an ensemble approach for improved short to intermediate term seismic potential evaluation pattern informatics pi load unload response ratio lurr state vector sv and accelerating moment release amr are four previously unrelated subjects which are sensitive in varying ways to the earthquake s source previous studies have indicated that the spatial extent of the stress perturbation caused by an earthquake scales with the moment of the event allowing us to combine these methods for seismic hazard evaluation the long range earthquake forecasting method pi is applied to search for the seismic hotspots and identify the areas where large earthquake could be expected and the lurr and sv methods are adopted to assess short to intermediate term seismic potential in each of the critical regions derived from the pi hotspots while the amr method is used to provide us with asymptotic estimates of time and magnitude of the potential earthquakes this new approach by combining the lurr sv and amr methods with the choice of identified area of pi hotspots is devised to augment current techniques for seismic hazard estimation using the approach we tested the strong earthquakes occurred in yunnan sichuan region china between january 1 2013 and december 31 2014 we found that most of the large earthquakes especially the earthquakes with magnitude greater than 6 0 occurred in the seismic hazard regions predicted similar results have been obtained in the prediction of annual earthquake tendency in chinese mainland in 2014 and 2015 the studies evidenced that the ensemble approach could be a useful tool to detect short to intermediate term precursory information of future large earthquakes

geoelectrical structure across the bohemian massif and the transition zone to the west carpathians abstract geoelectrical methods of magnetotelluric mt and geomagnetic deep soundings gds were employed to infer the electrical conductivity structure at depths of specific regions of the bohemian massif bm and in the transition zone between the bm and the west carpathians wcp transfer functions between components of temporal variations of the natural electromagnetic field induced in the earth by external sources were estimated and converted to electrical conductivity resistivity profiles while the results from other regions of the bm are noted in references the emphasis here is placed on the new analysis of mt gds data at field stations along the regional almost 500 km long deep seismic sounding profile no vi traversing the country from nw to se inversion of its results suggests a complex geoelectrical structure characteristic for each geological unit with layers of increased electrical conductivity at crustal and uppermost mantle depths the results also indicate strong fields of anomalous induction marking geoelectrical inhomogeneities at the eastern margin of the bm and in the foreland of the wcp

importance of small earthquakes for stress transfers and earthquake triggering 1 we estimate the relative importance of small and large earthquakes for static stress changes and for earthquake triggering assuming that earthquakes are triggered by static stress changes and that earthquakes are located on a fractal network of dimension d this model predicts that both the number of events triggered by an earthquake of magnitude m and the stress change induced by this earthquake at the location of other earthquakes increase with m as similar to 10 dm 2 the stronger the spatial clustering the larger the influence of small earthquakes on stress changes at the location of a future event as well as earthquake triggering if earthquake magnitudes follow the gutenberg richter law with b d 2 small earthquakes collectively dominate stress transfer and earthquake triggering because their greater frequency overcomes their smaller individual triggering potential using a southern california catalog we observe that the rate of seismicity triggered by an earthquake of magnitude m increases with m as 10 alpha m where alpha 1 05 0 05 we also find that the magnitude distribution of triggered earthquakes is independent of the triggering earthquake s magnitude m when alpha approximate to b small earthquakes are roughly as important to earthquake triggering as larger ones we evaluate the fractal correlation dimension d of hypocenters using two relocated catalogs for southern california the value of d measured for distances 0 1 r 5 km is d 1 54 for the shearer et al catalog and d 1 73 for the hauksson et al catalog the value of d reflects both the structure of the fault network and the nature of earthquake interactions by considering only those earthquake pairs with interevent times larger than 1000 days we can largely remove the effects of short term clustering then d approximate to 2 close to the value d 2 alpha 2 1 predicted by assuming that earthquake triggering is due to static stress the value d approximate to 2b implies that small earthquakes are as important as larger ones for stress transfers between earthquakes and that considering stress changes induced by small earthquakes should improve models of earthquake interactions

development of a combination approach for seismic hazard evaluation we developed a synth esis approach to augment current techniques for seismic hazard evaluation by combining four previously unrelated subjects the pattern informatics pi load unload response ratio lurr state vector sv and accelerating moment release amr methods since the pi is proposed in the premise that the change in the seismicity rate is a proxy for the change in the tectonic stress this method is used to quantify localized changes surrounding the epicenters of large earthquakes to objectively quantify the anomalous areas hot spots of the upcoming events on the short to intermediate term estimation we apply the lurr sv and amr methods to examine the hazard regions derived from the pi hot spots a predictive study of the 2014 earthquake tendency in chinese mainland using the seismic data from 1970 01 01 to 2014 10 01 shows that during jan 01 to oct 31 2014 most of the m 5 0 earthquakes especially the feb 12 m7 3 yutian may 30 m6 1 yingjiang aug 03 m6 5 ludian and oct 07 m6 6 earthquakes occurred in the seismic hazard regions predicted comparing the predictions produced by the pi and combination approaches it is clear that by using the combination approach we can screen out the false alarm regions from the pi estimation without reducing the hit rate and therefore effectively augment the predictive power of current techniques this provided evidence that the multi method combination approach may be a useful tool to detect precursory information of future large earthquakes

seismicity rate changes in association with the evolution of the stress field in northern aegean sea greece summary seismicity rate changes in northern aegean area were studied by applying the dieterich 1994 rate state formulation the study area was divided into four smaller ones that exhibit seismotectonic homogeneity and accommodate strong events with similar to identical focal mechanisms seismicity rate evaluation concerns the study period between 1981 december 19 and 2010 august 31 whereas the reference seismicity rate was estimated for the learning period lasting from 1970 january 1 to 1981 december 19 the coseismic slip of the strongest events mw 5 8 that occurred during the study period was considered to contribute to the stress field evolution along with the continuous tectonic loading stress changes were calculated just before and after each strong event and their influence was then examined in connection with the occurrence rate of the smaller magnitude events above the individually determined magnitude of completeness in each subarea and for the respective time intervals after defining the probability density function of seismicity distribution a rate state model was used to combine static coulomb stress changes cff with seismicity rates and to compare the observed with the expected rates of earthquake production for each time period and subarea different parameter values combinations were tested to evaluate the model sensitivity qualitative and quantitative correlations were performed for each one of the selected study periods the modelling approach resulted to satisfactory correlation between real and synthetic seismicity rates and is expected to constitute a useful mean for the time dependent seismic hazard assessment

a reappraisal of the 2005 kashmir mw 7 6 earthquake and its aftershocks seismotectonics of nw himalaya abstract we study the source properties of the 2005 kashmir earthquake and its aftershocks to unravel the seismotectonics of the nw himalayan syntaxis the mainshock and larger aftershocks have been simultaneously relocated using phase data we use back projection of high frequency energy from multiple teleseismic arrays to model the spatio temporal evolution of the mainshock rupture our analysis reveal a bilateral rupture which initially propagated se and then nw of the epicenter with an average rupture velocity of 2 km s 1 the area of maximum energy release is parallel to and bound by the surface rupture incorporating rupture propagation and velocity we model the mainshock as a line source using p and sh waveform inversion our result confirms that the mainshock occurred on a ne dipping 35 fault plane with centroid depth of 10 km integrated source time function show that majority of the energy was released in the first 20 s and was confined above the hypocenter from waveform inverted fault dimension and seismic moment we argue that the mainshock had an additional 25 km blind rupture beyond the nw himalayan syntaxis combining this with findings from previous studies we conjecture that the blind rupture propagated nw of the syntaxis underneath a weak detachment overlain by infra cambrian salt layer and terminated in a wedge thrust all moderate to large aftershocks nw of the mainshock rupture are concentrated at the edge of the blind rupture termination source modeling of these aftershocks reveal thrust mechanism with centroid depths of 2 10 km and fault planes oriented sub parallel to the mainshock rupture to study the influence of mainshock rupture on aftershock occurrence we compute coulomb failure stress on aftershock faults all these aftershocks lie in the positive coulomb stress change region this suggest that the aftershocks have been triggered by either co seismic or post seismic slip on the mainshock fault

a model of tectonic stress state and rate using the 1994 northridge earthquake sequence a model of the spatial and temporal distribution of seismicity both before and after the northridge california earthquake has been used to estimate the background stress state loading rate and some parameters relating to fault friction a detailed source model was used to calculate the stress change field from the northridge mainshock which was fit to the spatial distribution of seismicity agreement between the best fitting background stress state from seismicity modeling and the background stress state inferred from focal mechanisms was found to be 99 significant showing that the spatial distribution of seismicity contains information about the stress state the stress rate found for the northridge area 1 2 pa day 0 004 bar a is approximately a factor of 9 less than the stress rate expected from observed strain rates which implies that aseismic deformation is reducing seismic hazard in the los angeles basin the resulting estimate of the friction parameter a d 0 008 is similar to laboratory values if an effective normal stress much smaller than the overburden and similar to background stress magnitudes 70 mpa from the seismicity modeling is assumed to apply estimates of the magnitude of background stress gradient of stress with depth and effective coefficient of friction are quite uncertain

quantitative earthquake forecasts resulting from static stress triggering 1 in recent years the triggering of earthquakes has been discussed controversially with respect to the underlying mechanisms and the capability to evaluate the resulting seismic hazard apart from static stress interactions other mechanisms including dynamic stress transfer have been proposed to be part of a complex triggering process exploiting the theoretical relation between long term earthquake rates and stressing rate we demonstrate that static stress changes resulting from an earthquake rupture allow us to predict quantitatively the aftershock activity without tuning specific model parameters these forecasts are found to be in excellent agreement with all first order characteristics of aftershocks in particular 1 the total number 2 the power law distance decay 3 the scaling of the productivity with the main shock magnitude 4 the foreshock probability and 5 the empirical bath law providing the maximum aftershock magnitude which supports the conclusion that static stress transfer is the major mechanism of earthquake triggering

