 of 947 of the l chondrites contain shock veins in our data set 20 of the h chondrites and 8 3 of the ll chondrites but only 3 0 of the l chondrites contain solar noble gases remarkably about 62 of all brecciated h chondrites with noble gases analyzed contain solar noble gases compared to only around 11 and 10 of the brecciated l and ll chondrites respectively the identification of xenolithic clasts e g ci cm and ureilite like lithologies in primitive type 3 chondrites indicates simultaneous accretion of clasts and chondrules these clasts must have been formed early within the first 2 ma on subsequently destroyed precursor first generation parent bodies the formation of complex breccias witnesses the collisions between asteroids of very different lithologies and heritage although the onion shell configuration of primordial parent bodies is necessary in order to form the chondrites with different degrees of metamorphic overprint petrologic types 3 6 subsequent catastrophic fragmentation and reassembly to form asteroids with a rubble pile structure are required to explain certain features discussed in this work however distinct peaks in the cosmic ray exposure age distributions indicate that not too many impacts in the last 100 ma were responsible to deliver the majority of the ordinary chondritic meteoroids to earth yet this certainly does not tell anything about the number of last generation parent bodies that exist in the asteroid belt since s type asteroids are the most abundant type of asteroid in the inner main belt and thought to be the parent bodies of ordinary chondrites

simulations of strong ground motion in sw iberia for the 1969 february 28 ms 8 0 and the 1755 november 1 m 8 5 earthquakes i velocity model summary this is the first paper of a series of two concerning strong ground motion in sw iberia due to earthquakes originating from the adjacent atlantic area the aim of this paper is to build and calibrate a velocity model that will be used in the companion paper for seismic intensity modelling of the 1969 m s 8 0 and 1755 m 8 5 8 7 earthquakes taking into account the geological evolution of the region since the palaeozoic we build a 3 d velocity model down to the moho discontinuity substantially different from a simple 1 d layered model the velocity model presented in this paper is built a priori using information originating from a variety of geological and geophysical studies its resolution is sufficient to simulate realistically seismic wave propagation in the low frequency f 0 5 hz range which is the most significant for the study of the destructive effects of large earthquakes at a regional scale to validate the model we compute synthetic seismograms for three recent earthquakes of moderate magnitudes 4 6 m w 5 3 located offshore in the most seismically active area in the region synthetics are generated using a wave propagation code based on the finite difference method which was chosen for its simplicity and accuracy in the frequency range considered in this study 0 1 0 5 hz we compare simulated waveforms with threecomponent seismograms for 9 different stations traveltimes of the direct p waves and the amplitude of ground motion are accurately reproduced at all stations the frequency content of the seismograms fits the observations especially for the lowest frequencies investigated 0 1 0 3 hz for each earthquake the estimated seismic moment is in good agreement with values obtained by other authors using different methods we conclude that the velocity model provides encouraging results for the computation of low frequency seismograms in the region and can be used for the study of larger earthquakes for which the radiated wavefield has a predominant low frequency spectrum

location of the focus and tectonics of the focal region of the california earthquake of 18 april 1906 modern relocation constrains the hypocenter of the 18 april 1906 california earthquake within an 8 24 km southwest northeast trending zone to the north of san francisco that intersects the offshore san andreas fault system west of san francisco here we further constrain the location of the 1906 focus and examine the tectonics of the focal region using recent microseismicity relocated in a 3d model along with other seismological geological and marine evidence in agreement with previous work we associate the 1906 focus with an extensional right stepover in the san andreas fault system a zone of sea floor subsidence and complex normal and strike slip faulting we define a likely focal volume between lake merced and offshore of the golden gate centered near 37 77 n 122 55 w and 10 km depth we hypothesize possible 1906 rupture in this region by normal deformation around a 10 km long steeply west dipping structure trending about 20 clockwise to the san andreas fault zone and bilateral strike slip fault rupture along the san andreas fault system away from this structure rupture to the northwest on a vertical currently aseismic faulting structure under the golden gate fault and rupture to the southeast under the san francisco peninsula either along a steeply southwest dipping structure showing present day extensional tectonism or along a near vertical currently aseismic fault zone all three of these structures extend from the near surface to about 10 km depth we also identify a deeper 15 20 km long linear trend of clustered seismicity at 10 13 km depth rotated about 6 clockwise relative to the strike of the san andreas fault which connects the north end of the focal volume with the south end of the seismicity defining the southwest dipping structure under the san francisco peninsula we propose that this trend shows faulting at the base of a brittle upper crust in response to underlying shear in a ductile lower crust these interpretations on the focal region of the 1906 earthquake have implications for seismotectonic understanding earthquake monitoring and seismic hazard assessment in the san francisco bay area

the earthquakes of 29 july 2003 12 february 2007 and 17 december 2009 in the region of cape saint vincent sw iberia and their relation with the 1755 lisbon earthquake abstract the cape saint vincent region is of major seismological interest for its tectonic complexity and for the occurrence of the great 1755 lisbon earthquake no structure capable of generating such a large earthquake has yet been convincingly identified but all authors agree that there is a possibility of a similar earthquake occurring offshore of the cape sometime in the future to shed some light on the region s dynamics we here examine the mechanism of the three largest earthquakes to have occurred in the last 40 years west of the cape 29 july 2003 m w 5 3 12 february 2007 m w 6 1 and 17 december 2009 m w 5 5 by inversion of the body waves and the kinematic slip distribution we estimated the three earthquakes to have had similar characteristics dimensions maximum slip stress drop source time function focal depth and rupture velocity although there were differences in the geometry of the rupture that reflect the great seismotectonic complexity of the zone the focal mechanisms of the 2003 and 2007 earthquakes were similar corresponding to thrusting motion but the 2009 earthquake had a dip slip motion in a vertical plane as deduced from the slip distributions the three shocks show ne sw rupture planes with the energy released propagating to the ne compatible with the regional nw se horizontal compression produced by the convergence of the eurasian and african plates applied to the generation of the 1755 lisbon earthquake this direction of faulting would correspond to a complex rupture along ne sw trending thrust faults at the gorringe bank the horseshoe scarp and the marquis de pombal fault with the rupture propagating to the ne towards the portuguese coast such a model could explain that unusually large and tsunami generating earthquake

oxygen isotope evidence for rapid mixing of the hed meteorite parent body abstract the 16 o 17 o and 18 o abundances of howardites eucrites and diogenites have been used to assign them to a single hed parent body thought to be asteroid 4 vesta we report the first evidence of oxygen isotopic heterogeneity among hed meteorites indicating incompletely mixed sources new high precision oxygen isotope measurements of 34 hed meteorites reveal that most have the same 17 o consistent with a very rapid early history of large scale mixing on vesta however howardites are on average very slightly enriched in 16 o whereas ibitira caldera pasamonte and alha78132 are 16 o depleted compared to other investigated eucrites the 17 o of ibitira is completely different from all other heds measured some of the results for eucrites and diogenites can be explained by partial melting and rapid mixing of the interior of vesta others require a separate parent body or indicate that parts of the outer layer of vesta retained some primary isotopic heterogeneity the oxygen isotopic composition of howardites provides an upper limit for the amount of admixed carbonaceous chondritic material into the hed parent body regolith

rapid estimation of rupture extent for large earthquakes application to the 2004 m9 sumatra andaman mega thrust 1 rapid estimation of the rupture extent of large earthquakes is critical for tsunami warning and emergency response the hypocenter of a distant earthquake is determined from the first seismic p waves within about 15 minutes after the event however methods for determining the size and rupture extent of very large earthquakes rely on long period recordings and aftershock locations which are not available until several hours or more after the event here we introduce a method for rapid estimation of the rupture termination location for large earthquakes based on short period p wave recordings available about 30 minutes after an event the hypocenter and the rupture termination location provide estimates of the extent of rupture and the event size application to the 2004 m9 sumatra andaman earthquake gives a rupture termination location near the andaman islands about 1100 km north of the hypocenter and a rupture duration of about 8 minutes

crust mantle coupling in the gulf of cadiz sw iberia 1 in the gulf of cadiz and cape st vincent region at the sw iberian margin seismic catalogues report seismicity down to 100 km depth according to structural models for the region this includes earthquakes that occur in the uppermost continental mantle we invert regional waveforms to estimate moment tensors and centroid depths for moderate earthquakes obtaining eight solutions mw 3 8 to 5 3 between 6 and 60 km depth moment tensor solutions and previous source estimates show predominately reverse and strike slip faulting style with nnw sse oriented p axes close to plate convergence between africa and eurasia we obtain similar stress tensor estimates from crustal and upper mantle earthquakes both with sub horizontal nnw 1 axes this indicates analogous deformation in both domains and that earthquakes are unrelated to any subduction process

