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

test of the predictability of the pi method for recent large earthquakes in and near tibetan plateau five large earthquakes of m 7 0 based on the magnitude scale of the china earthquake networks center occurred in and near the tibetan plateau during 2008 2014 including the wenchuan m8 0 earthquake on may 12 2008 bjt in this paper the tibetan plateau was chosen to be the study region and calculating parameters of pattern informatics pi method with grid of 1 1 and forecasting time interval of 8 years were employed for the retrospective study according to the previous studies for m7 earthquake forecasting the sliding step of forecasting interval was 1 year and the hotspot diagrams of each forecasting interval since 2008 were obtained year by year the relationships among the hotspots and the m 7 0 earthquakes that occurred during the forecast intervals were studied the predictability of pi method was tested by verification of receiveroperating characteristic curve roc and r score the results show that the successive obvious hotspots occurred during the sliding forecasting intervals before four of the five earthquakes while hotspots only occurred in one forecasted interval without successive evolution process before one of the five earthquakes which indicates that four of the five large earthquakes could be forecasted well by pi method test results of the predictability of pi method by roc and r score show that positive prospect of pi method could be expected for long term earthquake forecast

a review of earthquake statistics fault and seismicity based models etas and bass there are two fundamentally different approaches to assessing the probabilistic risk of earthquake occurrence the first is fault based the statistical occurrence of earthquakes is determined for mapped faults the applicable models are renewal models in that a tectonic loading of faults is included the second approach is seismicity based the risk of future earthquakes is based on the past seismicity in the region these are also known as cluster models an example of a cluster model is the epidemic type aftershock sequence etas model in this paper we discuss an alternative branching aftershock sequence bass model in the bass model an initial or seed earthquake is specified the subsequent earthquakes are obtained from statistical distributions of magnitude time and location the magnitude scaling is based on a combination of the gutenberg richter scaling relation and the modified bath s law for the scaling relation of aftershock magnitudes relative to the magnitude of the main earthquake omori s law specifies the distribution of earthquake times and a modified form of omori s law specifies the distribution of earthquake locations unlike the etas model the bass model is fully self similar and is not sensitive to the low magnitude cutoff

seismic activity on neighbouring faults as a long term precursor to large earthquakes in the san francisco bay area activity in moderate size earthquakes accelerated in the several decades before the large california earthquakes of 1989 1906 and 1868 this type of precursor seems to require the presence of several major faults in close enough proximity to one another that moderate size shocks are selectively triggered on surrounding faults during the latter stages of the cycle of strain buildup to large earthquakes it may be possible to use quantitative aspects of similar seismic precursors to make predictions of large earthquakes on timescales of a few years to one decade

application of pattern recognition techniques to earthquake catalogs generated by model of segmented fault systems in three dimensional elastic solids techniques and seismicity parameters described by eneva and ben zion 1997 are used to examine synthetic earthquake catalogs generated by ben zion 1996 for precursory patterns of large model events different model realizations represent various levels of fault zone disorder these include models with uniform properties u a parkfield type asperity a fractal brittle properties f and multi size scale heterogeneities m the seismicity parameters used are based on information contained in typical earthquake catalogs reflecting earthquake distribution in space time and size the analysis highlights the complexity of the information content of the synthetic earthquake catalogs simple repetitive precursory signals have not been found however local extrema in the examined parameters are found to have significant association in time with large events thus our techniques and parameters may be useful for intermediate term earthquake prediction especially when parameters are used in combinations some analysis results are the same for all model realizations and some depend on the model features characterizing all catalogs are as follows 1 large model events are statistically predictable on the basis of patterns in the distribution of smaller events 2 for a given parameter the type of precursory extrema maxima or minima is the same for all models 3 the interparameter correlation for any parameter pair has the same sign positive or negative in all models 4 the large events are neither slip nor time predictable based on previous large events results that differ from model to model include the following 1 the degree of predictability of large events correlates with the degree of regularity in the assumed fault properties following the order u f a and m 2 there is no one to one correlation between type of precursory extrema maxima or minima and type of precursory trends increase or decrease this produces great variations in observable trends for any given parameter both from model to model and for different events in the same model 3 the interparameter correlations vary among models with the highest correlations in model f most discussed patterns are in agreement with observations from seismically active zones laboratory models and mining induced seismicity