postglacial rebound observed by lageos and the effective viscosity of the lower mantle sixty four observations of the orbital node made by the lageos satellite over a five year time interval reveal an acceleration of 8 1 or 1 8 x 10 to the 8 power arcseconds day 2 due to a source which is not presently modeled in the geodyn orbit determination computer program this acceleration cannot be explained by the ocean tide with 18 6 year period assuming it to be an equilibrium tide instead it seems to be due to postglacial rebound which changes the j 2 coefficient in the spherical harmonic expansion of the earth s gravitational field at the rate of 8 2 or 18 x 10 to the 19th power s this in turn accelerates the node this rate does not agree with the 32 x 10 to the 19th power s predicted by wu and peltier s 1982 l2 model which has upper and lower mantle effective viscosities of 10 to the 21st and 22nd powers pa s respectively it does agree well with their l1 model which gives about 10 x 10 to the 19th power s since the effective viscosity is 10 to the 21st power pa s throughout the entire mantle in the l1 model the results support the contentions that the efective viscosity is near 10 to the 21st power pa s everyhere in the mantle and this relatively low value for the effective viscosity may have permitted several degrees of polar wander due to glaciation during the quaternary ice age previously announced in star as n84 13705

a study of the coulomb stress and seismicity rate changes induced by the 2008 m w 7 9 wenchuan earthquake sw china abstract correlations between the calculated coulomb stress changes and observed seismicity rate changes after the wenchuan earthquake are investigated in this article three improvements are made in the calculation of static stress change including employing a dislocation method with triangular elements rather than traditional rectangular elements setting up a more realistic source slip model and a more complete receiver fault model and resolving stress changes on assumed receiver faults with spatially variable focal mechanisms based on well determined focal mechanisms at different calculation points the recorded aftershocks are mapped for comparison with the spatial distribution of stress changes the results indicate that the wenchuan earthquake encourages not only three major fault systems the east kunlun south of xianshuihe and west of qinling southern frontal but also several other regions including tazang north of min jiang north of pingwu qingchuan and west of chongqing in particular the eastern segment of longriba is shown to be quite dangerous with dramatic stress increase the influence of depth and frictional coefficient is analyzed the depth of calculation beyond the depth range of the source model will make a significant difference to the stress change map and thus cannot be neglected many aftershocks occurring in the stress shadow zone near the main rupture can be attributed to dynamic stress triggering and the fractal structure of the main fault the observed seismicity rate changes are compared with the static stress changes the results show that high background seismicity rates will amplify the effect of stress change the observed seismicity rate changes support the forecast rate of 10 year seismicity after the wenchuan earthquake based on the rate and state dependent friction model coulomb stresses increase on the focal mechanisms away from the main rupture which demonstrates the influence of the wenchuan earthquake over a wide range especially the focal mechanism for lushan earthquake undergoes a stress increase by more than 2 0 bars which suggests that the lushan earthquake has been effectively promoted by the wenchuan earthquake

the results of deep geomagnetic soundings in the west carpathians summary the results of geomagnetic soundings in the west carpathians are presented the number of observation sites in this region was approximately 90 the data treatment included the calculation of single station transfer functions and the separation of the fields into external and internal parts on some profiles the interpretation was based on the construction of two dimensional models explaining the observed features the observed distribution of geomagnetic induction vectors is very regular and the axis of the anomaly runs in the contact region between the outer and inner carpathians the thickness of the well conducting rock complex exceeds 10 km the well conducting rocks seem to be the sediments which accumulated in the contact region of the platform the asymmetry in the distribution of induction vector amplitudes on some profiles can be accounted for by asymmetrical geometry which is characteristic of the underthrusting of rocks

large scale crustal conductivity pattern in central europe and its correlation to deep tectonic structures the results of magnetovariational mv soundings are usually presented in the form of induction arrows however many examples show that the horizontal magnetic tensor hmt is more informative the distribution of some hmt invariants directly traces the location of well conducting rocks in the crust and upper mantle the hmt determination requires simultaneous observations in an entire region which is a substantial disadvantage yet it is possible to apply techniques capable of restoring all the magnetic field components necessary for hmt estimation from tipper data arrays alone these techniques exploit the spatial relationships between electromagnetic field components in a non conducting atmosphere for central europe a large data set of induction arrows has been collected by the effort of many groups during the last 50 years based on these data hmt values were calculated and the results are very significant the spatial behavior of certain hmt invariants demonstrates the presence of deeply seated well conducting rocks in the crust anomaly maximums display an arc shaped trend that may be genetically linked with the caledonian and or variscan margin thrust belts which developed following the collision between baltica and avalonia and or gondwana derived terranes respectively this is an important finding because the position of these deformation fronts in relation to the edge of the east european platform is still controversial

mantle phase transitions and the free air gravity anomalies over fennoscandia and laurentia the interpretation of free air gravity anomalies over present day centers of postglacial rebound has always been controversial we show that the observed gravity anomalies over both fennoscandia and laurentia and the associated relative sea level variations since deglaciation are explicable with a simple newtonian viscoelastic model of the earth if the earth model includes the density jumps in the mantle associated with the phase transitions at 420 and 670 km depth the result has important implications for mantle convection since the observed free air anomalies are very sensitive to the viscosity of the mantle beneath the deepest phase transition

how did the 2013 lushan earthquake ms 7 0 trigger its aftershocks insights from static coulomb stress change calculations the lushan earthquake ms7 0 occurred at 08 02 beijing time 00 02 utc on 20 april 2013 located on the eastern margin of the tibetan plateau where the 2008 ms8 0 wenchuan earthquake took place the other strong shock following the wenchuan earthquake occurred on the longmen shan thrust fault a large number of aftershocks were recorded after the mainshock to investigate how the aftershocks were triggered we firstly relocated the 6 month aftershock sequence by the double difference algorithm next we calculated coulomb failure stress changes imparted by the lushan mainshock both on the optimally oriented plane and on the aftershock nodal planes then we examined the correspondence between the coulomb failure stress changes and the spatial distribution of the aftershocks the computed results show that most of the aftershock hypocenters did not occur on the region with the positive coulomb stress changes caused by the lushan mainshock moreover the majority of aftershock nodal planes were brought away from failure by coseismic coulomb stresses this implies that coseismic static coulomb stress changes may not be the governing process for aftershock genesis in contrast postseismic stress transfer by processes of afterslip and pore fluid flow are assumed to play an important part in aftershock triggering based upon the spatiotemporal distribution of the aftershocks

the thickness of the continental lithosphere two independent sets of geophysical data are shown to be particularly sensitive to the thickness of the continental lithosphere both are connected with the response of the planet to the last deglaciation event of the current ice age the first set of data consists of relative sea level histories in the age range 0 10 kyr b p from sites along the eastern seaboard of north america such data appear to require a continental lithospheric thickness in excess of 200 km the second set of data consists of the ils record of the motion of the rotation pole over the time range 0 75 years b p which reveals a secular drift at the rate of 0 95 0 15 deg 106 years toward hudson bay when the viscosity profile of the mantle is fixed to that required to explain free air gravity and relative sea level data from within the ice margin and the observed nontidal acceleration of planetary rotation then these observations also suggest a continental lithospheric thickness of the same order

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

glacial isostatic adjustment i the forward problem summary the isostatic adjustment of a radially stratified visco elastic spheroid is treated using space time green functions for the associated surface mass load boundary value problem these impulse response functions are convolved with a heaviside function to give the time dependent deformation of the planet which would be produced by a unit point mass brought up from infinity at t 0 and allowed to remain on the surface the resulting heaviside green functions can be employed to simulate all of the important signatures of glacial isostatic adjustment given a space time dependent surface mass load consisting of ice sheet ablation histories and a model of the simultaneous filling of the ocean basins these source terms are simply convolved with the heaviside green function appropriate to a specific response signature a realistic model of the spatial distribution of the main late pleistocene ice loads and of their temporal disintegration is constructed the response of two visco elastic earth models is computed and compared to a global set of relaxation data relative sea level curves on the basis of this initial comparison of theory and observation the possibility that the lower mantle has a viscosity which is significantly in excess of the viscosity of the upper mantle is excluded in addition clear evidence of the presence of the lithosphere has been found in relaxation data from sites which were near the edge of the laurentide ice sheet such data should therefore prove useful as a basis for analysis of lateral variations in lithosphere thickness further extensions of the calculation are suggested

klippen belt flysch belt and inner western carpathian paleogene basin relations in the northern slovakia by magnetotelluric imaging the paper presents the interpretation of magnetotelluric measurements along the sw ne profile near stara ubov a northern slovakia the profile passes through the outer carpathian flysch belt klippen belt and ends in the inner western carpathians paleogene nw from ru bachy horst structure the interpretation of the older measurements from profile mt4 was utilized and moreover the 3 d geoelectrical model of studied region was constructed the magnetotelluric data interpretations verified the northern inclination of flysch belt structures and their smaller thickness out of klippen belt in direction to the carpathian electrical conductivity zone axis we consider this as a consequence of the flower structure more precisely the southern branch of the suture zone related to mentioned conductivity zone northerly from this zone the thickness of the outer carpathian flysch belt increases and the structures have inclination to the south i e to the subduction zone the contact of flysch belt with klippen belt has a fault character and it is subvertical slightly inclined to the north the southern boundary between klippen belt and inner western carpathians has also fault character and is very steep we detect the continuation of the ru bachy horst to the ne in the basement of inner western carpathian paleogene the structural discordance between this horst and klippen belt direction is a result of younger tectonic processes according to our results the depth distribution of the pre tertiary basement below the inner western carpathian units is non uniform the basement is broken to a number of partial blocks horsts and grabens