contributors to chromium isotope variation of meteorites we report the results of a comprehensive high precision survey of the cr isotopic compositions of primitive chondrites along with some differentiated meteorites to ensure complete dissolution of our samples they were first fused with lithium borate tetraborate at 1050 1000 c relative to the nist cr standard srm 3112a carbonaceous chondrites exhibit excesses in 54cr 52cr from 0 4 to 1 6e 1e 1 part in 10 000 and ordinary chondrites display a common 54cr 52cr deficit of 0 4e analyses of acid digestion residues of chondrites show that carbonaceous and ordinary chondrites share a common 54cr enriched carrier which is characterized by a large excess in 54cr 52cr up to 200e associated with a very small deficit in 53cr 52cr 2e we did not find 54cr anomalies in either bulk enstatite chondrites or in leachates of their acid digestion residues this either requires that the enstatite chondrite parent bodies did not incorporate the 54cr anomaly carrier phase during their accretion or the phase was destroyed by parent body metamorphism chromium in the terrestrial rocks and lunar samples analyzed here show no deviation from the nist srm 3112a cr standard the eucrite and martian meteorites studied exhibit small deficits in 54cr 52cr the 54cr 52cr variations among different meteorite classes suggest that there was a spatial and or temporal heterogeneity in the distribution of a 54cr rich component in the inner solar system we confirm the correlated excesses in 54cr 52cr and 53cr 52cr for bulk carbonaceous chondrites but the new data yield a steeper slope 6 6 than that reported in shukolyukov and lugmair 2006 the correlated excesses may affect the use of the mn cr chronometer in carbonaceous chondrites we could not confirm the bulk carbonaceous chondrite mn cr isochron reported by shukolyukov and lugmair 2006 and moynier et al 2007 mostly because we find much smaller total variations in e53cr 0 2 all bulk chondrites have small e53cr excesses up to 0 3 relative to the earth most likely reflecting the sub chondritic mn cr ratio of the earth the e53cr variations in chondrites do seem to grossly correlate with mn cr and yield an initial solar system 53mn 55mn value of 5 4 2 4 10 6 corresponding to an absolute age of 4566 4 2 2 ma nuclear interactions with cosmic rays result in coupled excesses in e54cr and e53cr with a 4 1 ratio in phases with high fe cr these are most dramatically demonstrated in the iron meteorite carbo showing excesses in e54cr of up to 140e these new results show that the mn cr chronometer should be used with caution in samples minerals with high fe cr and long cosmic ray exposure ages

the relative motion between africa and eurasia as derived from itrf2000 and gps data 1 studies of intra and inter plate deformation typically need a model describing the motions of the stable part of the tectonic plates for reference purposes we have developed deos2k a model for the current motion of seven major tectonic plates derived from space geodetic observations this paper focuses on relative motion between africa and eurasia in the past this motion has been poorly established because of poor data coverage for africa deos2k is based on itrf2000 altamimi et al 2002 and new african gps observations it is an improvement over the nuvel 1a model for predicting the present day relative motions of these two plates deos2k predicts in northeastern africa that africa eurasia relative motion is about 40 smaller in magnitude than nuvel 1a and trends more to the northwest this is consistent with independent local geodetic observations a similar shift in orientation clockwise is observed at the western tip of the plate boundary

fast kinematic waveform inversion and robustness analysis application to the 2007 mw 5 9 horseshoe abyssal plain earthquake offshore southwest iberia an m w 5 9 earthquake occurred beneath the horseshoe abyssal plain hap offshore southwest iberia on 12 february 2007 the region where the earthquake occurred has a high seismogenic and tsunamigenic potential the purpose of this paper is twofold 1 to extract information about the source of the earthquake that contributes to the understanding of regional tectonics and 2 to evaluate the applicability of a fast algorithm to study a moderate earthquake offshore mainland portugal we employed the kiwi tools which implement a multistep inversion algorithm to infer both the point and finite source properties of the earthquake in order to assess the robustness of our solutions we performed independent sets of inversions that take different datasets and assumptions e g green s functions passbands wave types as inputs we also performed bootstrap analyses in order to appraise the robustness of the source parameters we concluded that the 2007 hap earthquake centroid is located at 35 841 n 10 611 w at a depth of 39 km scalar moment m is consistently retrieved with an average value of graphic 1 moment magnitude m w 5 9 the finite fault parameters are difficult to resolve given the existing data approximately 70 of our bootstrap solutions indicate a true rupture plane that trends west northwest east southeast strike 128 dip 46 and rake 138 the location and strike of this fault plane coincide with the southwest iberian margin swim faults however the 46 dip is difficult to reconcile with the subvertical nature of the swim faults online material inversion results using teleseismic data prem and body waves only 1 embed inline graphic 1 gif

shock metamorphism of ordinary chondrites a revised petrographic classification of progressive stages of shock metamorphism of ordinary chondrites is proposed six stages of shock s1 to s6 are defined based on shock effects in olivine and plagioclase as recognized by thin section microscopy the characteristic shock effects of each shock stage are s1 unshocked sharp optical extinction of olivine s2 very weakly shocked undulatory extinction of olivine s3 weakly shocked planar fractures in olivine s4 moderately shocked mosaicism in olivine s5 strongly shocked isotropization of plagioclase maskelynite and planar deformation features in olivine and s6 very strongly shocked recrystallization of olivine sometimes combined with phase transformations ringwoodite and or phases produced by dissociation reactions s6 effects are always restricted to regions adjacent to melted portions of a sample which is otherwise only strongly shocked in stages s3 to s6 localized melting results from stress and temperature peaks which locally deviate from the equilibration shock pressure due to differences in shock impedance these melting effects are a opaque melt veins shock veins b melt pockets with interconnecting melt veins c melt dikes and d troilite metal deposits in fractures based on a critical evaluation of data from shock recovery experiments a shock pressure calibration for the six shock stages is proposed which defines the s1 s2 s2 s3 s3 s4 s4 s5 and s5 s6 transitions at 5 5 10 15 20 30 35 and 45 55 gpa respectively whole rock melting and formation of impact melt rocks or melt breccias occurs at about 75 90 gpa the symbol for the shock stage may be used in combination with the symbol for the petrologic type to abbreviate the complete classification of a chondrite e g h5 s3 we propose this new shock classification and pressure calibration system to replace previous systems which are out of date with respect to the pressure calibration nominally restricted to l chondrites and based on incomplete and in part illdefined sets of shock effects we have classified seventy six ordinary chondrites using the new classification system and conclude the following 1 1 shock effects and the sequence of progressively increasing degrees of shock metamorphism are very similar in h l and ll groups differences in the frequency distribution of shock stages are relatively minor e g l chondrites appear to have the largest fraction with stages s5 and s6 this suggests that the collisional histories of the h l and ll parent bodies were similar 2 2 petrologic type 3 chondrites are deficient in stages s4 to s6 and with increasing petrologic type the frequency of stages s4 to s6 increases we suggest that the more porous and volatile rich type 3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type volatiles trapped in pores cause shock induced dispersal of the shocked and melted material into small particles which are not expected to survive as meteorites 3 3 stage s3 is the most abundant in nearly all petrologic types 4 4 at shock pressures in excess of about 35 gpa s5 and s6 4he and 40ar are almost completely lost pressures below 10 gpa s1 and s2 do not cause noble gas losses

teleseismic location techniques and their application to earthquake clusters in the south central pacific abstract improved methods for single and multiple event hypocenter determinations are developed and applied to the problem of locating earthquake clusters in the south central pacific ocean bayesian statistical methods are used to incorporate a priori information about arrival time variance into the derivation of hypocenter confidence ellipsoids permitting a more realistic calculation of critical parameters in the case where the number of stations is small the diagonal elements of certain projection operators called data importances by minster et al 1974 are used to evaluate network balance the hypocentroid of an event cluster is defined to be the average location of events within the cluster and the deviations of individual hypocenters from the hypocentroid are called cluster vectors the problem of estimating the cluster vectors can be decoupled from the problem of estimating the hypocentroid by a simple but fundamental mathematical result here termed the hypocentroidal decomposition theorem the algorithm based on this analysis appears to have many advantages over other published methods for multiple event location both in its efficient use of available information and its computational speed the application of this method to three clusters of shallow intraplate seismicity in the south central pacific designated regions a b and c demonstrates that the seismicity within each cluster is very localized the rms lengths of the cluster vectors for each group of epicenters are estimated to be only 9 6 and 12 km respectively estimates of the epicentroids are

