mechanical interactions between rigid particles in a deforming ductile matrix analogue experiments in simple shear flow abstract the mechanical interaction between two or more particles is investigated in newtonian simple shear flow the experimental models allow observation of both the particle rotation and the deformation pattern around the particles the finite and instantaneous strain patterns around rigid particles are strongly heterogeneous and asymmetric with high finite strain zones aligned to the direction of maximum finite stretch these correspond to local flow with low vorticity number heterogeneous strain patterns around rigid particles spread over a distance of 1 2 times the particle length and this distance increases with increasing bulk strain where rigid particles are more concentrated these patterns coalesce and the overall pattern is then strongly controlled by the particles and cannot be simply related to the external boundary conditions in rocks the characteristic asymmetric strain pattern around rigid isolated particles is a reliable shear criterion which becomes unreliable with high concentrations of rigid particles particle rotation is significantly disturbed when the distance between adjacent particles of equal size is shorter than their length that is only in very concentrated suspensions of rigid particles in a composite shape fabric the development of the sub fabric corresponding to the smaller minerals will be more disturbed

strain partitioning and progressive deformation history in a transpressive belt northern appalachians abstract syntectonic fibres within rocks of the gaspetrough a mid paleozoic slate belt within part of the acadian orogen of the canadian appalachians record the complex structural evolution of a transpressive belt the fibres occur around pyrite framboids and can be divided into five segments which record four distinct structural stages all four structural stages are related to a single progressive deformation since fibre segments can be traced continuously from the first segments to the last fibre growth patterns within the gaspetrough clearly indicate that folding occurred during coaxial deformation during the first three structural stages these structural stages are 1 layer parallel shortening 2 combined flattening and rigid body rotation and 3 cleavage development strain associated with vertical extension during these three stages accounts for approximately 50 shortening within the slate belt during the last structural stage deformation resulting from regional simple shear continued to affect the entire slate belt as local flattening within cleavage planes produced horizontal extension and brought about further tightening of folds strain recorded by the horizontal fibre increments produced during simple shear accounts for 25 shortening in this part of the appalachians oblique convergence during the acadian orogeny was partitioned in time between strike slip and reverse faulting convergence was accommodated by folding flattening and reverse faulting during the first part of the deformation and later on by flattening and dextral transcurrent faulting

the relation between ground acceleration and earthquake source parameters theory and observations abstract a simple relation between the root mean square rms of the ground acceleration and earthquake spectral or source parameters is introduced in which 0 is the low frequency displacement spectral plateau f 0 is the corner frequency is an attenuation parameter and t is the data interval this result uses the omega square model for far field radiation and accounts for site specific attenuation the main advantage of the new relation with respect to that of hanks 1979 is that it relaxes the simplifying assumption that the spectral corner frequency is much smaller than the maximum corner frequency resulting from attenuation and that the spectrum may be approximated as being perfectly flat between the two frequencies the newly proposed relation is tested using a composite dataset of earthquake records from japan california mexico and taiwan excellent agreement is found between observed and predicted ground acceleration for any combination of corner frequencies thus use of the above relation enables the extrapolation of ground motion prediction equation inferred from the frequent small magnitude earthquakes to the rare large magnitudes this capacity is extremely useful near slow slip plate boundaries where the seismic moment release rates are low

fold axis parallel extension in an arcuate fold and thrust belt the case of the helvetic nappes abstract the helvetic nappes of western switzerland are discussed as an example of an arcuate foreland fold and thrust belt in which active fold axis parallel stretching occurred fold axis parallel extension is recorded by 1 1 incremental strain data from pressure shadow fibres the significance of pressure shadow fibres for the determination of the deformation history of a region is discussed pressure shadows are used to quantify the amount of and to describe the distribution of fold axis parallel extension occurring in the helvetic nappes 2 2 the extension directions of conjugate systems of en echelon veins it is shown that an analysis of the geometry of conjugate vein systems can reveal a regional deformation pattern the relative age of the conjugate en echelon vein systems in the helvetic deformation history can be assessed the geometry of the conjugate sets relative to the local anisotropy plane is described and the significance of the preferred orientation of their extension directions is discussed 3 3 fold axis parallel sections a comparison of the regional distribution of the fold axis parallel strain with the shape of the helvetic nappes in fold axis parallel sections shows that the fold axis parallel strain cannot be related to the footwall topography of the nappes it is concluded that the fold axis parallel extension in the helvetic nappes was induced by a change of direction of overthrust shear this change occurred late in the deformation history and was superposed on the already formed nappes the changing direction of overthrust shear is the expression of an overall anticlockwise rotation going on in the overthrusting alpine nappe pile relative to the european plate a rotation which lead to the arcuate shape of the western alps

