accelerating seismic crustal deformation in the north aegean trough greece summary a recently developed algorithm has been applied to define regions of the northern aegean in which accelerating seismic crustal deformation is currently occurring an elliptical such region has been found in the western part of the north aegean accelerating deformation which started three decades ago and has been released by the generation of intermediate magnitude earthquakes m 4 5 is still occurring based on these observations we can assume that this region is now in a state pre shock deformation that will lead to a critical point main shock the estimated basic parameters of this impending main shock are 39 7 n 23 7 e for the epicentre m 6 0 for the moment magnitude and tc 2001 1 for the origin time the corresponding uncertainties are less than 100 km for the epicentre 0 4 for the magnitude and 1 5 yr for the origin time

self driven mode switching of earthquake activity on a fault system theoretical results based on two different modeling approaches indicate that the seismic response of a fault system to steady tectonic loading can exhibit persisting fluctuations in the form of self driven switching of the response back and forth between two distinct modes of activity the first mode is associated with clusters of intense seismic activity including the largest possible earthquakes in the system and frequency size event statistics compatible with the characteristic earthquake distribution the second mode is characterized by relatively low moment release consisting only of small and intermediate size earthquakes and frequency size event statistics following a truncated power law the average duration of each activity mode scales with the time interval of a large earthquake cycle in the system the results are compatible with various long geologic paleoseismic and historical records the mode switching phenomenon may also exist in responses of other systems with many degrees of freedom and nonlinear dynamics 1999 elsevier science b v all rights reserved

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

geochemical characterization of selected western canada oils by c5 c8 compound specific isotope correlation csic abstract forty two oils condensates from the western canada sedimentary basin wcsb ranging in reservoir age from devonian to cretaceous are compared using the stable carbon isotopic ratio of individual hydrocarbons in the gasoline range fraction c 5 c 8 of these oils continuous flow isotope ratio mass spectrometry cf irms using a modified solid dilution purge and trap inletting system can provide reproducible isotopic ratios for the ca 26 dominant n iso and cyclo alkanes and aromatics in the gasoline range the resulting isotopic signatures or gasoline isotopograms for oils condensates provide a diagnostic geochemical technique for oil oil and oil source correlations in many instances the non straight chained hydrocarbons are more diagnostic than n alkanes hierarchical cluster analysis provides a non subjective approach to the treatment of individual isotopic information this study confirms that oils from similar or the same sources produce isotopic signatures that are highly correlated clear carbon isotopic relationships between individual hydrocarbon compounds in the oils suggest a steady state kinetic relationship for the generation of oil and gas as opposed to a thermodynamic equilibrium relationship this mechanism explains the consistent shift in isotopic ratios between similar compounds such as the methylalkanes and dimethylalkanes

accelerated preshock deformation of broad regions in the aegean area twenty four regions where accelerating deformation has been observed for a few decades before corresponding strong m 6 0 7 5 mainshocks are identified in the broader aegean area to a first approximation these preshock regions have elliptical shapes and the radius r in km of a circle with an area equal to the corresponding ellipse is related to the moment magnitude m of the mainshock by the equation log r 0 42 m 0 68 the dimension of each preshock region is about seven to ten times larger than the rupture zone fault length of the corresponding mainshock the time variation of the cumulative benioff strain was satisfactorily fitted by a power law relation which is predicted by statistical physics if the mainshock to which accelerating strain rates leads is considered as a critical point the duration t in years of the accelerating benioff strain release period is given by the relation log t 5 94 0 75 log s r where s r is the mean benioff strain rate release per year for 104 km2 in the preshock region calculated by the complete available data m 5 2 for the entire instrumental period 1911 1998 the importance of identifying and investigating such regions for better understanding the dynamics of the active part of the lithosphere as well as for earthquake prediction and time dependent seismic hazard assessment is discussed