patterns of seismic activity preceding large earthquakes we analyze the patterns of seismic activity which precede large events in a mechanical model of a fault the model generates a statistical distribution of events similar to that observed for a single fault with a scaling region consistent with the gutenberg richter law at small and moderate magnitudes and an excess of events at large magnitudes we find only slight variation in the scaling behavior during a loading cycle however we do observe systematic variations in space and time of the overall rate of activity in the model the activity accelerates dramatically preceding a large event and is usually a maximum hi the neighborhood of the future epicenter these results are compared to california seismicity data where we find that activity patterns vary regionally looking at patterns of activity in the san francisco bay area since 1948 we find an increase of activity on the calaveras fault near san jose beginning in the 1980s which if our model is relevant would forecast a large earthquake in that region the 1989 loma prieta earthquake occurred on the san andreas fault within 30 km of the section of the calaveras fault showing increased activity

temporal changes in the cumulative piecewise gradient of a variant of the gutenberg richter relationship and the imminence of extreme events abstract it is generally found that the relative frequencies of occurrence of earthquakes of different magnitudes in seismogenic zones have a power law distribution for a long term dataset the overall slope of this logarithmically transformed distribution is usually indicated by a best fit straight line and expressed as a b value this slope is stable and normally lies between 0 8 and 1 2 the actual value depending on the region examined and the threshold selected for data completeness the linearity of the distribution can be used to make statistical inferences about the potential for larger events over the long run and with appropriate reservations may even be extrapolated to magnitudes that are beyond recent experience we suggest the same information can also be viewed over shorter intervals in terms of an empirical piecewise distribution with relative frequencies of occurrence at adjacent magnitude steps controlling the local slope of the distribution an emergence through time of an excess number of lower magnitude earthquakes causes temporal changes to appear in the low end piecewise gradients of this distribution a marked excursion away from an overall uniform trend for the particular zone may be indicative of an imminent larger event on two separate occasions in 1982 and 1997 such temporal variations were seen in the magnitude distributions of sequences of events near tobago west indies and used to anticipate subsequent damaging mainshocks the recognition of temporal departures from overall linearity of the magnitude frequency relation in a suitable dataset may thus provide an evidential element that can contribute to earthquake forecasting this phenomenological approach was used in the analysis of the neic global dataset of earthquakes of magnitude 6 1 and bigger for the period 1973 2003 to explore its wider applicability trends in the piecewise gradients of the global data were interpreted as pointing to an imminent great earthquake perhaps exceeding magnitude 8 5 such an event did occur shortly afterwards in the form of the great sumatran earthquake of 2004 12 26 following that event global magnitude production continued to exhibit sharp imbalances in the lower magnitude bins indicating that another similar event was likely the second sumatran earthquake on 2005 03 28 satisfied that projection since that time a magnitude production imbalance persists in the global dataset suggesting the system could be poised to output an earthquake or earthquakes in the magnitude range 8 6 9 0 or even greater this contribution describes the piecewise gradient approach and examines its application to global earthquake data