itawa bhopji l3 5 chondrite regolith breccia fall classification and cosmogenic records a stony meteorite fell at itawa bhopji rajasthan india on 2000 may 30 this is the fifth recorded fall in a small area of rajasthan during the past decade the meteorite is an ordinary chondrite with light clasts in a dark matrix consisting of a mixture of equilibrated mainly type 5 and unequilibrated components olivine is fa24 26 and pyroxene fs20 22 but within the unequilibrated components olivine fa5 29 and low calcium pyroxene fs5 37 are highly variable based on petrographic studies and chemical analyses it is classified as l 3 5 regolith breccia studies of various cosmogenic records including several gamma emitting radionuclides varying in half life from 5 6 day 52mn to 0 73 ma 26al tracks and rare gases have been carried out the exposure age of the meteorite is estimated from cosmogenic components of rare gases to be 19 6 ma the track density varies by a factor of 3 from 4 to 12 x 10 6 cm 2 within the meteorite indicating a preatmospheric body of 9 cm radius corresponding to a meteoroid mass of 11 kg and small ablation 1 5 to 3 6 cm trapped components in various rare gases are high and the solar component is present in the dark portion of the meteorite large excess of neutron produced 82kr and 128xe in both the light and the dark lithology but very low 60co indicating low neutron fluxes received by the meteoroid in the interplanetary space are clear signatures of an additional irradiation on the parent body

probabilistic earthquake location in complex three dimensional velocity models application to switzerland 1 we present a new approach to determine precise and reliable hypocenter locations in the tectonically complex region of switzerland a three dimensional 3 d p wave velocity model to be used for earthquake relocation is obtained by simultaneously inverting arrival times of local earthquakes for hypocenter locations and 3 d p wave velocity structure a 3 d p wave velocity model derived from controlled source seismology css is used as an initial reference model the final 3 d model thus combines all available information from both css and local earthquake data the probabilistic nonlinear formulation of the earthquake location problem includes a complete description of location uncertainties and can be used with any kind of velocity model in particular the combination of nonlinear global search algorithms such as the oct tree importance sampling with probabilistic earthquake location provides a fast and reliable tool for earthquake location the comparison of hypocenter locations obtained routinely by the swiss seismological service sed to those relocated in the new 3 d velocity model using a probabilistic approach reveals no systematic shifts but does exhibit large individual shifts in some epicenter locations and focal depths we can attribute these large shifts in part to large uncertainties in the hypocenter location events with a low number of observations 8 and no observation within the critical focal depth distance typically show large location uncertainties improved hypocentral locations particularly for mine blasts and earthquakes whose routine hypocenter locations had been questionable confirm that improved velocity model and probabilistic earthquake location yield more precise and reliable hypocenter locations and associated location uncertainties for switzerland

the record of cosmogenic radiogenic fissiogenic and trapped noble gases in recently recovered chinese and other chondrites abstract we performed a comprehensive study of the noble gas isotopic abundances in thirty six chondrites including twenty seven chondrites recovered in china the large data base allows us to recognize some new characteristics of the nuclear record in chondritic matter the comparison of the trapped noble gas release pattern for ordinary and carbonaceous chondrites shows that the planetary trapped noble gases in ordinary chondrites are released mainly above 1200 c whereas 85 of these gases in carbonaceous chondrites are degassed at 200 c there exists a clear correlation of the fraction of trapped xe released at 1200 c and petrologic type of chondrites it thus appears that the carrier phases of the trapped noble gases in ordinary and in carbonaceous chondrites may not be the same the ngawi ll3 chondrite is solar gas rich the solar gases in meteorites and lunar surface material are mixtures of solar wind sw and solar energetic particles sep we show that the variations of the 3 he 4 he and 20 ne 22 ne ratios for solar gas rich meteorites and lunar surface material could be either due to preferential diffusive losses of the lighter isotopes of he and ne or due to a change of the sw sep flux ratio with time furthermore we demonstrate that the 81kr concentration is a function of the shielding depth of a sample within the meteoroid deviations from this depth dependency curve are observed for jilin h5 lishui l5 suizhou l6 and dongtai ll6 a complex exposure history for jilin is thus confirmed and is possible for the other three chondrites cosmic ray exposure ages are calculated based on six different nuclides 3he 21ne 38ar 83kr 126xe and 81kr kr in most cases good agreement is observed for the ages derived from the different methods quality classes are assigned to the exposure ages and the age distributions are discussed in some meteorites we observe effects induced by secondary cosmicray produced neutrons epithermal neutron fluxes jn 30 300 ev and fast neutron fluxes jn 5 mev are derived based on the reactions 79br n 80kr and 24mg n 21ne respectively and preatmospheric masses of the meteoroids are estimated we show that the ratio j n 30 300 ev j n 5 mev increases with increasing preatmospheric mass we introduce a 3he exposure age 21ne exposure age vs 4he gas retention age 40ar gas retention age diagram that is a powerful tool for distinguishing different thermal histories of meteoroids finally in some chondrites we observe xe produced by 244pu fission and calculate the time span between fission xe retention in these chondrites and that of the angra dos reis achondrite we find that the ordinary chondrites started to retain fission xe 48 30 ma earlier than angra dos reis we do not observe systematic differences between h l and ll or type 5 and 6 chondrites with respect to the time of fission xe retention

oxygen isotope studies of ordinary chondrites several stages in the evolution of ordinary chondritic meteorites are recorded in the oxygen isotopic composition of the meteorites and their separable components chondrules fragments clasts and matrix the whole rock isotopic compositions reflect the iron group of the meteorite h l or ll isotopic uniformity of h3 to h6 and l3 to l6 are consistent with closed system metamorphism within each parent body ll3 chondrites differ slightly from ll4 to ll6 implying a small degree of opensystem aqueous alteration and carbon reduction on the scale of individual chondrules the meteorites are isotopically heterogeneous allowing recognition of the solar nebular processes of chondrule formation chondrules for all classes of ordinary chondrites are derived from a common population which was separate from the population of chondrules in carbonaceous or enstatite chondrites chondrules define an isotopic mixing line dominated by exchange between 16o rich and 16o poor reservoirs the oxygen isotopic compositions of chondrites serve as fingerprints for identification of genetic association with other meteorite types achondrites and iron and for recognition of source materials in meteoritic breccias

the nanoscale mineralogy of fe ni sulfides in pristine and metamorphosed cm and cm ci like chondrites tapping a petrogenetic record we have sampled sulfide grains from one pristine cm2 chondrite yamato y 791198 one thermally metamorphosed cm2 chondrite y 793321 and two anomalous metamorphosed cm ci like chondrites y 86720 and belgica b 7904 by the focused ion beam fib technique and studied them by analytical transmission electron microscopy tem our study aims at exploring the potential of sulfide assemblages and microstructures to decipher processes and conditions of chondrite petrogenesis complex exsolution textures of pyrrhotite crystallographic nc type with n 6 troilite and pentlandite occur in grains of y 791198 and y 793321 additionally polycrystalline 4c pyrrhotite pentlandite magnetite aggregates occur in y 791198 pointing to diverse conditions of gas solid interactions in the solar nebula coarser exsolution textures of y 793321 grains indicate higher long term average temperatures in the 100 c range compared to y 791198 and other cm chondrites sulfide mineralogy of y 86720 and b 7904 is dominated by aggregates of pure troilite and metal indicating metamorphic equilibration at sulfur fugacities fs2 of the iron troilite buffer absence of magnetite in equilibrium with sulfide and metal in y 86720 indicates higher peak temperatures compared with b 7904 in which coexistence of troilite metal and magnetite constrains metamorphic temperature to less than 570 c nc pyrrhotite occurs in both meteorites as nm wide rims on troilite grains and together with frequent anhydrite indicates a retrograde metamorphic stage at higher fs2 slightly above the fayalite magnetite quartz pyrrhotite buffer fine grained troilite olivine intergrowths in both meteorites suggest the pre metamorphic presence of tochilinite serpentine interlayer phases pointing to mineralogical cm affinity pseudomorphs after euhedral pyrrhotite crystals in y 86720 in turn suggest ci affinity as do previously published o isotopic data of both meteorites