a reappraisal of postglacial decay times from richmond gulf and james bay canada decay times inferred from relative sea level rsl histories of previously glaciated regions provide a potentially important constraint on mantle rheology we present a new compilation of rsl data from richmond gulf and james bay canada this recompilation reveals errors in previous compilations that led to inaccurate estimates for the richmond gulf decay time in a series of recently published articles we derive updated estimates for the decay time at richmond gulf and james bay using a methodology that incorporates errors in both the age and the height of the sea level markers this exercise is guided by a series of synthetic rsl calculations that show that decay time estimates in the region can be significantly biased if the rsl time series are not corrected for global eustatic sea level trends or if the estimates are based on composite rsl histories derived by combining data from both the richmond gulf and the james bay regions our decay time analysis for richmond gulf applies the pioneering approach of walcott 1980 to a large database and we derive a value of 4 0 6 6 kyr where the range is defined by a misfit tolerance 10 per cent higher than the minimum our analysis for james bay is based on the uplift curve derived by hardy 1976 and we estimate a decay time of about 2 0 2 8 kyr the difference between our estimates for richmond gulf and james bay may be due to errors in the observational record from these regions but could also be influenced by lateral variations in lithospheric structure associated with the assembly of laurentia

deglaciation induced vertical motion of the north american continent and transient lower mantle rheology the last deglaciation event of the current ice age which began approximately 18 000 years ago and ended about 7000 years ago continues to exert a profound influence on the vertical motion of the solid earth in and surrounding the regions which were once ice covered observations of such vertical motions may be employed to constrain the radial viscoelastic structure of the planet and therefore to contribute in an important way to the understanding of geodynamic processes in general in this paper both present day rates of vertical motion as recorded on tide gauges and long time scale records of vertical motion as recorded in 14c controlled relative sea level histories are employed to refine previously constructed models of the radial viscoelastic structure an interesting sidelight to this analysis is the demonstration that the lower mantle viscosity inferred from the vertical motion data could represent a transient rather than the steady state value a fact which would help considerably to reconcile the small viscosity stratification required by the glacial rebound data with the large stratification which seems to be required by some recent analyses of the geoid height anomalies associated with internal density heterogeneity of the mantle which has been revealed by application of seismic tomographic techniques a further product of these new analyses is obtained by the application of the glacial isostatic adjustment model to filter this signal from the secular trends of relative sea level observed on tide gauges from both the east and west coasts of the north american continent these results may be important in the context of recently proposed scenarios of climatic change

triggering of seismicity at short timescales following californian earthquakes 1 a method for measuring seismicity rate changes caused by the occurrence of major earthquakes in the surrounding crust is proposed it is based on a nonstationary poisson modeling of earthquake activity an estimate of the seismicity rate change and a probability measure of seismicity triggering following a large shock are derived and the removal of the influence of independent aftershock sequences of other nearby previous earthquakes is attempted without using more traditional declustering techniques the seismicity rate change estimator is corrected for its natural bias in favor of positive changes at short timescales that has so far strongly hindered measures of seismicity quiescences three californian earthquakes are examined using this method the 1989 m7 1 loma prieta the 1992 m7 3 landers and the 1994 m6 7 northridge earthquakes positive triggering is very commonly observed as expected but quiescence is however more seldomly obtained for timescales up to 100 days after the main shock this relative absence of quiescence as compared to typical predictions of coulomb modeling for example is also independently observed through direct correlation analyses of californian seismicity the possibility that the stresses caused by the main shock are spatially highly variable may explain these observations

sensitivity of coulomb stress change to the parameters of the coulomb failure model a case study using the 2008 mw 7 9 wenchuan earthquake the coulomb stress change has been widely employed to interpret mainshock mainshock and mainshock aftershock triggering as well as interactions amongst earthquake faults and volcanoes this quantitative index is computed based on the coulomb failure criterion and is a function of fault parameters including the source and receiver fault geometries the friction coefficient on the receiver fault and skempton s coefficient of the host rock thus for the robust determination of the coulomb stress change the sensitivity of the coulomb stress change to these model parameters should be thoroughly assessed however notwithstanding numerous case studies almost no systematic investigation of the sensitivity of the coulomb stress change has been performed here we present an error estimator for the coulomb stress change and then quantitatively investigate the sensitivity of the coulomb stress change to the fault model parameters for the 2008 mw 7 9 wenchuan earthquake our results indicate that for this case the coulomb stress change is the most sensitive to the uncertainty in the dip angle of the receiver fault while the influences of the uncertainties in the slip model of the source fault the strike and rake angles of the receiver fault and the friction and skempton s coefficients cannot be neglected accordingly it is crucial to perform a realistic estimate of the uncertainty in the coulomb stress change by performing such calculation future coulomb stress analyses such as the stress triggering of earthquake sequence and the likelihoods of potential earthquakes could be based on more robust coulomb stress change maps

did the 2008 mw 7 9 wenchuan earthquake trigger the occurrence of the 2017 mw 6 5 jiuzhaigou earthquake in sichuan china

response of the san andreas fault to the 1983 coalinga nunez earthquakes an application of interaction based probabilities for parkfield 1 the parkfield cholame section of the san andreas fault site of an unfulfilled earthquake forecast in 1985 is the best monitored section of the world s most closely watched fault in 1983 the m 6 5 coalinga and m 6 0 nunez events struck 25 km northeast of parkfield seismicity rates climbed for 18 months along the creeping section of the san andreas north of parkfield and dropped for 6 years along the locked section to the south right lateral creep also slowed or reversed from parkfield south here we calculate that the coalinga sequence increased the shear and coulomb stress on the creeping section causing the rate of small shocks to rise until the added stress was shed by additional slip however the 1983 events decreased the shear and coulomb stress on the parkfield segment causing surface creep and seismicity rates to drop we use these observations to cast the likelihood of a parkfield earthquake into an interaction based probability which includes both the renewal of stress following the 1966 parkfield earthquake and the stress transfer from the 1983 coalinga events we calculate that the 1983 shocks dropped the 10 year probability of a m 6 parkfield earthquake by 22 from 54 22 to 42 23 and that the probability did not recover until about 1991 when seismicity and creep resumed our analysis may thus explain why the parkfield earthquake did not strike in the 1980s but not why it was absent in the 1990s we calculate a 58 17 probability of a m 6 parkfield earthquake during 2001 2011 index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 7260 seismology theory and modeling keywords coalinga earthquake parkfield stress change earthquake probability seismicity rate

a spatial random field model to characterize complexity in earthquake slip 1 finite fault source inversions reveal the spatial complexity of earthquake slip over the fault plane we develop a stochastic characterization of earthquake slip complexity based on published finite source rupture models in which we model the distribution of slip as a spatial random field the model most consistent with the data follows a von karman autocorrelation function acf for which the correlation lengths a increase with source dimension for earthquakes with large fault aspect ratios we observe substantial differences of the correlation length in the along strike a x and downdip a z directions increasing correlation length with increasing magnitude can be understood using concepts of dynamic rupture propagation the power spectrum of the slip distribution can also be well described with a power law decay i e a fractal distribution in which the fractal dimension d remains scale invariant with a median value d 2 29 0 23 while the comer wave number k c which is inversely proportional to source size decreases with earthquake magnitude accounting for larger slip patches for large magnitude events our stochastic slip model can be used to generate realizations of scenario earthquakes for near source ground motion simulations

magnetotelluric study of the eastern margin of the bohemian massif relations between the cadomian variscan and alpine orogeny eastern margin of the bohemian massif is a geologically remarkable area where three different orogenic cycles are meeting the oldest cadomian building a basement for younger cycles a younger variscan and the youngest alpine covering the older units in the past this area was investigated by gravimetry and seismic methods recently we have supplemented broadband magnetotelluric measurements within the period range of 0 001 1000 s carried out on 29 stations distributed along a 140 km long west east regional profile the profile direction was based on local geology and then confirmed by a dimensionality and directionality analysis data showed moderate effects of cultural noise in the signals and could be successfully processed by robust methods we carried out a 2d inversion of the data using the rebocc approach the inversion results confirm the known near surface geology and reveal deeper structures on the west and in the central part of the profile units of the bohemian massif the moldanubian zone the brunovistulicum are interpreted in the east the western carpathians units are encountered short period data agree well with the known near surface geology of all inner smaller units and bring new knowledge in particular on their thickness in the shallow structure several conductive anomalies have been identified which are hypothesized to be related to graphitized layers in the moldanubian zone from long period data a new image of the moldanubian brunovistulicum contact and about the structure of the brunovistulicum especially the brunovistulian massifs was obtained

