empirical ground motion attenuation relations for the eastern alps in the magnitude range 2 5 6 3 in this paper we use a large data set of seismometric and accelerometric recordings 3168 vertical and 1402 for each of the horizontal components collected by various networks in the eastern alps to estimate empirical ground motion attenuation relations valid in the magnitude range 2 5 6 3 for distances of up to 130 km relations are developed for horizontal and vertical peak ground acceleration and velocity arias intensity response spectral acceleration and fourier amplitude for 46 periods between 0 1 and 2 sec we adopt a simple magnitude dependent attenuation model predicting closer attenuation curves and decreasing distance attenuation for increasing magnitude we use truncated regression analysis to deal with the problem of non triggering stations with respect to other approaches our solution does not require any discarding of data or the knowledge of which stations did not trigger our relations agree with others suitable for the study region for magnitudes greater than 5 8 while they have a faster attenuation for lower magnitudes in an attempt to reduce the standard deviation we have introduced soil classification into the relation as well as a characterization of sites by means of h v ratios these ratios were estimated either by earthquakes receiver function or by the background seismic noise nakamura s ratios similar to findings in other studies the improvement obtained with soil classification is negligible while h v ratios reduce the standard deviation by up to 22 finally we have investigated the implications of these new relations for seismic hazard assessment considering two sites of interest located in northeastern italy udine and gemona in both cases the difference in the hazard estimates for return periods shorter than 100 years is notable with respect to all other available relations

high concentrations of manganese and sulfur in deposits on murray ridge endeavour crater mars mars reconnaissance orbiter hirise images and opportunity rover observations of the 22 km wide noachian age endeavour crater on mars show that the rim and surrounding terrains were densely fractured during the impact crater forming event fractures have also propagated upward into the overlying burns formation sandstones opportunity s observations show that the western crater rim segment called murray ridge is composed of impact breccias with basaltic compositions as well as occasional fracture filling calcium sulfate veins cook haven a gentle depression on murray ridge and the site where opportunity spent its sixth winter exposes highly fractured recessive outcrops that have relatively high concentrations of s and cl consistent with modest aqueous alteration opportunity s rover wheels serendipitously excavated and overturned several small rocks from a cook haven fracture zone extensive measurement campaigns were conducted on two of them pinnacle island and stuart island these rocks have the highest concentrations of mn and s measured to date by opportunity and occur as a relatively bright sulfate rich coating on basaltic rock capped by a thin deposit of one or more dark mn oxide phases intermixed with sulfate minerals we infer from these unique pinnacle island and stuart island rock measurements that subsurface precipitation of sulfate dominated coatings was followed by an interval of partial dissolution and reaction with one or more strong oxidants e g o 2 to produce the mn oxide mineral s intermixed with sulfate rich salt coatings in contrast to arid regions on earth where mn oxides are widely incorporated into coatings on surface rocks our results demonstrate that on mars the most likely place to deposit and preserve mn oxides was in fracture zones where migrating fluids intersected surface oxidants forming precipitates shielded from subsequent physical erosion

local magnitude in northeastern italy we consider a large data set of waveforms 5053 recordings for the horizontal components and 9933 for the vertical to calibrate a local magnitude scale valid for northeastern italy in the hypocentral distance range of 10 250 km the data refer to 1096 events occurring in the period january 1995 to december 2002 in the area between 44 4 and 47 6 n and 10 1 and 15 7 e for each available signal we simulate the corresponding wood anderson seismogram using the geometrical mean of the two horizontal peaks we simultaneously estimate the distance attenuation the station correction terms and the magnitude of the events estimations are obtained with the standard parametric approach accounting for the geometrical spreading and the anelastic attenuation and by using two different methods of nonparametric regression based on a stepwise linear approximation and on kernel functions respectively the nonparametric solutions agree and show stronger attenuation in the first 70 km than what was found in central california furthermore a noticeable discontinuity occurs around 100 km because later phase arrivals such discontinuity is not fitted well by the parametric curve we investigate the effect of magnitude dependent attenuation on magnitude estimation we also account for the bias induced by data truncation i e data loss due to the limited dynamics of the instruments the analysis shows that at short distances the standard magnitude independent attenuation model underestimates high magnitudes e g by 0 49 units at 10 km for magnitude 5 5 and overestimates low magnitudes e g by 0 17 units at 10 km for magnitude 1 5 0 34 units if we extrapolate the relation down to magnitude 0 5 finally various factors suggest one should adopt the solution proposed in the literature to redefine the m l scale such that m l 3 corresponds to 10 mm of motion on a wood anderson instrument at 17 km hypocentral distance