increasing critical sensitivity of the load unload response ratio before large earthquakes with identified stress accumulation pattern the load unload response ratio lurr method is proposed for short to intermediate term earthquake prediction yin x c chen x z song z p yin c 1995 a new approach to earthquake prediction the load unload response ratio lurr theory pure appl geophys 145 701 715 this method is based on measuring the ratio between benioff strains released during the time periods of loading and unloading corresponding to the coulomb failure stress change induced by earth tides on optimally oriented faults according to the method the lurr time series usually climb to an anomalously high peak prior to occurrence of a large earthquake previous studies have indicated that the size of critical seismogenic region selected for lurr measurements has great influence on the evaluation of lurr in this study we replace the circular region usually adopted in lurr practice with an area within which the tectonic stress change would mostly affect the coulomb stress on a potential seismogenic fault of a future event the coulomb stress change before a hypothetical earthquake is calculated based on a simple back slip dislocation model of the event this new algorithm by combining the lurr method with our choice of identified area with increased coulomb stress is devised to improve the sensitivity of lurr to measure criticality of stress accumulation before a large earthquake retrospective tests of this algorithm on four large earthquakes occurred in california over the last two decades show remarkable enhancement of the lurr precursory anomalies for some strong events of lesser magnitudes occurred in the same neighborhoods and during the same time periods significant anomalies are found if circular areas are used and are not found if increased coulomb stress areas are used for lurr data selection the unique feature of this algorithm may provide stronger constraints on forecasts of the size and location of future large events

an observational test of the stress accumulation model based on seismicity preceding the 1992 landers ca earthquake abstract we test the bowman and king bowman d d king g c p 2001a accelerating seismicity and stress accumulation before large earthquakes geophys res lett 28 21 4039 4042 bowman d d king g c p 2001b stress transfer and seismicity changes before large earthquakes c r acad sci paris 333 591 599 stress accumulation model by examining the evolution of seismicity rates prior to the 1992 landers california earthquake the stress accumulation sa model was developed to explain observations of accelerating seismicity preceding large earthquakes the model proposes that accelerating seismicity sequences result from the tectonic loading of large fault structures through aseismic slip in the elasto plastic lower crust this loading progressively increases the stress on smaller faults within a critical region around the main structure thereby causing the observed acceleration of precursory activity a secondary prediction of the sa model is that the precursory seismicity rates should increase first at the edges of the critical region with the rates gradually rising over time at closer distances to the main fault we test this prediction by examining year long seismicity rates between 1960 and 2004 as a function of distance from the landers rupture to quantify the significance of trends in the seismicity rates we auto correlate the data using a range of spatial and temporal lags we find weak evidence for increased seismicity rates propagating towards the landers rupture but cannot conclusively distinguish these results from those obtained for a random earthquake catalog however we find a strong indication of periodicity in the rate fluctuations as well as high correlation between activity 130 170 km from landers and seismicity rates within 50 km of the landers rupture temporally offset 1 5 2 years the implications of this spatio temporal correlation will be addressed in future studies

late holocene slip rate and recurrence of great earthquakes on the san andreas fault in northern california the slip rate of the san andreas fault 45 km north of san francisco at olema california is determined by matching offset segments of a buried late holocene stream channel stream deposits from 1 800 plus minus 78 yr b p are offset 42 5 plus minus 3 5 m across the active 1906 fault trace for a minimum late holocene slip rate of 24 plus minus 3 mm yr when local maximum coseismic displacements of 4 9 to 5 5 m from the 1906 earthquake are considered with this slip rate the recurrence of 1906 type earthquakes on the north coast segment of the san andreas fault falls within the interval of 221 plus minus 40 yr both comparable coseismic slip in 1906 and similar late holocene geologic slip rates at the olema site and a site 145 km northwest at point arena prentice 1989 suggest that the north coast segment behaves as a coherent rupture unit

