observations and modeling of rotational signals in the p coda constraints on crustal scattering abstract in addition to three classical components vertical north south and east west of ground translations recorded by a broadband seismometer a component of earthquake induced rotational ground motions around the vertical axis is consistently measured by a ring laser sensor located in wettzell southeast germany significant rotations around the vertical axis in the p coda of teleseismic signals are either directly visible or can be inferred through the investigation of cross correlation between the transverse component the component that is perpendicular to the great circle connecting the earthquake and the seismometer of translation acceleration and ring laser rotation rate theoretically in spherically symmetric isotropic media we should not observe rotational signals around the vertical axis before the onset of sh waves possible causes for the observed rotations in the p coda are 1 tilt ring laser coupling 2 anisotropy 3 topographic scattering and 4 p sh scattering in the crust here we show that p sh scattering in the 3d random crust can explain the observations and allow us to constrain crustal scattering properties

spatial and temporal distribution of slip for the 1999 chi chi taiwan earthquake we investigated the rupture process of the 1999 chi chi taiwan earth quake using high quality near source strong motion records broadband teleseismic displacement waveforms and well distributed global positioning system gps data the near source strong motion displacement waveforms recorded significant static offsets of up to 8 m the teleseismic displacement records show a significant pulse with duration of about 18 to 20 sec taking into account the surface displacements observed along the chelungpu fault we considered two fault geometries a single planar fault and a two segment fault with a northeast striking section near the north ern end using the finite fault model with variable slip vectors we derived two models of the temporal and spatial slip distribution of the earthquake the gps data provided good surface displacement constraints for the slip distribution determina tion the spatial slip distribution is generally consistent with field observations the results for the simple fault model show a large asperity located in the region about 25 to 55 km north of the hypocenter with maximum slip of about 15 m when we use the two segment model the asperity further extends to the region where the fault bends toward the northeast with a maximum slip of up to 20 m a large amount of right lateral slip beneath station tcu068 is necessary to explain its observed large west movement it implies a local converging slip at the corner where the fault bends to the northeast the slip amplitude near the hypocenter is about 3 to 6 m the seismic moments determined from the various data sets are within the range of 2 to 4 10 27 dyne cm most of the slip concentrated at shallow depths less than 10 km the total rupture duration is about 28 sec and the rupture velocity is 75 to 80 of the shear wave velocity the slip vector shows a clockwise rotation during the fault rupture the static stress drop of the large asperity region is comparable with the dynamic stress drop as observed directly from the slip velocity at the station near the large slip region

a comparison of spectral parameter kappa from small and moderate earthquakes using southern california anza seismic network data kappa is a one parameter estimator of the spectral amplitude decay with frequency of a seismogram low values 5 ms indicate limited attenuation of high frequency energy whereas higher values 40 ms indicate high frequency energy has been removed kappa is often assumed to be a site term and used in seismic designs we address two key questions about kappa 1 how to identify source path and site contributions to kappa and 2 can kappa estimates from smaller earthquakes and more readily accessible weak motion recordings be reasonably extrapolated to esti mate kappa of larger earthquakes the use of small earthquakes ml 3 5 earthquakes inside the network we find kappa from small earthquakes predicts the relative values of kappa for larger earthquakes e g measurements at stations pfo and knw are small compared with those at stations tro and snd for the snd and tro data however kappa values from small earth quakes overpredict those from moderate and large earthquakes site effects are the most important contributor to kappa estimates but the scatter within kappa measure ments at a given station is likely caused by a significant contribution from near the source perhaps related to near source scattering because of this source side varia bility care is recommended in using individual small events as green s functions to study source time effects of moderate and large events

quantitative analysis of reservoir rocks by microfocus x ray computerised tomography abstract microfocus computer tomography ct is a non destructive imaging technique that allows visualisation of internal features within non transparent objects such as sedimentary rocks with resolution as good as 10 m in three dimensions this technique is highly superior to medical ct widely used in geology and material sciences superior resolution is achieved by decreasing the x ray spot size which allows a decrease in the penumbra effect and an increase in primary magnification by placing the sample close to the x ray source since polychromatic x ray sources are used the technique is not free of artefacts application of filtering techniques is recommended to circumvent these artefacts and to achieve good quality images for quantitative analysis application of a dual energy approach allows quantification of density as well as effective atomic number distribution of internal features as the technique acquires data in 3d ct provides an ideal tool to link 2d thin section petrography to 3d petrophysical measurements or to be used within an upscaling approach a number of applications and the use of dual energy density and effective atomic number characterisations are presented attention is also paid to some of the limitations of this technique

slip distribution of the 2003 boumerdes zemmouri earthquake algeria from teleseismic gps and coastal uplift data 1 using a joint inversion of seismological waveforms and ground displacement observations we estimate several parameters of the fault geometry and rupture process of the mw 6 9 may 21 2003 boumerdes zemmouri earthquake the relocated epicenter is considered as a known parameter total rupture length rupture duration and maximum slip are 55 km from 3 4 e to 4 0 e 12 s and 3 m the modeled south dipping reverse fault oriented ene wsw outcrops a few km offshore which is consistent with the absence of observed surface rupture inland two shallow and relatively localized slip zones are found on both sides of the hypocenter to the sw between boumerdes and zemmouri slip is concentrated between 11 and 2 km depth to the ne between zemmouri and dellys slip is concentrated between 6 km depth and the sea floor various resolution tests indicate that our model is well constrained by the available data and help understanding which data constrains each parameter of the model

calibration of conodont color alteration using color image analysis a set of 40 polished sections of silurian and devonian conodonts with color alteration indices ranging from 1 0 to 8 0 was examined using color image analysis the color composition of each conodont specimen was determined by measuring the intensities of the red green and blue color components on several carefully selected areas the data were evaluated using nested analysis of variance the observed variance can be attributed to three different sources of error within the studied conodont population the variance due to rank amounts to an average 90 the variance due to taxonomic differences or type of conodont element is about 3 and thus of minor importance the heterogeneity within single specimens amounts to 6 and is also a minor source of variance the application of color image analysis helps characterize samples of different rank but similar optical properties color image analysis helps reduce the subjectivity of conodont color alteration studies