correlation of change in magnetotelluric parameters before and after sikkim himalayan earthquakes associated with stress variation abstract mt stations that were recorded before the moderate 5 3 mw 2006 sikkim himalaya earthquake had been reoccupied after 2007 mw 5 0 and 2011 mw 6 9 seismic activities we analyzed the broadband mt data 0 001 1000 s within the 60 km radius from epicenters location and within the focal depth range of 9 30 km the observed change in apparent resistivity in the period range of 0 001 10 s has shown a considerable post seismic decrease of the order 10 30 the 2d geoelectric model constructed with post seismic acquired data also reveals the feature of a decrease in resistivity c1 the relative change decrease of observed apparent resistivity obs after 2006 2007 and 2011 earthquakes find a correlation with combined stress drop 11 18 2 mpa values estimated by arms approach the correlation is further strengthened by a similar change in relative apparent resistivities 2d model derived from 2d model with stress drop integrated stress drop values attribute to the accumulated apparent stresses a 0 23 that reveals the area might be subjugated to 0 6 1 2 mpa stress before 2006 1 1 5 mpa stress before 2007 and 1 7 2 9 mpa before 2011 earthquakes occurrence development of micro cracks and generation of aqueous fluids is possible due to such stressed and slow rate of relentless thrust shear environment within the area of crust therefore resistivity could have been decreased with a fluid transition from compression to dilatancy zones at different depth levels before each earthquake and further decreased upon subsequent stress drops associated with strong ground motions we interpreted that maximum stress might be dropped in dilatational zones oblique to the maximum compression stress directions along n200e n s and nnw sse before 2006 2007 and 2011 earthquakes and resulted in a considerable decrease in apparent resistivity along e w te mode i e yx component

a kinematic analysis incorporating incremental strain data for the frontal pennine zones of the western french alps abstract an incremental and finite strain study of the zones adjacent to the frontal pennine thrust fpt has been undertaken using syntectonic fibres taken from veins pyrite type pressure shadows and similar fringes from around pebbles in conglomeratic rocks the resultant strain data together with detailed mapping of local deformational geometries and regional trends has shown that the pennine zones show a more complex structural history than previously envisaged the structural analysis divides the pennine zones into two regions north and south of creve tete the southern termination of the valais basin the zones to the south of creve tete mont fut valbuche nielard and aiguille d arves show an essentially piggy back thrust sequence directed towards the foreland in which the elongation of the strain ellipse initially parallels the transport direction wnw but finally rotates to become sub parallel to the tectonic strike nne ssw the structures of the valais zone to the north of creve tete are more complex with both n and wnw verging folds thrusts and strike slip faults here the long axis of the strain ellipse appears initially to parallel the tectonic strike ne sw this is followed by a rotation into the late transport direction wnw this localised alternation between strike and transport parallelism is problematic specific examples of strike parallel extension may be explained in terms of radial transport buttressing against earlier extensional structures strike slip motion and or stretching over lateral culmination walls the major division in fibre pattern north and south of creve tete however is best explained as being a function of compartmentalization of deformation styles between adjacent areas models which invoke a dominant deformation mechanism e g thrust tectonics along the entirety of the alpine chain thus need to be rethought similarly the recognition of widespread strike parallel extension suggests that two dimensional balanced section techniques are simplistic giving only minimum shortening estimates in a single direction and thus failing to reflect the true situation