premonitory spreading of seismicity over the faults network in southern california precursor accord 1 we establish a connection between geometry of the faults network in a region and seismicity preceding the strong earthquakes in the intermediate term timescale of years previous studies of observed and computer simulated seismicity demonstrated that strong earthquakes are preceded in that timescale by the rise of seismic activity in a lower magnitude range here we explore a complementary phenomenon spreading of activity over the fault network this phenomenon is depicted by the seismicity pattern accord defined as a simultaneous rise of seismicity in a sufficiently large number of fault zones hence its name pattern accord has been found recently in synthetic seismicity generated by the colliding cascades cc model the present study demonstrates this pattern in observed seismicity of southern california we applied to observations a prediction algorithm based on the pattern accord scaled to the target magnitude 7 5 the pattern accord emerges within a few years before each of the three largest earthquakes in southern california kern county 1952 landers 1992 and hector mine 1999 and at no other time scaled to the target magnitude interval from 6 5 to 7 4 the pattern accord precedes six out of nine earthquakes the duration of alarms in both cases is about 30 of the time considered we repeated prediction with different combinations of adjustable numerical parameters of the algorithm summing up the success and error scores on an error diagram this numerical experiment shows that the prediction results are stable under moderate variations of adjustable parameters the final test would be as always an advance prediction the pattern accord has a simple physical explanation connected with equilibrium of the crustal blocks system under the impact of tectonic driving forces at the same time accord is a manifestation of a broader phenomenon premonitory increase of earthquakes correlation range the latter phenomenon was found for the first time in the cc model although it was hypothesized by one of the authors much earlier

increased correlation range of seismicity before large events manifested by earthquake chains earthquake chains are clusters of moderate size earthquakes which extend over large distances and are formed by statistically rare pairs of events that are close in space and time neighbors earthquake chains are supposed to be precursors of large earthquakes with lead times of a few months here we substantiate this hypothesis by mass testing it using a random earthquake catalog also we study stability under variation of parameters and some properties of the chains we found two invariant parameters they characterize the spatial and energy scales of earthquake correlation both parameters of the chains show good correlation with the magnitudes of the earthquakes they precede earthquake chains are known as the first stage of the earthquake prediction algorithm reverse tracing of precursors rtp now tested in forward prediction a discussion of the complete rtp algorithm is outside the scope of this paper but the results presented here are important to substantiate the rtp approach

load unload response ratio and accelerating moment energy release critical region scaling and earthquake prediction the main idea of the load unload response ratio lurr is that when a system is stable its response to loading corresponds to its response to unloading whereas when the system is approaching an unstable state the response to loading and unloading becomes quite different high lurr values and observations of accelerating moment energy release amr aer prior to large earthquakes have led different research groups to suggest intermediate term earthquake prediction is possible and imply that the lurr and amr aer observations may have a similar physical origin to study this possibility we conducted a retrospective examination of several australian and chinese earthquakes with magnitudes ranging from 5 0 to 7 9 including australia s deadly newcastle earthquake and the devastating tangshan earthquake both lurr values and best fit power law time to failure functions were computed using data within a range of distances from the epicenter like the best fit power law fits in amr aer the lurr value was optimal using data within a certain epicentral distance implying a critical region for lurr furthermore lurr critical region size scales with mainshock magnitude and is similar to the amr aer critical region size these results suggest a common physical origin for both the amr aer and lurr observations further research may provide clues that yield an understanding of this mechanism and help lead to a solid foundation for intermediate term earthquake prediction

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

application of a modified pattern informatics method to forecasting the locations of future large earthquakes in the central japan we propose a modification of the pattern informatics pi method that has been developed for forecasting the locations of future large earthquakes this forecast is based on analyzing the space time patterns of past earthquakes to find possible locations where future large earthquakes are expected to occur a characteristic of our modification is that the effect of errors in the locations of past earthquakes on the output forecast is reduced we apply the modified and original methods to seismicity in the central part of japan and compared the forecast performances we also invoke the relative intensity ri of seismic activity and randomized catalogs to constitute null hypotheses we do statistical tests using the molchan and relative operating characteristic roc diagrams and the log likelihoods and show that the forecast for using the modified pi method is generally better than the competing original pi forecast and the forecasts from the null hypotheses using the bootstrap technique with monte carlo simulations we further confirm that earthquake sequences simulated based on the modified pi forecast can be statistically the same as the real earthquake sequence so that the forecast is acceptable the main and innovative science in this paper is the modification of the pi method and the demonstration of its applicability showing a considerable promise as an intermediate term earthquake forecasting tool