the ml scale in southern california measurements 9 941 of peak amplitudes on wood anderson instruments or simulated wood anderson instruments in the southern california seismographic network for 972 earthquakes primarily located in southern california were studied with the aim of determining a new distance correction curve for use in determining the local magnitude m l events in the mammoth lakes area were found to give an unusual attenuation pattern and were excluded from the analysis as were readings from any one earthquake at distances beyond the first occurrence of amplitudes less than 0 3 mm the remaining 7 355 amplitudes from 814 earthquakes yielded the following equation for m l distance correction log a 0 log a 0 1 110log r 100 0 00189 r 100 3 0 where r is hypocentral distance in kilometers a new set of station corrections was also determined from the analysis the standard deviation of the m l residuals obtained by using this curve and the station corrections was 0 21 the data used to derive the equation came from earthquakes with hypocentral distances ranging from about 10 to 700 km and focal depths down to 20 km with most depths less than 10 km the log a 0 values from this equation are similar to the standard values listed in richter 1958 for 50 200 km the effect at close distances is consistent with that found in several other studies and is simply due to a difference in the observed 1 r geometrical spreading for body waves and the 1 r 2 spreading assumed by gutenberg and richter in the construction of the log a 0 table m l s computed from our curve and those reported in the caltech catalog show a systematic dependence on magnitude small earthquakes have larger magnitudes than in the catalog and large earthquakes have smaller magnitudes by as much as 0 6 units to a large extent these systematic differences are due to the nonuniform distribution of data in magnitude distance space small earthquakes are preferentially recorded at close distances relative to large earthquakes for large earthquakes however the difference in the two magnitudes is not solely due to the new correction for attenuation magnitudes computed using richter s log a 0 curve are also low relative to the catalog values the differences in that case may be due to subjective judgment on the part of those determining the catalog magnitudes the use of data other than the caltech wood anderson seismographs the use of different station corrections or the use of teleseismic magnitude determinations whatever their cause the departures at large magnitude may explain a 1 0 0 7 proportionality found by luco 1982 between m l s determined from real wood anderson records and those from records synthesized from strong motion instruments if it were not for the biases in reported magnitudes luco s finding would imply a magnitude dependent shape in the attenuation curves we studied residuals in three magnitude classes 2 0 m l 3 5 3 5 m l 5 5 and 5 5 m l 7 0 and found no support for such a magnitude dependence based on our results we propose that local magnitude scales be defined such that m l 3 correspond to 10 mm of motion on a wood anderson instrument at 17 km hypocentral distance rather than 1 mm of motion at 100 km this is consistent with the original definition of magnitude in southern california and will allow more meaningful comparison of earthquakes in regions having very different attenuation of waves within the first 100 km

forecasting strong aftershocks in earthquake clusters from northeastern italy and western slovenia abstract in this study we propose an analysis of the earthquake clusters that occurred in north eastern italy and western slovenia from 1977 to today given a mainshock generating alarm in the population we are interested in forecasting if a similar magnitude earthquake will follow we classify the earthquake clusters associated with mainshocks of magnitude mm into two classes if the strongest aftershock has a magnitude mm 1 swarms or large aftershock seismic sequences as type a otherwise smaller aftershocks seismic sequences as type b a large aftershock following a main shock can cause significant damages to already weakened buildings and infrastructures so a timely advisory information to the civil protection is of great interest for effective decision making for the first time we applied to a new catalogue a pattern recognition algorithm for cluster type forecasting that we developed for all italy gentili and di giovambattista 2017 thanks to the lower completeness magnitude of the local ogs catalogue compared to the national one and to a new version of the algorithm we were able to lower the threshold of the clusters mainshocks magnitude from 4 5 to 3 7 the method has been validated by rigorous statistical tests we tested the algorithm on the 1976 highly destructive earthquake cluster mainshock magnitude 6 5 the strongest in the last 80 years in the region and we retrospectively forecasted it as an a cluster successful results were obtained also on other three smaller earthquake clusters in 2019

local magnitude determinations for intermountain seismic belt earthquakes from broadband digital data the university of utah seismograph stations uuss earthquake catalogs for the utah and yellowstone national park regions contain two types of size measurements local magnitude m l and coda magnitude m c which is calibrated against m l from 1962 through 1993 uuss calculated m l values for southern and central intermountain seismic belt earthquakes using maximum peak to peak p p amplitudes on paper records from one to five wood anderson w a seismographs in utah for m l determinations of earthquakes since 1994 uuss has utilized synthetic w a seismograms from u s national seismic network and uuss broadband digital telemetry stations in the region which numbered 23 by the end of our study period on 30 june 2002 this change has greatly increased the percentage of earthquakes for which m l can be determined it is now possible to determine m l for all m 3 earthquakes in the utah and yellowstone regions and earthquakes as small as m to maintain continuity in the magnitudes in the uuss earthquake catalogs we determined empirical m l station corrections that minimize differences between m l s calculated from paper and synthetic w a records application of these station corrections in combination with distance corrections from richter 1958 which have been in use at uuss since 1962 produces m l values that do not show any significant distance dependence m l determinations for the utah and yellowstone regions for 1981 2002 using our station corrections and richter s distance corrections have provided a reliable data set for recalibrating the m c scales for these regions our revised m l values are consistent with available moment magnitude determinations for intermountain seismic belt earthquakes to facilitate automatic m l measurements we analyzed the distribution of the times of maximum p p amplitudes in synthetic w a records a 30 sec time window for maximum amplitudes beginning 5 sec before the predicted sg time encompasses 95 of the maximum p p amplitudes in our judgment this time window represents a good compromise between maximizing the chances of capturing the maximum amplitude and minimizing the risk of including other seismic events