modern style plate subduction preserved in the palaeoproterozoic west african craton the timing of onset of modern style plate tectonics on earth is debated analysis of rocks in the west african metamorphic province which is more than 2 gyr old reveals that some minerals formed under conditions similar to those in modern day subduction zones suggesting that subduction occurred on the palaeoproterozoic earth

precursors to the kalapana m 7 2 earthquake the kalapana hawaii earthquake of november 1975 had a rupture length of 40 to 50 km and was located on the south flank of the active volcano kilauea the source mechanism was dip slip normal faulting on a plane dipping 20 degrees to the se with the greatest principal stress oriented in that direction and accumulated by volcanic intrusions into kilauea s rifts the source area of the 1975 earthquake was subject to intensive geological and geophysical research for many years before this earthquake because of its proximity to the volcano we studied the distribution of epicenters for small earthquakes from 1962 to 1975 seven seismographs located within 3 km of the aftershock area had been in operation for 3 to 10 years before the mainshock and geodetic triangulations and trilaterations in the source area had been carried out repeatedly since 1914 we found that precursory changes occurred throughout most of the rupture area but in two distinctly different patterns in the larger outer anomalous area the seismicity rate was decreased by 50 during the 3 8 years before the mainshock in addition several geodetic lines indicated anomalous strain release during this time within two inner areas the seismicity remained high then increased shortly before the mainshock in one of the inner areas a p wave travel time delay of 0 2 s could be detected which began about 3 5 years before the mainshock within the other inner anomalous area geodetic strain was accumulating until the first half of 1975 when 3 5 10 4 strain 35 bars was released aseismically by contrast the outer anomalous volume was experiencing strain softening from 1970 1971 on we interpret these observations as indicating that strain softening by fault creep in the outer anomalous area transferred stress into two major asperities locked portions of the fault a velocity decrease and foreshocks were observed in one asperity and high stress accumulation in the other implying that dilatancy of the crust probably occurred our model is qualitatively supported by the independent evidence of strong motion records which show that the kalapana earthquake was a complex multiple rupture we conclude that the kalapana earthquake was preceded by a preparatory process which lasted 3 8 0 3 years and which had dimensions of 45 10 km covering approximately the aftershock area

a systematic spatiotemporal test of the critical point hypothesis for large earthquakes 1 the critical point hypothesis for large earthquakes predicts two different precursory phenomena in space and time an accelerating moment release and the growth of the spatial correlation length the objective of this work is to investigate both methods with respect to their predictive power a systematic statistical test based on appropriate random earthquake catalogs allows to quantify the correlations of a precursory pattern with the subsequent mainshock activity the analysis of target earthquakes in california since 1960 with magnitudes m mcut reveals that these correlations increase systematically with growing mcut and correlations at greater than 95 confidence are observed for mcut 6 5 in the case of the spatial correlation length in particular the seismicity patterns are found to be significantly correlated with each of the largest earthquakes m 7 0 individually the acceleration of the moment release has a similar trend but is less significant

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

accelerating seismic crustal deformation in the southern aegean area a region of intense accelerating seismic crustal deformation has been identified in the southwestern part of the hellenic arc broader area of cythera island the identification is performed using a detailed parametric grid search of the broader southern aegean area for accelerating energy release behavior the identified region has similar properties with past preshock critical regions which have been identified for strong mainshocks in the aegean area based on such observations which suggest that this region is at a critical state that can lead to a critical point that is to the generation of a mainshock an estimation is made of the possible epicenter coordinates magnitude and origin time of this oncoming large m 7 0 earthquake the estimation procedure is validated on the basis of retrospective analysis of strong events in the aegean area as well as by appropriate application on synthetic random catalogs these results the existence of similar observations of accelerating seismic deformation in eastern part of southern aegean and independent information on the time distribution of large earthquakes m 6 8 for the whole southern aegean indicate that the generation of strong earthquakes in this area in the next few years must be considered as very probable