modeling seismicity rate changes during the 1997 umbria marche sequence central italy through a rate and state dependent model 1 we model the spatial and temporal pattern of seismicity during a sequence of moderate magnitude normal faulting earthquakes which struck in 1997 the umbria marche sector of northern apennines italy by applying the dieterich 1994 rate and state dependent constitutive approach the goal is to investigate the rate of earthquake production caused by repeated coseismic stress changes computed through a 3 d elastic dislocation model in a homogeneous half space the reference seismicity rate is assumed time independent and it is estimated by smoothing the seismicity that occurred in the previous decade without declustering we propose an analytical relation for deriving the stressing rate directly from the reference seismicity rate this allows us to perform a tuning of the constitutive parameter a where a accounts for the direct effect of friction in the rate and state dependent model and is the effective normal stress into the dieterich model through a maximum likelihood method which yields for this seismic sequence a best fitting value equal to 0 04 mpa our computations show that although seven out of eight main shocks are located in areas of increased rate of earthquake production numerous aftershocks are located in seismicity shadows our simulations point out that the adopted value of a strongly affects the pattern of both seismicity shadow and areas of enhanced rate of earthquake production we conclude that solely accounting for static stress changes caused by the main shocks of this seismic sequence is not sufficient to forecast the complex spatial and temporal evolution of seismicity

estimating tectonic stress rate and state with landers aftershocks a new method of analyzing the location and timing of aftershocks that makes possible estimates of the rate at which faults in the area are being loaded with stress has been developed this new method is an application of a theory of aftershocks proposed by dieterich 1994 the stress step from the mainshock triggers the aftershocks which release energy stored by tectonic loading and the mainshock and the tectonic stressing rate is responsible for the background activity thus a comparison of the number of aftershocks with the rate of background activity as a function of stress step can provide an estimate of tectonic stress rate this method requires analysis of a catalog which includes background activity as well as aftershocks the method has been applied to the aftershocks of the 1992 landers california earthquake the tectonic stress rate estimated for the mojave block is 1 2 pa d which corresponds to a repeat time for large events of 14 000 years and suggests that much of the observed strain in the mojave is anelastic the southern san andreas fault system is found to have a stress fate of 100 pa d which corresponds to a repeat time of 270 years and is consistent with primarily elastic strain accommodation inversions for the best fitting background stress state are consistent with fits of focal mechanisms and support an effective friction coefficient near 0 6 fits to the aftershock decay provide estimates of the dieterich friction parameter ad ranging from 0 02 if lithostatic pore fluids are present to 0 0003 if they are not

the use of earthquake rate changes as a stress meter at kilauea volcano stress changes in the earth s crust are generally estimated from model calculations that use near surface deformation as an observational constraint but the widespread correlation of changes of earthquake activity with stress has led to suggestions that stress changes might be calculated from earthquake occurrence rates obtained from seismicity catalogues although this possibility has considerable appeal because seismicity data are routinely collected and have good spatial and temporal resolution the method has not yet proven successful owing to the non linearity of earthquake rate changes with respect to both stress and time here however we present two methods for inverting earthquake rate data to infer stress changes using a formulation for the stress and time dependence of earthquake rates application of these methods at kilauea volcano in hawaii yields good agreement with independent estimates indicating that earthquake rates can provide a practical remote sensing stress meter

deep resistivity structure of the trans european suture zone in central poland summary the deep resistivity structure was estimated along a 400 km profile in central poland crossing the malopolska massif mm the lysogory unit lu the trans european suture zone tesz and ending at the east european craton eec magnetotelluric transfer functions corresponding to 20 sites were supplemented by magnetovariational responses obtained at the geomagnetic observatories situated at the same tectonic units such a combination made it possible to extend the initial period range which is from fractions of a second to several hours up to months in order to reliably cover crustal and upper mantle depths the geoelectrical structures revealed using 2 d inversions do not contradict the known features of the lithosphere structure determined using seismic and gravity data along the profile the subsurface conductance varying from approximately 10 siemens at the inner part of the eec to about 600 siemens in the tesz is produced by sediments the deep part of which contains conductive highly mineralized water the existence of two crustal conductive faults at the southwest and northeast of the tesz were established mainly by the use of induction arrows it was also revealed that rather high mantle conductivity beneath the mm lu and tesz at depths of about 150 200 km contrasts with the resistive upper mantle of the eec this can be interpreted as the decrease of asthenosphere conductance and or as its submersion beneath the eec generally the results confirm the idea that the tesz forms not only specific seismic boundaries but also causes peculiar conductivity anomalies in the crust and upper mantle

measurement requirements for glacial uplift detection of nonadiabatic density gradients in the mantle recent isotope studies have rekindled interest in the possibility that the mantle may be chemically stratified and therefore nonadiabatic previous calculations of the last ice age are compatible only with a 1022p mantle calculations of the isostatic response of an adiabatic partially nonadiabatic and fully nonadiabatic 1022p mantle to the load cycle of the last ice age show that the uplift responses of an adiabatic and even partially nonadiabatic mantle are very different however geoid perturbations mask these differences and the emergence curves of the two mantle types are nearly identical except in the regions near and under the ice loads at the early stages of isostatic readjustment the calculations suggest that we must seek shoreline emergence data around glaciated areas more than 6000 years before present if nonadiabatic density gradients in the mantle are to be detected from emergence data

on induction effects at eiscat and image magnetometer stations summary when ground based magnetometer data are used for ionospheric magnetospheric studies it is important to know the external ionospheric magnetospheric and internal telluric contributions to the observed total variation to study them we calculate geomagnetic induction vectors and apply the siebert kertz separation method using data from the eiscat and image magnetometer stations in fennoscandia induction vectors in the period range 20 2560s show the expected and dominating ocean effect near the arctic ocean at masi a small scale inland anomaly is detected in addition to the ocean effect at hankasalmi a man made anomaly due to the nearby stare radar is present the source effect on induction vectors at high latitudes is briefly investigated by separating the magnetic variations of several bay events at image stations into external and internal parts we study the importance of the large scale induction in the recordings depending very much on the particular event the internal horizontal part is 10 30 per cent of the total field in the auroral electrojet region and its relative contribution increases in more distant regions the internal contribution of the vertical field at inland stations is 10 40 per cent having an opposite sign to the total field or 10 30 per cent having the same sign as the total field depending on the location with respect to the ionospheric currents and to the ocean results are also discussed using a thin sheet model

new constraints on transient lower mantle rheology and internal mantle buoyancy from glacial rebound data a model of mantle rheology which has an explicit transient component of its relaxation spectrum is shown to reconcile two apparently conflicting inferences of lower mantle viscosity if recent analyses of isostatic geoid anomalies are correct in requiring a large increase of viscosity with depth then the weak viscosity stratification demanded by postglacial rebound data implies the importance of such rheological behaviour at least in the earth s lower mantle

the sensitivity of the loa unload response ratio and critical region selection before large earthquakes occurrence of a large earthquake could be predicted by anomalous temporal increase of the load unload response ratio lurr previous studies have indicated that the stress field that existed before a large earthquake may have a strong influence on the evaluation of lurr in this paper 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 this algorithm is devised to increase the sensitivity of lurr to measure criticality of stress accumulation before a large earthquake in the algorithm we assess the stress change and identify the areas with increased coulomb stress before an earthquake using a simple back slip dislocation model of the event retrospective tests of this algorithm on some disastrous earthquakes that occurred in the chinese mainland in recent years show remarkable enhancement of the lurr precursory anomalies by using the hypothetical faults for the large earthquake prediction we further illustrate that the new algorithm is more sensitive to detect future earthquake of a particular magnitude range and location than the circular region algorithm hence where sufficient information of the regional fault tectonics is given the coulomb stress algorithm can be used to augment current lurr technique for seismic hazard estimation

evidence from the ad 2000 izu islands earthquake swarm that stressing rate governs seismicity magma intrusions and eruptions commonly produce abrupt changes in seismicity far from magma conduits that cannot be associated with the diffusion of pore fluids or heat such swarm seismicity also migrates with time and often exhibits a dog bone shaped distribution the largest earthquakes in swarms produce aftershocks that obey an omori type exponential temporal decay but the duration of the aftershock sequences is drastically reduced relative to normal earthquake activity here we use one of the most energetic swarms ever recorded to study the dependence of these properties on the stress imparted by a magma intrusion a 1 000 fold increase in seismicity rate and a 1 000 fold decrease in aftershock duration occurred during the two month long dyke intrusion we find that the seismicity rate is proportional to the calculated stressing rate and that the duration of aftershock sequences is inversely proportional to the stressing rate this behaviour is in accord with a laboratory based rate state constitutive law suggesting an explanation for the occurrence of earthquake swarms any sustained increase in stressing rate whether due to an intrusion extrusion or creep event should produce such seismological behaviour

modeling of kashmir aftershock decay based on static coulomb stress changes and laboratory derived rate and state dependent friction law we model the spatial and temporal evolution of october 8 2005 kashmir earthquake s aftershock activity using the rate and state dependent friction model incorporating uncertainties in computed coseismic stress perturbations we estimated the best possible value for frictional resistance a n background seismicity rate r and coefficient of stress variation cv using maximum log likelihood method for the whole kashmir earthquake sequence we measure a frictional resistance a n 0 0185 mpa r 20 m3 7 events year and cv 0 94 0 01 the spatial and temporal forecasted seismicity rate of modeled aftershocks fits well with the spatial and temporal distribution of observed aftershocks that occurred in the regions with positive static stress changes as well as in the apparent stress shadow region to quantify the effect of secondary aftershock triggering we have re run the estimations for 100 stochastically declustered catalogs showing that the effect of aftershock induced secondary stress changes is obviously minor compared to the overall uncertainties and that the stress variability related to uncertain slip model inversions and receiver mechanisms remains the major factor to provide a reasonable data fit