local earthquake magnitude scale and seismicity rate for the ethiopian rift a calibrated local earthquake magnitude scale is essential for quantitative analyses of seismicity in ethiopia effective monitoring of earthquakes and resulting assessment of seismic hazard are especially important as regions with seismic and volcanic activity coincide with regions of economic significance and population growth we have developed a local magnitude m l scale for the northern main ethiopian rift mer using earthquake data collected during 2001 2003 on 122 three component broadband seismic stations waveform data from 2139 local earthquakes were corrected for instrument response and convolved with the nominal wood anderson torsion seismograph response appropriate for the original definition of local magnitude the hypocentral distances considered are 5 to 800 km with the best represented range from 5 to 150 km a total of 30 908 maximum zero to peak amplitudes awa were incorporated into a direct linear inversion for individual earthquake local magnitudes m l 244 station factors c and 2 linear distance dependent factors n k in the distance correction term log a o of the equation for local magnitude m l log awa log a o c the resulting distance correction is given by log a o 1 196997log r 17 0 001066 r 17 2 which implies that ground motion attenuation is relatively high consistent with ongoing magma intrusion and the presence of shallow magma reservoirs beneath the mer station corrections significantly reduce m l residuals and range between 0 42 m l units the catalog of earthquakes is complete above m l 2 1 and the annual cumulative seismicity rate follows the relation log n 4 5 1 13 m l our results are critical for accurate routine quantitative analysis of past current and future seismicity in ethiopia

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

alpha particle x ray spectrometer apxs results from gusev crater and calibration report 1 the chemical composition of rocks and soils on mars analyzed during the mars exploration rover spirit mission was determined by x ray analyses with the alpha particle x ray spectrometer apxs details of the data analysis method and the instrument calibration are presented measurements performed on mars to address geometry effects and background contributions are shown cross calibration measurements among several instrument sensors and sources are discussed an unintentional swap of the two flight instruments is evaluated new concentration data acquired during the first 470 sols of rover spirit in gusev crater are presented there are two geological regions the gusev plains and the columbia hills the plains contain soils that are very similar to previous landing sites on mars a meteoritic component in the soil is identified rocks in the plains revealed thin weathering rinds the underlying abraded rock was classified as primitive basalt one of these rocks contained significant br that is probably associated with vein filling material of different composition one of the trenches showed large subsurface enrichments of mg s and br disturbed soils and rocks in the columbia hills revealed different elemental compositions these rocks are significantly weathered and enriched in mobile elements such as p s cl or br even abraded rock surfaces have high br concentrations thus in contrast to the rocks and soils in the gusev plains the columbia hills material shows more significant evidence of ancient aqueous alteration

athena microscopic imager investigation 1 the athena science payload on the mars exploration rovers mer includes the microscopic imager mi the mi is a fixed focus camera mounted on the end of an extendable instrument arm the instrument deployment device idd the mi was designed to acquire images at a spatial resolution of 30 microns pixel over a broad spectral range 400 700 nm the mi uses the same electronics design as the other mer cameras but has optics that yield a field of view of 31 31 mm across a 1024 1024 pixel ccd image the mi acquires images using only solar or skylight illumination of the target surface a contact sensor is used to place the mi slightly closer to the target surface than its best focus distance about 66 mm allowing concave surfaces to be imaged in good focus coarse focusing 2 mm precision is achieved by moving the idd away from a rock target after the contact sensor has been activated the mi optics are protected from the martian environment by a retractable dust cover the dust cover includes a kapton window that is tinted orange to restrict the spectral bandpass to 500 700 nm allowing color information to be obtained by taking images with the dust cover open and closed mi data will be used to place other mer instrument data in context and to aid in petrologic and geologic interpretations of rocks and soils on mars

source parameter analysis of microearthquakes recorded around the underground gas storage in the montello collalto area southeastern alps italy abstract the study of seismic source parameters is crucial for understanding the origin of seismicity and retrieving information on the energy balance and the stress involved in earthquake rupture processes in active tectonic areas where underground industrial activities are carried out such parameters may help to understand whether earthquakes are induced triggered or natural the montello collalto area southeastern alps is located in an active tectonic environment and hosts a depleted natural reservoir used to store gas since 2012 a high quality seismic network monitors the microseismicity occurring around the underground gas storage reservoir to understand if the storage activity might induce seismicity in this paper we estimate the source parameters of low magnitude events representative of the seismicity occurring in the area surrounding the reservoir the analysis includes a preliminary removal of the site effects specifically computed within this study from all the records then using a parametric multistep inversion scheme we estimate the seismic moment the corner frequency and the static stress drop that can be set as reference for the microseismicity occurring in the study area all the investigated earthquakes show low seismic efficiency compatible with overshoot processes which is typical of natural i e tectonic earthquakes our procedure can be implemented in other tectonic regions hosting underground industrial activities to support the decisional processes related to real time monitoring

correspondence and least squares analyses of soil and rock compositions for the viking lander 1 and pathfinder landing sites correspondence analysis is a dual q and r mode factor analysis that allows simultaneous visualization of relationships between normalized variables and samples the usefulness of the technique is first illustrated with an analysis of a simulated feldspar compositional data set and then applied to analysis of patterns among variables and samples for compositions obtained for viking lander 1 soils and pathfinder rocks and soils for the martian data the first two factors capture 90 of the variance data projected onto the plane defined by these two factors fall within a mixing triangle defined by three geologically plausible end members basaltic shergottite andesite and a halide kieserite evaporite however examination of data projected onto the second and third factors shows that the compositions are systematically displaced from the mixing triangle plane in the same general direction as the fe vector inclusion of a fe oxide e g hematite or maghemite as a reasonable fourth end member forms a mixing tetrahedron that encapsulates the data least squares mixing analysis of the data with these four end members and the elemental suite measured at both landing sites si al ti fe mg ca s cl implies that aeolian dust on rocks is a physical mixture of basalt and andesite derived materials in approximately equal proportions soil components at the two landing sites are similar to each other and less basalt like than the aeolian dust and viking 1 soils are more andesite rich than the pathfinder soils