precursory seismic quiescence seventeen cases of precursory seismic quiescence to mainshocks with magnitudes fromml 4 7 toms 8 0 are summarized the amount of rate decrease ranges from 45 to 90 the significance of these changes varies between 90 and 99 99 the assumption that the background rate is approximately constant is fulfilled in most crustal volumes studied all quiescence anomalies seem to have abrupt beginnings and the rate during the anomalous period is fairly constant the duration of the precursors ranges from 15 to 75 months and it is not clear what factors determine that time at least three successful predictions have been based on seismic quiescence these cases have shown that mainshocks can be predicted based on quiescence but they have also shown that the interpretation of the data in real time is difficult and nonunique if a false alarm is defined as a period of quiescence with a significance level larger than a precursory quiescence in the same tectonic area then we estimate based on searches in four areas that the false alarm rate may be on the order of 50 failure to predict may be expected in perhaps 50 of mainshocks even in carefully monitored areas quiescence cannot be used as a precursor in tectonic environments with low seismic activity most characteristics of the phenomenon are still poorly defined but data exist which probably permit at least a doubling of the presently available data on case histories

increased long range intermediate magnitude earthquake activity prior to strong earthquakes in california we study the space time relationships between strong earthquakes in california and the intermediate magnitude earthquakes that both precede and follow them all 11 earthquakes in california with nominal magnitudes greater than or equal to 6 8 from 1941 to 1993 were preceded by an increase in the rate of occurrence of earthquakes having magnitudes greater than 5 1 ten of the 11 earthquakes occurred when or shortly after the intermediate magnitude activity was greater than its 75th percentile three of these strong earthquakes are in a conventional space time foreshock aftershock relationship with others of the 11 strong events the precursory activity is concentrated in regions having linear dimensions of the order of a few hundred kilometers these dimensions are significantly larger than the estimated fracture lengths of the ensuing strong earthquakes the correlations are ill defined for smaller earthquakes and are almost unidentifiable for earthquakes with magnitudes less than about 4 6 the precursors to the strong earthquakes appear over a time interval of the order of 5 to 10 years before the strong earthquake although the onset was about 25 years before the san francisco earthquake in the case of the loma prieta and san francisco earthquakes the onset of increased activity appears to be relatively abrupt the increased activity is either switched off abruptly to distances of the order of hundreds of kilometers shortly after the occurrence of a strong earthquake or the strong events are themselves part of a precursory pattern of continuing high activity before a second strong earthquake that takes place soon thereafter with subsequent extinction of activity after it thus the intermediate magnitude precursors do not directly influence the time and location of the subsequent strong event but the strong event has a strong influence on the stress field in the vicinity of intermediate magnitude earthquakes to distances of the order of many times the scale size of the strong earthquake

seismic quiescence as an indicator for large earthquakes in a system of self organized criticality seismically active fault systems may be in a state of self organized criticality soc investigations of simple soc models have suggested that earthquakes might be inherently unpredictable in this paper we analyze the question of predictability in a more complex and realistic soc model which consists of a spring block system with transient creep characteristics additionally to the power law distribution of earthquake sizes this model reproduces also foreshock and aftershock sequences aside from a short term increase of seismicity immediately prior to large model earthquakes these events are preceded on average by an intermediate term period of reduced seismicity the stronger and the longer the duration of this period the larger on average is the subsequent mainshock we find that the detection of seismic quiescence can improve the time independent hazard assessment the improvement is most significant for the largest target events