active deformation in old oceanic lithosphere and significance for earthquake hazard seismic imaging of the coral patch ridge area and neighboring abyssal plains sw iberian margin recently acquired high resolution multichannel seismic profiles together with bathymetric and sub bottom profiler data from the external part of the gulf of cadiz iberia africa plate boundary reveal active deformation involving old mesozoic oceanic lithosphere this area is located 180 km offshore the sw iberian peninsula and embraces the prominent ne sw trending coral patch ridge and part of the surrounding deep horseshoe and seine abyssal plains e w trending dextral strike slip faults showing surface deformation of flower like structures predominate in the horseshoe abyssal plain whereas ne sw trending compressive structures prevail in the coral patch ridge and seine hills although the coral patch ridge region is characterized by subdued seismic activity the area is not free from seismic hazard most of the newly mapped faults correspond to active blind thrusts and strike slip faults that are able to generate large magnitude earthquakes mw 7 2 8 4 this may represent a significant earthquake and tsunami hazard that has been overlooked so far

seismic sources on the iberia african plate boundary and their tectonic implications the plate boundary between iberia and africa has been studied using data on seismicity and focal mechanisms the region has been divided into three areas a the gulf of cadiz b the betics alboran sea and northern morocco and c algeria seismicity shows a complex behavior large shallow earthquakes h 30 km occur in areas a and c and moderate shocks in area b intermediate depth activity 30 h 150 km is located in area b the depth earthquakes h 650 km are located to the south of granada moment rate slip velocity andhvalues have been estimated for shallow shocks and show similar characteristics for the gulf of cadiz and algeria and quite different ones for the central region focal mechanisms of 80 selected shallow earthquakes 8 mb 4 show thrust faulting in the gulf of cadiz and algeria with horizontal nnw sse compression and normal faulting in the alboran sea with e w extension focal mechanisms of 26 intermediate depth earthquakes in the alboran sea display vertical motions with a predominant plane trending e w solutions for very deep shocks correspond to vertical dip slip along n s trends frohlich diagrams and seismic moment tensors show different behavior in the gulf of cadiz betic alboran sea and northern morocco and northern algeria for shallow events the stress pattern of intermediate depth and very deep earthquakes has different directions vertical extension in the nw se direction for intermediate depth earthquakes and tension and pressure axes dipping about 45 o for very deep earthquakes regional stress pattern may result from the collision between the african plate and iberia with extension and subduction of lithospheric material in the alboran sea at intermediate depth the very deep seismicity may be correlated with older subduction processes

macrochondrules in chondrites formation by melting of mega sized dust aggregates and or by rapid collisions at high temperatures seventy four macrochondrules with sizes 3 mm were studied considering the extraordinary size of the chondrules occasionally achieving a mass of 1000 times and more the mass of a normal sized chondrule the conditions in the formation process must have been somewhat different compared with the conditions for the formation of the common chondrules macrochondrules are typically rich in olivine and texturally similar to specific chondrule types barred radial porphyritic and cryptocrystalline of normal sized chondrules however our studies show that most of the macrochondrules are fine grained or have elongated crystals mostly bo rp and c which lead to the assumption that they were once totally molten and cooled quite rapidly porphyritic chondrules belong to the least abundant types of macrochondrules this distribution of chondrule types is highly unusual and just a reverse of the distribution of chondrule types among the typical sized chondrules in most chondrite groups except for the ch and cb chondrites new chondrule subtypes like radial olivine ro or multi radial mr chondrules are defined to better describe the textures of certain large chondrules macrochondrules may have formed due to melting of huge precursor dust aggregates or due to rapid collisions of superheated melt droplets which led to the growth of large molten spherules in regions with high dust densities and high electrostatic attraction

almahata sitta fragment ms ch characterization of a new chondrite type abstract among the several hundred mostly small meteorite fragments recovered within the almahata sitta strewn field one fragment ms ch weighing 5 68 g was detected that represents a new type of chondritic meteorite the detection of short lived cosmogenic radionuclides clearly indicates that this chondrite fragment results from a fresh meteorite fall consistent with the almahata sitta event in october 2008 the fundamental mineralogical characteristics of the almahata sitta fragment ms ch can be summarized as follows 1 the almost equilibrated olivine has high fa contents of about 36 mole the fragment is of petrologic type 3 8 0 1 2 the metal abundance of the rock is on the order of 2 5 vol 3 the mean chondrule size has been determined to be roughly 450 m 4 point counting and imaging indicate that the matrix abundance is approximately 45 vol 5 cr spinels have much lower tio2 concentrations than typical spinels within r chondrites 6 calcium aluminum rich inclusions are spinel rich and severely altered having abundant na and or cl rich alteration products spinel also contains significant concentrations of fe and zn 7 magnetites and platinum group element rich phases sulfides tellurides and arsenides characteristic of both r and ck chondrites were not found in fragment ms ch and 8 the mean oxygen isotope composition of three small fragments of almahata sitta ms ch is 17o 4 35 18o 4 94 and 17o 1 76 the oxygen isotopes relate ms ch to r chondrites no established chondrite group having all these characteristics exists

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

focal mechanisms for sub crustal earthquakes in the gulf of cadiz from a dense obs deployment 1 an eleven month deployment of 25 ocean bottom seismometers provides an unprecedented opportunity to study low magnitude local earthquakes in the complex transpressive plate boundary setting of the gulf of cadiz known for the 1755 lisbon earthquake and tsunami 36 relocated earthquakes ml 2 2 to 4 8 concentrate at 40 60 km depth near the base of the seismogenic layer in 140 ma old oceanic mantle lithosphere and roughly align along two perpendicular nne ssw and wnw ese striking structures first motion focal mechanisms indicate compressive stress for the cluster close to the northern horseshoe fault termination which trends perpendicular to plate convergence focal mechanisms for the second cluster near the southern termination of the horseshoe fault indicate a strike slip regime providing evidence for present day activity of a dextral shear zone proposed to represent the eurasia africa plate contact we hypothesize that regional tectonics is characterized by slip partitioning

seismotectonics of the horseshoe abyssal plain and gorringe bank eastern atlantic ocean constraints from ocean bottom seismometer data at the eastern end of the azores gloria transform fault system to the southwest of portugal the plate boundary between africa and iberia is a region where deformation is accommodated over a wide tectonically active area the region has unleashed large earthquakes and tsunamis including the mw 8 5 great lisbon earthquake of 1755 although the source region of the 1755 earthquake is still disputed most proposals include a source location in the vicinity of the horseshoe abyssal plain hap which is bounded by the 5000 m high gorringe bank gb in this study we characterise seismic activity in the region using data recorded by two local networks of ocean bottom seismometers obs the networks were deployed in the eastern hap and at the gb the dataset allowed the detection of 160 local earthquakes these earthquakes cluster around the gb to the sw of cabo sao vicente and in the hap focal depths indicate deep seated earthquakes with depths increasing from 20 35 km mean of 26 1 7 2 km at the gb to 15 45 km mean 31 5 km 10 5 km under the hap seismic activity thus extends down to levels that are deeper than those mapped by active seismic profiling with the majority of events occurring within the mantle thermal modelling suggests that temperatures of approximately 600 c characterise the base of the seismogenic brittle lithosphere at 45 km depth the large source depth and thermal structure supports previous suggestions that catastrophic seismic rupture through the lithospheric mantle may indeed occur in the area

oxygen isotopic compositions of enstatite chondrites and aubrites oxygen isotopic compositions have been measured for ten eh chondrites eight el chondrites and nine aubrites the mean 18o and 17o values are 5 31 and 2 74 5 57 and 2 96 5 24 and 2 70 respectively within the eh group more equilibrated meteorites are fractionated toward higher heavy isotope abundances than the less equilibrated meteorites small departures of individual meteorites from a common mass fractionation occur for some of the eh samples the aubrites may be genetically related to either the eh or el group or to both almost all of the measured isotopic compositions are indistinguishable from the terrestrial oxygen isotope fractionation line suggesting a genetic relationship among the earth the moon and the enstatite the meteorites

noble gases in 21 saharan ll chondrites exposure ages and possible pairings nineteen ll chondrites and two l ll chondrites adrar 003 and tanezrouft 010 from the saharan desert of algeria and libya have been analysed for their he ne and ar composition as well as for their abundance of 84kr and 132xe calculated 21ne cosmic ray exposure ages vary between 2 and 35 ma the age distribution is consistent with that of modern ll chondrite falls except that no dominant peaks can be observed especially not the one related to a 15 ma collisional event however the lack of young exposure ages of 8 ma is obvious this is a characteristic feature of ll chondrites only one of the 21 ll chondrites namely acfer 066 contains solar gases and is thus considered a regolith breccia three specimens reveal considerable loss of 3he probably due to periods of elevated temperatures in orbits with small perihelion distances furthermore severe loss of 4he and 40ar is found in two samples considering possible pairings we suggest 14 individual falls basically on the basis of the noble gas data the petrographic sub classification and by taking the find location into consideration however there are constraints on confirming pairings solely on the basis of our studies thus we can only exclude individual samples with a unique noble gas fingerprint from paired specimens