seismic clusters analysis in northeastern italy by the nearest neighbor approach abstract the main features of earthquake clusters in northeastern italy are explored with the aim to get new insights on local scale patterns of seismicity in the area the study is based on a systematic analysis of robustly and uniformly detected seismic clusters which are identified by a statistical method based on nearest neighbor distances of events in the space time energy domain the method permits us to highlight and investigate the internal structure of earthquake sequences and to differentiate the spatial properties of seismicity according to the different topological features of the clusters structure to analyze seismicity of northeastern italy we use information from local ogs bulletins compiled at the national institute of oceanography and experimental geophysics since 1977 a preliminary reappraisal of the earthquake bulletins is carried out and the area of sufficient completeness is outlined various techniques are considered to estimate the scaling parameters that characterize earthquakes occurrence in the region namely the b value and the fractal dimension of epicenters distribution required for the application of the nearest neighbor technique specifically average robust estimates of the parameters of the unified scaling law for earthquakes usle are assessed for the whole outlined region and are used to compute the nearest neighbor distances clusters identification by the nearest neighbor method turn out quite reliable and robust with respect to the minimum magnitude cutoff of the input catalog the identified clusters are well consistent with those obtained from manual aftershocks identification of selected sequences we demonstrate that the earthquake clusters have distinct preferred geographic locations and we identify two areas that differ substantially in the examined clustering properties specifically burst like sequences are associated with the north western part and swarm like sequences with the south eastern part of the study region the territorial heterogeneity of earthquakes clustering is in good agreement with spatial variability of scaling parameters identified by the usle in particular the fractal dimension is higher to the west about 1 2 1 4 suggesting a spatially more distributed seismicity compared to the eastern parte of the investigated territory where fractal dimension is very low about 0 8 1 0

source parameters and stress release of seismic sequences occurred in the friuli venezia giulia region northeastern italy and in western slovenia abstract the source parameters of the major events of a swarm and of two seismic sequences occurred in the friuli area northeastern italy and in western slovenia were estimated the claut swarm c96 occurred since the end of january to june 1996 with a md 4 3 major shock and it appears composed of three sub sequences the two sequences are the kobarid sequence k98 started on april 12 1998 with a md 5 6 mainshock and the m te sernio s02 sequence caused by the february 14 2002 earthquake md 4 9 acceleration and velocity data recorded by the local seismic network of the istituto nazionale di oceanografia e di geofisica sperimenale ogs and corrected for attenuation were employed to estimate seismic moments and radiated energies source dimensions were inferred from the computed corner frequencies and the stress release was estimated from the brune stress drop the apparent stress and the rms stress drop on the whole seismic moments range from 1 7 1012 to 1 1 1017 n m and radiated energies are in the range 106 1013 j brune stress drops are scattered and do not show any evidence of a self similarity breakdown for sources down to 130 m radius the radiated seismic energy scales as a function of seismic moment with a slope of the scaling relation that decreases for increasing seismic moments the mechanism of stress release was analyzed by computing the parameter of zuniga zuniga r 1993 frictional overshoot and partial stress drop which one bull seismol soc am 83 939 944 the k98 and s02 sequences are characterized by a wide range of the parameter with stress drop mechanism varying from partial locking to overshoot cases the values of the c96 swarm are more homogeneous and close to the orowan s condition the radiated seismic energy and the ratio of stress drop between mainshock and aftershocks appear different among the analyzed cases we therefore investigated the relationship between the stress parameters of the main shock and the energy radiated by the aftershock sequences for this purpose we also estimated the source parameters of two other sequences occurred in the area with mainshocks of md 4 1 and 5 1 respectively we found a positive correlation between the brune stress drop of the mainshock and the ratio between the radiated energy of the mainshock and the summation of the energies radiated by the aftershocks

isotopic diffusion in cold snow and firn molecular mixing in cold snow and firn is ordinarily controlled by vapor diffusion diffusion through or along the ice matrix is slow whereas diffusion from the air to within separate grains is comparatively rapid thus mixing occurs in the vapor phase and exchange with the local ice involves all the water molecules a quantification of these concepts is applied to the diffusion of oxygen isotopic depth profiles in southern greenland and at dome c antarctica it successfully describes the smoothing of measured profiles the smoothing rate is strongly dependent on temperature and density of the firn

ancient impact and aqueous processes at endeavour crater mars the rover opportunity has investigated the rim of endeavour crater a large ancient impact crater on mars basaltic breccias produced by the impact form the rim deposits with stratigraphy similar to that observed at similar sized craters on earth highly localized zinc enrichments in some breccia materials suggest hydrothermal alteration of rim deposits gypsum rich veins cut sedimentary rocks adjacent to the crater rim the gypsum was precipitated from low temperature aqueous fluids flowing upward from the ancient materials of the rim leading temporarily to potentially habitable conditions and providing some of the waters involved in formation of the ubiquitous sulfate rich sandstones of the meridiani region

