the evolution of regional seismicity between large earthquakes 1 we describe a simple model that links static stress coulomb modeling to the regional seismicity around a major fault unlike conventional coulomb stress techniques which calculate stress changes we model the evolution of the stress field relative to the failure stress background seismicity is attributed to inhomogeneities in the stress field which are created by adding a random field that creates local regions above the failure stress the inhomogeneous field is chosen such that when these patches fail the resulting earthquake size distribution follows a gutenburg richter law immediately following a large event the model produces regions of increased seismicity aftershocks where the overall stress field has been elevated and regions of reduced seismicity where the stress field has been reduced stress shadows the high stress levels in the aftershock regions decrease due to loading following the main event combined with the stress shadow from the main event this results in a broad seismically quiet region of lowered stress around the epicenter pre event seismicity appears as the original stress shadows finally fill as a result of loading the increase in seismicity initially occurs several fault lengths away from the main fault and moves inward as the event approaches as a result of this effect the seismic moment release in the region around the future epicenter increases as the event approaches synthetic catalogues generated by this model are virtually indistinguishable from real earthquake sequences in california and washington

evaluation of the results for an intermediate term prediction of the 8 january 2006 mw 6 9 cythera earthquake in the southwestern aegean during the past few decades the critical earthquake model which is based on observations concerning accelerating seismic deformation and concepts of the critical point dynamics has been proposed by various seismologists as a useful tool for intermediate term earthquake prediction a refined approach of this model has been previously applied to search for preshock critical regions in the southern aegean using all available data until the middle of 2002 a critical region corre sponding to a large mainshock had been identified papazachos et al 2002a b in the southwestern part of the aegean near the cythera island the predicted in 2002 parameters for this ensuing earthquake are u 36 5 n k 22 7 e for the epicental geographic coordinates with a model uncertainty of 120 km focal depth 100 km moment magnitude m 6 9 0 5 and origin time tc 2006 4 2 0 the generation of the strong cythera earthquake on 8 january 2006 with m 6 9 epicenter coordinates u 36 2 n and k 23 4 e and a focal depth of h 65 km satisfies this intermediate term prediction the region where significant macroseismic effects were anticipated from the predicted mainshock cythera south peloponnesus west crete and west cyclades corresponds to the area where damage by the 8 january 2006 strong earthquake has been observed the verification of this prediction is strong evidence that the intermediate term prediction of strong earthquakes is potentially feasible but additional forward testing of the model is needed to validate this result

a test of the precursory accelerating moment release model on some recent new zealand earthquakes the proposal that the moment release rate increases in a systematic way in a large region around a forthcoming large earthquake is tested using three recent large new zealand events the three events 1993 1995 magnitudes 6 7 7 0 occurred in varied tectonic settings for all three events a circular precursory region can be found such that the moment release rate of the included seismicity is modelled significantly better by the proposed accelerating model than by a linear moment release model although in one case the result is dubious the best such regions have radii from 122 to 167 km roughly in accord with previous observations world wide but are offset by 50 60 km from the associated main shock epicentre a grid search procedure is used to test whether these three earthquakes could have been forecast using the accelerating moment release model for two of the earthquakes the result is positive in terms of location but the main shock times are only loosely constrained

scaling invariance of crack surfaces the morphology of fractured rock surfaces is studied in terms of their scaling invariance fresh brittle fractures of granite and gneiss were sampled with a mechanical laboratory profilometer and 1 1 dimensional parallel profiles were added to build actual maps of the surfaces a first step in the scaling invariance description is a self affine analysis using three independent methods the root mean square and the maximum minimum difference of the height are shown to follow a power law with the sample length the return probability and the fourier spectrum are also computed all these approaches converge to a unique self affine exponent 0 80 analysis over a broad statistical set provides a reproducibility error of 0 05 no significant differences between the isotropic granite and the markedly anisotropic gneiss appear for the scaling exponents an analysis of the profilometer shows that the two main drawbacks of the setup are not significant in these analyses the systematic errors of the scaling analysis are estimated for the different methods isotropy of the scaling invariance within the mean fracture plane is shown either with the result obtained from different fracture orientations or with the two dimensional fourier spectrum of the surface topography itself the analysis is brought further into the multifractal framework the structure functions are shown to have power law behavior and their scaling exponent varies nonlinearly with the moment order finally the corresponding conserved process belongs to a universal multifractal class with 1 5 for the levy index and c1 0 3 for the fractal codimension of the mean singularities the three indices and c1 completely characterize the scale invariance the multifractal behavior is significant for physical properties which depend on high order moments like contact according to this study and that of other groups the self affine exponent is constant over a large range of scales and for different fracture modes and various materials this opens the possibility that there exists a form of universality in the cracking process it appears that only the prefactor of the roughness is dependent on material and mode

fractal geometry characterization of geothermal reservoir fracture networks as a new procedure for modeling geothermal energy extraction systems a two dimensional modeling technique for subsurface fracture networks on the basis of fractal geometry is presented models of fracture networks are generated by distributing fractures randomly in space and by using the fractal relation between fracture length r and the number of fractures n expressed with a fractal dimension d as n cr exp d where c is a constant that signifies the fracture density within the rock mass this procedure makes it possible to characterize geothermal reservoirs by parameters measured from field data such as from core sampling in this characterization the fracture density parameter c of a geothermal reservoir is used as a parameter to model the subsurface fracture network using this fracture network model the connectivities of the water flow paths between wells are calculated by means of a monte carlo simulation and the result is then compared with that derived from a percolation model we show that many fewer fractures are required to connect two wells for the fracture network model than for the percolation model the transmissivities between wells for the fracture network model are also obtained as a function of the fracture density parametermore c the results show that the transmissivities in geothermal reservoirs are significantly dependent upon the fracture density of rock mass and they can be predicted from the fracture density parameter c of the reservoirs less

laboratory earthquakes the sub rayleigh to supershear rupture transition we report on the experimental observation of spontaneously nucleated supershear rupture and on the visualization of sub rayleigh to supershear rupture transitions in frictionally held interfaces the laboratory experiments mimic natural earthquakes the results suggest that under certain conditions supershear rupture propagation can be facilitated during large earthquake events

fluid flow through rough fractures in rocks i high resolution aperture determinations abstract full characterisation of rough fracture surfaces and the resulting variable apertures is an important step in the drive towards an improved understanding of the factors which control fluid flow through rocks a number of surface profiling techniques exist such as needle or laser profiling however these techniques are difficult and time consuming to apply to the total area of a fracture because they involve measuring a large number of parallel profiles which are then difficult to align accurately hence although a single profile may have high resolution in the z direction and the direction of the profile the fracture surface has a much lower resolution due to alignment errors we have developed and improved considerably a previously existing optical concept for obtaining the topography of a fracture surface where the information about surface heights is measured simultaneously the method relies on the construction of high fidelity transparent models of the fracture surface which are imaged while covered with dyed and undyed water the resulting images are converted to topography by a simple calibration procedure that makes use of the lambert beer law this method utilises in house optiprof software which provides considerably more control over the imaging process than previous attempts at optical profiling we have applied the technique to a range of rock fractures and test pieces and have found the technique to work reliably with lateral resolutions of 15 m and a vertical resolution of 15 m although all these could be improved by increasing the pixel count and the bit depth of the camera respectively