a new fractal approach to the clustering of earthquakes physical fractal abstract traditional fractal analysis methods of earthquake temporal clustering treat earthquake events as mathematical points without mass in time smalley et al 1987 the results obtained by these methods mainly reflect the seismic behavior of numerous small earthquakes a sieve method of physical fractal analysis has been developed in the present article in which a series of magnitude sieves are used to study the fractal behavior of earthquakes with different magnitudes fractal analyses of earthquake clustering are conducted for three regions northern china mainland of china and southern california we find that all the earthquake subsets of each region show nearly the same fractal dimension d 0 3 for northern china and the mainland of china and d 0 4 for southern california the scaling ranges in which the corresponding earthquake subsets under consideration exhibit fractal features vary from subset to subset the method has the potential application to characterizing the fractal behavior of earthquake clustering for different regions

decadal to centennial fluctuations in the intensity of the eastern tropical north pacific oxygen minimum zone during the last 1200 years oxygen minimum zones omzs located below highly productive marine regions are sites of microbially mediated denitrification and biogeochemical cycling that have global significance the intensity of omzs fluctuates naturally however the degree of these fluctuations and a comprehensive understanding of the factors that drive these fluctuations on decadal to centennial time scales is lacking our high resolution near annual record of 15nsed from laminated sediments at the pescadero slope in the gulf of california eastern tropical north pacific fluctuates between maximum values of 10 5 and minimum values of 8 0 over the past 1200 years an analysis of the relationship between 15no3 and o2 in the water column suggests that the observed range of 15nsed values is equivalent to an approximately 8 m fluctuation in o2 content and that these changes can occur in less than 25 years our findings show that the omz typically intensifies quickly and contracts gradually the average rate of omz intensification 0 24 m o2 yr is twice as fast as the rate of omz reoxygenation spectral analyses of the 15nsed record and br cl counts with the latter are used as a proxy for organic carbon preservation suggest that the pacific decadal oscillation and the suess devries solar cycle solar irradiance may influence the intensity of the omz and carbon production export during the late holocene coherence between 15nsed and weight percent organic carbon also suggests that similar mechanisms influence both omz fluctuations and variation in organic carbon production export

a new approach to estimating hazard posed by debris flows in the westfjords of iceland abstract the aim of this study is to improve the assessment of hazard posed by debris flows to the people and settlements of northwest iceland by studying very recent examples from above the town of isafjor ur and other nearby localities debris flows are a recognised hazard in the region above isafjor ur they occur with particularly high frequency and have appreciable volumes up to 14 000 m 3 we have used airborne laser altimeter lidar and differential global positioning system gps data to produce isopach maps of flows that occurred in 1999 2007 and 2008 our data show that these flows begin depositing at higher slope gradients and are also more mobile than hillslope debris flows reported by other authors above a 19 slope erosion is initiated independent of the distance along the flowpath using the isopach maps and associated field observations we have found a relationship between ground slope and patterns in deposition volume we have used this finding as a basis for an empirical model that enables an estimate of the total travel distance and final thickness of future debris flows to be calculated this has enabled us to identify areas of the town which are at risk some of these are not obvious without this analysis this model is notable for its simplicity which allows future debris flow characteristics to be predicted without the need to determine the precise fluid dynamic parameters of the flow such as viscosity and velocity which are required to implement more complex models

new observational information on the precursory accelerating and decelerating strain energy release recent reliable data are used to study the behavior of seismic activity before 46 strong shallow earthquakes m 6 0 which correspond to five complete samples of mainshocks these samples include 6 mainshocks m 6 0 7 1 that occurred in western mediterranean since 1980 17 mainshocks m 6 0 7 2 which occurred in the aegean greece and surrounding area since 1980 5 mainshocks m 6 4 7 5 that occurred in anatolia since 1980 12 mainshocks m 6 0 7 3 that occurred in california since 1980 and 6 mainshocks m 7 0 8 3 that occurred in japan since 1990 in all 46 cases a similar precursory seismicity pattern is observed specifically it is observed that accelerating benioff strain square root of seismic energy release caused by preshocks occurs in a broad circular region critical region with a radius about eight times larger than the fault length of the mainshock in agreement with results obtained by various research groups during the last two decades however in a much smaller circular region seismogenic region with a radius about four times the fault length the corresponding preshock strain decelerates with the time to the mainshock the time variation of the strain follows in both cases a power law but the exponent power is smaller than unit m 0 3 in the case of the accelerating preshock strain and larger than unit m 3 0 in the case of the decelerating preshock strain predictive properties of this decelerating in accelerating out strain model are expressed by empirical relations the possibility of using this model for intermediate term earthquake prediction is discussed and the relative model uncertainties are estimated