coda waves a review the analysis and interpretation of coda waves have received increasing attention since the early seventies in the past few years interest in this subject has spread worldwide and the study of high frequency seismic coda waves has become a very important seismological topic as a conclusion of the studies accomplished in this time coda waves are considered the result of scattering processes caused by heterogeneities acting on seismic waves p ands waves play a particularly important role in this interaction the process introduces an attenuation which added to the intrinsic absorption gives the observed apparent attenuation therefore coda waves constitute a thumbprint left by the heterogeneities on the seismograms coda waves offer decisive information about the mechanism of how scattering and attenuation take place this review describes coda waves in detail and summarizes the work done in this subject to 1986 the relation between coda waves and attenuation in the context of research on seismic scattering problems is stressed particular attention has been given to the application of coda waves to estimate source and medium parameters the state of the art of the temporal variations of coda wave shape and the possible use of these variations as an earthquake precursor also are presented care has been taken to introduce the statistical models used to deal with the heterogeneities responsible for scattering

interrelations of mesoscopic structures and strain across a small regional fold virginia appalachians abstract small regional folds such as the clover hollow anticline of the narrows thrust sheet in southwest virginia u s a are considered to be large buckle folds expressing lateral shortening above a subsurface decollement cleavage mesoscopic and regional folds and contraction faults have developed in these rocks under anchimetamorphic conditions in a single protracted deformation during thrust sheet emplacement the contraction faults dominate the structure at all scales three fault associations isolated contraction faults contraction faults in series and complex fault zones with intense folding determine the pattern and intensity of local structures regional displacement transfer of strain along and across faults has produced local variations in structural style duplex like systems of second order faults terminate laterally into zones of intense folding and third order faulting fold tightness cleavage intensity strain magnitude and total longitudinal strain e t are maximum in these regions contraction faults in this thrust sheet have propagated along zones of high strain rate associated with mesoscopic folding and intense cleavage regional hinge migration and greater structural complexity along the southeast limb of the clover hollow anticline are considered to be due to emplacement of the adjacent thrust sheet

the use of syntectonic fibres to determine strain estimates and deformation paths an appraisal abstract fibrous pressure shadows developed adjacent to rigid brittle inclusions are familiar features in many tectonites belief that these structures reflect the deformation path as once adjacent grains move apart has led to the derivation of a variety of techniques to determine both incremental and finite strain estimates these methods which can be divided into rigid fibre models e g durney and ramsay and deformable fibre models e g ellis display potentially serious problems when applied to field examples recent studies of microstructures within veins and pressure shadows support the concept that syntectonic fibre complexes can reflect deformation paths and are therefore useful markers of incremental and finite strain the problems mentioned therefore stem directly from the application of the techniques worked examples using these techniques give a variety of strain values dependent upon the extent to which a particular technique allows for volume change or fibre deformation this is useful locally however if the results are to be meaningful on a regional scale then it is imperative that the same technique be applied in the analysis of all fibres regardless of the local deformation path in such studies the merits of a particular technique in determining a correct strain value come second to allowing the spatial distribution of strain to be determined semi quantitatively and thus allowing comparison of similarly derived results with one another

book reviewthe techniques of modern structural geology vol 1 strain analysis j g ramsay and m i huber academic press london 1983 xiii 307 pp us 55 00 28 00 hardcover

revised ml determination for crustal earthquakes in taiwan the local magnitude scale m l is an empirically derived scale anchored to a zero magnitude reference event richter defined the amplitude of ground shaking at an epicentral distance of 100 km for a zero magnitude earthquake in southern california the crustal attenuation characteristics of taiwan result in a relatively high ml when compared to moment magnitude mw we therefore define a revised ml scale for crustal earthquakes in the taiwan region that is more consistent with mw using observed peak ground shaking and mw we determine a new log a0 curve of ground shaking versus hypocentral distance r for a zero magnitude earthquake and station correction factors the log a0 curve determined in this study is log a r 0 332 1 568 log r 0 280 0 using this new log a0 curve and station corrections the new ml is more consistent with mw with a 0 2 magnitude unit uncertainty the new log a0 curve has a value of 2 80 at the distance of 100 km compared to the anchor point of log a0 3 at the same distance as defined by richter for southern california this means that the current ml estimates in taiwan which use richter s definition average 0 2 magnitude units larger than their mw the station correction factors also determined are large from 0 40 to 0 52 magnitude units the use of station corrections in routine seismic network operation in taiwan will improve magnitude estimates this is particularly important for smaller events when recording stations may be pre dominantly on either hard rock or soft soil sites which could lead to under or overestimates of the magnitude by up to half a magnitude unit