a new estimation of the decay of aftershock density with distance to the mainshock we investigate how aftershocks are spatially distributed relative to the mainshock compared to previous studies ours focuses on earthquakes causally related to the mainshock rather than on aftershocks of previous aftershocks we show that this distinction can be made objectively but becomes uncertain at long time scales and large distances analyzing a regional earthquake data set it is found that at time t following a mainshock of magnitude m the probability of finding an aftershock at distance r relative to the mainshock fault decays as r where is typically between 1 7 and 2 1 for 3 m 6 and is independent of m for r less than 10 to 20 km and t less than 1 day uncertainties on this probability at larger r and t do not allow for a correct estimation of this spatial decay we further show that a static stress model coupled with a rate and state friction model predicts a similar decay with an exponent 2 2 in the same space and time intervals this suggests that static stress changes could explain the repartition of aftershocks around the mainshock even at distances larger than 10 times the rupture length

aftershock modeling based on uncertain stress calculations 1 we discuss the impact of uncertainties in computed coseismic stress perturbations on the seismicity rate changes forecasted through a rate and state dependent frictional model we aim to understand how the variability of coulomb stress changes affects the correlation between predicted and observed changes in the rate of earthquake production we use the aftershock activity following the 1992 m7 3 landers california earthquake as a case study to accomplish these tasks we first analyze the variability of stress changes resulting from the use of different published slip distributions we find that the standard deviation of the uncertainty is of the same size as the absolute stress change and that their ratio the coefficient of variation cv is approximately constant in space this uncertainty has a strong impact on the forecasted aftershock activity if a rate and state frictional model is considered we use the early aftershocks to invert for friction parameters and the coefficient of variation by means of the maximum likelihood method we show that when the uncertainties are properly taken into account the inversion yields stable results which fit the spatiotemporal aftershock sequence the analysis of the 1992 landers sequence demonstrates that accounting for realistic uncertainties in stress changes strongly improves the correlation between modeled and observed seismicity rate changes for this sequence we measure a friction parameter asn 0 017 mpa and a coefficient of stress variation cv 0 95

refined models of the conductivity distribution at the transition from the bohemian massif to the west carpathians using stochastic mcmc thin sheet inversion of the geomagnetic induction data although volume 3d modeling solutions has become widespread in recent time thin sheet approximation of earth s conductivity distribution can still serve as a useful tool when quasi 3d conductivity structures in the heterogeneous subsurface are investigated and the available database of observations is limited to long period electromagnetic induction data from large scale deep sounding arrays we present results of stochastic monte carlo markov chains mcmc inversion of long period induction arrows based on the bayesian statistics strategy we concentrated on the different methodological aspects of mcmc for gibbs sampling and for adaptive metropolis algorithm together with convergence of these methods the results are presented on a case study from the transition zone between the bohemian massif and the west carpathians where a phantom effect caused by superposition of the prominent sw ne trending carpathian conductivity anomaly and nw se trending anomalous structure related to the fault system at the eastern boundary of the bohemian massif appears

glacial isostatic adjustment and the free air gravity anomaly as a constraint on deep mantle viscosity summary a gravitationally self consistent theory for relative sea level variations forced by pleistocene deglaciation events is employed to explore the extent to which rsl and free air gravity observations together constrain the viscosity of the mantle beneath the seismic discontinuity at 670 km depth a trade off is revealed between errors in the assumed deglaciation history and errors in the inferred value of the viscosity of the lower mantle taking full account of such uncertainty plausible values of the viscosity beneath the transition region are bounded above by 1023 poise cgs units the preferred value is at least a factor of 2 lower than this and is strongly constrained by the observed free air gravity anomaly over hudson bay the calculations described in detail here show for the first time that the relatively large gravity anomalies observed over sites of wurm wisconsin deglaciation do not require any pronounced increase of mantle viscosity with depth in order to explain them

southern california hypocenter relocation with waveform cross correlation part 2 results using source specific station terms and cluster analysis we obtain precise relative relocations for more than 340 000 southern california earthquakes between 1984 and 2002 by applying the source specific station term ssst method to existing p and s phase picks and a differential lo cation method to about 208 000 events within similar event clusters identified with waveform cross correlation the entire catalog is first relocated by using existing phase picks a reference 1d velocity model and the ssst method of richards dinger and shearer 2000 we also perform separate relocations of imperial valley events by using a velocity model more suited to this region next we apply cluster analysis to the waveform cross correlation output to identify similar event clusters we re locate earthquakes within each similar event cluster by using the differential times alone keeping the cluster centroid fixed to its initial ssst location we estimate standard errors for the relative locations from the internal consistency of differential locations between individual event pairs these errors are often as small as tens of meters in many cases the relocated events within each similar event cluster align in planar features suggestive of faults we observe a surprising number of such faults at small scales that strike nearly perpendicular to the main seismicity trends in general the fine scale details of the seismicity reveal a great deal of structural com plexity in southern california fault systems

high frequency spectral falloff of earthquakes fractal dimension of complex rupture b value and the scaling of strength on faults the high frequency falloff omega sup minus gamma of earthquake displacement spectra and the b value of aftershock sequences are attributed to the character of spatially varying strength along fault zones the author assumes that the high frequency energy of a main shock is produced by a self similar distribution of subevents where the number of subevents with radii greated than r is proportional to r sup minus d d being the fractal dimension in this model an earthquake is composed of a hierarchical set of smaller earthquakes the static stress drop is parameterized to be proportional to r sup eta and strength is assumed to be proportional to static stress drop he finds that a distribution of subevents with d 2 and stress drop independent of seismic moment eta 0 produces a main shock with an omega sup minus 2 falloff if the subevent areas fill the rupture area of the main shock by equating subevents to islands of high stress of a random self similar stress field on a fault he relates d to the scaling of strength on a fault such that d 2 minus eta thus d 2 corresponds to constant stress drop scaling eta 0 and scale invariant fault strength amore self similar model of aftershock rupture zones on a fault is used to determine the relationship between the b value the size distribution of aftershock rupture zones and the scaling of strength on a fault the b value for aftershock sequences on a fault is found to equal 3 minus 1 5 eta 3 eta therefore this model indicates that the typically observed spectral falloffs of omega sup minus 2 and b values of 1 can be entirely caused by scale invariant strength eta 0 along fault zones less

a paleoclimate model of northern hemisphere ice sheets abstract a model for predicting the growth and decay of ice sheets based on the astronomical theory of climate change is presented the purpose of the study in part is to isolate the role of the ice sheet physics and earth response under varying ice load by simplifying to the extreme the role of the hydrosphere atmosphere ice sheet physics and the response of the lithosphere asthenosphere under the ice load are modeled explicitly insolation anomalies taken at a fixed latitude directly force latitudinal displacement of the snow line accumulation rate a and ablation rate a evaluated at mean sea level are specificed as external constants a a decrease linearly with ice sheet elevation rough tuning of the model to the general shape of the ice volume record of the last two major glacials determines the external constants model predictions of the ages of several events in the last major glaciation compare well with the radiological ages the six glacial terminatios i vi over the last 600 000 yr are identified and the predicted ages compare reasonably well with the 18 o record for two deep sea cores a direct comparison of model power spectra of ice volume as a function of period with spectra of the 18 o record shows apparent underprediction of power near 100 000 yr when a quantitative but heuristic method for taking into account the red noise spectrum evident in the geological records is used a much more favorable comparison is possible the model prediction lends support to the hypothesis that the nonlinearity of the ice sheet physics is responsible for the 100 000 yr periodicity in the geological record of the late pleistocene

sensitivity of static stress calculations to the earthquake slip distribution 1 the apparent strong correlation between coulomb stress changes and the spatial distribution of aftershocks suggests the possibility of making near real time estimations of areas at risk of experiencing off fault aftershocks in order to do this in practice a number of issues must first be addressed including the extent to which the main shock slip must be known in detail before a meaningful stress map can be constructed here we investigate this issue by constructing a time ordered sequence of slip solutions for the landers earthquake computing coulomb stress changes for each solution and quantitatively comparing the stress field with the observed aftershocks by 1 resolving the coulomb stress change onto the aftershock nodal planes and calculating the percentage of events consistent with triggering and 2 constructing a two dimensional map of coulomb stress and computing the correlation coefficient between the positive and negative areas and the locations of the aftershocks we find that slip solutions based on empirical relations and either focal mechanism or moment tensor data produce stress fields inconsistent with the observed spatial distribution of aftershocks whereas slip solutions incorporating the correct rupture geometry but greatly simplified slip produce stress fields consistent with the aftershock distribution when very near fault events are excluded we further find that resolving stress perturbations onto earthquake nodal planes and computing the percentage of events experiencing positive coulomb stress provides a poor measure of success because of the limited range of structures on which events occur and the compatibility of the main shock stress field with these structures our results support the hypothesis that coulomb stress changes affect the spatial distribution of aftershocks and suggest that meaningful calculations of coulomb stress can be made as soon as an earthquake s rupture geometry is well constrained

complex local moho topography in the western carpathians indication of the alcapa and the european plate contact seismic data from deep refraction and wide angle reflection profiles intersecting the western carpathians show distinct upper mantle pn phases with anomalous apparent velocities identified in the first and later arrivals their systematic analysis indicates that such phases are present in numerous seismic sections both for in line and off line shots they are observed in data from profiles intersecting the carpathians in the west at the contact with the bohemian massif similar feature was also found in data at the northern edge of the carpathians at the contact with the north european platform modelling of these anomalous pn phases shows that they originate due to local structural anomalies of the moho discontinuity detected in several places along the western carpathian arc such anomalies are located in close lateral proximity of the pieniny klippen belt representing the contact between the stable european plate in the north and the alcapa alpine carpathian pannonian microplate in the south thus the complex local moho topography modelled from the pn phases suggests tectonic relation to the formation of the carpathian orogen the result is supported by correlation with the large scale carpathian conductivity anomaly modelled in the carpathians at a mid crustal level relative lateral position of these two structures together with the pieniny klippen belt at the surface delineates a zone affected by deformations at various depths along the whole western carpathian arc