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

a proposed method for locating the critical region of a future earthquake using the critical earthquake concept using the critical point concept and extending bowman s idea of critical earthquake we develop an intersecting circle method to locate the critical region a simulation check shows that this method is effective in finding a given critical region we selected several real cases from new zealand and china and used this method to find the critical regions before the occurrence of large earthquakes the result shows that this method is valid for detecting a critical region and the epicenter of mainshock might be in the critical region

precursory seismic activation and critical point phenomena in this paper we relate the behavior of seismicity prior to a characteristic earthquake to the excitation in proximity to a spinodal instability we illustrate the spinodal instability as the upper limit of superheated water prior to a steam explosion we draw an analogy between the steam explosion and a characteristic earthquake and show that the power law activation associated with the spinodal instability is essentially identical to the power law increase in benioff strain observed prior to characteristic earthquakes we find that theory and actual data give very similar results

accelerated seismic release and related aspects of seismicity patterns on earthquake faults observational studies indicate that large earthquakes are sometimes preceded by phases of accelerated seismic release asr characterized by cumulative benioff strain following a power law timeto failure relation with a term tf t m where tr is the failure time of the large event and observed values of m are close to 0 3 we discuss properties of asr and related aspects of seismicity patterns associated with several theoretical frameworks the subcritical crack growth approach developed to describe deformation on a crack prior to the occurrence of dynamic rupture predicts great variability and low asymptotic values of the exponent m that are not compatible with observed asr phases statistical physics studies assuming that system size failures in a deforming region correspond to critical phase transitions predict establishment of long range correlations of dynamic variables and power law statistics before large events using stress and earthquake histories simulated by the model of ben zion 1996 for a discrete fault with quenched heterogeneities in a 3 d elastic half space we show that large model earthquakes are associated with nonrepeating cyclical establishment and destruction of long range stress correlations accompanied by nonstationary cumulative benioff strain release we then analyze results associated with a regional lithospheric model consisting of a seismogenic upper crust governed by the damage rheology of lyakhovsky et al 39 over a viscoelastic substrate we demonstrate analytically for a simplified 1 d case that the employed damage rheology leads to a singular power law equation for strain proportional to t f t 1 3 and a nonsingular power law relation for cumulative benioff strain proportional to t f t 1 3 a simple approximate generalization of the latter for regional cumulative benioff strain is obtained by adding to the result a linear function of time representing a stationary background release to go beyond the analytical expectations we examine results generated by various realizations of the regional lithospheric model producing seismicity following the characteristic frequency size statistics gutenberg richter power law distribution and mode switching activity we find that phases of asr exist only when the seismicity preceding a given large event has broad frequency size statistics in such cases the simulated asr phases can be fitted well by the singular analytical relation with m 1 3 the nonsingular equation with m 0 2 and the generalized version of the latter including a linear term with m 1 3 the obtained good fits with all three relations highlight the difficulty of deriving reliable information on functional forms and parameter values from such data sets the activation process in the simulated asr phases is found to be accommodated both by increasing rates of moderate events and increasing average event size with the former starting a few years earlier than the latter the lack of asr in portions of the seismicity not having broad frequency size statistics may explain why some large earthquakes are preceded by asr and other are not the results suggest that observations of moderate and large events contain two complementary end member predictive signals on the time of future large earthquakes in portions of seismicity following the characteristic earthquake distribution such information exists directly in the associated quasi periodic temporal distribution of large events in portions of seismicity having broad frequency size statistics withrandom or clustered temporal distribution of large events the asr phases have predictive information the extent to which natural seismicity may be understood in terms of these end member cases remains to be clarified continuing studies of evolving stress and other dynamic variables in model calculations combined with advanced analyses of simulated and observed seismicity patterns may lead to improvements in existing forecasting strategies

statistical physics approach to understanding the multiscale dynamics of earthquake fault systems 1 earthquakes and the faults upon which they occur interact over a wide range of spatial and temporal scales in addition many aspects of regional seismicity appear to be stochastic both in space and time however within this complexity there is considerable self organization we argue that the occurrence of earthquakes is a problem that can be attacked using the fundamentals of statistical physics concepts of statistical physics associated with phase changes and critical points have been successfully applied to a variety of cellular automata models examples include sandpile models forest fire models and particularly slider block models these models exhibit avalanche behavior very similar to observed seismicity a fundamental question is whether variations in seismicity can be used to successfully forecast the occurrence of earthquakes several attempts have been made to utilize precursory seismic activation and quiescence to make earthquake forecasts some of which show promise