imaging active faulting in a region of distributed deformation from the joint clustering of focal mechanisms and hypocentres application to the azores western mediterranean region abstract the matching between linear trends of hypocentres and fault planes indicated by focal mechanisms fms is frequently used to infer the location and geometry of active faults this practice works well in regions of fast lithospheric deformation where earthquake patterns are clear and major structures accommodate the bulk of deformation but typically fails in regions of slow and distributed deformation we present a new joint fm and hypocentre cluster algorithm that is able to detect systematically the consistency between hypocentre lineations and fms even in regions of distributed deformation we apply the method to the azores western mediterranean region with particular emphasis on western iberia the analysis relies on a compilation of hypocentres and fms taken from regional and global earthquake catalogues academic theses and technical reports complemented by new fms for western iberia the joint clustering algorithm images both well known and new seismo tectonic features the azores triple junction is characterised by fms with vertical pressure p axes in good agreement with the divergent setting and the iberian domain is characterised by nw se oriented p axes indicating a response of the lithosphere to the ongoing oblique convergence between nubia and eurasia several earthquakes remain unclustered in the western mediterranean domain which may indicate a response to local stresses the major regions of consistent faulting that we identify are the mid atlantic ridge the terceira rift the trans alboran shear zone and the north coast of algeria in addition other smaller earthquake clusters present a good match between epicentre lineations and fm fault planes these clusters may signal single active faults or wide zones of distributed but consistent faulting mainland portugal is dominated by strike slip earthquakes with fault planes coincident with the predominant nne ssw and wnw ese oriented earthquake lineations clusters offshore sw iberia are predominantly strike slip or reverse confirming previous suggestions of slip partitioning

the oxygen isotope composition of almahata sitta abstract eleven fragments of the meteorite almahata sitta ahs have been analyzed for oxygen isotopes the fragments were separately collected as individual stones from the meteorite s linear strewn field in the nubian desert each of the fragments represents a sample of a different and distinct portion of asteroid 2008 tc3 ten of the fragments span the same range of values of 18o 17o and 17o and follow the same trend along the carbonaceous chondrite anhydrous minerals ccam line as monomict and polymict members of the ureilite family of meteorites the oxygen isotope composition of fragment 25 is consistent with its resemblance petrographically to an h5 ordinary chondrite our results demonstrate that a single small asteroidal parent body asteroid 2008 tc3 only 4 m in length encompassed the entire range of variation in oxygen isotope compositions measured for monomict and polymict ureilites

fall recovery and characterization of the novato l6 chondrite breccia the novato l6 chondrite fragmental breccia fell in california on 17 october 2012 and was recovered after the cameras for allsky meteor surveillance cams project determined the meteor s trajectory between 95 and 46 km altitude the final fragmentation from 42 to 22 km altitude was exceptionally well documented by digital photographs the first sample was recovered before rain hit the area first results from a consortium study of the meteorite s characterization cosmogenic and radiogenic nuclides origin and conditions of the fall are presented some meteorites did not retain fusion crust and show evidence of spallation before entry the meteoroid was 35 5 cm in diameter mass 80 35 kg with a cosmic ray exposure age of 9 1 ma if it had a one stage exposure history a two stage exposure history is more likely with lower shielding in the last few ma thermoluminescence data suggest a collision event within the last similar to 0 1 ma novato probably belonged to the class of shocked l chondrites that have a common shock age of 470 ma based on the u th he age of 420 220 ma the measured orbits of novato jesenice and innisfree are consistent with a proposed origin of these shocked l chondrites in the gefion asteroid family perhaps directly via the 5 2 mean motion resonance with jupiter novato experienced a stronger compaction than did other l6 chondrites of shock stage s4 despite this a freshly broken surface shows a wide range of organic compounds less

seismic evidence of exhumed mantle rock basement at the gorringe bank and the adjacent horseshoe and tagus abyssal plains sw iberia the gorringe bank is a gigantic seamount that separates the horseshoe and tagus abyssal plains offshore sw iberia in a zone that hosts the convergent boundary between the africa and eurasia plates although the region has been the focus of numerous investigations since the early 1970s the lack of appropriate geophysical data makes the nature of the basement and thus the origin of the structures still debated in this work we present combined p wave seismic velocity and gravity models along a transect that crosses the gorringe bank from the tagus to the horseshoe abyssal plains the p wave velocity structure of the basement is similar in the tagus and horseshoe plains it shows a 2 5 3 0 km thick top layer with a velocity gradient twice stronger than oceanic layer 2 and an abrupt change to an underlying layer with a five fold weaker gradient velocity and density is lower beneath the gorringe bank probably due to enhanced fracturing that have led to rock disaggregation in the sediment starved northern flank in contrast to previous velocity models of this region there is no evidence of a sharp crust mantle boundary in any of the record sections the modelling results indicate that the sediment overlays directly serpentinite rock exhumed from the mantle with a degree of serpentinization decreasing from a maximum of 70 80 under the top of gorringe bank to less than 5 at a depth of 20 km we propose that the three domains were originally part of a single serpentine rock band of nature and possibly origin similar to the iberia abyssal plain ocean continent transition which was probably generated during the earliest phase of the north atlantic opening that followed continental crust breakup early cretaceous during the miocene the nw se trending eurasia africa convergence resulted in thrusting of the southeastern segment of the exhumed serpentinite band over the northwestern one forming the gorringe bank the local deformation associated to plate convergence and uplift could have promoted pervasive rock fracturing of the overriding plate leading eventually to rock disaggregation in the northern flank of the gb which could be now a potential source of rock avalanches and tsunamis

asteroid 2008 tc 3 almahata sitta a spectacular breccia containing many different ureilitic and chondritic lithologies abstract asteroid 2008 tc3 impacted earth in northern sudan on october 7 2008 the meteorite named almahata sitta was classified as a polymict ureilite in this study 40 small pieces from different fragments collected in the almahata sitta strewn field were investigated and a large number of different lithologies were found some of these fragments are ureilitic in origin whereas others are clearly chondritic as all are relatively fresh w0 w0 1 and as short lived cosmogenic radioisotopes were detected within two of the chondritic fragments there is strong evidence that most if not all belong to the almahata sitta meteorite fall the fragments can roughly be subdivided into achondritic ureilitic 23 samples and chondritic lithologies 17 samples among the ureilitic rocks are at least 10 different lithologies a similar number of different chondritic lithologies also exist most chondritic fragments belong to at least seven different e chondrite rock types eh3 el3 4 el6 el breccias several different types of el and eh impact melt rocks and impact melt breccias some of the latter are shock darkened in addition two h group ordinary chondrite lithologies were identified and one sample of a chondrite type that is so far unique the latter has some affinities to r chondrites oxygen isotope compositions of 14 fragments provide further fundamental information on the lithological heterogeneity of the almahata sitta meteorite based on the findings presented in this study the reflectance spectrum of asteroid 2008 tc3 has to be evaluated in a new light

thermal infrared emission spectroscopy of the pyroxene mineral series the thermal infrared emissivity spectra of coarse particulate samples of compositions in the pyroxene series display reststrahlen features absorptions that distinguish not only orthorhombic from monoclinic structures but also major end members within the two structural groups as well as minerals within solid solution series the exact number of reststrahlen features observed and their positions are dependent on mineral structure and cation occupancy of the m1 and m2 sites end member quadrilateral pyroxenes mg2si2o6 fe2si2o6 ca mg fe si2o6 are easily distinguished from each other and from minerals in the nonquadrilateral series nafesi2o6 na al fe si2o6 lialsi2o6 furthermore among quadrilateral pyroxenes variations in mg mg fe are linearly correlated with several band locations as are variations in ca content in high ca clinopyroxenes in both quadrilateral and nonquadrilateral compositions christiansen feature positions are also diagnostic no correlations with minor constituents of the order of 0 05 atoms per formula unit were observed the detailed spectral characteristics of pyroxenes and their variability as a function of structure and cation occupancy are presented here with determinative curves for the identification of pyroxene composition these data have important implications for the interpretation of spectral data from both laboratory and remote sensing instruments because they should permit a more detailed determination of pyroxene composition in measured unknown pure mineral and bulk compositions dominated by surface scattering i e all particulates greater than 65 m and solid samples