in flight calibration and performance of the mars exploration rover panoramic camera pancam instruments 1 the mars exploration rover panoramic camera mer pancam instruments have acquired more than 60 000 high resolution multispectral stereoscopic images of soil rocks and sky at the gusev crater and meridiani planum landing sites since january 2004 these images combined with other mer data sets have enabled new discoveries about the composition mineralogy and geologic geochemical evolution of both sites one key to the success of pancam in contributing to the overall success of mer has been the development of a calibration pipeline that can quickly remove instrumental artifacts and generate both absolute radiance and relative reflectance images with high accuracy and precision in order to influence tactical rover driving and in situ sampling decisions this paper describes in detail the methods assumptions and models algorithms in the calibration pipeline developed for pancam images based on new measurements and refinements performed primarily from flight data acquired on mars major calibration steps include modeling and removal of detector bias signal active and readout region dark current electronic shutter smear and pixel to pixel responsivity flatfield variations pancam images are calibrated to radiance w m2 nm sr using refined preflight derived calibration coefficients or radiance factor i f using near in time measurements of the pancam calibration target and a model of aeolian dust deposition on the target as a function of time we are able to verify that the absolute radiance calibration of most pancam images is accurate to within about 10 or less and that the filter to filter and pixel to pixel precision of the calibrated relative reflectance data both based on measurements of the pancam calibration target are typically about 3 and 1 or less respectively examples are also presented of scientific applications made possible by the high fidelity of the calibrated pancam data these include 11 color visible to near ir spectral analysis calculation of true color and chromaticity values and generation of super resolution image data products this work represents a follow on and enhancement to the pancam preflight calibration process described by bell et al 2003

empirical distance attenuation and the local magnitude scale for northwest iran abstract we have derived an empirical attenuation curve for a local magnitude scale in northwest iran using a large data set of local earthquakes that occurred from 1996 to 2009 investigation shows that using one half the peak to peak value tends to underestimate the magnitude of an event by as much as 0 07 magnitude units in comparison with using the zero to peak value additionally using a vector sum of horizontal measurements overestimates the m l values by 0 16 magnitude units in comparison with magnitude values that are determined using arithmetic means of horizontal measurements we simulated the corresponding wood anderson seismograms for over 133 000 available waveforms after preliminary analysis the data set was subdivided in order to derive a local magnitude scale for northwestern iran the distance attenuation curve station correction terms and the magnitude of events were simultaneously estimated using parametric and nonparametric approaches in both approaches estimations and separate attenuation curves were determined by using vertical and horizontal measurements these two approaches yielded very similar results the distance attenuation curves that resulted in a nonparametric approach are given by log a 0 0 9252log 0 0030 0 8496 and log a 0 0 9993log 0 0029 0 7114 for the vertical and horizontal components respectively where is the epicentral distance in kilometers the distances considered ranged from 1 to 500 km applying these distance correction terms to the data set show that there are no obvious trends in magnitude residual with distance also using the station corrections reduces the magnitude residuals by as much as 0 07 magnitude units

retrieval of compositional end members from mars exploration rover opportunity observations in a soil filled fracture in marathon valley endeavour crater rim the opportunity rover investigated a gentle swale on the rim of endeavour crater called marathon valley where a series of bright planar outcrops are cut into polygons by fractures a wheel scuff performed on one of the soil filled fracture zones revealed the presence of three end members identified on the basis of pancam multispectral imaging observations covering 0 4 to 1 m red and dark pebbles and a bright soil clod multiple overlapping alpha particle x ray spectrometer apxs measurements were collected on three targets within the scuff zone the field of view of each apxs measurement contained various proportions of the pancam based end members application of a log maximum likelihood method for retrieving the composition of the end members using the 10 apxs measurements shows that the dark pebble end member is compositionally similar to average mars soil with slightly elevated s and fe in contrast the red pebble end member exhibits enrichments in al and si and is depleted in fe and mg relative to average mars soil the soil clod end member is enriched in mg s and ni thermodynamic modeling of the soil clod end member composition indicates a dominance of sulfate minerals we hypothesize that acidic fluids in fractures leached and oxidized the basaltic host rock forming the red pebbles and then evaporated to leave behind sulfate cemented soil

a local magnitude scale for southern italy local magnitude scale has been defined for southern italy in the area monitored by the recently installed irpinia seismic network waveforms recorded from more than 100 events of small magnitude are processed to extract synthetic wood anderson traces assuming a general description of peak displacement scaling with the distance by means of linear and logarithmic contributions a global exploration of the parameter space is performed by a grid search method with the aim of investigating the correlation between the two decay contributions and seeking for a physical solution of the problem assuming an l2 norm we found m loga 1 79 log r 0 58 yielding an error on the single estimation smaller than 0 2 at least when the hypocenter location is accurate station corrections are investigated through the station residuals referring to the average value of the magnitude using a z test we found that some stations exhibit a correction term significantly different from 0 the use of the peak acceleration and peak velocity as indicators of the magnitude is also investigated

a local magnitude scale for crustal earthquakes in italy abstract in this study a new local magnitude m l scale is derived for the italian region from the analysis of seismic signals recorded by a dense broadband network between 2003 and 2009 the m l computation is performed by measuring peak amplitudes of synthetic wood anderson seismograms based on the original definition by richter 1935 these amplitudes are inverted for earthquake magnitudes site corrections and the distance dependent term that corrects amplitudes for geometrical spreading and scattering anelastic attenuation the latter is expressed as a function of r hypocentral distance and log r by means of a two parameter linear form and is constrained at the distance of 100 km in accordance with richter s definition using the newly derived distance dependent term and site corrections magnitudes are consistently estimated for the stations recording each earthquake within an overall root mean square residual of 0 18 no anomalous trend with distance is appreciable in the magnitude residuals for the italian region as a whole or for smaller areas along the italian peninsula the only exception is represented by northeastern italy where increasingly negative residuals are observed for distances decreasing below 100 km the spatial pattern of site corrections reveals contrasting attenuation properties of the crust between the tyrrhenian side of the italian peninsula high attenuation west of the apennines and the adriatic side low attenuation east of the apennines as previously found in other studies finally the magnitudes computed with the new m l scale are compared with global estimates of body wave magnitude m b and with local and regional estimates of moment magnitude m w they display a satisfactory agreement in most of the magnitude range considered roughly from 3 to 5 5 online material tables of station parameters maximum amplitudes and magnitude