retrospective on the accelerating seismic release asr hypothesis controversy and new horizons abstract the hypothesis that large earthquakes may be preceded by a period of accelerating seismicity or accelerating seismic release asr was proposed about twenty years ago a compilation of almost one hundred peer reviewed publications on this topic since the late 1980s to the present day shows that the rate of asr studies increased gradually until 2004 but decreased afterwards this negative trend is amplified by a recent increase in the number of negative results and criticisms of the asr hypothesis the author suggests that much of the recent negativity regarding this topic is due to the formulation of this hypothesis as a power law fit to cumulative seismicity series this approach is intrinsically linked to the consensus for criticality evident from an overview of the asr literature to explain the emergence of power laws in earthquake populations the holistic view of the earth s crust as a complex system restricts seismicity pattern analyses to the study of main features such as power laws while a reductionist view would allow for more refined ones such a paradigm shift or sea change might be under way in the asr literature where in 2007 a new approach was proposed to explain the asr power law from combined concepts of elastic rebound and geometry reductionism versus holism is a fundamental problem that not only applies to the study of asr but also to the broader field of earthquake physics and earthquake predictability science

numerical investigation of alternative fracture stiffness measures and their respective scaling behaviours we study the mechanical deformation of fractures under normal stress via tangent and specific fracture stiffnesses for different length scales using numerical simulations and analytical insights first we revisit an equivalent elastic layer model that leads to two expressions the tangent stiffness is the sum of an intrinsic stiffness and the normal stress and the specific stiffness is the tangent stiffness divided by the fracture aperture at current stress second we simulate the deformation of rough fractures using a boundary element method where fracture surfaces represented by elastic asperities on an elastic half space follow a self affine distribution a large number of statistically identical parent fractures are generated from which sub fractures of smaller dimensions are extracted the self affine distribution implies that the stressfree fracture aperture increases with fracture length with a power law in agreement with the chosen hurst exponent all simulated fractures exhibit an increase in the specific stiffness with stress and an average decrease with increase in length consistent with field observations the simulated specific and tangent stiffnesses are well described by the equivalent layer model provided the intrinsic stiffness slightly decreases with fracture length following a power law by combining numerical simulations and the analytical model the effect of scale and stress on fracture stiffness measures can be easily separated using the concept of intrinsic stiffness we learn that the primary reason for the variability in specific stiffness with length comes from the fact that the typical aperture of the self affine fractures itself scales with the length of the fractures

sequential approach to joint flow seismic inversion for improved characterization of fractured media seismic interpretation of subsurface structures is traditionally performed without any account of flow behavior here we present a methodology for characterizing fractured geologic reservoirs by integrating flow and seismic data the key element of the proposed approach is the identification within the inversion of the intimate relation between fracture compliance and fracture transmissivity which determine the acoustic and flow responses of a fractured reservoir respectively owing to the strong but highly uncertain dependence of fracture transmissivity on fracture compliance the modeled flow response in a fractured reservoir is highly sensitive to the geophysical interpretation by means of synthetic models we show that by incorporating flow data well pressures and tracer breakthrough curves into the inversion workflow we can simultaneously reduce the error in the seismic interpretation and improve predictions of the reservoir flow dynamics while the inversion results are robust with respect to noise in the data for this synthetic example the applicability of the methodology remains to be tested for more complex synthetic models and field cases

space time etas models and an improved extension for sensitive detection of anomalous seismicity such as quiescence and activation in a given region we need a suitable statistical reference model that represents a normal seismic activity in the region the regional occurrence rate of the earthquakes is modeled as a function of previous activity the specific form of which is based on empirical laws in time and space such as the modified omori formula and the utsu seki scaling law of aftershock area against magnitude respectively this manuscript summarizes the development of the epidemic type aftershock sequence etas model and proposes an extended version of the best fitted space time model that was suggested in ogata ogata y 1998 space time point process models for earthquake occurrences ann inst statist math 50 379 402 this model indicates significantly better fit to seismicity in various regions in and around japan d 2005 elsevier b v all rights reserved

characterization of rough walled fractures in crystalline rocks the full characterization of the rough surfaces of fractures and their resulting apertures is an important step in the drive toward an improved understanding of the factors which control fluid flow through rocks this is crucial in igneous and metamorphic rocks since fractures in these rocks may form the only significant pathways for fluid migration here we describe a three pronged approach for the full characterization of rough fracture surfaces in a selection of crystalline rocks using a suite of software developed in house firstly profiling is carried out using an optical method which converts images of epoxy fracture surfaces covered with dyed water into topographies using the lambert beer law many hardware and software optiprof developments give this method the upper hand over previous attempts at spectrophotometric analysis it is not possible to profile every fracture surface therefore numerical modelling of fluid flow is carried out using synthetic fractures with rough fracture surfaces that are representative of the natural rock fractures parafrac allows the analysis and parametrization of fracture surfaces and apertures synfrac enables the numerical synthesis of fracture surfaces and apertures with prescribed basic parameters both procedures take full account of the complex matching properties of the fracture surfaces as a function of wavelength as well as anisotropy within the properties defining the fracture surfaces and their resulting aperture they have been rigorously tested on a large suite of synthetic fractures as well as real rock fractures these tests have allowed relationships between the standard deviation of surface asperity heights the fractal dimension and the matching parameters to be related to the resulting aperture of the fractures

self propping and fluid flow in slightly offset joints at high effective pressures we have made laboratory measurements of joint closure and permeability of both well and poorly mated laboratory produced joints in westerly granite under joint normal stresses to 160 mpa appropriate to midcrustal depths we have also made detailed topographic measurements of the joint surfaces both before and after pressure testing the purpose of the study was to characterize and understand the hydraulic behavior of joints under conditions where fluid migration under natural settings is known to occur but where physical conditions namely high lithostatic load suggest that the presence of open fluid conducting joints might be improbable normal stress was applied by hydrostatic confinement of cylindrical samples each containing a single axial tensile fracture experiments were performed at room temperature under conditions designed to minimize chemical effects of dissolution or precipitation we found that while a mated joint can be completely closed by the application of high normal stresses the same joint laterally offset by 0 53 mm remains open and many orders of magnitude more hydraulically conductive than the mated joint even at highest stresses detailed topographic observations are consistent with self propping of the offset joint permanent damage to the surfaces of the offset joint is not widespread but occurs at isolated locales covering about 10 of the surface damage is confined to regions of negative convex upward curvature such as summits and the edges of plateaus approximately 20 of the joint surface is in wall to wall contact at 160 mpa and the flow tortuosity thus induced is probably the cause of the breakdown of the parallel plate approximation for fluid flow in the offset joint

seismicity precursors to large earthquakes unified in a stress accumulation framework 1 various seismicity patterns before large earthquakes have been reported in the literature they include foreshocks medium term acceleration and short term activation quiescence doughnut patterns and event migration the existence of these precursory patterns is however debated here we develop an approach based on the concept of stress accumulation to unify and categorize all claimed seismic precursors in a same physical framework we first extend the non critical precursory accelerating seismicity theory n c past which already explains most precursors to additionally include short term activation theoretical results are then compared to the time series observed prior to the 2009mw 6 3 l aquila italy earthquake we finally show that different precursory paths are possible before large earthquakes with possible coupling of different patterns or non occurrence of any this is described by a logic tree defined from the combined probabilities of occurrence of the mainshock at a given stress state and of precursory silent slip on the fault in the case of the l aquila earthquake the observed precursory path is coupling of quiescence and accelerating seismic release followed by activation these results provide guidelines for future research on earthquake predictability