seismogenic structure in a tectonic suture zone with new constraints from 2006 mw6 1 taitung earthquake 1 a mw 6 1 earthquake occurred on april 1st 2006 near taitung eastern taiwan it produced significant coseismic ground displacements and a large number of aftershocks in the ensuing month this event provides an opportunity to diagnose the seismogenic structure in the southern longitudinal valley lv of eastern taiwan long viewed as one of the collision sutures between the philippine sea and the eurasian plates with precisely relocated main and aftershock hypocenters focal mechanisms for m 3 8 events and coseismic ground displacements from strong motion records we determine a main shock dislocation model our results indicate that the main shock occurred on a high angle fault azimuth 198 dip 77 the model comprises a fault with two segments the main shock and a large number of aftershocks are associated with the northern segment that exhibited predominantly left lateral strike slip motion in agreement with p wave first motions and waveform usgs solutions the southern segment exhibits a slightly larger thrust component in agreement with cmt solutions tectonically this event highlights a nne trending fault on the west side of the lv which is predominantly strike slip the aftershocks clustered to the east of the main shock which exhibit mainly thrust mechanisms indicate that shortening is still acting on the sedimentary materials deposited between the coastal and central ranges prior to collision as a result the southern lv is undergoing slip partitioning along different faults which has never been specified before

the 2000 tottori earthquake a shallow earthquake with no surface rupture and slip properties controlled by depth the m w 6 8 tottori earthquake japan does not exhibit any surface trace but was particularly well instrumented strong motion displacement records and gps coseismic data are used to constrain the evolution of the slip on the fault plane in time and space we adopt in this study a two plane fault geometry based on aftershock distributions and analysis of close station records in a first step our inversion allowed surface slip the model obtained has a significant surface slip which contradicts the absence of clear surface slip reported by geologists in a second step models with no slip at the surface buried faults compatible with geological observations have been tested the tests with different fault depths show that when slip is allowed to occur close to the surface the fit to seismological and geodetic data is increased these tests confirm that slip actually occurred at shallow depth despite the nonuniqueness of the solution all the inverted source models show 1 a large slip amplitude patch at a depth of about 4 5 km and 2 relatively small slip in the hypocentral area the rupture velocity is about 2750 m s in the asperity region the total rupture duration is about 8 s the slip distribution seems to be controlled by the variation of fault properties with depth another feature that could control the rupture of this earthquake is a fault plane almost perpendicular to the main fault nw of the epicenter which apparently inhibits further rupture propagation

application of colour image analysis in coal petrology abstract the olympus cue 3 colour image analysis system cias offers various processing and statistical functions for the analysis of two dimensional images of a variety of materials based on the colour characteristics and geometric properties of structural and textural elements in this investigation the applicability of cias to coal petrology is described four high volatile bituminous coal samples from the westphalian coal measures of well kemperkoul 1 the netherlands have been analysed using cias as well as conventional point count analysis a statistical comparison of the results shows that cias is competitive to conventional coal petrological analysis the reduction of processing time by 50 and the improvement of the repeatability suggests that cias deserves serious consideration as an efficient alternative to conventional maceral group analysis

kinematics of the mw 7 2 12 november 1999 duzce turkey earthquake the november 12 1999 duzce earthquake ruptured a 40 km long fault segment of the north anatolian fault system immediately to the east of the august 17 1999 izmit rupture we use displacements of 32 sites derived from gps measurements immediately before and after the duzce earthquake to estimate the geometry and slip distribution of the coseismic rupture the 51 northward dipping rupture plane the rake of the slip vector average 3 76 0 04 m right lateral 0 76 0 04 m normal slip and the slip distribution inferred from the gps data are consistent with seismic observations and the distribution of surface offsets measured in the field the geodetically determined moment magnitude is mw 7 2 the duzce earthquake had the highest slip to rupture length ratio of any historic earthquake along the north anatolian fault this is consistent with the duzce earthquake being a part of a composite rupture with the preceding izmit event

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

gradiometry for polarized seismic waves 1 wave gradiometry for a generic point source wave model in cylindrical coordinates is developed to utilize the horizontal components of seismic wavefields attributes of p sv and sh waves such as horizontal slowness and its change the change in geometrical spreading the change in radiation pattern azimuth of propagation and wave polarization can be determined by measuring the horizontal strains and rotations of the wavefield along with three components of displacement gradiometer cells composed of an array of three component seismographs can be used to provide estimates of the wave gradients alternatively a single three component seismograph collocated with an areal strainmeter for p sv waves or a rotation sensor for sh waves can be used to estimate wave polarization and the slowness amplitude behavior of one aspect of the wavefield wave gradients are computed for the 1 april 2007 solomon island earthquake using data from the anza seismic network in southern california and show excellent consistency among stations of the network azimuth and slowness of various long period teleseismic waves are recovered using gradiometry analysis the consistency of strains computed from the broadband array suggests that they may be used to calibrate plate boundary observatory tensor strainmeters in the region

near real time magnitude determination for large crustal earthquakes abstract we introduce an empirical method of near real time near field magnitude determination for large m 6 5 crustal earthquakes time integration over the strong shaking duration on the absolute values of the acceleration records is carried out for nearby stations surrounding many large earthquake sources in taiwan the integrated quantity here denoted as total effective shaking is used in a regression process to derive an empirical relationship for a quick mw determination useful for a reliable real time operation in earthquake rapid reporting and earthquake early warning systems ewss