classification of seismic patterns in a hierarchical model of rupture a new phase diagram for seismicity summary i present a detailed description of the temporal properties of seismicity in a hierarchical model of rupture incorporating healing and faulting at the microscopic scale a stochastic process controls transitions between a solid and a broken state with respect to the local stress from the distribution of broken elements geometric rules of interaction determine the state of fracturing of domains of larger dimensions and the shape of the stress redistribution then any point in space evolves with respect to its state of stress and its state of fracturing measured at different length scales applied to a single fault zone under a constant loading rate this model of seismicity reproduces the main characteristics of the seismic catalogues gutenberg richter law for the magnitude frequency relationship omori law for the aftershock decay rate clustering of major events swarms of earthquakes seismicity of creeping segment and seismic noise i infer that the control parameter is the dimensionless parameter a the ratio between a characteristic time of healing and a characteristic time of loading following the magnitude of a different seismic scenarios emerge if a 1 the system is in a critical state and largest events can occur over a wide range of timescales e g clustering of major events if a 1 the system is in subcritical states controlled by healing and the fault zone may be creeping one particular feature is that the amplitude of the stress stored in the fault zone decreases and the frequency of large events increases as the critical state is approached this can be interpreted as a weakening process i propose a new phase diagram of seismicity to illustrate an alternative to the classical seismic cycle picture

circum pacific seismic potential 1989 1999 the seismic potential for 96 segments of simple plate boundaries around the circum pacific region is presented in terms of the conditional probability for the occurrence of either large or great interplate earthquakes during the next 5 10 and 20 years i e 1989 1994 1989 1999 and 1989 2009 this study represents the first probabilistic summary of seismic potential on this scale and involves the comparison of plate boundary segments that exhibit varying recurrence times magnitudes and tectonic regimes presenting these data in a probabilistic framework provides a basis for the uniform comparison of seismic hazard between these differing fault segments as well as accounting for individual variations in recurrence time along a specific fault segment and uncertainties in the determination of the average recurrence time

on the instability of avalanching glaciers the instability of hanging glaciers and more generally of avalanching glaciers is discussed on the basis of observations performed on several glaciers located in the european alps a classification of avalanching glaciers is proposed which allows a primary appreciation of the danger inherent in these glaciers on the basis of field observations and results of numerical simulations of crevassing the fracture processes which lead to major icefalls as well as their recurrence are analyzed a method for predicting the time of failure is then discussed the disaggregation of the unstable ice masses usually observed prior to large icefalls is investigated and its implications for the forecasting of icefalls analyzed