acadian strike slip tectonics in the gaspe region quebec appalachians at the southern margin of the cambro ordovician humber zone in the quebec appalachians on gaspe peninsula three structural units of middle ordovician to middle devonian cover rocks of the gaspe belt are in large part bounded by long straight longitudinal faults in one of these units the aroostook perce anticlinorium several structural features which can be ascribed to acadian deformation are controlled by three subparallel dextral strike slip longitudinal faults grande riviere grand pabos and riviere garin these faults follow bands of intense deformation contrasting with the mildly to moderately deformed intervals that separate them most of the structural features observed rotated oblique folds and cleavage subsidiary riedel and tension faults and offsets of markers can be integrated in a model of strike slip tectonics that operated in ductile brittle conditions a late increment of deformation in the form of conjugate cleavages and minor faults is restricted to the bands of high strain an anticlockwise transection of the synfolding cleavage in relation to the oblique hinges may be a feature of the rotational deformation the combined dextral strike slip that can be measured within the three major longitudinal fault zones amounts to 138 km to which can be added 17 km of ductile movement in the intervals for a total of 155 km

strain fabric associated with the meade thrust sheet implications for cross section balancing abstract emplacement of the meade thrust sheet southeastern idaho u s a was accompanied by the development of a strain fabric and significant footwall deformation characteristics of the strain fabric are based on strain estimates using pressure solution cleavage and deformed fossils within the jurassic twin creek formation the strain fabric formed during early layer parallel shortening at the thrust front and accommodates from 10 to 35 shortening within the incipient thrust sheet footwall strata were later folded above a detachment at the base of the twin creek formation and the early strain fabric was passively rotated the structural development of this area consisting of 1 strain fabric development 2 folding of the footwall and 3 the truncation of footwall structures by imbricates of the meade thrust are placed in a relative time frame to aid in section reconstruction the passive reorientation of the strain fabric and the truncation and incorporation of footwall structures into the thrust sheet are used as kinematic and geometric constraints for cross section balancing we present a sequential retrodeformation of the meade thrust sheet in which strain is removed from the cross section at the appropriate geometric stages in the deformation these sections illustrate some methods by which strain data can be incorporated into cross sections and also indicate the difficulty involved in balancing cross sections of internally deformed thrust sheets interpretation of these sections suggests that a significant amount of footwall deformation accompanied the emplacement of the meade thrust sheet and that footwall deformation is strongly controlled by the local stratigraphic package the sections also illustrate that the earliest deformation within a thrust sheet may be unrelated to motion on the underlying incipient thrust and that the trace of a thrust fault which cuts previously deformed strata will not restore to a typical ramp and flat geometry

p wave attenuation with implications for earthquake early warning several widely implemented and tested earthquake early warning algorithms employ empirical equations that relate earthquake magnitudes with ground motion peak amplitudes and hypocentral distances this approach is effective to the extent that the offline dataset available for setting the fitting coefficients in those equations is of sufficient quality and quantity however to address the problem of having a limited dataset it is instructive to gain physical understanding of the main factors controlling the p wave attenuation in this study theoretical expressions are derived that relate the root mean square rms of the p wave displacement d rms and velocity v rms to the seismic moment stress drop and hypocentral distance the theoretical attenuation laws are then validated against observed attenuation using earthquake data from southern california and japan good agreement is found between observed and predicted ground motions the similar ground motion attenuation in california and japan suggests that the attenuation laws are similarly applicable for the two regions and implies that they may also be implemented in other regions without having to go through a lengthy calibration phase because d rms is more strongly dependent on the seismic moment than v rms use of the attenuation law for d rms yields better magnitude prediction than that of v rms it is shown that the d rms to v rms ratio is proportional to the characteristic length of the rupture and that the stress drop is a function of the seismic moment and the cube of d rms v rms this result paves the way for a new stress drop determination scheme that is totally independent of previously used approaches finally it is shown that the rms of the ground motions are proportional to their peak values