the mw 7 7 tocopilla earthquake of 14 november 2007 at the southern edge of the northern chile seismic gap rupture in the deep part of the coupled plate interface the slip distribution of the mw 7 7 tocopilla earthquake was obtained from the joint inversion of teleseismic and strong motion data rupture occurred as underthrusting at the base of the seismically coupled plate interface mainly between 35 and 50 km depth from the hypocenter located below the coast 25 km south of the town of tocopilla the rupture propagated 50 km northward and 100 km southward overall the slip distribution was dominated by two slip patches one near the hypo center and the other 70 km to the south where slip reached its maximum value 3 m an additional branch of moderate slip propagated at shallower depth toward the west near the northern tip of the mejillones peninsula rupture velocity remained close to 2 8 km sec with a total rupture duration of 45 sec the first 2 weeks of aftershocks located with a local seismic network display a strong correlation with the slip distri bution the 2007 rupture ended below the mejillones peninsula where the 1995 an tofagasta rupture also ended ruegg et al 1996 delouis et al 1997 pritchard et al 2006 this corroborates the role of barrier played by this structure the downdip end of the seismically coupled zone at 50 km depth evidenced by previous studies for the 1995 event is also confirmed the 2007 tocopilla earthquake contributed only mod erately to the rupturing of the great northern chile seismic gap which still has the capacity for generating a much larger underthrusting event

mw estimation from crustal coda waves recorded on analog seismograms abstract accurate magnitude determinations are important issues when producing seismicity catalogs aimed at assessing seismic hazard especially in moderate seismicity regions when only a few seismic stations are available the stability of coda wave amplitudes presents great advantages as compared to s lg wave amplitudes for estimating magnitude we develop a method for processing coda waves to determine the moment magnitude m w that is valid both for recent digital short period records and old analog short period seismograms because spectral analyses of paper records are most often not possible we fit the coda envelopes of the raw time signal our empirical representation of the coda envelope is tested with synthetics and its parameters are determined using 109 earthquakes digitally recorded at 12 stations of the laboratoire de detection et de geophysique ldg french velocimetric network between 1997 and 2013 the coda parameters are adapted to the four broad geological zones that can be defined in france within each zone this model matches the observed coda wave envelope for m w between 3 4 and 5 3 synthetic coda signals computed from the regional quality factors q c f within the 0 3 7 hz frequency band of the instrument show that the frequency and regional variation of q c are enough to explain the coda shape of the raw signal this empirical coda model is only valid for events with corner frequency larger than the 1 hz cutoff frequency of the ldg instrument when applying this raw signal envelope model to actual data the site effect at each station must be accounted for from this empirical coda model we obtain stable corrected coda amplitudes that can be directly converted into m w by linear regression

rotational motions observed during an earthquake swarm in april 1998 offshore ito japan abstract we observed six components of ground rotational and translational motions in a near field region during an earthquake swarm in april 1998 offshore ito izu peninsula japan to check the reliability of our observation using a motionpack sensor we installed an 8301f sensor which is an inertial angular displacement sensor with a higher sensitivity than motionpack the noise level of the motionpack is much higher than that of the 8301f but the waveforms of these signal components are quite similar to each other suggesting that the motionpack records rotational rate correctly but with higher noise our observation made known a linear correlation between the maximum rotational displacements around the vertical axis and the maximum translational velocities the waveforms of rotational motion around the vertical axis are analogous to those of translational horizontal velocities suggesting the linear correlation between maximum values these rotational motions are much larger than those calculated by array data at the san andreas fault this large discrepancy might be explained by one or more of the following effects the difference in the spatial scale of rotational motion by single gyro measurement and by array observation the effect of the precipitous topography at the station of the offshore ito swarm and the difference of the degree of maturation between the san andreas fault and the swarm regions of offshore ito

beam hardening artifact reduction in microfocus computed tomography for improved quantitative coal characterization microfocus computed tomography ct is a non destructive technique allowing visualization of the internal microstructure of objects this technique can be used to quantify the maceral content and to define the cleat system within coal samples however a number of artifacts intrinsic to the technique hamper the optimal quantitative use of ct one of the most important artifacts is beam hardening which generates streaks on the images near dense inclusions such as ankerite or pyrite and makes the border of the sample appear denser than in reality these artifacts can be minimized by using a dual energy method in which two sets of scans taken at a different energy level are combined in this study existing dual energy methods are combined into a new technique and adapted to be more ideally suitable for coal samples the method is calibrated with an artificial sample made of a plexiglas cylinder in which two aluminum rods are built in plexiglas and aluminum were selected since their x ray attenuation properties are similar to those of vitrinite and dense phases such as ankerite respectively the method is tested on a coal sample bearing relatively high percentages of iron minerals the corrected and uncorrected images from one representative slice through the sample are compared with reflected light microscopy images from the corresponding polished surface the results show that the applied approach creates images in which the border does not appear denser than in reality and in which the artificial streaks near dense inclusions are removed in addition size measurements of the ankerite veins and grains in the sample are much more accurate based on the corrected images it is therefore assumed that the proposed dual energy algorithm minimizes the beam hardening artifact however the corrected images have a lower signal to noise ratio than the uncorrected images consequently this approach magnifies to some extent other artifacts noise scatter and partial volume effect which are also present in the uncorrected images some solutions to correct for these artifacts and to improve the developed dual energy method are proposed

petrophysical characterization of tight oil sandstones by microscale x ray computed tomography abstract tight oil sandstones have complex pore structure due to multiple pore types and multiscale pore size ranging from several nanometers to dozens of microns in this study petrophyiscal properties of tight oil sandstones were quantified based on microscale x ray computed tomography xct imaging techniques the pore types in gray scale images were identified porosity pore size distribution psd and pore connectivity were analyzed from segmented image stacks and their permeability was calculated by representative elementary volume rev scale lattice boltzmann method lbm three types of pores including residual interparticle pores grain dissolution pores and micro fractures were identified a multi threshold segmentation algorithm was applied to segment the image stacks into three constituents namely pore matrix and clay the calculated volumetric fraction of the pore constituent from the segmented image stacks was smaller than experimental porosity because a certain amount of porosity was also contributed by clay constituent the psd of the samples was found to be unimodal in the range of 3 69 m with the peak at around 10 15 m the clay constituent led to the increase in the overall connectivity of the images stacks indicating that clays bridged the isolated pores by assigning appropriate porosity and permeability to the clay constituent calculated permeability of the samples using rev scale lbm well matched the experimental data this study provides new insight into characterization of pore structure of tight oil sandstones by xct technique