influence of glacial isostatic adjustment on tide gauge measurements of secular sea level change modem tide gage records of secular sea level change are strongly contaminated by the ongoing influence of glacial isostatic adjustment in this paper we employ an accurate high resolution model of the glacial isostatic adjustment process to filter this signal from time series consisting of annual mean heights observed on over 500 tide gages from which records of duration longer than 10 years are available these records are all contained in the archive of the permanent service for mean sea level at bidston in the united kingdom prior to removal of the isostatic adjustment contamination from these records the secular sea level change signal is seen to exhibit both rising and falling levels depending upon geographic location with regions of falling level corresponding to those that were ice covered during the last glaciation event of the present ice age after filtering the geographic heterogeneity in rates is considerably reduced so much so that a globally coherent component consisting of a rise of sea level at a rate of 2 4 0 9 mm yr 1 is revealed this could conceivably be driven by the greenhouse effect although no particular mechanism has been unambiguously identified by our analyses we investigate the impact of a number of different variants of the analysis procedure upon the inferred global signal

nanoseismicity and picoseismicity rate changes from static stress triggering caused by a mw 2 2 earthquake in mponeng gold mine south africa static stress changes following large earthquakes are known to affect the rate and distribution of aftershocks yet this process has not been thoroughly investigated for nanoseismicity and picoseismicity at centimeter length scales here we utilize a unique data set of m 3 4 earthquakes following a mw 2 2 earthquake in mponeng gold mine south africa that was recorded during a quiet interval in the mine to investigate if rate and state based modeling is valid for shallow mining induced seismicity we use dieterich s 1994 rate and state dependent formulation for earthquake productivity which requires estimation of four parameters 1 coulomb stress changes due to the main shock 2 the reference seismicity rate 3 frictional resistance parameter and 4 the duration of aftershock relaxation time comparisons of the modeled spatiotemporal patterns of seismicity based on two different source models with the observed distribution show that while the spatial patterns match well the rate of modeled aftershocks is lower than the observed rate to test our model we used three metrics of the goodness of fit evaluation the null hypothesis of no significant difference between modeled and observed seismicity rates was only rejected in the depth interval containing the main shock results show that mining induced earthquakes may be followed by a stress relaxation expressed through aftershocks located on the rupture plane and in regions of positive coulomb stress change furthermore we demonstrate that the main features of the temporal and spatial distributions of very small mining induced earthquakes can be successfully determined using rate and state based stress modeling

a seismicity burst following the 2010 m 6 4 jiashian earthquake implications for short term seismic hazards in southern taiwan abstract following the 4 march 2010 mw 6 4 jiashian earthquake the seismicity rate in southern taiwan was determined to be significantly higher than before the quake and aroused seismic hazard awareness in this work seismic hazards were investigated in terms of earthquake activity the coulomb stress change the rate and state friction model and short term seismic hazard assessments the significantly higher seismicity rate that followed the 2010 jiashian earthquake was found to mainly be attributed to aftershock decay in terms of the modified omori formula the results suggest that aftershock duration may continue until the end of 2012 the spatial migration of seismicity was modeled using the coulomb stress changes of large earthquakes most of the consequent events were distributed in the vicinity of large earthquakes the observations corresponded to a remarkable stress increase within the same area additionally large events were located within regions with stress increases promoted by previous earthquakes the results confirm interactive relationships between large events by considering time dependency the seismicity rate evolution was estimated using the rate and state friction model the results indicated that a high seismic rate will persist at least until the end of 2012 short term probabilistic seismic hazard assessments were also applied in terms of the probability of strong ground motion using this application a sudden jump in seismic hazards in southern taiwan was accompanied by each large earthquake at the end of 2012 it is expected that hazards will return to a background level our results may be valuable in the future to decision makers and public officials engaged in seismic hazard mitigation

seismic constraints on the morphology of deep slabs residual sphere images from deep earthquakes not only detect the presence of slab associated velocity anomalies but also lend insight into the flow and deformation of lithosphere subducted into the lower mantle we have compared travel times from deep events in the kuril and mariana arcs with the seismic velocity anomalies implied by kinematical models that thicken the slab perpendicular to its plane by reducing the vertical velocity of the flow with depth we assume that the details of the deformation whether the slab buckles imbricates fragments etc are averaged out along the ray paths and hence our models constrain the scale not the mode of slab thickening the deep event travel times are best fit by undeformed models but the ability of the residual sphere method to resolve slab thickness is limited by ray bending effects although the mariana times are consistent with advective thickening factors of 5 or more factors larger than 3 are ruled out by the kuril data for all models examined the data require that slab material extends to depths of 900 1000 km global tomographic models and regional studies which delineate high velocity anomalies in the lower mantle beneath zones of cenozoic subduction are consistent with our results as is recent work on pulse distortion by slab gradients comparison of observed and predicted rates of seismic moment release suggests that if substantial advective thickening does occur it is largely aseismic

forecasting the evolution of seismicity in southern california animations built on earthquake stress transfer 1 we develop a forecast model to reproduce the distribution of main shocks aftershocks and surrounding seismicity observed during 1986 2003 in a 300 310 km area centered on the 1992 m 7 3 landers earthquake to parse the catalog into frames with equal numbers of aftershocks we animate seismicity in log time increments that lengthen after each main shock this reveals aftershock zone migration expansion and densification we implement a rate state algorithm that incorporates the static stress transferred by each m 6 shock and then evolves coulomb stress changes amplify the background seismicity so small stress changes produce large changes in seismicity rate in areas of high background seismicity similarly seismicity rate declines in the stress shadows are evident only in areas with previously high seismicity rates thus a key constituent of the model is the background seismicity rate which we smooth from 1981 to 1986 seismicity the mean correlation coefficient between observed and predicted m 1 4 shocks the minimum magnitude of completeness is 0 52 for 1986 2003 and 0 63 for 1992 2003 a control standard aftershock model yields 0 54 and 0 52 for the same periods four m 6 0 shocks struck during the test period three are located at sites where the expected seismicity rate falls above the 92 percentile and one is located above the 75 percentile the model thus reproduces much but certainly not all of the observed spatial and temporal seismicity from which we infer that the decaying effect of stress transferred by successive main shocks influences seismicity for decades finally we offer a m 5 earthquake forecast for 2005 2015 assigning probabilities to 324 10 10 km cells

afterslip and aftershocks in the rate and state friction law istituto nazionale di geofisica e vulcanologia italy ingv centre national de la recherche scientifique cnrs exxonmobil upstream research company

improving empirical aftershock modeling based on additional source information 1 several mechanisms are proposed to underlie earthquake triggering including static stress interactions and dynamic stress transfer significant differences of these mechanisms are particularly expected in the spatial distribution of aftershocks however testing the different hypotheses is challenging because it requires the consideration of the large uncertainties involved in stress calculations as well as the appropriate consideration of secondary aftershock triggering which is related to stress changes induced by smaller pre and aftershocks in order to evaluate the forecast capability of different mechanisms we take the effect of smaller magnitude earthquakes into account by using the epidemic type aftershock sequence etas model where the spatial probability distribution of direct aftershocks if available is correlated to alternative source information and mechanisms we test surface shaking rupture geometry and slip distributions as an approximation of the shaking level we use shakemap data which are available in near real time after a main shock and thus could be used for first order forecasts of the spatial aftershock distribution alternatively we test the use of empirical decay laws related to minimum fault distance and coulomb stress change calculations based on published and random slip models for comparison we analyze the likelihood values of the different model combinations in the case of several well known aftershock sequences 1992 landers 1999 hector mine 2004 parkfield our test shows that the fault geometry is the most valuable information for improving aftershock forecasts furthermore we find that static stress maps can additionally improve the forecasts of off fault aftershock locations while the integration of ground shaking data could not upgrade the results significantly

spatial and temporal distribution of slip for the 1992 landers california earthquake we have determined a source rupture model for the 1992 landers earthquake m w 7 2 compatible with multiple data sets spanning a frequency range from zero to 0 5 hz geodetic survey displacements near field and regional strong motions broadband teleseismic waveforms and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface our fault parameterization involves a variable slip multiple segment finite fault model which treats the diverse data sets in a self consistent manner allowing them to be inverted both independently and in unison the high quality data available for the landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern in all models consistent features include the following 1 similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 10 26 dyne cm seismic potency of 2 3 to 2 7 km 3 2 very heterogeneous unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km though slip is limited to shallower regions in some areas 3 a total rupture duration of 24 sec and an average rupture velocity of 2 7 km sec and 4 substantial variations of slip with depth relative to measured surface offsets the extended rupture length and duration of the landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter duration strike slip events our imaging allows visualization of the rupture evolution including local differences in slip durations and variations in rupture velocity rupture velocity decreases markedly at shallow depths as well as near regions of slip transfer from one fault segment to the next as rupture propagates northwestward along the multiply segmented fault length the rupture front slows as it reaches the northern limit of the johnson valley landers faults where slip is transferred to the southern homestead valley fault an abrupt acceleration is apparent following the transfer this process is repeated and is more pronounced as slip is again passed from the northern homestead valley fault to the emerson fault although the largest surface offsets were observed at the northern end of the rupture our modeling indicates that substantial rupture was also relatively shallow less than 10 km in this region