3d simulations of multi segment thrust fault rupture thrust faults such as those that underlie the los angeles basin are typically segmented by tear faults that offset the thrust fault segments we perform 3d finite difference simulations of earthquake rupture to evaluate the effectiveness of these offsets in retarding rupture the simulations include orthogonal intersecting faults to model the interaction of the thrust fault segments with the tear fault for reasonable assumptions for fault segment length strength and stress drop rupture can jump offsets of up to 2 km if a tear fault is present consistent with observations of well studied thrust earthquakes absent a tear fault the maximum offset that can be breached is an order of magnitude smaller

fluid flow in synthetic rough fractures and application to the hachimantai geothermal hot dry rock test site fracture profiles from the hachimantai geothermal hot dry rock hdr test site in northern japan have been measured and analyzed to characterise their geometrical properties these properties have been used to create a population of numerical synthetic fractures that were tuned to imitate all the geometric and statistical properties of the natural fracture described in a companion paper such fractures have been used as input boundary conditions in three types of modeling 1 simple elastic normal closure relating the aperture of the fracture to applied normal load 2 hagen poiseuille calculations of fluid transmissivity in the fracture as a function of normal load fracture fluid pressure and temperature 3 two dimensional flow modeling within the rough walled fracture using reynolds equation the modeled closure of these fractures provided a realistic relationship between normal and fracture fluid pressure and aperture when this pressure aperture relationship was combined with a hagen poiseuille approach to calculating fluid transmissivity in the fracture we obtained results which when compared with data from field transmissivity tests at the hachimantai site showed that the functional dependence of fluid transmissivity with fracture fluid pressure was well modeled but overestimated by a factor of about 2 reynolds equation flow modeling was carried out in the synthetic fracture to ascertain the extent to which the hagen poiseuille law was overestimating the transmissivity due to the rough surfaces affecting the fluid flow in the fracture when the calculations were corrected for this effect the overestimation in the fluid transmissivity was reduced considerably

roughness of natural fault surfaces the roughness of fault surfaces is important in the mechanics of fault slip and could play a role in determining whether sliding occurs via earthquakes or fault creep we have made preliminary measurements of the power spectral density of several fault surfaces over the wavelength range from 10 5 to 1 m using field and laboratory scale profilimeters the fault surfaces are strongly anisotropic profiles parallel to the slip direction have amplitudes about one order of magnitude lower than those perpendicular to the slip direction over most of the wavelength interval measured fault roughness perpendicular to the slip direction is similar to the roughness of natural joints the greater smoothness in the slip direction presumably represents wear resulting from slip combining our data with previous measurements of the roughness spectrum of the san andreas fault shows that fault surfaces are fractal over nearly eleven orders of magnitude in wavelength

3d digital rock modeling of the fractal properties of pore structures abstract fractal parameters of porous media have been a focus of study in petroleum engineering and hydrogeology for several decades because they provide an effective way to describe the complexity of pore structure across a wide range of scales this paper combines 3d process driven digital rock modeling with fractal analysis in order to understand the effect of varying sorting compaction cementation and the fine grain fraction of binary models on the fractal parameters and specific surface area of porous media digital rock models drms were constructed to simulate sandstone using a process driven modeling technique which simulates sedimentation the fractal parameters of the resulting pore geometry were calculated using the box counting method on 2d and 3d representations of the drms our simulations indicate that increasing compaction or cementation lead to significant decreases in fractal dimension specific surface area ssp and porosity showing that these two diagenetic processes can affect the pore microstructure of the rock significantly while interface fractal dimension di and ssp both increase slightly with decreases in sorting grain size variety and porosity decreases slightly examining the behavior of binary models the porosity of our digital models shows a v shaped curve as fine grain fraction increases from 0 to 1 consistent with but higher than the theoretical values which we attribute to incomplete packing of the grains arising from the simplified packing algorithm and finite boundary of models the value of both ssp and di increase as the fine grain fraction increases however we must notice that the porosity may be underestimated and the fractal dimension may be overestimated when we use models consisting of very fine spherical grains due to the effect of image resolution

an observational test of the origin of accelerating moment release before large earthquakes 1 a progressive increase of seismic activity distributed over a wide region around a future earthquake epicenter is termed accelerating moment release amr this phenomenon has been observed in several studies over the last 15 years although there is no consensus about the physical origin of the effect in a recent hypothesis known as the stress accumulation sa model the amr is thought to result from the last stage of loading in the earthquake cycle in this view the increasing seismicity is due to minor stress release as the whole region becomes sufficiently stressed for the major event to occur the stress accumulation model makes specific predictions about the distribution of events in an amr sequence because the amr is predicted to be a result of loading on the main fault the precursory activity should be concentrated in the positive lobes of the far field stresses calculated by a backslip dislocation model of the main shock to test this model amr is first found in optimal circular regions around the epicenters of each of the m w 6 5 earthquakes in central and southern california since 1950 a backslip dislocation model is then used to determine which of the precursory events occur in the regions predicted by stress accumulation amr is shown to occur preferentially in the lobes of the backslip stress field predicted by the stress accumulation model

ergodicity and earthquake catalogs forecast testing and resulting implications recently the equilibrium property of ergodicity was identified in an earthquake fault system tiampoet al phys rev lett 91 238501 2003 phys rev e 75 066107 2007 ergodicity in this context not only requires that the system is stationary for these networks at the applicable spatial and temporal scales but also implies that they are in a state of metastable equilibrium one in which the ensemble averages can be substituted for temporal averages when studying their behavior in space and time in this work we show that this property can be used to identify those regions of parameter space which are stationary when applied to the seismicity of two naturally occurring earthquake fault networks we apply this measure to one particular seismicity based forecasting tool the pattern informatics index tiampoet al europhys lett 60 481 487 2002 rundleet al proc national acad sci u s a suppl 1 99 2463 2002 in order to test the hypothesis that the identification of ergodic regions can be used to improve and optimize forecasts that rely on historic seismicity catalogs we also apply the same measure to synthetic catalogs in order to better understand the physical process that affects this accuracy we show that in particular ergodic regions defined by magnitude and time period provide more reliable forecasts of future events in both natural and synthetic catalogs and that these improvements can be directly related to specific features or properties of the catalogs that impact the behavior of their spatial and temporal statistics