the effectiveness of a distant accelerometer array to compute seismic source parameters the april 2009 l aquila earthquake case history the 6 april 2009 mw 6 3 l aquila earthquake central italy has been recorded by the irpinia seismic network isnet about 250 km southeast of the epicenter up to 19 three component accelerometer stations could be used to infer the main source parameters with different seismological methods we obtained an approximate location of the event from arrival times and array based back azimuth measurements and estimated the local magnitude 6 1 from an at tenuation relation for southern italy assuming an omega square spectral model we inverted s wave displacement spectra for moment magnitude 6 3 corner frequency 0 33 hz stress drop 2 5 mpa and apparent stress 1 6 mpa waveform modeling using a point source and an extended source model provided consistent moment tensors with a centroid depth around 6 km and a prevalently normal fault plane solution with a dominant directivity toward the southeast the relatively high corner frequency and an overestimated moment magnitude of 6 4 from moment tensor inversions are attributed to the rupture directivity effect to image the rupture geometry we implemented a beamforming technique that back projects the recorded direct p wave amplitudes into the earthquake source region a northwest southeast striking rupture of 17 km length is imaged propagat ing with an average velocity up to 3 km s this value is significantly higher than our estimate of 2 2 km s from s wave spectra our case study demonstrates that the use of array techniques and a dense accelerometer network can provide quick and robust estimates of source parameters of moderate sized earthquakes located outside the network

kinematic inversion of the 2004 m 6 0 parkfield earthquake including an approximation to site effects the 2004 m 6 0 parkfield earthquake yielded one of the largest amounts of near source strong ground motion seismic data ever we invert strong motion seismograms to obtain a model for the space time distribution of coseismic slip on the fault to reduce noise in the inversion we take into account local amplifications that affect each station by using records of the 1983 m 6 5 coalinga earthquake site amplification correlates well with large peak ground velocities registered during the 2004 parkfield mainshock the inversion for a kinematic rupture model yields a nonunique solution we therefore analyze various rupture models that explain the data equally well our preferred rupture model identifies a primary zone of high slip surrounding the hypocenter where the maximum slip is 57 cm a secondary slip area over which contours are not well resolved is located northwest of the hypo center the rupture speed is highly heterogeneous we infer an average rupture ve locity of 2 8 km sec close to the hypocenter and of 3 3 km sec in the secondary region of large slip to the northwest of the hypocenter by correlation of our rupture model with both microseismicity and velocity structure we identify six patches on the fault plane that behave in seismically distinct ways online material kinematic rupture model parameters

fmnear determination of focal mechanism and first estimate of rupture directivity using near source records and a linear distribution of point sources abstract the fmnear method is based on both the waveform inversion of near source seismic records and on a linear finite source model the primary source parameters that are determined are the moment magnitude m w the double couple focal mechanism strike dip and rake and the distribution of seismic moment along strike which provides a first order estimate of rupture length and directivity source depth is also explored an advantage of the approach is the use of the finite source model directly within the search of the focal mechanism this strategy allows the inclusion of strong motion records at short distances for moderate to very large earthquakes m w 5 5 however for moderate to small earthquakes m w m w 4 5 to 9 0 test cases incorporate continental events recorded by a large number of well distributed stations and less favorable cases in its present form the fmnear approach is very well adapted to continental earthquakes surrounded by seismic stations but it can also give informative results in more difficult configurations the fmnear method is now ready for fully automated determinations and is already implemented in near real time online material details on inversion parameters flow charts of the fmnear method figures of waveform modeling and sensitivity for selected events and table of velocity models

porosity and permeability characterization of coal a micro computed tomography study abstract a unique contrast agent technique using x ray micro computed tomography micro ct was developed for studying micrometer sized features in coal the technique allows for the visualization of coal fractures not visible with conventional imaging methods a late permian medium volatile bituminous coal from moura coal mine was imaged and the resulting three dimensional coal cleat system was extracted for fluid flow simulations the results demonstrate a direct relationship between coal lithotype and permeability i e bright coals offer more permeability than dull coals however there was no direct relationship between porosity and permeability for any given lithotype scanning electron microscope and energy dispersive spectrometry sem eds together with x ray diffraction xrd methods were used for identifying mineral matter at high resolution after segmentation of the micro ct image mineral phase was removed from the segmented data and it was found that permeability was significantly improved by increasing cleat void space and connectivity suggesting that enhanced recovery methods could target de mineralization techniques overall only the epigenetic mineral phases in the bright band influenced permeability while lithotype had a stronger impact on permeability than porosity coal lithotype and mineralization are important evaluation criteria when considering coal seam gas development sites

deformation during the 12 november 1999 duzce turkey earthquake from gps and insar data only 87 days after the mw 7 5 17 august 1999 izmit earthquake the duzce earthquake ruptured a ca 40 km long adjoining strand of the north anatolian fault naf system to the east we used displacements of 50 global positioning system gps sites together with interferometric synthetic aperture radar insar range change data spanning the event to estimate the geometry and slip distribution of the coseismic rupture postseismic deformation transients from the duzce earth quake and the preceding i zmit event that are included in some of the measurements are corrected for using dislocation models fit to gps data spanning the various time periods nonlinear inversions for fault geometry indicate that the rupture occurred on a ca 54 north dipping oblique normal right lateral fault distributed slip inver sions indicate maximum strike slip near the center of the duzce fault close to the earthquake hypocenter slip magnitude and depth of faulting decrease to the west and east of the hypocenter both gps and insar data suggest that normal slip is restricted to the shallow portion of the rupture the duzce earthquake had the highest slip to rupture length ratio of any historic earthquake along the naf