impact of the receiver fault distribution on aftershock activity 1 aftershock models are usually based either on purely empirical relations ignoring the physical mechanism or on deterministic calculations of stress changes on a predefined receiver fault orientation here we investigate the effect of considering more realistic fault systems in models based on static coulomb stress changes for that purpose we perform earthquake simulations with elastic half space stress interactions rate and state dependent frictional earthquake nucleation and extended ruptures with heterogeneous fractal slip distributions we find that the consideration of earthquake nucleation on multiple receiver fault orientations does not influence the shape of the temporal omori type aftershock decay but changes significantly the predicted spatial patterns and the total number of triggered events so called stress shadows with decreased activity almost vanish and activation decays continuously with increasing distance from the main shock rupture the total aftershock productivity which is shown to be almost independent of the assumed background rate increases significantly if multiple receiver fault planes exist the application to the 1992 m7 3 landers california aftershock sequence indicates a good agreement with the locations and the total productivity of the observed directly triggered aftershocks

cumulative coulomb stress triggering as an explanation for the canterbury new zealand aftershock sequence initial conditions are everything using 2 years of aftershock data and three fault plane solutions for each of the initial m7 1 darfield earthquake and the larger m 6 aftershocks we conduct a detailed examination of coulomb stress transfer in the canterbury 2010 2011 earthquake sequence moment tensor solutions exist for 283 of the events with m ge 3 6 while 713 other events of m ge 3 6 have only hypocentre and magnitude information available we look at various methods for deciding between the two possible mechanisms for the 283 events with moment tensor solutions including conformation to observed surface faulting and maximum delta cff transfer from the darfield main shock for the remaining events imputation methods for the mechanism including nearest neighbour kernel smoothing and optimal plane methods are considered fault length width and depth are arrived at via a suite of scaling relations a large 50 70 proportion of the faults considered were calculated to have initial loading in excess of the final stress drop the majority of faults that accumulated positive delta cff during the sequence were encouraged by the main shock failure but on the other hand of the faults that failed during the sequence more than 50 of faults appeared to have accumulated a negative delta cff from all preceding failures during the sequence these results were qualitatively insensitive to any of the factors considered we conclude that there is much unknown about how coulomb stress triggering works in practice

continental lithospheric thickness and deglaciation induced true polar wander the secular drift of the earth s rotation pole which is evident in ils data is a memory of the planet of the last deglaciation event of the current ice age in order to fit the observed rate and direction of drift with an earth model whose viscosity profile is capable of reconciling the free air gravity and relative sea level data of postglacial rebound requires a lithospheric thickness which is substantially in excess of that which might be considered an appropriate average thickness for the entire planet this required thickness which is greater than 250 km is nevertheless in accord with independent estimates of the thickness of the continental lithosphere

anomalous induction zone near the eastern margin of the bohemian massif abstract wiese vectors induction vectors field separation and a physical statistical approach were used to identify a zone of geoelectrical inhomogeneity near the eastern margin of the bohemian massif this zone seems to mark an important geological and tectonic boundary separating two different tectogenes the spatial distribution of the induction characteristics along five profiles traversing the boundary suggests a general 3 d model of internal geoelectrical geological structure for the region common reference transfer functions and corresponding in and out of phase vectors calculated by relating the data at a particular station and a common reference station were also derived as a tool for mapping internal geoelectrical structure

structural constraints on the spatial distribution of aftershocks 1 calculations of static stress changes due to large earthquakes have shown that the spatial distribution of aftershocks is predictable to first order with aftershocks primarily occurring in areas experiencing positive stress changes delineation of these areas relies on resolving the stress perturbation onto planes with known orientations common practice is to use poorly constrained regional stress information to compute optimally oriented failure planes assuming that they exist everywhere here we show that this assumption is not supported by observation but rather that aftershock failure planes are controlled by geological structure we argue that useful aftershock hazard estimates are better made by replacing information on regional stress with statistical measures of structural orientations

pleistocene deglaciation and the earth s rotation a new analysis summary this paper is concerned with an analysis of the effect of the pleistocene glacial cycle upon the earth s rotation we demonstrate that two important geophysical observables may be explained as aspects of the rotational response to surface mass loading by ice sheets these are the astronomically observed non tidal component of the acceleration of planetary rotation and the secular drift of the rotation pole relative to the surface geography which is evident in the ils pole path the former observation is shown to provide an unambiguous constraint upon the viscosity of the planetary mantle and requires a depth dependence of this parameter which is the same as that which has previously been inferred in studies of the relative sea level variations and free air gravity anomalies associated with post glacial rebound the observed secular drift of the pole cannot provide an independent estimate of the viscosity of the mantle because it depends jointly upon mantle viscosity and lithospheric thickness with the viscosity profile fixed by the rebound data the observed speed of polar wander suggests a continental lithospheric thickness which is in excess of that appropriate for old ocean basins but nevertheless in accord with independent constraints

response of seismic activity in mines to the stress changes due to mining induced strong seismic events the influence of the static stress transfer due to two stronger seismic events from one mine section on subsequent seismicity linked to the same section is studied the first strong tremor was provoked by destressing blasting the static stress transfer caused by this tremor had apparently a triggering effect for the occurrence of the second strong event this second event occurred in less than three weeks after the first one and on the area of simultaneous enhancement of both shear and normal components of the coulomb stress change caused by the first event it appears also that in the next few months the cumulative stress change due to both the events influenced significantly the location and rate of smaller subsequent events interestingly contrary to the results of previous analyses the negative coulomb stress changes turn out to have a major role in this respect the coseismic stress change impact even seems to prevail over the influence of time varying stress alteration caused by advancement of the mining front

can coseismic stress variability suppress seismicity shadows insights from a rate and state friction model 1 the paucity of detectable seismicity shadows in the days months following a main shock has raised the question as to whether dynamic rather than static triggering could be the main mechanism driving the seismicity at these timescales the lack of correlation between the stress unloading of the main fault and the typically vigourous aftershock production taking place on it however suggests that the spatial heterogeneity of the coseismic stress change could also be a factor in the apparent suppression of seismicity shadows at least on the main fault here we study whether this stress variability can indeed be an important aspect in the stress modeling of earthquake sequences a rate and state friction model of seismicity is used in conjunction with realistic levels of stress heterogeneity at the earthquake nucleation scale 1 10 m as predicted from these friction laws based on scale invariant models of coseismic slip distribution in this model a relatively weak on fault quiescence is delayed by months to years because of the high stress heterogeneity delayed quiescences due to slip heterogeneity are similarly predicted at distances of up to about half the rupture length away from the fault we also postulate that off fault seismicity can be significantly controlled by stress variability that originates from small scale crustal heterogeneity and the complexity in fault geometries rather than mapping stress changes by providing a single stress value at every grid point these results suggest that an estimate of the likely stress variability acting at the nucleation scale is also needed especially when trying to account for the seismicity occurring at relatively short timescales

glacial isostatic adjustment in the static gravity field of fennoscandia in the central part of fennoscandia the crust is currently rising because of the delayed response of the viscous mantle to melting of the late pleistocene ice sheet this process called glacial isostatic adjustment gia causes a negative anomaly in the present day static gravity field as isostatic equilibrium has not been reached yet several studies have tried to use this anomaly as a constraint on models of gia but the uncertainty in crustal and upper mantle structures has not been fully taken into account therefore our aim is to revisit this using improved crustal models and compensation techniques we find that in contrast with other studies the effect of crustal anomalies on the gravity field cannot be effectively removed because of uncertainties in the crustal and upper mantle density models our second aim is to estimate the effects on geophysical models which assume isostatic equilibrium after correcting the observed gravity field with numerical models for gia we show that correcting for gia in geophysical modelling can give changes of several kilometer in the thickness of structural layers of modeled lithosphere which is a small but significant correction correcting the gravity field for gia prior to assuming isostatic equilibrium and inferring density anomalies might be relevant in other areas with ongoing postglacial rebound such as north america and the polar regions

onto what planes should coulomb stress perturbations be resolved 1 coulomb stress maps are produced by computing the tensorial stress perturbation due to an earthquake rupture and resolving this tensor onto planes of a particular orientation it is often assumed that aftershock fault planes are optimally oriented in other words the regional stress and coseismic stress change are used to compute the orientation of planes most likely to fail and the coseismic stress is resolved onto these orientations this practice assumes that faults capable of sustaining aftershocks exist at all orientations an assumption contradicted by the observation that aftershock focal mechanisms have strong preferred orientations consistent with mapped structural trends here we systematically investigate the best planes onto which stress should be resolved for the landers hector mine loma prieta and northridge earthquakes by quantitatively comparing observed aftershock distributions with stress maps based on optimally oriented planes two and three dimensional main shock orientation and regional structural trend we find that the best model differs between different tectonic regions but that in all cases models that incorporate the regional stress field tend to produce stress maps that best fit the observed aftershock distributions although not all such models do so equally well our results suggest that when the regional stress field is poorly defined or in structurally complex areas the best model may be to fix the strike of the planes upon which the stress is to be resolved to that of the main shock but allow the dip and rake to vary

viscous gravitational relaxation summary this paper is concerned with a detailed examination of the response of maxwell models of the planet to surface mass loads particular attention is devoted to an examination of the factors which determine the isostatic response since the understanding of this response is crucial in a number of different geodynamic problems one particular example which we discuss in detail is concerned with the prediction of free air gravity anomalies produced by large scale deglaciation events using the methods developed here we are able to provide the first direct assessment of the importance of initial isostatic disequilibrium on the observed relative sea level variations and free air gravity anomalies forced by the melting of the laurentide ice sheet we are therefore able to estimate the extent to which such initial disequilibrium might influence the inference of mantle viscosity from isostatic adjustment data our calculations establish that free air gravity data although they are sensitive to the degree of initial disequilibrium provide an extremely high quality constraint upon the viscosity of the lower mantle