smectite deposits in marathon valley endeavour crater mars identified using crism hyperspectral reflectance data the 100 m wide marathon valley crosscuts the cape tribulation rim segment of the 22 km diameter noachian age endeavour impact crater on mars single scattering albedo spectra retrieved from three compact reconnaissance imaging spectrometer for mars crism full resolution targeted frt regularized to 18 m pixel and two along track oversampled ato regularized to 12 m pixel observations indicate the presence of fe3 mg2 smectite exposures located in marathon valley with combination vibration metal oh absorption strength comparable to smectite spectral signatures in mawrth vallis the opportunity rover was directed to the exposures and documented the presence of shoemaker formation impact breccias that have been isochemically altered likely by fracture controlled aqueous fluids

stress and strain tensors based on focal mechanisms in the seismotectonic framework of the friuli venezia giulia region northeastern italy the principal axes of stress and strain are inferred for the seismotectonic zones of the friuli venezia giulia region which forms the eastern part of the european southern alps this region corresponds to a polyphase deformational belt formed during the meso and neoalpine compressions from the eocene to plio quaternary several distinct seismotectonic zones are recognized by comparing seismological and tectonic characteristics inference of the stress and strain tensors is based on 243 fault plane solutions corresponding to earthquakes occurring between 1984 and 2001 magnitude range 2 1 5 6 the analysis reveals two main regional stress patterns a strike slip regime active in the eastern and northwestern parts of the area under study and dominant thrusting processes in the central and western zones the orientation of the maximum principal stress varies from north northwest south southeast to north northeast south southwest the stress magnitude ratio of the calculated stress tensors varies from 0 4 to 0 7 the orientation of the maximum shortening axis is generally north northwest south southeast changing to north northeast south southwest in the southeastern part of the region for most seismotectonic domains the inferred strain pattern is quite concordant with the surface tectonics the orientations of the principal axes of stress and strain are in most cases similar the complex regional tectonic structure consisting of two indented tectonic wedges appears to control the patterns of horizontal stress and strain

earthquake relocations crustal rheology and active deformation in the central eastern alps n italy abstract a revised seismic catalogue 1994 2007 for the central eastern alps n italy is presented 396 earthquake relocations for local magnitudes in the 1 2 5 3 range are performed using a 3d crustal velocity structure and probabilistic locations the location procedure is validated by computing a set of 41 quarry shot solutions and all the results both about shots and seismic events are compared with those obtained using the routine location procedure results are shown for five contiguous seismotectonic domains as supported by geological and geophysical evidence e g fault systems crustal tomography focal mechanisms types earthquake hypocentres are mostly located in the upper crust 0 15 km of depth in good agreement with thermo rheological models about the brittle ductile transitions 8 9 km of depth and total crustal strengths 1 0 2 0 tn m 1 epicentres are clustered and or aligned along present day active geological structures the proposed seismotectonic model shows dominant compression along the giudicarie and belluno bassano montello thrusts with strain partitioning along the dominant right lateral strike slip faults of the schio vicenza domain the present day deformation of the southern alps and the internal alpine chain is compatible with adria indentation and the related crustal stress distribution

rock abrasion tool mars exploration rover mission 1 the rock abrasion tool rat is an integral part of the athena science payload serving primarily as the geologist s rock hammer the rat will expose fresh surfaces of martian rocks to other instruments on the payload the rat also brushes dust and debris from an excavated hole or unaltered rocks to accomplish these tasks autonomously the rat a sophisticated 3 axis precision controlled device was designed data products derived from rat telemetry enable the rat to also act as an important rock physical properties science instrument the returned rat grinding and penetration rate data will be inverted and compared to a rock library on the earth the design is also very compact and lightweight the rat is contained within a cylinder 128 mm long and 85 mm in diameter and has a mass of 687 g

ancient aqueous environments at endeavour crater mars opportunity has investigated in detail rocks on the rim of the noachian age endeavour crater where orbital spectral reflectance signatures indicate the presence of fe 3 rich smectites the signatures are associated with fine grained layered rocks containing spherules of diagenetic or impact origin the layered rocks are overlain by breccias and both units are cut by calcium sulfate veins precipitated from fluids that circulated after the endeavour impact compositional data for fractures in the layered rocks suggest formation of al rich smectites by aqueous leaching evidence is thus preserved for water rock interactions before and after the impact with aqueous environments of slightly acidic to circum neutral ph that would have been more favorable for prebiotic chemistry and microorganisms than those recorded by younger sulfate rich rocks at meridiani planum