high resolution three dimensional imaging of coal using microfocus x ray computed tomography with special reference to modes of mineral occurrence abstract samples of coal from the sydney and bowen basins of eastern australia have been imaged at high resolution using a large field 3d microfocus x ray computed tomography ct system with special but not exclusive attention to evaluating the modes of occurrence of the mineral matter within the coal the samples imaged were 110 mm 25 mm 19 mm 10 mm and 4 mm in size yielding voxel dimensions of 54 30 12 6 and 3 m respectively data collection was carried out using a helical stage providing images with 20002 voxels in the horizontal x y plane and up to 3500 voxels high three dimensional image blocks derived from the scans were examined as cross sections along orthogonal planes and as perspective images manipulated to be viewed from any angle imaging after saturating the coal with x ray attenuating brine was also carried out to highlight the distribution of connected micro pores and cleats and improve the detail of features seen within the samples features evaluated within the coals included the size and three dimensional distribution of siderite nodules and different types of mineral infillings in petrifactions of maceral components individual macerals could also be identified within the coal based partly on x ray density and partly on the associated porosity and structure in some cases high resolution images enabled the nature of individual plant particles to be identified within the coal samples mineral filled cleats and open fractures were also evaluated including the origin of radiating fracture patterns around siderite nodules in vitrinite in some cases several generations of cleat and or fractures could be distinguished and the sequence of their formation and infilling was interpreted complementary analyses of the mineral matter in the samples were carried out using x ray diffraction as well as examination of polished sections by optical microscopy examination images obtained from the ct scans were also registered against sem edx and qemscan images of polished sections prepared from the same samples after scanning providing a more definitive basis for identifying the different components and for integrating ct data with results from other petrographic and electron microscope studies

correlation of 3d computerized tomographic scans and 2d colour image analysis of westphalian coal by means of multivariate statistics abstract core material containing westphalian vitrinite rich coal from the north of belgium campine basin has been investigated by colour image analysis and computerized tomography the relative 3d density distribution of the investigated core material was determined by non destructive x ray computerized tomography colour image analyses of polished sections of the same piece of core material provided data concerning the corresponding maceral composition and mineral content of the coal the application of both methods to the same piece of rock allowed for a first order cross correlation of different rock properties by multivariate statistical analysis density estimates of macerals were made the combination of both techniques is very useful in a study of fracture systems in core material and density calibration of computerized tomographic scans of rock constituents

computer axial tomography investigation of polymetallic nodules abstract polymetallic nodules collected from the clarion clipperton region of the north pacific ocean have been investigated by using a siemens somatrom hiq computer tomograph the reconstructed tomographies show much details in the internal structure of the nodules such as nucleus shape and origin primary and secondary growth surfaces highly mineralized areas and the fracture network in addition reconstructed 3d images of nodules have been obtained computer axial tomography proves to be a remarkably useful method for this typed of investigation

transient stresses at parkfield california produced by the m 7 4 landers earthquake of june 28 1992 observations from the upsar dense seismograph array the m 7 4 landers earthquake triggered widespread seismicity in the western united states because the transient dynamic stresses induced at regional distances by the landers surface waves are much larger than the expected static stresses the magnitude and the characteristics of the dynamic stresses may bear upon the earthquake triggering mechanism the landers earthquake was recorded on the upsar u s geological survey parkfield small aperture array array a group of 14 triaxial accelerometers located within a 1 square km region 10 km southwest of the town of parkfield california 412 km northwest of the landers epicenter no triggered earthquakes were observed at parkfield multiple filter analysis shows that the displacements obtained by double integration are dominated by the fundamental mode love and rayleigh modes with some higher mode contributions for periods shorter than 10 s most of the surface waves propagated along the great circle path from landers but a late arriving surface wave appears to have been scattered from the sierra nevada mountains we used a standard geodetic inversion procedure to determine the surface strain and stress tensors as functions of time from the observed displacements peak dynamic strains and stresses at earth s surface are about 7 strain and 0 035 mpa respectively and they have a flat amplitude spectrum between 2 s and 15 s period these stresses agree well with stresses predicted from a simple equation using the ground velocity spectrum observed at a single station peak stresses ranged from about 0 035 mpa at the surface to about 0 12 mpa between 2 and 14 km depth with the sharp increase of stress away from the surface resulting from the rapid increase of rigidity with depth and from the influence of mode shapes because of the free surface boundary conditions the horizontal components of the stress tensor tend to dominate in the top 5 6 km of the crust which might cause triggered seismicity to have strike slip or normal mechanisms comparison of dynamic stresses induced by the landers loma prieta and petrolia earthquakes at a variety of sites indicates that the landers stresses were not spectacularly larger than those induced by the other sources landers dynamic stresses were comparable to coalinga static stresses at parkfield the effective strain caused by landers at parkfield where no earthquakes were triggered are the same amplitude as those at some sites in nevada where earthquakes were triggered comparing various authors observations of dynamic stresses there is no obvious characteristic of these stresses that correlates with the triggered seismicity

long lasting transcurrent tectonics in sw alps evidenced by neogene to present day stress fields abstract the sw alps are an active orogen undergoing intra mountainous extension and peripheral compression we discuss the significance of syn orogenic extension based on a comparison of paleo stress derived from fault slip data inversion reflecting the long term

magnitude estimation using the first three seconds p wave amplitude in earthquake early warning 1 pd is the peak amplitude of displacement in the first three seconds after the arrival of the p wave we investigated the attenuation of pd with the hypocentral distance r in southern california as a function of magnitude m and obtained the following relationship log pd 3 463 0 729 m 1 374 log r 0 305 given an earthquake location determined by the p wave arrival times at stations close to the epicenter this relationship can be used to define a so called pd magnitude of earthquakes our result shows that for earthquakes in southern california the pd magnitudes agree with the catalog magnitudes with a standard deviation of 0 18 for events less than magnitude 6 5 therefore pd is a robust measurement for estimating the magnitudes of earthquakes and has practical application in earthquake early warning systems citation wu y m and l zhao 2006 magnitude estimation using the first three seconds p wave amplitude in earthquake early warning geophys res lett 33 l16312 doi 10 1029 2006gl026871