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

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

evolution of moderate seismicity in the san francisco bay region 1850 to 1993 seismicity changes related to the occurrence of large and great earthquakes the rate of seismic activity of moderate size m 5 5 earthquakes in the san francisco bay sfb region has varied considerably during the past 150 years as measured by the rate of seismic moment release seismic activity in the sfb region is observed to accelerate prior to m 7 0 earthquakes in 1868 1906 and 1989 and then to decelerate following them we examine these seismicity changes in the context of the evolution of the stress field in the sfb region as a result of strain accumulation and release using a model of dislocations in an elastic halfspace we use a coulomb failure function cff to take into account changes in both shear and normal stresses on potential failure planes of varying strike and dip in the sfb region we find that the occurrence of a large or great earthquake creates a stress shadow a region where the stress driving earthquake deformation is decreased interseismic strain accumulation acts to reverse this process gradually bringing faults in the sfb region out of the stress shadow of a previous large or great earthquake and back into a state where earthquake failure is possible as the stress shadow generated by a large or great earthquake disappears it migrates inward toward the fault associated with that large or great event the observed changes in the rate of occurrence of moderate earthquakes in the sfb region are broadly consistent with this model in detail the decrease in seismicity throughout most of the sfb region and a localized increase in the monterey bay region following the great 1906 earthquake is consistent with our predicted stress changes the timing and location of moderate size earthquakes when the rate of seismicity increases again in the 1950s is consistent with areas in which the 1906 stress shadow had been eliminated by strain accumulation in the sfb region those earthquakes that are most inconsistent with our stress evolution model including the 1911 earthquake southeast of san jose are found to occur in regions where dip slip faulting is common in addition to strike slip the 1906 earthquake brought that zone of dip slip faulting closer to failure suggesting that the 1911 event may have been a reverse faulting earthquake rather than a strike slip one similar to the 1984 morgan hill earthquake the occurrence of activity on faults very close to the san andreas such as the lake elsman earthquakes of 1988 and 1989 appear to be associated with the last disappearence of the stress shadow on the loma prieta segment of the san andreas fault thus events of that type may represent an intermediate term precursor to a large earthquake such as the 1989 loma prieta event much of the moderate size earthquake activity in the sfb region appears to be modulated in time by the buildup and release of stress in large and great earthquakes a tensorial approach to earthquake prediction i e taking into account changes in the components of the stress tensor has several advantages over examining scalar changes such as those in seismic activity and moment release rates this tensorial approach allows for both activation and quiescence but in different subregions prior to as well as after large earthquakes

stress transfer to the denali and other regional faults from the m 9 2 alaska earthquake of 1964 stress transfer from the great 1964 prince william sound earthquake is modeled on the denali fault including the denali totschunda fault segments that ruptured in 2002 and on other regional fault systems where m 7 5 and larger earth quakes have occurred since 1900 the results indicate that analysis of coulomb stress transfer from the dominant earthquake in a region is a potentially powerful tool in assessing time varying earthquake hazard modeled coulomb stress increases on the northern denali and totschunda faults from the great 1964 earthquake coincide with zones that ruptured in the 2002 denali fault earthquake although stress on the susitna glacier thrust plane where the 2002 event initiated was decreased a southeasterly trending coulomb stress transect along the right lateral totschunda fairweather queen charlotte trend shows stress transfer from the 1964 event advancing slip on the totschunda fairweather and queen charlotte segments including the southern fairweather segment that ruptured in 1972 stress transfer retarding right lateral strike slip was observed from the southern part of the totschunda fault to the northern end of the fairweather fault 1958 rupture this region encompasses a gap with shallow thrust faulting but with little evidence of strike slip faulting connecting the segments to the northwest and southeast stress transfer toward failure was computed on the north south trending right lateral strike slip faults in the gulf of alaska that ruptured in 1987 and 1988 with inhibitory stress changes at the northern end of the northernmost 1987 rupture the northern denali and totschunda faults including the zones that ruptured in the 2002 earthquakes follow very closely within 3 for about 90 an arc of a circle of radius 375 km the center of this circle is within a few kilometers of the intersection at depth of the patton bay fault with the alaskan megathrust this inferred asperity edge may be the pole of counterclockwise rotation of the block south of the denali fault these observations suggest that the asperity and its recurrent rupture in great earthquakes as in 1964 may have influenced the tectonics of the region during the later stages of evolution of the denali strike slip fault system