non critical precursory accelerating seismicity theory nc past and limits of the power law fit methodology abstract the hypothesis that accelerating moment release amr is a precursor to large earthquakes is still debated on one hand amr has been claimed to be observed in many cases and on the other hand it has been proposed that apparent amr is only due to data fitting the debate is in general focused on the validity of the c value curvature parameter which permits to quantify amr i e cumulative benioff strain through time or more generally precursory accelerating seismicity pas i e cumulative number of events through time contrary to previous studies which compare c value optimization in real seismicity catalogues and in random synthetic catalogues i test c value optimization in theoretical synthetic catalogues in that particular case i assume that pas exists and that it can be explained by the non critical precursory accelerating seismicity theory nc past this theory demonstrates that pas can emerge from the background seismicity because of the decrease due to loading of the size of a stress shadow due to a previous earthquake i improve the nc past by integrating the following characteristics of the background seismicity 1 the density of random events outside the stress shadow b0 and 2 the noise ratio b b0 with b being the density of random events inside the stress shadow then i perform a spatiotemporal search of pas using the power law fit methodology i e c value and compare the optimal signal to the expected spatiotemporal extent of the theoretical signal first i show that the optimal starting time and spatial extent of pas are poorly controlled due in part to the intrinsic properties of the c value but also to the random behavior of background seismicity second i show that theoretical pas is identified by an optimal c value clear acceleration only if the regional seismic activity b0 is high and the noise ratio b b0 is low otherwise the signal tends to disappear and the c value becomes unstable as a consequence even if the power law fit methodology is a simple approach to test the presence of pas and can help provide a better understanding of the process engaged it seems inadequate for robust systematic prospective forecasts

comment on relationship between accelerating seismicity and quiescence two precursors to large earthquakes by arnaud mignan and rita di giovambattista

fault interactions and large complex earthquakes in the los angeles area faults in complex tectonic environments interact in various ways including triggered rupture of one fault by another that may increase seismic hazard in the surrounding region we model static and dynamic fault interactions between the strike slip and thrust fault systems in southern california we find that rupture of the sierra madre cucamonga thrust fault system is unlikely to trigger rupture of the san andreas or san jacinto strike slip faults however a large northern san jacinto fault earthquake could trigger a cascading rupture of the sierra madre cucamonga system potentially causing a moment magnitude 7 5 to 7 8 earthquake on the edge of the los angeles metropolitan region

accelerating seismicity and stress accumulation before large earthquakes the stress field that existed before a large earth quake can be calculated based on the known source parame ters of the event this stress field can be used to define a region that shows greater seismic moment rate changes prior to the event than arbitrarily shaped regions allowing us to link two previously unrelated subjects coulomb stress interactions and accelerating seismicity before large earthquakes as an example we have examined all m 6 5 earthquakes in california since 1950 while we illustrate the model using seismicity in california the technique i s general and can be applied to any tectonically active re gion we show that where sufficient knowledge of the re gional tectonics exists this method can be used to aug ment current techniques for seismic hazard estimation

fractal dimension of fault systems in japan fractal structure in rock fracture geometry at various scales based on fault maps whether or not the fracture geometry of rocks is self similar was examined by using a box counting algorithm the statistical self similarity fractal structure of the fault fracture systems holds well at the scale of about 2 to 20 km the fractal dimension in japan varied from 1 05 to 1 60 the fractal dimension is about 1 5 1 6 at the central part of the japan arc and decreases with distance from the center at a smaller scale the fractal structure also holds well in the rock fracture geometry the fractal dimension of the north izu peninsula fault system branching faults is 1 49 at the scale of 0 625 to 10 km the fractal dimension of rock fracture geometry at the scale order of 10 1 to 10 2 meters is about 1 49 1 61 the upper limit of the fractal dimension of rock fracture geometry is about 1 6 judging from the estimation of fractal dimension on actual fracture geometry of rocks this value may impose a restraint on modeling of faulting and the fracture process of rocks

evolving towards a critical point a review of accelerating seismic moment energy release prior to large and great earthquakes there is growing evidence that some proportion of large and great earthquakes are preceded by a period of accelerating seismic activity of moderate sized earthquakes these moderate earthquakes occur during the years to decades prior to the occurrence of the large or great event and over a region larger than its rupture zone the size of the region in which these moderate earthquakes occur scales with the size of the ensuing mainshock at least in continental regions a number of numerical simulation studies of faults and fault systems also exhibit similar behavior the combined observational and simulation evidence suggests that the period of increased moment release in moderate earthquakes signals the establishment of long wavelength correlations in the regional stress field the central hypothesis in the critical point model for regional seismicity is that it is only during these time periods that a region of the earth s crust is truly in or near a self organized critical soc state such that small earthquakes are capable of cascading into much larger events the occurrence of a large or great earthquake appears to dissipate a sufficient proportion of the accumulated regional strain to destroy these long wavelength stress correlations and bring the region out of a soc state continued tectonic strain accumulation and stress transfer during smaller earthquakes eventually re establishes the long wavelength stress correlations that allow for the occurrence of larger events these increases in activity occur over longer periods and larger regions than quiescence which is usually observed within the rupture zone of a coming large event the two phenomena appear to have different physical bases and are not incompatible with one another

beyond laboratory scale prediction for channeling flows through subsurface rock fractures with heterogeneous aperture distributions revealed by laboratory evaluation the present study evaluates aperture distributions and fluid flow characteristics for variously sized laboratory scale granite fractures under confining stress as a significant result of the laboratory investigation the contact area in fracture plane was found to be virtually independent of scale by combining this characteristic with the self affine fractal nature of fracture surfaces a novel method for predicting fracture aperture distributions beyond laboratory scale is developed validity of this method is revealed through reproduction of the results of laboratory investigation and the maximum aperture fracture length relations which are reported in the literature for natural fractures the present study finally predicts conceivable scale dependencies of fluid flows through joints fractures without shear displacement and faults fractures with shear displacement both joint and fault aperture distributions are characterized by a scale independent contact area a scale dependent geometric mean and a scale independent geometric standard deviation of aperture the contact areas for joints and faults are approximately 60 and 40 changes in the geometric means of joint and fault apertures m em joint and em fault with fracture length m l are approximated by em joint 1 102 l0 1 and em fault 1 103 l0 7 whereas the geometric standard deviations of both joint and fault apertures are approximately 3 fluid flows through both joints and faults are characterized by formations of preferential flow paths i e channeling flows with scale independent flow areas of approximately 10 whereas the joint and fault permeabilities m2 kjoint and kfault are scale dependent and are approximated as kjoint 1 10 12 l0 2 and kfault 1 10 8 l1 1

testing the pattern informatics index on synthetic seismicity catalogs based on the non critical past abstract the non critical precursory accelerating seismicity theory or non critical past has recently been proposed to explain the formation of accelerating seismicity that may be observed before large earthquakes it has led to the possibility of constructing synthetic seismicity catalogs where patterns of accelerating seismicity activation and quiescence which occur in the same space time window can be evaluated by existing forecasting techniques in this study the pattern informatics or pi index is tested on synthetic catalogs where a realistic spatiotemporal clustering has been added on top of the theoretical precursory seismicity we show that the pi index is successful at identifying the precursory quiescent signal but fails in identifying precursory accelerating seismicity directly being more sensitive to aftershock sequences of background events than to the activation like behavior of the acceleration formed by background events alone we also show that the pi index has a high success rate in finding precursory quiescence even for a low signal to noise ratio as for the few false negatives they are usually due to interfering aftershocks as well which skew seismicity rates to higher means the non critical past by helping to better understand the behavior of the pi algorithm in synthetic catalogs gives new perspectives on how to improve it and on how to use it in real catalogs