coseismic and postseismic fault slip for the 17 august 1999 m 7 5 izmit turkey earthquake we use global positioning system gps observations and elastic half space models to estimate the distribution of coseismic and postseismic slip along the izmit earthquake rupture our results indicate that large coseismic slip reaching 5 7 meters is confined to the upper 10 kilometers of the crust correlates with structurally distinct fault segments and is relatively low near the hypocenter continued surface deformation during the first 75 days after the earthquake indicates an aseismic fault slip of as much as 0 43 meters on and below the coseismic rupture these observations are consistent with a transition from unstable episodic large earthquakes to stable fault creep sliding at the base of the seismogenic zone

rupture processes of the 1999 august 17 izmit and november 12 duzce turkey earthquakes summary we derive the rupture history of the 1999 august 17 izmit mw 7 4 and 1999 november 12 duzce mw 7 1 earthquakes in turkey from teleseismic body waves using broad band data of the global seismograph network aftershock locations and mapped surface breaks the centroid solutions indicate strike slip mechanisms for both events the izmit earthquake was characterized by rupture propagating predominantly eastwards it consisted of a main rupture lasting about 25 s followed within 1 min by two more events of mw 6 9 and mw 7 0 with the teleseismic data we could not resolve the westward extent of rupture into the marmara sea however an upper bound of the seismic moment release west of the epicentre of the izmit event is estimated to be 1 9 1019 n m the duzce earthquake lasted about 14 s and was characterized by a bilateral mode of rupture in excellent agreement with mapped surface breaks and aftershock locations

joint inversion of insar gps teleseismic and strong motion data for the spatial and temporal distribution of earthquake slip application to the 1999 izmit mainshock the space time distribution of slip of the 17 august 1999 izmit earthquake is investigated by inverting synthetic aperture radar sar interferometry and global positioning system gps data together with teleseismic broadband and near field strong motion records surface offsets are used as an added constraint special emphasis is given to analysis of the resolution of the different data sets we use a four segment finite fault model and a nonlinear inversion scheme allowing slip to vary in amplitude direction and duration as well as variable rupture velocity from the inversion of synthetic data we find that the best spatial resolution can be expected in the upper half of the fault model above 12 km where coverage of the interferometric sar data is good western half of the rupture and near the gps and strong motion stations teleseismic data are found to have a lower resolution that is more evenly distributed over the fault model the joint inversion of all the data sets has an increased resolving power compared with the separate inversions and gives a more robust description of the space and time distribution of slip our study shows the importance of resolution tests in evaluating the reliability of earthquake kinematic models and it confirms that an excellent fit of a single kind of data does not necessarily imply a good retrieval of the kinematic properties of an earthquake the izmit rupture which is almost pure right lateral strike slip faulting is dominated by the bilateral breaking of a central asperity located between 29 7 e about 10 km west of the city of golcuk and 30 4 e eastern margin of sapanka lake with slip reaching 6 8 m in the depth range 6 12 km the western termination of the rupture is found near the city of yalova but large slip ends around 29 7 e about 10 km east of hersek delta a second area of large slip is required by all the data sets further east toward the city of duzce between 30 7 e and 31 1 e karadere and duzce faults this eastern slip zone which is separated from the main central asperity by an area of greatly reduced slip is less well constrained by the data however a strong motion station near the city of duzce helps to locate a high slip patch near 31 1 e in the depth range 6 12 km the total seismic moment resulting from the joint inversion is 2 4 1027 dyne cm most of the energy release occurred in a short time less than 15 sec corresponding to the bilateral breaking of the central asperity rupture propagation is relatively uniform and fast toward the west with a rupture velocity close to 3 5 km sec propagation of large slip toward the east is initially slower but it accelerates during a short time interval about 10 sec after rupture nucleation eastward progression then slows down to less than 2 km sec after 15 sec and rupture almost vanishes in amplitude ca 20 sec after initiation rupture propagation then proceeds on the easternmost karadere and duzce fault segments east of 30 7 e from 22 to ca 50 sec supershear rupture propagation is not required for modeling the waveforms considered in this study the hypocenter of the duzce earthquake which occurred 3 months later 12 november 1999 m w 7 2 is located in the immediate vicinity of the easternmost slip patch of the izmit earthquake manuscript received 28 july 2000

source rupture process of the kocaeli turkey earthquake of august 17 1999 obtained by joint inversion of near field data and teleseismic data the rupture process of the 1999 turkey earthquake is examined using both near field strong motion data and teleseismic body wave data the derived source parameters are as follows strike dip slip 268 86 180 nearly pure strike slip the seismic moment mo 1 7 1020 nm mw 7 4 the source duration 20 sec the fault length 70 km the fault width 15 km the rupture process is characterized by an asymmetric bilateral rupture propagation and smooth slip it consists of two major fault segments a rupture propagating to the west and a second rupture propagating to the east the maximum dislocation and the maximum dislocation velocity are 6 3 m and 2 7 m s respectively both found at the former segment the average dislocation is about 4 m the extent of the coseismic rupture suggests that a considerable part of the anticipated seismic gap remains unruptured

rotational motions induced by the m8 1 tokachi oki earthquake september 25 2003 1 we report the first consistent observations of rotational motions around a vertical axis induced by distant large earthquakes it is standard in seismology to observe three components up down n s e w of earthquake induced translational ground motions using inertial seismometers however only recently ring laser technology has provided the required sensitivity for observations of the theoretically predicted rotational part of ground motion generated by seismic waves in a wide distance range and frequency band here we show that the rotations observed are consistent in waveform and amplitude with collocated recordings of transverse accelerations recorded by a standard seismometer this suggests that rotations may become a new observable for seismology and related fields with the potential of providing complementary information on earthquake source processes structural properties and ground shaking