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

including strain data in balanced cross sections abstract almost all published balanced cross sections include cleaved and or strained rocks and may therefore violate the requirement that bed lengths and formation areas are preserved between undeformed and deformed states knowledge of distortions presence and type of cleavage and overprinting relations in poly deformed segments are necessary to define area changes related to volume loss strike elongation and poly deformation work in the southern and central appalachians has shown variation in structural complexity and changing deformation styles both along and across the thrust belt this necessitates separate treatment of individual sheets during balancing regions of little or no interstratal slip pinning points should be chosen for each thrust sheet and each fold strain in the sheet in external sheets where deformation intensity increases towards thrusts pin points should be back limb inflection points in intermediate and internal sheets where cleavage is approximately coeval with folding pin points should be at fold hinges where cleavage and strain are heterogeneously developed throughout a stratigraphic sequence a line length balance using massive relatively uncleaved beds e g knox group southern appalachians can be used as a basis for restoring the section unstraining of deformed layers given strain data and cleavage trajectories for individual thrust sheets provides line lengths and formation areas which can be fitted to the key bed of the undeformed section cleavages which partially or fully postdate folding indicate continued shortening in the thrust wedge and modify earlier pinning points in upper sheets these cleavages and poly deformed segments are difficult to restore as strain data are generally scarce in the metamorphosed internal thrust sheets

thrust related strain gradients and thrusting mechanisms in a chevron folded sequence southeastern australia an e directed imbricate fan thrust system within a chevron folded monotonous quartz rich turbidite succession shows marked gradients in strain from the upper to lower parts of individual thrust sheets upper parts of thrust sheets show low to moderate strains xz strains 30 1 tight inclined chevron folds ila 30 with predominantly w dipping axial surfaces intense phyllitic cleavage with a strong down dip mineral stretching lineation and long curved tapering quartz pressure shadows on pyrite such differences in fold geometry the intensity of the cleavage and the geometry of quartz fibres in pressure shadows require thrust sheet emplacement to be synchronous with the internal deformation of sheets thrust sheets show a change from an approximately constant volume plane strain coaxial deformation in their upper parts to non coaxial high strain deformation with incremental i between those expected for pure shear and simple shear i e 0 i 5 45 in their basal parts observed geometries and intensities reflect partitioning of strain and deformation mechanisms within individual thrust sheet volumes both during the initiation and propagation of subsurface detachment faults and with their emplacement to shallower crustal levels strain softening related to chevron folding and more intense cleavage development within a 500 m basal zone has controlled the emplacement of these turbidite dominated thrust sheets transport and internal deformation of the thrust sheets did not involve gravitationally induced spreading but required either a push from the rear or some form of underthrusting

spectral analysis of k net and kik net data in japan part ii on attenuation characteristics source spectra and site response of borehole and surface stations abstract in this study we apply a nonparametric spectral inversion scheme to a data set of accelerograms recorded by the k net and kik net networks in japan in order to derive attenuation characteristics source spectra and site response for this purpose we use a total of more than 67 000 s wave records from 2178 earthquakes m jma 2 7 8 obtained at 1555 stations at the earth s surface and more than 29 000 records from 1826 events recorded at 637 borehole stations at depths of 100 to 3000 m attenuation characteristics are investigated in five separate regions showing that crustal q depicts lower values in central compared to southern japan and a significant frequency dependence is observed in every region the source spectra follow the 2 model with higher stress drops for subcrustal earthquakes as compared with crustal ones while strong amplification effects dominate the site contributions for the surface sensors those for the borehole sensors are characterized by smaller variability nevertheless consistent with observations from deconvolution of borehole surface recording pairs downgoing wave effects are visible in the site contributions for many borehole stations finally the site amplification functions obtained at the surface are compared with surface to borehole s b and horizontal to vertical h v spectral ratios showing that the s b ratios generally provide better estimates of the horizontal amplification than the h v ratios due to amplification of the vertical component of ground motion