relationship between accelerating seismicity and quiescence two precursors to large earthquakes 1 the non critical precursory accelerating seismicity theory past has been proposed recently to explain the formation of accelerating seismicity increase of the a value observed before large earthquakes in particular it predicts that precursory accelerating seismicity should occur in the same spatiotemporal window as quiescence in this first combined study we start by determining the spatiotemporal extent of quiescence observed prior to the 1997 mw 6 umbria marche earthquake italy using the rtl region time length algorithm we then show that background events located in that spatiotemporal window form a clear acceleration as expected by the non critical past this result is a step forward in the understanding of precursory seismicity by relating two of the principal patterns that can precede large earthquakes

anomalous seismicity and accelerating moment release preceding the 2001 and 2002 earthquakes in northern baja california mexico an algorithm recently developed by rundle et al 2002 to find regions of anomalous seismic activity associated with large earthquakes identified the location of an mw 5 6 earthquake near calexico mexico in this paper we analyze the regional seismicity before this event and a nearby mw 5 7 event using time to failure algorithms developed by bowman et al 1998 and bowman and king 2001a b the former finds the radius of a circular region surrounding the epicenter that optimizes the time to failure acceleration of seismic release the latter optimizes acceleration based on the expected stress accumulation pattern for a dislocation source both methods found a period of accelerating seismicity in an optimal region the size of which agrees with previously proposed scaling relations this positive result suggests that the rundle algorithm may provide a useful technique to identify regions of accelerating seismicity which can then be analyzed using signal optimization time to failure techniques

a mathematical formulation of accelerating moment release based on the stress accumulation model large earthquakes can be preceded by a period of accelerating seismic activity of moderate sized earthquakes this phenomenon usually termed accelerating moment release has yet to be clearly understood a new mathematical formulation of accelerating moment release is obtained from simple stress transfer considerations following the recently proposed stress accumulation model this model based on the concept of elastic rebound simulates accelerating seismicity from theoretical stress changes during an idealized seismic cycle in this view accelerating moment release is simply the consequence of the decrease due to loading of the size of a stress shadow due to a previous earthquake we show that a power law time to failure equation can be expressed as a function of the loading rate on the fault that is going to rupture we also show that the m value which is the power law exponent can be defined as m d 3 with d a parameter that takes into account the geometrical shape of the stress lobes and the distribution of active faults in the stress accumulation model the power law is not due to critical processes

pattern dynamics and forecast methods in seismically active regions large extended fault systems such as those in california demonstrate complex space time seismicity patterns which include repetitive events precursory activity and quiescence and aftershock sequences although the characteristics of these patterns can be qualitatively described a systematic quantitative analysis remains elusive our research suggests that a new pattern dynamics methodology can be used to define a unique finite set of seismicity patterns for a given fault system in addition while a long sought goal of earthquake research has been the reliable forecasting of these events very little progress has been made in developing a successful consistent methodology in this report we document the discovery of systematic space time variations in seismicity from southern california using a new technique here we present examples of this analysis technique on data obtained prior to events in seismically active areas that show coherent regions associated with the future occurrence of major earthquakes in the same areas these results strongly support the hypothesis that seismic activity is highly correlated across many space and time scales within large volumes of the earth s crust

growth of correlated pore scale structures in sedimentary rocks a dynamical model this report explores statistical models and geochemical observations to determine new insights into the formation of sedimentary rock

nonlinear dynamic rupture inversion of the 2000 western tottori japan earthquake 1 we have developed a systematic nonlinear inversion method for estimating rupture propagation and the underlying dynamic parameters for large historical earthquakes the rupture modeling is carried out using a three dimensional finite difference method and the inversion is implemented by a neighbourhood algorithm minimizing the misfit between computed and observed near fault seismograms we test the method by estimating the stress drop within 32 regions on the causative fault for the 2000 magnitude 6 6 western tottori japan earthquake while the dynamic models show both similarities and differences with the conventional kinematic models our method provides an ensemble of physically correct models with plausible rupture propagation for the earthquake

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

a seismic quiescence before the 2017 mw 7 3 sarpol zahab iran earthquake detection and analysis by improved rtl method abstract a major earthquake with magnitude mw 7 3 struck sarpol zahab kermanshah province iran on november 12 2017 causing extended damage and casualties the epicenter was located in the northwestern part of the zagros mountain range an active belt originated by the arabia eurasia collision we explore seismicity preceding this earthquake by using the iranian seismological center instrumental earthquake catalog igtu with the aim to identify possible anomalies in background seismicity that can be related with this and other future large events for this purpose we used a method for intermediate term forecasts of large earthquakes namely the region time length rtl algorithm which analyzes declustered catalogs and is sensitive to quiescences that may precede major earthquakes rtl has been progressively refined and has been applied in several regions worldwide during the last decades to decluster the earthquake catalog we used a quite novel approach based on the nearest neigbour distances between events in the space time energy domain a method that preserves the background seismicity while removing the clustered component the retrospective application of rtl algorithm to the area surrounding the mainshock epicenter highlights two significant quiescences one preceding the sarpol zahab mw 7 3 earthquake and the other occurring before a mw 5 7 earthquake which struck the same region on november 2013 the quiescences duration ranges from few months to one year and is compatible with earlier results from different regions of the world in addition we applied an enhanced variant of rtl algorithm which allows us drawing maps for the whole study region and that shows only quiescences consistently detected for different choices of the free parameters and hence more stable the resulting map for northwestern iran calculated for the time span 1 june 2017 11 november 2017 evidences two broad quiescence regions oriented nw se along the zagros belt one located to the north evidences a significant seismic anomaly corresponding to the sarpol zahab earthquake which disappeares immediately after the event the second one located in the southeastern part of the study region persists up to the end of the available catalog october 4 2018

seismic imaging of the 1999 izmit turkey rupture inferred from the near fault recordings we use near fault accelerograms to infer the space time history of rupture on the fault during the izmit earthquake the records show that the ground displacement and velocity near the fault were surprisingly simple rupture propagated toward the west at a velocity of about 3 km s and toward the east at a remarkably high average velocity of 4 7 km s over a distance of about 45 km before decelerating to about 3 1 km s on the eastern segment slip on the fault is particularly large down to a depth of 20 km on the central portion of the fault where it reaches about 7 m slip is large also below 10 km on the eastern fault segment and this may have contributed to the loading of shear stress on the duzce fault on the western fault segment large slip seems confined to shallow depths

euclidean and fractal models for the description of rock surface roughness accurate description of the topography of rock surfaces is essential because surface roughness affects frictional strength the flow of fluids in joints and fractures the seismic behavior of faults and the formation of gouge and breccia in fault zones real rock surfaces can be described using self similar and self affine fractal models of surface roughness if a surface is self similar a small portion of the surface when magnified isotropically will appear statistically identical to the entire surface if a surface is self affine a magnified portion of the surface will only appear statistically identical to the entire surface if different magnifications are used for the directions parallel and perpendicular to the surface at least two parameters are required to describe a fractal model one parameter typically describes how roughness changes with scale while the other specifies the variance or surface slope at a reference scale the divider method and the spectral method are in common use to determine the best fit fractal model from surface profile data power spectra from self similar surfaces have slopes of 3 on log log plots of power spectral density versus spatial frequency while spectra from self affine surfaces have slopes other than 3 power spectra can be interpreted with greater facility if dimensionless amplitude to wavelength ratios are contoured on plots of power spectral density versus frequency the topography of many natural rock surfaces including both fractures and faults is approximately self similar within the 6 5 order of magnitude wide wavelength band of 10 m to 40 m within smaller wavelength bands natural rock surfaces may exhibit self affine behavior