evidence from tm anomalies for non ci refractory lithophile element proportions in terrestrial planets and achondrites thulium is a heavy rare earth element ree whose geochemical behavior is intermediate between er and yb and that is not expected to be decoupled from these elements during accretion of planetary bodies and geological processes however irregularities in ree volatilities at higher temperature could have decoupled the rees relative to one another during the early stages of condensation of the solar nebula indeed positive tm anomalies are found in some refractory inclusions from carbonaceous chondrites and it is possible that large scale nebular reservoirs displaying positive or negative tm anomalies were formed during the early history of the solar system we analyzed a series of meteorites and terrestrial rocks in order to evaluate the existence of tm anomalies in planetary materials relative to cis ivuna type carbonaceous chondrites carbonaceous chondrites display unresolved or positive tm anomalies while most of the noncarbonaceous chondrites show slightly negative tm anomalies quantification of these anomalies in terrestrial samples is complicated when samples display fractionated heavy ree patterns taking this effect into account we show that the earth mars vesta the aubrite and ureilite parent bodies display small negative anomalies tm tm 0 975 very similar to those found in ordinary and enstatite chondrites we suggest that a slight negative tm anomaly relative to ci is a widespread feature of the materials from the inner solar system this finding suggests that ci chondrites may not be appropriate for normalizing ree abundance patterns of most planetary materials as they may be enriched in a high temperature refractory component with non solar composition the presence of tm anomalies at a bulk planetary scale is to this day the strongest piece of evidence that refractory lithophile elements are not present in constant proportions in planetary bodies

a reassessment of outer rise seismicity and its implications for the mechanics of oceanic lithosphere we use body waveform modelling to constrain the source parameters of earthquakes occurring globally in oceanic lithosphere beneath the subduction zone outer rise and outer trench slope these data are then used to map the stress state in the lithosphere of the downgoing plate as it bends into the subduction zone our results provide new constraints on the faulting of oceanic lithosphere at the outer rise which is important for understanding the transmission of plate driving forces through the subduction system in all cases shallow normal faulting earthquakes are observed at the top of the plate and are separated in depth from any deeper thrust faulting earthquakes no temporal variation associated with large thrust faulting earthquakes on the subduction interface is seen in the depth extent of each type of faulting at the outer rise the transition depth from trench normal extension to compression is found to vary in agreement with models in which deformation is driven by the combination of in plane stresses and bending stresses resulting principally from slab pull combining the seismologically derived constraints on the thickness of the elastic core of the plate with estimates of the plate curvature we place upper bounds on the strength of the lithosphere at the outer rise which is required to be 300 mpa for a constant yield stress model or governed by an effective coefficient of friction of 0 3

shock and thermal history of northwest africa 4859 an annealed impact melt breccia of ll chondrite parentage containing unusual igneous features and pentlandite abstract northwest africa 4859 nwa 4859 is a meteorite of ll chondrite parentage that shows unusual igneous features and contains widely distributed pentlandite the most obvious unusual feature is a high proportion of large 3 cm diameter igneous textured enclaves lites interpreted as shock melts that were intruded into an ll chondrite host one such lite appears to have been produced by whole rock melting of ll chondrite initial rapid partial crystallization and subsequent slow cooling of the residual melt in the host to produce a differentiated object other unusual features include mm sized overgrowth objects fine grained plagioclase rich bands and coarse troilite 7 mm across grains all these features are interpreted as having crystallized from melts produced by a single transient shock event followed by slow cooling a subsequent shock event of moderate s3 intensity produced veining and transformed some of the pyroxene into the clinoenstatite polytype pentlandite together with associated troilite in nwa 4859 probably formed by the breakdown of a monosulfide precursor phase at low temperature 230 c following the second shock event nwa 4859 is interpreted to be an unusual impact melt breccia that contains shock melt which crystallized in different forms at depth within the parent body

seismic evidence for the presence of jurassic oceanic crust in the central gulf of cadiz sw iberian margin abstract we investigate the crustal structure of the sw iberian margin along a 340 km long refraction and wide angle reflection seismic profile crossing from the central gulf of cadiz to the variscan continental margin in the algarve southern portugal the seismic velocity and crustal geometry model obtained by joint refraction and reflection travel time inversion reveal three distinct crustal domains the 28 30 km thick variscan crust in the north a 60 km wide transition zone offshore where the crust abruptly thins 20 km and finally a 7 km thick and 150 km wide crustal section that appears to be oceanic in nature the oceanic crust is overlain by a 1 3 km thick section of mesozoic to eocene sediments with an additional 3 4 km of low velocity unconsolidated sediments on top belonging to the miocene age gulf of cadiz imbricated wedge the sharp transition between continental and oceanic crust is best explained by an initial rifting setting as a transform margin during the early jurassic that followed the continental break up in the central atlantic the narrow oceanic basin would have formed during an oblique rifting and seafloor spreading episode between iberia and africa that started shortly thereafter bajocian and lasted up to the initiation of oceanic spreading in the north atlantic at the tithonian late jurassic earliest cretaceous the velocity model displays four wide prominent south dipping low velocity anomalies which seem to be related with the presence of crustal scale faults previously identified in the area some of which could well be extensional faults generated during this rifting episode we propose that this oceanic plate segment is the last remnant of an oceanic corridor that once connected the alpine tethys with the atlantic ocean so it is in turn one of the oldest oceanic crustal fragments currently preserved on earth the presence of oceanic crust in the central gulf of cadiz is consistent with geodynamic models suggesting the existence of a narrow westward retreating oceanic slab beneath the gibraltar arc alboran basin system

single link cluster analysis of earthquake aftershocks decay laws and regional variations using single link cluster analysis the authors investigate how various properties of aftershock sequences depend on their tectonic regime and focal depth for international seismological centre earthquakes of m sub b ge 4 8 they find that earthquakes deeper than 70 km have the fewest and smallest aftershock sequences even after accounting for differences in detectability and maximum magnitude they find that ridge transform earthquakes have smaller aftershock sequences that shallow subduction zone earthquakes among different subduction zones they find that zones with high moment release rates possess larger aftershock sequences comparing ridge transform zones they find those with slower spreading rates possess larger aftershock sequences by transposing origin times of several different aftershock sequences as if all had main shocks occurring at time zero they are able to study the properties of aftershock sequences which individually have too few aftershocks to study by other means secondary events determined by single link cluster analysis follow a modified omori s power law decay for time separations of 0 1 day to 20 days from the parent event with p values ranging from 0 539 plus minus 0 022 intermediate and deep focus earthquakes to 0 928 plus minus 0 024 ridge transform earthquakes they find that earthquake foreshocks and multiplets also follow a modified omori s law atmore greater times from the main shock the decay is steeper than a power law decay more like an exponential decay aftershocks in the adak catalog m sub b ge 2 0 show a marked decrease in activity between 40 and 50 km depth they speculate that the observed differences in number of aftershocks and p values may be caused by variations in fault heterogeneity or in fluid pressures less