introduction to the special issue on rotational seismology and engineering applications rotational seismology is an emerging field for studying all aspects of ro tational ground motions induced by earthquakes explosions and ambient vibrations it is of interest to a wide range of geophysical disciplines including strong motion seismology broadband seismology earthquake engineering earthquake physics seis mic instrumentation seismic hazards seismotectonics and geodesy as well as to physicists using earth based observatories for detecting gravitational waves generated by astronomical sources predicted by einstein in 1916 in this introduction to the bssa special issue on rotational seismology and engineering applications we will include 1 some background information 2 a summary of the recent events that led to this special issue and 3 an overview of its 51 papers 27 articles 11 short notes 4 reviews 6 tutorials and 3 supplementary articles our comments on these 51 papers are very brief and give just a hint of what the papers are about papers in this special issue demonstrate that earthquake monitoring cannot be limited to measuring only the three components of translational motion we also need to simultaneously measure the three components of rotational motion and the many components of strains a golden opportunity to improve our understanding of earth quakes lies in the near field of large earthquakes within about 25 km of the earthquake ruptures where nonlinear rock and soil response influences ground motions in a com plicated way

bituminite a tem view abstract an illinois coal high volatile bituminous b of carboniferous age containing typical bituminite has been examined by transmission electron microscopy tem to supplement observations with the light microscope with tem the bituminite has a fine fairly regular structure including voids of a characteristic shape this structure is almost certainly inherited from a botanical precursor and is thought to represent much altered remains of former colonies of algae probably green algae the present remains contain abundant lipid rich globules and probably also include matter of algal and bacterial origin which cannot be resolved even at tem resolutions

slip distribution on a thrust fault at a plate boundary the 2003 chengkung earthquake taiwan summary the 2003 chengkung earthquake mw 6 8 occurred on the east dipping chihshang fault of eastern taiwan a listric fault with dominant reverse motion a joint inversion taking into account geodetic gps and seismological accelerometric and teleseismic data is performed this modelling highlights the rupture process behaviour on the fault plane at depth the coseismic rupture developed essentially between 12 and 26 km depth expanding laterally by about 30 km towards the ssw two slip patches dominated with slip values exceeding 1 5 m during the 30 s of the whole process the rupture propagation decelerated with time starting at 3 4 0 3 km s 1 in the two main slip patches and ending with velocities below 1 6 0 1 km s 1 the 48 hr of aftershocks that followed the main shock are distributed essentially inside the coseismic slip patches on the fault surface except in the deepest southern part of the fault where slip is less resolved the results of our modelling illustrate the particular behaviour of the 2003 chengkung earthquake where the coseismic slip rapidly diminished towards the surface in good agreement with the observation of fast post seismic slip followed by interseismic creep along the chihshang fault

a method for rapid determination of moment magnitude mw for moderate to large earthquakes from the near field spectra of strong motion records mwsynth seismic moment and the corresponding moment magnitude mw are clas sically obtained from the spectrum of far field body waves near field records are generally not used for that purpose particularly in the case of large earthquakes be cause different types of wave arrive simultaneously preventing the definition of a simple relation between the seismic moment and the spectrum we developed an orig inal method to determine mw from the displacement spectra of near field records the spectral amplitude at low frequency obtained from the real records is compared to that of synthetic records computed using kinematic rupture models scaled with mw syn thetic records are computed and averaged for various fault orientations and for epi central distances ranging from 1 to 100 km the initial portion of the spectrum affected by baseline shift in the acceleration records is automatically identified and removed by high pass filtering using a cutoff frequency adapted to each station the synthetic spectral values as a function of moment magnitude epicentral distance and filtering are computed only once and stored in tables the spectral amplitudes of the real records are simply interpolated in the tables of synthetic data allowing a fast determination of mw the method has been validated using 22 shallow earthquakes depth 50 km with magnitude ranging from 3 9 to 7 7 we show that a window of 80 sec of signal after the earthquake origin time provides robust values of mw for the whole magnitude range considered here shorter time windows may be used but with mw underestimated for large events the method is well suited for near real time fast determination of mw

dynamic deformations of shallow sediments in the valley of mexico part i three dimensional strains and rotations recorded on a seismic array abstract we study the spatial variation in earthquake ground motions or equivalently the dynamic displacement gradient field using a novel analysis procedure borrowed from geodesy seismic data recorded in the valley of mexico by a microarray of three three component surface accelerographs and two three component accelerographs at depths of 30 m and 102 m constrain our estimates of the dynamic displacement gradient field from which strains and rotations derive for four moderate earthquakes at distances of 250 to 300 km our study focuses on the effects of low velocity surface materials on the deformation at the surface the gradients corresponding to deformation across vertical planes dominate and vertical axis rotations are of similar magnitudes as strains the greatest peak surface gradient we observed was 206 strain for the 14 september 1995 m w 7 5 earthquake at a distance of 300 km however much larger gradients occur across horizontal planes u z where u is a horizontal displacement and z is depth at some depth between 0 and 30 m these values are about a factor 10 greater than the corresponding gradient components at the surface u z for the 14 september earthquake equaled or exceeded 665 strain at depth the dynamic deformations experienced in mexico city undoubtedly have occurred before and will occur again in other densely populated areas however in many other regions the sediment response will not remain linear and elastic resulting instead in liquefaction and ground failure

effect of baseline corrections on displacements and response spectra for several recordings of the 1999 chi chi taiwan earthquake displacements derived from many of the accelerogram recordings of the 1999 chi chi taiwan earthquake show drifts when only a simple baseline de rived from the pre event portion of the record is removed from the records the appearance of the velocity and displacement records suggests that changes in the zero level of the acceleration are responsible for these drifts the source of the shifts in zero level are unknown but in at least one case it is almost certainly due to tilting of the ground this article illustrates the effect on the ground velocity ground dis placement and response spectra of several schemes for accounting for these baseline shifts a wide range of final displacements can be obtained for various choices of baseline correction and comparison with nearby gps stations none of which are colocated with the accelerograph stations do not help in choosing the appropriate baseline correction the results suggest that final displacements estimated from the records should be used with caution the most important conclusion for earthquake engineering purposes however is that the response spectra for periods less than about 20 sec are usually unaffected by the baseline correction although limited to the analysis of only a small number of recordings the results may have more general significance both for the many other recordings of this earthquake and for data that will be obtained in the future from similar high quality accelerograph networks now being installed or soon to be installed in many parts of the world