shaking from injection induced earthquakes in the central and eastern united states abstract in this study i consider the ground motions generated by 11 moderate m w 4 0 5 6 earthquakes in the central and eastern united states that are thought or suspected to be induced by fluid injection using spatially rich intensity data from the u s geological survey did you feel it system i show the distance decay of intensities for all events is consistent with that observed for tectonic earthquakes in the region but for all of the events intensities are lower than the values predicted from an intensity prediction equation that successfully characterizes intensities for regional tectonic events i introduce an effective intensity magnitude m ie defined as the magnitude that on average would generate a given intensity distribution for all 11 events m ie is lower than the event magnitude by 0 4 1 3 magnitude units with an average difference of 0 82 units this suggests stress drops of injection induced earthquakes are systematically lower than tectonic earthquakes by an estimated factor of 2 10 however relatively limited data suggest intensities for epicentral distances less than 10 km are more commensurate with expectations for the event magnitude which can be reasonably explained by the shallow focal depth of the events the results suggest damage from injection induced earthquakes will be especially concentrated in the immediate epicentral region

reply to comment on the relation between ground acceleration and earthquake source parameters theory and observations by itzhak lior and alon ziv by j enrique luco

crack seal fibre growth mechanisms and their significance in the development of oriented layer silicate microstructures abstract an analysis of crack seal fibre growth mechanisms has shown two important implications of the crack seal process for the interpretation of microstructures in low grade metamorphic rocks 1 1 the ability of fibre growth to track the incremental separation history of crack walls depends on details of the nucleation and growth mechanisms 2 2 fibrous crystals may develop cristallographic preferred orientations in certain crack seal situations the microstructures of layer silicates and associated phases developed in several examples of syntectonic intragranular microfracture sites and veins indicates that layer silicate 001 and grain shape preferred orientation can develop during crack seal deformation by oriented growth mechanisms during successive crack seal increments preferred orientation may develop in response to an interaction between anisotropic growth kinetics and the displacement history resulting in preferential rejoining by syntaxial overgrowth of pulled apart grains having fast growth directions parallel to the incremental displacement direction across a microcrack preferred orientation may also be developed and enhanced in crack seal growth sites by overgrowth of previously oriented layer silicates in the microcrack walls in this case the crystallographic preferred orientation need not be simply related to the displacement history during crack seal fibre growth since crack seal processes may operate on all scales down to the minimum size of a microfracture in a deforming rock such mechanisms of layer silicate preferred orientation development are expected to be very significant in developing and enhancing foliation during deformation involving microfracture and solution transfer processes

strain partitioning in the helvetic thrust belt of eastern switzerland from the leading edge to the internal zone abstract the strain and strain partitioning in the helvetic thrust belt are analysed in order to determine their variation across the belt from the external thin skinned portion to the internal thick skinned portion and in order to begin the detailed mechanical analysis of the entire fold and thrust belt coarse grained limestones of jurassic and cretaceous age were chosen for analysis because they can be traced from the external to the internal zones the strain within a bed is partitioned into three components transgranular pressure solution microfaults veins twinning granular and intragranular exclusive of twinning crystal plasticity associated with recrystallization transgranular strain was very important in the early history of the helvetic nappes giving way to twinning at a later stage under tectonic burial twinning strain was early in the infrahelvetic complex giving way to intracrystalline deformation at the later stage of burial the transition from transgranular to intragranular dominated strain occurred at a vitrinite reflectance value of 3 5 significantly below the greenschist grade of metamorphism in a large scale fold at the leading edge of the helvetic nappes transgranular strains were associated with the buckling stage of the fold and twinning occurred during fold tightening in more internal parts of the helvetic nappes twinning strains are also late with regard to transgranular strains but here their pattern corresponds to the regional finite strain pattern in the internal zone the infrahelvetic complex twinning seems to have been an early event and records an initial layer parallel shortening followed by regional internal deformation with intragranular strains