manganese chromium isotope systematics of carbonaceous chondrites abstract in this article we present the results of cr isotope investigations of different types of carbonaceous chondrites and of the pallasite eagle station the 53 cr 52 cr ratios in the bulk samples of carbonaceous chondrites are correlated with 55 mn 52 cr ratios the slope of the correlation line yields a 53 mn 55 mn ratio of 8 5 1 5 10 6 at the time of mn cr fractionation mapping this ratio onto an absolute time scale yields a time for this event of 4568 1 0 8 1 1 ma ago this time is very similar to the formation age of efremovka cais of 4567 2 0 6 ma y amelin a n krot i d hutcheon a a ulyanov lead isotopic ages of chondrules and calcium aluminum rich inclusions science 297 2002 1678 1683 to a time of the chondrule formation of 4568 1 ma ago l e nyquist d lindstrom d mittlefehldt c y shih h wiesmann s wentworth r martinez manganese chromium formation intervals for chondrules from the bishunpur and chainpur meteorites meteorit planet sci 36 2001 911 938 which most likely constrains early global high temperature mn cr fractionation in a nebular setting the bulk samples of carbonaceous chondrites exhibit clear 54 cr excesses 54 cr that are correlated with the 53 cr excesses 53 cr and also with mn cr ratios one possible explanation of this correlation is that 54 cr is also radiogenic like 53 cr and was formed by the decay of the short lived parent radionuclide 54 mn the very short half life of 54 mn of 312 days would require that both short lived radionuclides 53 mn and 54 mn were generated locally in spallation reactions during the early period of an active sun the alternative and possibly more plausible explanation is the heterogeneous addition of presolar material the presolar component enriched in 54 cr is mostly contained in the matrix of carbonaceous chondrites the relative amount of matrix decreases in the sequence ci cm co cv a large proportion of mn is associated with the matrix while cr preferentially resides in the chondrules thus the mn cr ratio also follows the sequence ci cm co cv and is correlated with 54 cr the acid resistant residues of carbonaceous chondrites are characterized by relatively large excesses of 54 cr and moderate deficits of 53 cr the magnitude of these excesses and deficits decreases in the sequence ci cm cv and may imply that cr in the cm and cv residues is increasingly more equilibrated with cr from the rest of the meteorites the 53 cr 52 cr and 54 cr 52 cr ratios in the residues are anti correlated indicating that there are at least two cr components of possibly presolar origin all residues have large excesses of the most neutron rich ti isotope 50 ti the pattern of 50 ti does not exactly follow that observed for 54 cr but it is generally similar the cr isotope systematic of the pallasite eagle station indicates that the precursor of this meteorite was a cv type material the 53 mn 53 cr system indicates that the cr isotopes equilibrated in this meteorite 4557 5 0 6 ma ago

global survey of aftershock area expansion patterns we developed an objective method to define the aftershock areas of large earthquakes as a function of time after the main shock the definition is based upon the amount of energy released by aftershocks the spatial distribution of the energy release is first determined and is contoured the 1 day aftershock area is defined by a contour line corresponding to the energy release level of 10 15 6 ergs 100 km 2 day the 10 day 100 day and 1 y aftershock areas are similarly defined by contour lines corresponding to 10 14 8 10 14 0 and 10 13 5 ergs 100 km 2 day respectively we also define the expansion ratios at time t by the ratio of the aftershock area at t to that at 1 day using this method we study the aftershock area expansion patterns of 44 large m s 7 5 and five moderate shallow earthquakes which occurred from 1963 to 1980 each aftershock sequence is examined at four different times i e 1 day 10 days 100 days and 1 y after the main event we define the aftershock area expansion ratios and e by s 100 s 1 and l 100 l 1 respectively here s t and l t are the area and the length of the aftershock area respectively at time t our study suggests that a distinct regional variation of aftershock area expansion patterns is present it is strongly correlated with the tectonic environment in general the subduction zones of the mariana type have large expansion ratios and those of the chilean type have small expansion ratios some earthquakes that occurred in the areas of complex bathymetry such as aseismic ridges tend to have large expansion ratios these results can be explained in terms of an asperity model of fault zones in which a fault plane is represented by a distribution of strong spots called the asperities and weak zones surrounding the asperities the rupture immediately after the main shock mostly involves asperities after the main rupture is completed the stress change caused by the main shock gradually propagates outward into the surrounding weak zones this stress propagation manifests itself as expansion of aftershock activity in this simple picture if the fault zone is represented by relatively large asperities separated by small weak zones chilean type then little expansion of aftershock activity would be expected on the other hand if relatively small asperities are sparsely distributed mariana type significant expansion occurs the actual distribution of asperities is likely to be more complex than the two cases described above however we would expect that the expansion ratio is in general proportional to the spatial ratio of the total asperity area to the fault area

rapid three dimensional hypocentral determination using a master station method a master station ms method is presented in this paper to rapidly determine hypocenters in three dimensional 3 d heterogeneous velocities an equal differential time edt surface is defined as the collection of all spatial points that satisfy the time difference between two arrivals which can be two picks at two stations or two different phase picks at one station the edt surface is independent of the origin time and will contain the hypocenter for an event with j arrivals there are j 1 independent edt surfaces the ms method determines the hypocenter that satisfies two types of constraints to be traversed by most edt surfaces and to yield minimum travel time residual statistics the statistics include both the residual variance and the amplitude of the origin time error the combined use of the edt surfaces and residual statistics allows for a unique determination of the hypocenter and origin time using different types of phase arrivals in principle only three arrivals are minimally required to constrain a unique solution if three different stations are used for a 3 d velocity model the edt surfaces and the residual statistics can be computed efficiently using a reference file created by moser s 1991 ray tracing method an illustration of the ms method is given for 27 small events that occurred in southern california using a p wave velocity model modified from that of magistrale et al 1992 the average misfit between the bulletin hypocenters and the new solutions is 3 8 km if a 3 d velocity model is accurate the ms method can be a viable means of hypocenter determination

traveltime measurements from noise correlation stability and detection of instrumental time shifts we test the feasibility of using green s functions extracted from records of ambient seismic noise to monitor temporal changes in the earth crust properties by repeated measurements at regional distances we use about 11 yr of continuous recordings to extract surface waves between three pairs of stations in california the correlations are computed in a moving 1 month window and we analyse the temporal evolution of measured interstation traveltimes the comparison of the arrival times in the positive and negative correlation time of rayleigh and love waves allows us to separate time shifts associated with any form of physical change in the medium those resulting from clock drift or other instrumental errors and those due to change in the localization of the noise sources this separation is based on the principle of time symmetry when possible we perform our analysis in two different period bands 5 10 and 10 20 s the results indicate that significant instrumental time errors 0 5 s are present in the data these time shifts can be measured and tested by closure relation and finally corrected independently of any velocity model the traveltime series show a periodic oscillation that we interpret as the signature of the seasonal variation of the region of origin of the seismic noise between 1999 and 2005 the final arrival time fluctuations have a variance of the order of 0 01 s this allows us to measure interstation traveltimes with errors smaller than 0 3 per cent of the interstation traveltime and smaller than 1 per cent of the used wave period this level of accuracy was not sufficient to detect clear physical variation of crustal velocity during the considered 11 yr between the three stations in california such changes may be more easily detectable when considering pairs of stations more closely located to each other and in the vicinity of tectonically active faults or volcanoes

magnetic classification of stony meteorites 2 non ordinary chondrites a database of magnetic susceptibility measurements on different non ordinary chondrites c e r and ungrouped populations is presented and compared to our previous similar work on ordinary chondrites it provides an exhaustive study of the amount of iron nickel magnetic phases essentially metal and magnetite in these meteorites in contrast with all the other classes cm and cv show a wide range of magnetic mineral content with a two orders of magnitude variation of whether this is due to primary parent body differences metamorphism or alteration remains unclear c34 and c2 yield similar values to the ones shown by ck and cm respectively by order of increasing the classes with well grouped are r co ck ci kak cr e ch cb based on magnetism eh and el classes have indistinguishable metal content outliers that we suggest may need to have their classifications reconsidered are acfer 202 co elephant moraine eet 96026 c45 meteorite hills met 01149 and northwest africa nwa 521 ck asuka a 88198 lapaz icefield lap 031156 and sahara 98248 r values can also be used to define affinities of ungrouped chondrites and propose pairing particularly in the case of cm and cv meteorites

micro seismicity in the gulf of cadiz is there a link between micro seismicity high magnitude earthquakes and active faults abstract the gulf of cadiz seismicity is characterized by persistent low to intermediate magnitude earthquakes occasionally punctuated by high magnitude events such as the m 8 7 1755 great lisbon earthquake and the m 7 9 event of february 28th 1969 micro seismicity was recorded during 11 months by a temporary network of 25 ocean bottom seismometers obss in an area of high seismic activity encompassing the potential source areas of the mentioned large magnitude earthquakes we combined micro seismicity analysis with processing and interpretation of deep crustal seismic reflection profiles and available refraction data to investigate the possible tectonic control of the seismicity in the gulf of cadiz area three controlling mechanisms are explored i active tectonic structures ii transitions between different lithospheric domains and inherited mesozoic structures and iii fault weakening mechanisms our results show that micro seismicity is mostly located in the upper mantle and is associated with tectonic inversion of extensional rift structures and to the transition between different lithospheric rheological domains even though the crustal structure is well imaged in the seismic profiles and in the bathymetry crustal faults show low to negligible seismic activity a possible explanation for this is that the crustal thrusts are thin skinned structures rooting in relatively shallow sub horizontal decollements associated with aseismic serpentinization levels at the top of the lithospheric mantle therefore co seismic slip along crustal thrusts may only occur during large magnitude events while for most of the inter seismic cycle these thrusts remain locked or slip aseismically we further speculate that high magnitude earthquake s ruptures may only nucleate in the lithospheric mantle and then propagate into the crust across the serpentinized layers