global observational properties of the critical earthquake model the preshock critical regions of 20 mainshocks with magnitudes between 6 4 and 8 3 which occurred recently since 1980 in a variety of seismotectonic regimes greece anatolia himalayas japan california were identified and investigated all these strong earthquakes were preceded by accelerating time to mainshock seismic crustal deformation benioff strain the time variation of the cumulative benioff strain follows a power law with a power value m 0 3 in very good agreement with theoretical considerations we observed that the dimension of the critical region increased with increasing mainshock magnitude and with decreasing long term seismicity rate of the region an increase of the duration of this critical preshock phenomenon with decreasing long term seismicity rate was also observed this spatial and temporal scaling expresses characteristics of the critical earthquake model which are of importance for earthquake prediction research we also showed that the critical region of an oncoming mainshock coincides with the preparing region of this shock where other precursory phenomena can be observed

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

earthquake rupture as a critical point consequences for telluric precursors abstract earthquakes are related to rupture phenomena in complex statistical systems of cracks we first review some available information suggesting that rupture in earthquakes is a critical point the consequences of this hypothesis on several phenomena are then discussed in particular we focus our attention on a simple theory of electroseismic activity based on mechano electrical transduction effects such as the piezoelectric or the pressure induced polarization effect the neighbourhood of the rupture threshold is characterized by a specific response which could correspond to telluric wave activity observed as precursors of earthquakes

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

palaeomagnetism of east siberian traps and kimberlites two new poles and palaeogeographic reconstructions at about 360 and 250 ma summary we studied basalt sills and dykes and kimberlite pipes from the eastern part of the siberian platform these are spread out over a few hundred kilometres and are divided into two age groups late permian early triassic mir aikhal and olenyek regions and late devonian early carboniferous viluy and markha basins aikhal region the palaeomagnetic poles determined for each sill or dyke are statistically different from each other but averaging all corresponding directions from these sills and dykes with those from kimberlites of different generations yields results with acceptable statistics this is probably due to the averaging out of secular variation and or changes in magnetic polarity the resulting palaeomagnetic poles allow one to reconstruct the palaeopositions of siberia during the two large flood basalt events at about 360 and 250 ma a significant rotation of the siberian platform during the devonian and carboniferous is suggested the new data are in general agreement with some earlier palaeomagnetic poles for the late permian early triassic traps of the tungusska basin and significantly reduce uncertainties for previous late devonian early carboniferous siberian poles which were very scattered together with geological and absolute age data the palaeomagnetic data support the hypothesis that kimberlite magmatism and trap intrusions were both rapid and relatively close in time the 360 ma event is emerging as a magmatic event with considerable extent over the russian and siberian platforms related to incipient continental break up and triple junction formation possibly at or near the time of the frasnian famennian mass extinction

triggering of the 1999 mw 7 1 hector mine earthquake by aftershocks of the 1992 mw 7 3 landers earthquake 1 there is strong observational evidence that the 1999 mw 7 1 hector mine earthquake in the mojave desert california was triggered by the nearby 1992 mw 7 3 landers earthquake many authors have proposed that the landers earthquake directly stressed the hector mine fault our model of the landers aftershock sequence however suggests there is an 85 chance that the hector mine hypocenter was actually triggered by a chain of smaller earthquakes that was initiated by the landers main shock we perform our model simulations using the monte carlo method based on the gutenberg richter relationship omori s law bath s law and assumptions that all earthquakes including aftershocks are capable of producing aftershocks and that aftershocks produce their own aftershocks at the same rate that other earthquakes do in general our simulations show that if it has been more than several days since an m 7 main shock most new aftershocks will be the result of secondary triggering these secondary aftershocks are not physically constrained to occur where the original main shock increased stress this may explain the significant fraction of aftershocks that have been found to occur in main shock stress shadows in static coulomb stress triggering studies