high frequency attenuation of shear waves in the southeastern alps and northern dinarides summary we investigated the high frequency attenuation of s waves in the southeastern alps and northern external dinarides using waveforms from 331 earthquakes 3 0 mw 6 5 the spectral decay parameter k was computed using 1345 three component high quality records collected by the italian strong motion network ran and by the short period seismometric network of northeastern italy nei in the period 1976 2007 weak motion data from 11 stations of the nei network and strong motion data collected by five accelerometers of the ran were analysed the k parameter was estimated in the 0 250 km distance range in a frequency band extending from the corner frequency of the event up to 25 or 45 hz using the amplitudeaccelerationfourierspectraofs waves theobservedrecord to recordvariabilityof k was modelled by applying a generalized inversion procedure using both parametric and nonparametric approaches our results evidence that k is independent on earthquake size while it shows both site and distance dependence stations of the nei network present the same increase of k with epicentral distance re and show values of the zero distance k parameter k0 s between 0 017 and 0 053 s for the whole region the k increase with distance can be describedthroughalinearmodelwithslopedk dre 1 4 0 1 10 4 skm 1 assumingan average s wave velocity 3 34 km s 1 between 5 and 15 km depth we estimate an average frequency independent quality factor qi 2140 for the corresponding crustal layer the non parametric approach evidences a weak positive concavity of the curve that describes the k increase withre at about 90 km distance this result can be approximated through a piecewise linear function with slopes of 1 0 10 4 and 1 7 10 4 sk m 1 in accordance with a three layers model where moving from the intermediate to the bottom layer both qi and decrease two regional dependences were found data from earthquakes located westward to the nei network evidence weaker attenuation properties probably because of s wave reflections from different parts of the moho discontinuity under the eastern po plain at about 25 30 km depth while earthquakes located eastward in western slovenia where the moho deepens up to 45 50 km evidence a higher attenuation moreover the k estimates obtained with data from earthquakes located in the area of the 1998 mw 5 7 and 2004 mw 5 2 kobarid events are 0 017 s higher than the values predicted for the whole region probably because of the high level of fracturing that characterizes fault zones the comparison between measured and theoretical values of k computed at a few stations with available s wave velocity profiles reveals that the major contribution to the total k0 s is due to the sedimentary column from surface to 800 m depth the hard rock section contribution is limited to 0 005 s in accordance with a maximum contribution of 0 010 s predicted by the non parametric inversion

the 1998 bovec krn mountain slovenia earthquake sequence we study the 1998 bovec krn mountain slovenia earthquake sequence by combining hypocenters relocation strong motion inversion digital elevation modelling and field geology the main shock ms 5 7 a 12 km right lateral strike slip event on the dinaric fault system occurred on a sub vertical fault plane the rupture confined between 3 and 9 km depth with no evidence of surface faulting propagated bilaterally within two structural barriers the northwestern barrier is at the junction between dinaric and alpine structures where there is a sharp change in the geometry of faulting the southeastern barrier is within the dinaric system and its surface expression corresponds to the tolminka spring perched basin a 1 km restraining step over at this site the bovec krn earthquake fault overlaps with a 30 km strike slip fault segment that is free of aftershocks and could be undergoing an increase of stress this fault system represents the northern branch of the idrija right lateral fault

nonparametric description of peak acceleration as a function of magnitude distance and site in guerrero mexico this article describes the peak accelerations observed on a network of strong motion accelerographs above the subduction zone in guerrero mexico as a function of magnitude and hypocentral distance our empirical description differs from regression analysis however in that it produces a table of values of peak acceleration for selected values of m and r and an interpolation rule to obtain peak acceleration at intermediate values with this approach the existence and extent of saturation of peak acceleration as magnitude increases is dictated by the data and unlimited flexibility is allowed in the distance dependence of the peak acceleration this nonparametric approach does not allow extrapolation beyond the range of the data and is thus most useful when the data spans a large magnitude and distance range after 7 yr of recording the digital guerrero accelerograph network has obtained enough data to test the concept the records include events with magnitudes ranging from under 3 to 8 1 with all magnitudes recorded at distances ranging from nearly directly above the rupture to distances where acceleration has become too small to trigger the instruments the data used in this study consist of 528 recordings each three components from 146 earthquakes that occurred between 1985 and 1990 all but one station are on rock sites since all the accelerograms are recorded by one of 30 stations there is an average of about 18 records for each station the results suggest that at short distances about 14 to 25 km from the fault as magnitude increases the peak horizontal acceleration saturates at about 20 g however unlike small earthquakes peak accelerations decrease very slowly with increased distance from the rupture in a large magnitude station corrections for peak acceleration reduced the rms misfit by about 15 for the horizontal component by 12 for the vertical component and by 21 for the ratio for some stations horizontal corrections are close to vertical corrections but others show very different site effects on horizonal and vertical components the ratios of peak vertical acceleration to peak horizontal acceleration show a very weak tendency to decrease as magnitude increases and this tendency is further reduced at most distances after correction for average site effects the average value of this ratio is 0 70 before the station correction after these corrections for 55 events with known stress drop the residual between the predicted peak acceleration and the observed peak acceleration is correlated with stress drop although scattered the observations are consistent with a theoretical prediction that amax 0 80