the contact between opposing fault surfaces at dixie valley nevada and implications for fault mechanics well exposed normal fault surfaces from dixie valley nevada provide a unique opportunity to study the contact properties of fault surfaces because it is possible to examine both the hanging wall and footwall surfaces of a fault zone which was once seismically active the topography of the individual surfaces as well as the aperture or gap between the two surfaces was measured using surface profiling instruments and a resin replication technique these measurements enable frictional parameters of the surfaces most notably the characteristic decay distance dc to be calculated using contact theory although the individual surfaces are approximately self similar and fractal the aperture between the opposing surfaces is a stationary quantity because the surfaces are well correlated at dimensions larger than approximately 2 mm consequently contact theory can be used to calculate an average size for contact spots between the surfaces and by inference a characteristic decay distance dc for frictional slip between the surfaces direct inspection of resin replicas of the aperture allows an independent estimate of average contact spot size both approaches give contact spot diameters of 0 16 mm and dc of 0 01 0 1 mm because the individual surfaces of the fault are fractal and approximately self similar correlation between the surfaces should decrease significantly during slip events particularly if slip rates are high seismic events decreased correlation between the surfaces should lead to larger contact spot sizes and hence larger dc thus critical slip distances for natural faults should evolve concurrently with seismic fault slip

hydrologic mechanisms governing fluid flow in a partially saturated fractured porous medium in contrast to the saturated zone within which fluid moves rapidly along fractures the fractures with apertures large relative to the size of matrix pores will desaturate first during the drainage process and the bulk of fluid flow would be through interconnected pores in the matrix within a partially drained fracture the presence of a relatively continuous air phase will produce practically an infinite resistance to liquid flow in the direction parallel to the fracture the residual liquid will be held by capillary force in regions around fracture contact areas where the apertures are small normal to the fracture surfaces the drained portion of the fractures will reduce the effective area for liquid flow from one matrix block to another matrix block a general statistical theory is constructed for flow along the fracture and for flow between the matrix blocks to the fractures under partially saturated conditions results are obtained from an aperture distribution model for fracture saturation hydraulic conductivity and effective matrix fracture flow areas as functions of pressure the effects of distortion of flow paths by the air pockets are taken into account by a phase separation constriction factor in a generalized cubic law for fracture flow under a partially saturated condition the reduction of matrix fracture flow area is taken into account by summing the aperture distribution function to a saturation cutoff aperture which is inversely proportional to the suction head drainage from a column of fractured tuff is simulated using available parameters for the densely welded tuff of the topopah spring member at yucca mountain southern nevada the column is bounded by discrete vertical fractures and dissected by horizontal fractures with the fracture spacings determined by the frequencies and orientations of fractured cores the fraction of fracture surfaces with coatings is assumed to correspond to the fraction of in situ fracture contact area the characteristic curves for the matrix are based on laboratory measurements of tuff samples from the cases simulated for the fractured porous columns with discrete vertical and horizontal fractures and porous matrix blocks explicitly taken into account it is observed that the highly transient changes from fully saturated conditions to partially saturated conditions are extremely sensitive to the fracture properties however the quasi steady changes of the fluid flow of a partially saturated fractured porous system could be approximately simulated without taking the fractures into account

emergence of anomalous transport in stressed rough fractures abstract we report the emergence of anomalous non fickian transport through a rough walled fracture as a result of increasing normal stress on the fracture we show that the origin of this anomalous transport behavior can be traced to the emergence of a heterogeneous flow field dominated by preferential channels and stagnation zones as a result of the larger number of contacts in a highly stressed fracture we show that the velocity distribution determines the late time scaling of particle spreading and velocity correlation determines the magnitude of spreading and the transition time from the initial ballistic regime to the asymptotic anomalous behavior we also propose a spatial markov model that reproduces the transport behavior at the scale of the entire fracture with only three physical parameters our results point to a heretofore unrecognized link between geomechanics and particle transport in fractured media

seismicity based earthquake forecasting techniques ten years of progress abstract earthquake fault systems interact over a broad spectrum of spatial and temporal scales and in recent years studies of the regional seismicity in a variety of regions have produced a number of new techniques for seismicity based earthquake forecasting while a wide variety of physical assumptions and statistical approaches are incorporated into the various methodologies they all endeavor to accurately replicate the statistics and properties of both the historic and instrumental seismic records as a result the last ten years have seen significant progress in the field of intermediate and short term seismicity based earthquake forecasting these include general agreement on the need for prospective testing and successful attempts to standardize both evaluation methods and the appropriate null hypotheses here we differentiate the predominant approaches into models based upon techniques for identifying particular physical processes and those that filter or smooth the seismicity comparison of the methods suggests that while smoothed seismicity models provide improved forecast capability over longer time periods higher probability gain over shorter time periods is achieved with methods that integrate statistical techniques with our knowledge of the physical process such as the epidemic type aftershock sequence etas model or those related to changes in the b value for example in general while both classes of seismicity based forecasts are limited by the relatively short time period available for the instrumental catalog significant advances have been made in our understanding of both the limitations and potential of seismicity based earthquake forecasting there is general agreement that both short term forecasting on the order of days to weeks and longer term forecasting over five to ten year periods is within reach this recent progress serves to illuminate both the critical nature of the different temporal scales intrinsic to the earthquake process and the importance of high quality seismic data for the accurate quantification of time dependent earthquake hazard

fault steps and the dynamic rupture process 2 d numerical simulations of a spontaneously propagating shear fracture fault steps may have controlled the sizes of the 1966 parkfield 1968 borrego mountain 1979 imperial valley 1979 coyote lake and the 1987 superstition hills earthquakes this project investigates the effect of fault steps of various geometries on the dynamic rupture process we have used a finite difference code to simulate spontaneous rupture propagation in two dimensions we employ a slip weakening fracture criterion as the condition for rupture propagation and examine how rupture on one plane initiates rupture on parallel fault planes the geometry of the two parallel fault planes allows for stepover widths of 0 5 to 10 0 km and overlaps of 5 to 5 km our results demonstrate that the spontaneous rupture on the first fault segment continues to propagate onto the second fault segment for a range of geometries for both compressional and dilational fault steps a major difference between the compressional and dilational cases is that a dilational step requires a longer time delay between the rupture front reaching the end of the first fault segment and initiating rupture on the second segment therefore our dynamic study implies that a compressional step will be jumped quickly whereas a dilational step will cause a time delay leading to a lower apparent rupture velocity we also find that the rupture is capable of jumping a wider dilational step than compressional step