seismicity source mechanisms and tectonics of the azores gibraltar plate boundary abstract a study and partial revision of the seismicity and source mechanisms of earthquakes are presented for the oceanic plate boundary of eurasia and africa from the azores islands to the strait of gibraltar focal mechanisms of 36 earthquakes wave form modelling of 4 and seismic moments and dimensions of 28 have been calculated these results indicate that the boundary is divided into three sections with different characteristics the azores the central section and the east section the azores section has high seismicity of moderate magnitude and a low slip rate 0 76 cm yr the predominant mechanism is normal or transform faulting with horizontal tensions on average in a n25 e direction in the central section large earthquakes occur with strike slip right lateral motion along faults in an e w direction there is a high slip rate 3 39 cm yr the east section is of more complex nature large earthquakes also occur but the predominant mechanism is reverse faulting with a horizontal pressure axis in the n30 w direction resulting in underthrusting of africa from the slip vectors the pole of rotation for the african plate is located at 28 2 n 21 1 w nearer to the boundary than previous locations close to the continent there is a continuation in the ocean crust of some structural features of the iberian peninsula

the aster spectral library version 2 0 abstract the advanced spaceborne thermal emission reflection radiometer aster on nasa s terra platform has been widely used in geological and other science studies in support of aster studies a library of natural and man made materials was compiled as the aster spectral library v1 2 and made available from http speclib jpl nasa gov the library is a collection of contributions in a standard format with ancillary data from the jet propulsion laboratory jpl johns hopkins university jhu and the united states geological survey usgs a new version of the library v2 0 is now available online or via cd which includes major additions to the mineral and rock spectra the aster library provides a comprehensive collection of over 2300 spectra of a wide variety of materials covering the wavelength range 0 4 15 4 m

eastern segment of the azores gibraltar line central eastern atlantic an oceanic plate boundary with diffuse compressional deformation new seismic reflection images across the eastern segment of the azores gibraltar line west of the collisional area between the african and iberian plates have revealed a complex pattern of compressional deformation involving the mesozoic oceanic lithosphere the compressional deformation developed in a region of slow plate convergence and is diffused at different lithospheric levels across an area spanning 200 km from the gorringe ridge to the seine plain the convergence between the african and iberian plates has been active since tertiary time and our results indicate that no subduction zone exists across this part of the plate boundary

jesenice a new meteorite fall from slovenia abstract on april 9 2009 at 3 00 cest a very bright fireball appeared over carinthia and the karavanke mountains the meteoroid entered the atmosphere at a very steep angle and disintegrated into a large number of objects two main objects were seen as separate fireballs up to an altitude of approximately 5 km and witnesses reported loud explosions three stones were found with a total weight of approximately 3 611 kg the measured activity of short lived cosmogenic radionuclides clearly indicates that two specimens result from a very recent meteorite fall all cosmogenic radionuclide concentrations suggest a rather small preatmospheric radius of 1 7 ga 4he and approximately 4 3 ga 40ar jesenice seems not to have been strongly affected by the catastrophic disruption of the l chondrite parent body approximately 500 ma ago

re evaluation of seismic intensities and relocation of 1969 saint vincent cape seismic sequence a comparison with the 1755 lisbon earthquake seismic intensity for the february 28 1969 mw 7 8 earthquake have been re evaluated using original documents in local archives such as contemporary newspapers council minutes monographic studies among other sources for spain portugal and morocco and answers to macroseismic questionnaires for morocco this information is used to plot a new intensity map for the whole region affected by the earthquake portugal spain and morocco the intensity values vary from viii to ix in the e w coast of algarve southern portugal to ii iii furthermore we have relocated the hypocentres for main shock and 24 aftershocks using a new 3d crustal velocity model for the gulf of cadiz region and a non linear probabilistic location methodology most of them previously lacking a depth estimate the new locations show an e w distribution of epicenters with focus located in the uppermost mantle most of them with depths between 30 and 50 km no earthquakes have been located at depths shallower than 30 km a comparison between peak ground accelerations pgas estimated from the observed intensities for the 1969 and the lisbon 1755 earthquakes and synthetic pga values generated assuming two different scenarios using the 1969 and 2009 earthquakes for the 1755 lisbon event shows that the observed damage produced by the 1755 earthquake may be better explained assuming a reverse dip slip mechanism oriented in ne sw direction similar to that of the 2009 earthquake rather than assuming focal mechanism similar to that of the 1969 earthquake

mineralogy petrology chronology and exposure history of the chelyabinsk meteorite and parent body three masses of the chelyabinsk meteorite have been studied with a wide range of analytical techniques to understand the mineralogical variation and thermal history of the chelyabinsk parent body the samples exhibit little to no postentry oxidation via mossbauer and raman spectroscopy indicating their fresh character but despite the rapid collection and care of handling some low levels of terrestrial contamination did nonetheless result detailed studies show three distinct lithologies indicative of a genomict breccia a light colored lithology is ll5 material that has experienced thermal metamorphism and subsequent shock at levels near s4 the second lithology is a shock darkened ll5 material in which the darkening is caused by melt and metal troilite veins along grain boundaries the third lithology is an impact melt breccia that formed at high temperatures 1600 c and it experienced rapid cooling and degassing of s2 gas portions of light and dark lithologies from chel 101 and the impact melt breccias chel 102 and chel 103 were prepared and analyzed for rb sr sm nd and ar ar dating when combined with results from other studies and chronometers at least eight impact events e g 4 53 ga 4 45 ga 3 73 ga 2 81 ga 1 46 ga 852 ma 312 ma and 27 ma are clearly identified for chelyabinsk indicating a complex history of impacts and heating events finally noble gases yield young cosmic ray exposure ages near 1 ma these young ages together with the absence of measurable cosmogenic derived sm and cr indicate that chelyabinsk may have been derived from a recent breakup event on an neo of ll chondrite composition

seismicity and focal mechanisms in south spain abstract recent improvements in regional seismological networks allow a better definition of the seismicity and the determination of focal mechanisms in south spain this region is part of the lithospheric plate boundary between africa and eurasia and shows a continuous seismic activity of moderate magnitude m h h 650 km earthquakes also occurring in the region eight fault plane solutions have been determined that can be related to the tectonics of the area the solutions for the shallow shocks are compatible with regional stresses with horizontal compressions in nw se direction and tensions in e w direction that produce normal faulting along the n30 to 60 w and n10 to 30 e systems of faults the mechanisms of the intermediate depth shocks can be explained in terms of a subduction zone from africa in a nw direction that is under compression

synchronizing seismic networks with ambient noise summary the technique of retrieving green s functions by pairwise correlation of a random wavefield is used to estimate the stability of the timing system of a seismic network the method is demonstrated with data from a network consisting of stations with four independent clocks and gps receivers for a two years period daily measurements of the timing error of each of the four systems are obtained these measurements can be used to correct the timing of the data in periods without gps reception the accuracy of this method can exceed the precision of the internal station clocks already after a single day of uncorrected drift

the l3 6 chondritic regolith breccia northwest africa nwa 869 i petrology chemistry oxygen isotopes and ar ar age determinations northwest africa nwa 869 consists of thousands of individual stones with an estimated total weight of about 7 metric tons it is an l3 6 chondrite and probably represents the largest sample of the rare regolith breccias from the l chondrite asteroid it contains unequilibrated and equilibrated chondrite clasts some of which display shock darkening impact melt rocks imrs both clast free and clast poor are strongly depleted in fe ni metal and sulfides an unequilibrated microbreccia two different light inclusions and two different sio2 bearing objects were found although the matrix of this breccia appears partly clastic it is not a simple mixture of fine grained debris formed from the above lithologies but mainly represents an additional specific lithology of low petrologic type we speculate that this material stems from a region of the parent body that was only weakly consolidated one imr clast and one sio2 bearing object show 17o values similar to bulk nwa 869 suggesting that both are related to the host rock in contrast one light inclusion and one imr clast appear to be unrelated to nwa 869 suggesting that the imr clast is contaminated with impactor material 40ar 39ar analyses of a type 4 chondrite clast yield a plateau age of 4402 7 ma which is interpreted to be the result of impact heating other impact events are recorded by an imr clast at 1790 36 ma and a shock darkened clast at 2216 40 ma demonstrating that nwa 869 escaped major reset in the course of the event at approximately 470 ma that affected many l chondrites