vnir multispectral observations of aqueous alteration materials by the pancams on the spirit and opportunity mars exploration rovers multispectral visible and near infrared vnir observations from the mars exploration rover pancam multispectral stereo camera systems are consistent with materials having been subjected to various aqueous processes ferric oxides in the form of hematite in the burns and grasberg formations of meridiani planum have been well characterized by opportunity on the basis of strong 535 and 864 nm absorptions and positive 754 1009 nm and 934 1009 nm slopes on the rim of noachian aged endeavour crater opportunity has observed light toned veins with high ca and s as determined by the rover s alpha particle x ray spectrometer apxs and a negative 934 1009 nm slope in vnir spectra extracted from pancam data indicative of a 1000 nm h2o overtone absorption together these observations indicate that the veins are composed of gypsum rocks overturned by opportunity on the murray ridge portion of the endeavour crater rim display dark and light toned coatings the dark toned coatings have a red featureless slope that is consistent with the slope observed in laboratory spectra of high valence manganese oxide minerals potential mn oxide coatings may also be associated with some exposures of the grasberg formation apxs results for high mg and s in the light toned coatings of the murray ridge overturned rocks and a negative 934 1009 nm slope are consistent with hydrated mg sulfates opportunity has also observed spectral features in rocks that are consistent with orbital observations of fe smectites as well as al smectites and possible hydrated silica in light toned fracture fill materials the spirit rover observed sulfate rich light toned soils exposed by the rover s wheels several of these soil observations contained spectral features such as a broad absorption centered near 800 nm consistent with ferric sulfate minerals a finding confirmed by the rover s mossbauer spectrometer spirit also excavated light toned si rich soils these soils have a flat near infrared spectrum with a drop in reflectance from 934 1009 nm that is consistent with free water contained in voids or adsorbed onto the surface of the silica

calibration of an ml scale in northwestern turkey from 1999 izmit aftershocks a local magnitude scale is derived for northwestern turkey using data collected by a temporary network installed by the german task force for earthquakes after the 1999 izmit earthquake m w 7 4 and the permanent sapanca bolu network we computed wood anderson seismograms for over 5353 arrivals at 27 three component stations from 530 earthquakes the hypocentral distances considered range from 5 to 140 km with the best represented range being from 5 to 70 km we inverted the measured amplitudes following both the nonparametric richter s 1958 and parametric bakun and joyner 1984 approaches these methods yield consistent magnitude values and station corrections however the calculated nonparametric distance correction log a implies that ground motion attenuation is higher than what is accounted for by the equation calibrated in central california in the range 5 62 km the best fit is provided by log a log r 17 0 00960 r 17 2 this equation is obtained constraining the geometrical spreading parameter n to 1 the calculated value of k 0 00960 confirms that in this range of distance seismic waves could propagate through a low q volume station corrections which allow for a significant reduction of m l residuals range between 0 5 magnitude units suggesting a strong influence of local site effects on the amplitude of ground motion in accord with the obtained attenuation and station corrections the magnitudes of the considered events range from 0 4 to 4 8

the richter scale its development and use for determining earthquake source parameters abstract the m l scale introduced by richter in 1935 is the antecedent of every magnitude scale in use today the scale is defined such that a magnitude 3 earthquake recorded on a wood anderson torsion seismometer at a distance of 100 km would write a record with a peak excursion of 1 mm to be useful some means are needed to correct recordings to the standard distance of 100 km richter provides a table of correction values which he terms log a o the latest of which is contained in his 1958 textbook a new analysis of over 9000 readings from almost 1000 earthquakes in the southern california region was recently completed to redetermine the log a o values although some systematic differences were found between this analysis and richter s values such that using richter s values would lead to underand overestimates of m l at distances less than 40 km and greater than 200 km respectively the accuracy of his values is remarkable in view of the small number of data used in their determination richter s corrections for the distance attenuation of the peak amplitudes on wood anderson seismographs apply only to the southern california region of course and should not be used in other areas without first checking to make sure that they are applicable often in the past this has not been done but recently a number of papers have been published determining the corrections for other areas if there are significant differences in the attenuation within 100 km between regions then the definition of the magnitude at 100 km could lead to difficulty in comparing the sizes of earthquakes in various parts of the world to alleviate this it is proposed that the scale be defined such that a magnitude 3 corresponds to 10 mm of motion at 17 km this is consistent both with richter s definition of m l at 100 km and with the newly determined distance corrections in the southern california region aside from the obvious and original use as a means of cataloguing earthquakes according to size m l has been used in predictions of ground shaking as a function of distance and magnitude it has also been used in estimating energy and seismic moment there is a good correlation of peak ground velocity and the peak motion on a wood anderson instrument at the same location as well as an observationally defined and theoretically predicted nonlinear relation between m l and seismic moment an important byproduct of the establishment of the m l scale is the continuous operation of the network of wood anderson seismographs on which the scale is based the records from these instruments can be used to make relative comparisons of amplitudes and waveforms of recent and historic earthquakes furthermore because of the moderate gain the instruments can write onscale records from great earthquakes at teleseismic distances and thus can provide important information about the energy radiated from such earthquakes at frequencies where many instruments have saturated

a local magnitude scale for the western great basin eastern sierra nevada from synthetic wood anderson seismograms abstract we have computed synthetic wood anderson seismograms for over 1100 arrivals at 10 three component broadband digital stations in the unr western great basin eastern sierra nevada network these represent all the available records from local earthquakes over magnitude 3 5 between 1990 and june of 1993 plus selected events of smaller magnitude there were 77 events ranging in magnitude from 2 2 to 5 9 including four events over magnitude 5 the distances considered ranged from 15 to 600 km with the best represented range being from 30 to 450 km we invert these measurements to determine distance and station corrections appropriate for a local magnitude scale constrained by richter9s original definition that an earthquake of m l 3 will cause a 1 mm zero to peak deflection of the wood anderson seismogram at 100 km from the epicenter the results between 30 and 450 km were essentially independent of choice of curve fitting parameters in the 30 to 500 km distance region the smooth distance correction curves were very similar to that determined by richter 1958 which is still used for southern california earthquakes we propose to use richter9s distance correction curve in reporting amplitude magnitudes from our digital network