on the nature and dynamics of the seismogenetic systems of north california usa an analysis based on non extensive statistical physics abstract we examine the nature of the seismogenetic system in north california usa by searching for evidence of complexity and non extensivity in the earthquake record we attempt to determine whether earthquakes are generated by a self excited poisson process in which case they obey boltzmann gibbs thermodynamics or by a critical process in which long range interactions in non equilibrium states are expected correlation and the thermodynamics deviate from the boltzmann gibbs formalism emphasis is given to background seismicity since it is generally agreed that aftershock sequences comprise correlated sets we use the complete and homogeneous earthquake catalogue published by the north california earthquake data centre in which aftershocks are either included or have been removed by a stochastic declustering procedure we examine multivariate cumulative frequency distributions of earthquake magnitudes interevent time and interevent distance in the context of non extensive statistical physics which is a generalization of extensive boltzmann gibbs thermodynamics to non equilibrating non extensive systems our results indicate that the seismogenetic systems of north california are generally sub extensive complex and non poissonian the background seismicity exhibits long range interaction as evidenced by the overall increase of correlation observed by declustering the earthquake catalogues as well as by the high correlation observed for earthquakes separated by long interevent distances it is also important to emphasize that two subsystems with rather different properties appear to exist the correlation observed along the sierra nevada range walker lane is quasi stationary and indicates a self organized critical fault system conversely the north segment of the san andreas fault exhibits changes in the level of correlation with reference to the large loma prieta event of 1989 and thus has attributes of critical point behaviour albeit without acceleration of seismic release rates soc appears to be a likely explanation of complexity mechanisms but since there are other ways by which complexity may emerge additional work is required before assertive conclusions can be drawn

a dislocation model of strain accumulation and release at a subduction zone strain accumulation and release at a subduction zone are attributed to stick slip on the main thrust zone and steady aseismic slip on the remainder of the plate interface this process can be described as a superposition of steady state subduction and a repetitive cycle of slip on the main thrust zone consisting of steady normal slip at the plate convergence rate plus occasional thrust events that recover the accumulated normal slip because steady state subduction does not contribute to the deformation at the free surface deformation observed there is completely equivalent to that produced by the slip cycle alone the response to that slip is simply the response of a particular earth model to embedded dislocations for a purely elastic earth model the deformation cycle consists of a coseismic offset followed by a linear in time recovery to the initial value during the interval between earthquakes for an elastic viscoelastic earth model elastic lithosphere over a viscoelastic asthenosphere the postearthquake recovery is not linear in time records of local uplift as a function of time indicate that the long term postseimic recovery is approximately linear suggesting that elastic earth models are adequate to describe the deformation cycle however the deformation predicted for amore simple elastic half space earth does not reproduce the deformation observed along the subduction zones in japna at all well if stick slip is restricted to the main thrust zone as recognized earlier by shimazaki seno and kato the uplift profiles could be explained if stick slips were postulated to extend along the plate interface beyond the main thrust zone to a depth of perhaps 100 km but independent evidence suggests that stick slip at such depths if unlikely less

fracture aperture reconstruction and determination of hydrological properties a case study at draix french alps we propose two techniques for fracture aperture reconstruction the first one is a correlation technique that estimates the normal aperture or the tangential shift across a discontinuity whose sides present geometrical similarities the only required material is a pair of appropriately controlled images of each side here the images are maps of the corresponding side topography obtained from laser profilometry assuming a purely normal opening it is possible from two corresponding sides of a given discontinuity in a core log to infer the precise geometry of the in situ aperture the second technique allows to retrieve the three dimensional geometry of a sealed discontinuity from non independent topography measurements of both sides both techniques are applied to discontinuities extracted from a core drilled down to 20 m in a fractured marl formation at draix french alps the probability density functions of the aperture of the sealed and open discontinuities are shown to be gaussian at the sample scale the sealed fracture aperture is self affine while the open one shows a cross over from a self affine regime at very small scales to an uncorrelated regime at largest scales after extrapolating those scaling laws at the scale of the whole formation we discuss when the aperture roughness affects the hydraulic properties of the draix fractured bedrock the overall estimated permeability is significant 10 9 10 8 m2 consistently with some previous indirect inferences copyright 2011 john wiley sons ltd

flow enhancement of a rough fracture we study experimentally and numerically the permeability of a rough fracture at laboratory scale when viscous forces are dominating low reynolds number the experimental setup includes a granite fracture surface 10 10 cm opened in mode i it allows a continuous opening of the fracture parallel to its mean plane the fracture roughness is measured and characterized in terms of self affine heterogeneities its isotropy is checked the departure from the cubic law is measured as a function of the aperture opening for mean separations between 4 0 and 10 3 mm and the pressure drop orientation by rotating the fracture by 90 degrees a strongly anisotropic hydraulic behavior is observed and results from the geometrical heterogeneities that exist up to the fracture macro scale

intermediate term earthquake prediction using precursory events in the new madrid seismic zone abstract earthquake prediction may be possible for some mainshock events the time to failure method described by varnes 1989 and bufe and varnes 1990 uses precursory events foreshocks to define an accelerated energy release curve by fitting an equation to the data a predicted time of failure and magnitude can be calculated until recently this method has been used in only a few studies in tectonically active areas and for moderate to large magnitude mainshock events using the microearthquake network data set from the new madrid seismic zone nmsz which is reasonably complete for earthquakes of magnitude 1 5 in the area of interest the method has yielded predicted values of past events as small as m b 3 5 the network data set used in this evaluation covers the time interval from 29 june 1974 to 20 july 1995 for the nmsz there have been 36 earthquakes of magnitude 3 5 over the 21 yr period in which the network has been operating because precursory events are required for the application of the time to failure method mainshocks that occurred before 1980 do not have enough data to adequately define the accelerated energy release curve therefore we utilized the 26 earthquakes that occurred after 1980 and that had a magnitude 3 5 sixteen of the 26 mainshock events were modeled in most cases the precursory sequences yielded predicted times of failure and magnitudes that were reasonably close to the actual mainshock values the remaining mainshocks including those occurring before 1980 could not be modeled due to either 1 not enough events to adequately define the precursory sequence or 2 interfering events that disrupt the accelerated energy release curve in addition two events were modeled from the nuttli catalog nuttli 1979 along with one that used a combination of both catalogs nineteen earthquakes with magnitudes 3 5 were evaluated using the time to failure method the first calculation using the time to failure method gave predicted results with large error bounds essentially no upper bound on the predicted magnitude an empirical relationship between parameters has helped to constrain the range of the predicted magnitude and to a lesser extent the estimated time of failure this relationship modifies the time to failure equation and yields predicted values for magnitudes that have an upper limit another empirical relationship suggests that the logarithm of the moment of the mainshock increases linearly with the logarithm of the size of the precursory event search diameter the relative seismicity of the region also influences the optimum search diameter used to find precursory events in addition to the evaluation of the acceleration sequences associated with the mainshocks an analysis of the occurrence of false positive acceleration sequences acceleration sequences that do not end in a mainshock was conducted the preliminary false positive analysis was conducted by randomly selecting potential mainshock locations the results yielded a false positive acceleration sequence occurrence rate of 2 with the incorporation of the empirical relationships into the time to failure method the potential for future intermediate term earthquake predictions for the nmsz is encouraging