stress correlation function evolution in lattice solid elasto dynamic models of shear and fracture zones and earthquake prediction it has been argued that power law time to failure fits for cumulative benioff strain and an evolution in size frequency statistics in the lead up to large earthquakes are evidence that the crust behaves as a critical point cp system if so intermediate term earthquake prediction is possible however this hypothesis has not been proven if the crust does behave as a cp system stress correlation lengths should grow in the lead up to large events through the action of small to moderate ruptures and drop sharply once a large event occurs however this evolution in stress correlation lengths cannot be observed directly here we show using the lattice solid model to describe discontinuous elasto dynamic systems subjected to shear and compression that it is for possible correlation lengths to exhibit cp type evolution in the case of a granular system subjected to shear this evolution occurs in the lead up to the largest event and is accompanied by an increasing rate of moderate sized events and power law acceleration of benioff strain release in the case of an intact sample system subjected to compression the evolution occurs only after a mature fracture system has developed the results support the existence of a physical mechanism for intermediate term earthquake forecasting and suggest this mechanism is fault system dependent this offers an explanation of why accelerating benioff strain release is not observed prior to all large earthquakes the results prove the existence of an underlying evolution in discontinuous elasto dynamic systems which is capable of providing a basis for forecasting catastrophic failure and earthquakes

re evaluation of several large historic earthquakes in the vicinity of the loma prieta and peninsular segments of the san andreas fault california abstract the size and location of several of the largest 19th century earthquakes in the san francisco bay area including the june 1838 8 october 1865 21 october 1868 and 24 april 1890 events are re evaluated by comparing these historic events to several modern events in particular the 1989 loma prieta earthquake similar high intensities in the monterey bay area during both the 1989 and 1838 events indicate that the 1838 shock probably ruptured the loma prieta segment in addition to the peninsular segment of the san andreas fault if so the resulting earthquake would have been of moment magnitude m w 7 2 thus like segments of many other plate boundaries the loma prieta segment exhibits heterogeneous rupture in that sometimes it ruptures with the peninsular segment as in 1906 and probably in 1838 and at other times it ruptures alone as in 1989 in contrast the area of high intensities generated by the 1865 earthquake was centered in the santa clara valley and the eastern foothills of the santa cruz mountains indicating that the 1865 shock probably was located northeast of the loma prieta rupture and not on the san andreas fault in addition the felt areas taken to be one of the best measures of relative source size of modified mercalli intensities mmi v and vi for the 1865 shock are considerably smaller than that of the 1989 event relationships between felt areas of intensities v and vi and moment magnitude are developed for the san francisco bay area based on these relationships the average computed moment magnitudes for the 1865 1868 and 1890 earthquakes are 6 51 0 18 6 84 0 20 and 6 32 0 16 respectively if these results are correct then the loma prieta segment taken to include all faults within the san andreas fault zone i e within a zone up to a few kilometers wide appears to rupture with or without the peninsular segment every 76 11 years these data on repeat times may be the most accurate information now available for ascertaining the date of future rupture of that segment and for testing recurrence models the smaller size of the 1865 earthquake would be consistent with it being part of the long term seismic build up to the 1868 event rather than being paired with it as events of similar size if the 1865 earthquake did occur northeast of the loma prieta segment then a future source of that type located closer to san jose and the santa clara valley could pose a considerable hazard to the southern san francisco bay area on going searches of letters and diaries of missionaries and early settlers could yield new information that should help to further constrain the locations and magnitudes of these and other historic earthquakes

theory of time dependent rupture in the earth at a velocity x which is a well defined function of k this propagation is stable and quasi static and is referred to as subcritical crack growth we shall use the terms stable quasistatic and subcritical to mean propagation at velocities much less than the sonic velocities of the medium this behavior results from stress induced corrosion at the crack tip the principal corrodent for the present application being h20 this behavior has been firmly established in the laboratory for mode i tensile cracks in a wide variety of materials ineluding silicates and silicate glasses see cholz 1968a 1972a martin 1972 wiederhorn and bolz 1970 atkinson 1979 lawn and wilshaw 1975 knott 1973 the form of the relationship between k and x does not vary significantly with the material only the parameters in the law vary as an example we show in figure 1 data on subcritical crack growth in quartz after atkinson 1979 the empirical relationship is found to take the form