what can be learned from rotational motions excited by earthquakes summary one answer to the question posed in the title is that we will have more accurate data for arrival times of sh waves because the rotational component around the vertical axis is sensitive to sh waves although not to p sv waves importantly there is another answer related to seismic sources which will be discussed in this paper generally not only dislocations commonly used in earthquake models but also other kind of defects could contribute to producing seismic waves in particular rotational strains at earthquake sources directly generate rotational components in seismic waves employing the geometrical theory of defects we obtain a general expression for the rotational motion of seismic waves as a function of the parameters of source defects using this expression together with one for translational motion we can estimate the rotational strain tensor and the spatial variation of slip velocity in the source area of earthquakes these quantities will be large at the edges of a fault plane due to spatially rapid changes of slip on the fault and or a formation of tensile fractures

coseismic versus interseismic ground deformations fault rupture inversion and segmentation revealed by 2003 mw 6 8 chengkung earthquake in eastern taiwan 1 the 2003 chengkung earthquake mw 6 8 provided diagnostic evidence for a source model showing the deformation process of the seismogenic chihshang fault in eastern taiwan the aftershocks show a fault bend at a depth of 18 km coseismic ground displacements recorded by strong motion records allow us to deduce instant rupturing of this event our resulting model shows a fault length of 33 km and dip slip dominant rupture on fault plane deeper than 18 km estimated coseismic displacements constrain two fault planes one at 5 18 km depth dipping 60 e and 18 36 km depth dipping 45 e the uppermost fault plane of the chihshang fault 0 5 km did not break immediately after the main shock however it may have a major role in after slip and even interseismic ground deformation the taiyuan basin developed in the hanging wall is a geomorphic feature consistent with and adequately explained by coseismic ground displacements

computer axial tomography in geosciences an overview abstract computer axial tomography cat is one of the most adequate non destructive techniques for the investigation of the internal structure of a large category of objects this method based on the attenuation of x or gamma ray generates digital images which map the numerical values of the linear attenuation coefficient of a section or of the entire volume of the investigated sample depending on the energy of the utilized radiation as well as on the effective atomic number of the sample cat can furnish with a spatial resolution of 0 01 0 5 mm quantitative as well as qualitative information concerning local density or chemical composition of the sample in geosciences cat has been successfully applied to the investigation of bulk density moisture content or macroporosity of the soil soil plant water system oil sand or shales small scale heterogeneities in siltstone or sandstone diamonds in kimberlite mineralization layers in manganese nodules local structure of marine sediments or coal composition the method has also been used for the investigation of the rock mechanical properties rock permeability fracture network two or three phase flow or residual oil distribution in carbonate cores a review of the actual applications of cat in soil science sedimentology coal geology as well as rock mechanics is presented all these applications reveal the great potential of cat in geoscience investigations

earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records 1 we show that the low pass filtered peak amplitudes of initial p and s wave seismic signals recorded in the vicinity of an occurring earthquake source correlates with the earthquake magnitude and may be used for real time estimation of the event size in seismic early warning applications the earthquake size can be therefore estimated using only a couple of seconds of signal from the p or s wave onsets i e while the rupture itself is still propagating and rupture dimension is far from complete we argue that dynamic stress release and or slip duration on the fault in the very early stage of seismic fracture scales both with the observed peak amplitude and with the elastic energy available for fracture propagation the probability that a fracture grows to a larger size should scale with the energy initially available citation zollo a m lancieri and s nielsen 2006 earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records geophys res lett 33 l23312 doi 10 1029 2006gl027795

slip history and dynamic implications of the 1999 chi chi taiwan earthquake we investigate the rupture process of the 1999 chi chi taiwan earthquake using extensive near source observations including three component velocity waveforms at 36 strong motion stations and 119 gps measurements a three plane fault geometry derived from our previous inversion using only static data ji et al 2001 is applied the slip amplitude rake angle rupture initiation time and risetime function are inverted simultaneously with a recently developed finite fault inverse method that combines a wavelet transform approach with a simulated annealing algorithm ji et al 2002b the inversion results are validated by the forward prediction of an independent data set the teleseismic p and sh ground velocities with notable agreement the results show that the total seismic moment release of this earthquake is 2 7 10 20 n m and that most of the slip occurred in a triangular shaped asperity involving two fault segments which is consistent with our previous static inversion the rupture front propagates with an average rupture velocity of 2 0 km s 1 and the average slip duration risetime is 7 2 s several interesting observations related to the temporal evolution of the chi chi earthquake are also investigated including 1 the strong effect of the sinuous fault plane of the chelungpu fault on spatial and temporal variations in slip history 2 the intersection of fault 1 and fault 2 not being a strong impediment to the rupture propagation and 3 the observation that the peak slip velocity near the surface is in general higher than on the deeper portion of the fault plane as predicted by dynamic modeling

ground rotational motions recorded in near source region of earthquakes large rotational motions excited by earthquakes are recorded during an earthquake swarm of march 1997 offshore ito in izu peninsula japan the largest rotational velocity recorded at kaw is 2 6 10 2 rad s around the north south axis during an earthquake of magnitude 5 2 at 14 09 gmt on march 3 the rotational motions around the vertical axis excited by the largest event is 3 3 10 3 rad s considering a spatial variation of slip velocity which directly relates to excitation of a rotational motion we apply a simple point source model to the largest event and succeed in explaining the observed rotational motion around the vertical axis