discrete characteristics of the aftershock sequence of the 2011 van earthquake an intraplate earthquake of magnitude mw 7 2 occurred on a ne sw trending blind oblique thrust fault in accretionary orogen the van region of eastern anatolia on october 23 2011 the aftershock seismicity in the van earthquake was not continuous but rather highly discrete this shed light on the chaotic nonuniformity of the event distribution and played key roles in determining the seismic coupling between the rupturing process and seismogeneity i analyzed the discrete statistical mechanics of the 2011 van mainshock aftershock sequence with an estimation of the non dimensional tuning parameters consisting of temporal clusters c and the random rn distribution of aftershocks range of size scales ross strength change ed temperature t p value of temporal decay material parameter r value seismic coupling and q value of aftershock distribution i also investigated the frequency size fs temporal t statistics and the sequential characteristics of aftershock dynamics using discrete approach and examined the discrete evolutionary periods of the van earthquake gutenberg richter gr distribution my study revealed that the fs and t statistical properties of aftershock sequence represent the gutenberg richter gr distribution clustered c in time and random rn poisson distribution respectively the overall statistical behavior of the aftershock sequence shows that the van earthquake originated in a discrete structural framework with high seismic coupling under highly variable faulting conditions my analyses relate this larger dip slip event to a discrete seismogenesis with two main components of complex fracturing and branching framework of the ruptured fault and dynamic strengthening and hardening behavior of the earthquake the results indicate two dynamic cases the first is associated with aperiodic nature of aftershock distribution indicating a time independent poissonian event the second is associated with variable slip model varying loading rates and high seismic coupling along the ruptured area this study concludes that the aperiodic statistical behavior of the van aftershock sequence is one of the results of the time independent poissonian seismic deformation in the 2011 van earthquake

predictive modeling of the seismic cycle of the greater san francisco bay region the seismic cycle for the san francisco bay region is synthesized by a model combining the pre and post 1906 seismic histories the long term acceleration of seismic release seismic moment benioff strain release or event count in the seismic cycle and the shorter term accelerations preceding the larger earthquakes within that cycle are modeled using an empirical predictive technique called time to failure analysis in which rate of seismic release is proportional to an inverse power of the remaining time to failure the exponent of time to failure in the accelerating sequences appears to be scale invariant and the length of the full cycle is estimated at 269 50 years the 1989 loma prieta earthquake which is the culmination of the first subcycle in the present long term seismic cycle should have been predictable with an uncertainty of 2 years in time and 0 5 in magnitude although the specific location at loma prieta was not predictable by this technique if our model is correct and if the loma prieta earthquake is the culmination of a subcycle the san francisco bay region should be entering a relatively long 20 50 years period of seismic quiescence above magnitude 6 a great earthquake such as the 1906 san francisco event would appear to be more than a century in the future

influence of fracture scale heterogeneity on the flow properties of three dimensional discrete fracture networks dfn while permeability scaling of fractured media has been so far studied independently at the fracture and network scales we propose a numerical analysis of the combined effect of fracture scale heterogeneities and the network scale topology the analysis is based on 2 106 discrete fracture network dfns simulations performed with highly robust numerical methods fracture local apertures are distributed according to a truncated gaussian law and exhibit self affine spatial correlations up to a cutoff scale lc network structures range widely over sparse and dense systems of short long or widely distributed fracture sizes and display a large variety of fracture interconnections flow bottlenecks and dead ends at the fracture scale accounting for aperture heterogeneities leads to a reduction of the equivalent fracture transmissivity of up to a factor of 6 as compared to the parallel plate of identical mean aperture at the network scale a significant coupling is observed in most cases between flow heterogeneities at the fracture and at the network scale the upscaling from the fracture to the network scale modifies the impact of fracture roughness on the measured permeability this change can be quantified by the measure a2 which is analogous to the more classical power averaging exponent used with heterogeneous porous media and whose magnitude results from the competition of two effects i the permeability is enhanced by the highly transmissive zones within the fractures that can bridge fracture intersections within a fracture plane ii it is reduced by the closed and low transmissive areas that break up connectivity and flow paths citation de dreuzy j r y meheust and g pichot 2012 influence of fracture scale heterogeneity

seismic activity in the sumatra java region prior to the december 26 2004 mw 9 0 9 3 and march 28 2005 mw 8 7 earthquakes a promising approach to assessing seismic hazards has been to combine the concept of seismic gaps with coulomb stress change modeling to refine short term earthquake probability estimates however in practice the large uncertainties in the seismic histories of most tectonically active regions limit this approach since a stress increase is only important when a fault is already close to failure in contrast recent work has suggested that accelerated moment release amr can help to identify when a stretch of fault is approaching failure without any knowledge of the seismic history of the region amr can be identified in the regions around the sumatra subduction system that must have been stressed before the 26 december 2004 and 28 march 2005 earthquakes the effect is clearest for the epicentral regions with less than a 2 probability that it could occur in a random catalogue less clear amr is associated with the regions north of sumatra around the nicobar and andaman islands where rupture in the december 2004 earthquake was less vigorous no amr is found for the region of the 1833 sumatran earthquake suggesting that an event in this region in the near future is unlikely amr similar to that before the december 2004 and march 2005 events is found for a 750 km stretch of the southeastern sumatra and western java subduction system suggesting that it is close to failure should the whole of this stretch break in a single event the magnitude could be similar to the december 2004 earthquake

simple mathematical model of a rough fracture a simple mathematical model of rough walled fractures in rock is described which requires the specification of only three main parameters the fractal dimension the rms roughness at a reference length scale and a length scale describing the degree of mismatch between the two fracture surfaces fractured samples collected from natural joints and laboratory specimens have been profiled to determine the range of these three parameters in nature it is shown how this surface roughness model can be implemented on a computer allowing future detailed study of the mechanical and transport properties of single fractures and the scale dependence of these properties

evidence for a supershear transient during the 2002 denali fault earthquake elastodynamic considerations suggest that the acceleration of ruptures to supershear velocities is accompanied by the release of rayleigh waves along the fault from the stress breakdown zone these waves generate a secondary slip pulse trailing the rupture front but manifest almost entirely in ground motion perpendicular to the fault in the near source region we construct a spontaneously propagating rupture model exhibiting these features and use it to explain ground motions recorded during the 2002 denali fault earthquake at pump station 10 located 3 km from the fault we show that the initial pulses on both the fault normal and fault parallel components are due to the supershear stress release on the fault whereas the later arriving fault normal pulses result from the trailing subshear slip pulse on the fault online material mpeg movies of rupture history and ground motion

synthetic rough fractures in rocks natural fractures serve a very important function in the transport of fluid through rocks as well as in the flow of electrical charge and heat the creation of numerically synthesized fractures can aid the study of the physical processes connected with fractures synthetic fracture is the term used to describe fractures that are created numerically in such a way that they share the same mean geometrical characteristics as specific natural fractures measured by profiling by a process known as tuning we have modified methods for producing synthetic rough surfaces whose geometric properties are tuned to mimic natural fracture surfaces in rocks in order to create synthetic fractures that are statistically identical to those found in rocks one important such modification has been the incorporation of a method that allows the surfaces to be matched at long wavelengths and unmatched at short wavelengths with the degree of matching varying smoothly in between as it does for real fractures we have compared numerically synthetic fractures created using the new method with fractures created using an existing technique that uses a mismatch wavelength as a sudden discontinuity between matched and unmatched behavior as well as data from fractures in real rocks this comparison has shown that the new technique provides much more realistic numerically synthesized fractures than previous methods synthetic fractures created with the new method have been used in normal closure and fluid flow modeling and the results are reported in a companion paper