pleistocene deglaciation and the global gravity field the present day global geoid and free air gravity anomaly signals induced by pleistocene deglaciation have been computed along with their secular variations a revised green function has been derived for the free air gravity anomaly and we find that an earth model with a lower mantle viscosity moderately larger than the upper mantle value satisfies observations of the anomaly over both hudson s bay and fennoscandia using this preferred earth model the predicted global geoid anomaly map is characterized by peak negative values of 36 7 9 4 and 21 9 m over hudson s bay northern europe and antarctica respectively and by a smooth small amplitude 2 5 m upwarping over the major ocean basins although the field has an order of magnitude less power than the observed there is a significant spatial correlation between the two inferences of mantle viscosity based upon comparisons between the observed geoid and the computed deglaciation induced anomaly are hampered by the large contribution from the convective circulation in the earth s mantle we have subtracted a predicted convection signal based on seismic tomography from the observed field however the residual geoid thus obtained is still too inaccurate to allow a useful comparison in contrast a filtered version of the observed geoid over canada which retains harmonic coefficients in the degree range 10 22 provides a relatively uncontaminated by convection datum that is indeed satisfied by the preferred earth model secular variations in the earth s gravitational field are naturally dominated by the signal from pleistocene deglaciation in this respect we compute zonal harmonics in the expansion of the present day rate of change of the geopotential and in particular we predict amplitudes comparable to that for the previously analysed j2 for j4 j5 j7 and j9 all of which reflect in large part the response due to the melting of the massive laurentide ice sheet this analysis suggests that measurement of these higher order secular variations of the zonal harmonics based upon analysis of long time series of lageos ranging data could provide very useful additional constraints on the radial variation of mantle viscosity these constraints along with all others described in this paper are shown to be relatively insensitive to assumptions concerning the deflection during the glacial isostatic adjustment process of the 400 and 670 km density discontinuities within the mantle

comparison of the 2 d and quasi 3 d geoelectric models of the ukrainian eastern carpathians and their link to the tectonic structure

extending earthquakes reach through cascading earthquakes whatever their size can trigger other earthquakes mainshocks cause aftershocks to occur which in turn activate their own local aftershock sequences resulting in a cascade of triggering that extends the reach of the initial mainshock a long lasting difficulty is to determine which earthquakes are connected either directly or indirectly here we show that this causal structure can be found probabilistically with no a priori model nor parameterization large regional earthquakes are found to have a short direct influence in comparison to the overall aftershock sequence duration relative to these large mainshocks small earthquakes collectively have a greater effect on triggering hence cascade triggering is a key component in earthquake interactions

response of the san jacinto fault zone to static stress changes from the 1992 landers earthquake we perform an analysis of the seismicity response of the san jacinto fault zone to static coulomb stress changes from the 1992 landers earthquake sequence results show that in general stress changes forecast rate changes well we find a significant positive correlation between the change in rate and the magnitude of the coulomb stress change with a correlation coefficient of 0 76 equivalent to 5 6 when compared to a 0 null hypothesis furthermore although the correlations are less clear over negative than positive stress changes there is evidence of some coulomb stress dependent quiescence on stress shadows models that account for heterogeneity in reference seismicity show clear improvements in their predictions of spatial variability of aftershock rates compared to those that assume uniform reference we find also that better performance is obtained 1 using a time dependent coulomb rate state model compared to a time independent exponential model and 2 using structurally constrained rather than optimal target fault orientations these results are an important step in the validation of coulomb stress based methods for quantitative seismicity forecasting we conclude that the correspondence between the predictions of coulomb stress models for aftershock seismicity may be sensitive to strong heterogeneity in aftershock locations and orientations associated with the presence of large scale structure in aftershock study areas in these cases we suggest that where the regional structure is mapped incorporating it explicitly into coulomb stress models may improve the performance of quantitative coulomb stress based forecasts

a constitutive law for rate of earthquake production and its application to earthquake clustering seismicity is modeled as a sequence of earthquake nucleation events in which the distribution of initial conditions over the population of nucleation sources and stress ing history control the timing of earthquakes the model is implemented using solutions for nucleation of unstable fault slip on faults with experimentally derived rate and state dependent fault properties this yields a general state variable constitutive formulation for rate of earthquake production resulting from an applied stressing history to illustrate and test the model some characteristics of seismicity following a stress step have been explored it is proposed that various features of earthquake clustering arise from sensi tivity of nucleation times to the stress changes induced by prior earthquakes the model gives the characteristic omori aftershock decay law and interprets aftershock parameters in terms of stress change and stressing rate earthquake data appear to support a model prediction that aftershock duration defined as the time for rates to return to the back ground seismicity rate is proportional to mainshock recurrence time observed spatial and temporal clustering of earthquake pairs arises as a consequence of the spatial depen dence of stress changes of the first event of the pair and stress sensitive time dependent nucleation applications of the constitutive formulation are not restricted to the simple stress step models investigated here it may be applied to stressing histories of arbitrary complexity the apparent success at modeling clustering phenomena suggests the possibil ity of using the formulation to estimate short to intermediate term earthquake probabil ities following occurrence of other earthquakes and for inversion of temporal variations of earthquake rates for changes in driving stress

stress transferred by the 1995 mw 6 9 kobe japan shock effect on aftershocks and future earthquake probabilities the kobe earthquake struck at the edge of the densely populated osaka kyoto corridor in southwest japan we investigate how the earthquake transferred stress to nearby faults altering their proximity to failure and thus changing earthquake probabilities we find that relative to the pre kobe seismicity kobe aftershocks were concentrated in regions of calculated coulomb stress increase and less common in regions of stress decrease we quantify this relationship by forming the spatial correlation between the seismicity rate change and the coulomb stress change the correlation is significant for stress changes greater than 0 2 1 0 bars 0 02 0 1 mpa and the nonlinear dependence of seismicity rate change on stress change is compatible with a state and rate dependent formulation for earthquake occurrence we extend this analysis to future mainshocks by resolving the stress changes on major faults within 100 km of kobe and calculating the change in probability caused by these stress changes transient effects of the stress changes are incorporated by the state dependent constitutive relation which amplifies the permanent stress changes during the aftershock period earthquake probability framed in this manner is highly time dependent much more so than is assumed in current practice because the probabilities depend on several poorly known parameters of the major faults we estimate uncertainties of the probabilities by monte carlo simulation this enables us to include uncertainties on the elapsed time since the last earthquake the repeat time and its variability and the period of aftershock decay we estimate that a calculated 3 bar 0 3 mpa stress increase on the eastern section of the arima takatsuki tectonic line attl near kyoto causes fivefold increase in the 30 year probability of a subsequent large earthquake near kyoto a 2 bar 0 2 mpa stress decrease on the western section of the attl results in a reduction in probability by a factor of 140 to 2000 the probability of a mw 6 9 earthquake within 50 km of osaka during 1997 2007 is estimated to have risen from 5 6 before the kobe earthquake to 7 11 afterward during 1997 2027 it is estimated to have risen from 14 16 before kobe to 16 22

a variety of aftershock decays in the rate and state friction model due to the effect of secondary aftershocks implications derived from an analysis of real aftershock sequences the model based on rate and state dependent friction law reproduces the temporal decay of an aftershock sequence with the p value of the omori utsu law equal to 1 if we simply assume a constant stress rate over time however because p values vary in real aftershock sequences this model requires some modification this study examined the effect of secondary aftershocks on the variety of the p value a large aftershock causes a stepwise stress increase in the aftershock area and the expected seismicity rate derived from the friction law also increases abruptly these multiple increases in the seismicity rate during its decay following a mainshock could cause variation in the apparent p value in this study a model incorporating this idea is applied to two aftershock sequences observed in japan and is shown to substantially modify the modeling of aftershock activity

lithospheric and upper mantle structures results of electromagnetic soundings in europe abstract information on electrical conductivity of the subsurface at a crustal scale is inferred mainly from magnetotelluric mt and magnetometer data the latter include both magnetometer array studies mv and geomagnetic depth soundings gds locally controlled source data e g data from d c and very low frequency vlf resistivity surveys frequency soundings and airborne electromagnetic mappings provide information on near surface structures e g on exposures of deeper conductors the variety of electromagnetic methods provides an efficient zooming ability for structures from a regional scale of hundreds of kilometres to small local details of some metres thus both the mapping of large scale crustal conductivity structures and a detail study of the anomalous structures are possible the electrical conductivity of the crust and upper mantle is described within the plate tectonic framework examples of structures which become electrically conductive at different phases of the process are shown using the results of electromagnetic soundings in various tectonic environments in europe it is shown how the crustal conductors can be interpreted as ancient and modern tectonic markers these include structures from the fennoscandian shield precambrian extensional basins and collisional zones the carpathians scotland and ireland suture zones and the pannonian basin extensional basin and thrust zones as well as conductors detected along the european geotraverse e g the terrain boundaries and the decollement of the variscan thrusting an example which considers the lower crustal conductivity from the fennoscandian shield shows rather large lateral variations in conductance of the lower crust varying from 1 s to several hundreds of siemens estimates of the depth of the asthenospheric conducting layer within the european territory also vary considerably shallowest depths are detected beneath extensional regions the pannonian basin and the rhinegraben 40 80 km whereas depths of 200 km or over or the absence of a conducting layer are detected beneath the alps and old precambrian cratons among the key areas where electromagnetic investigations should play an essential role are the deep structure of the east european platform boundaries of archaean and proterozoic terrains the structure of the teisseyre tornquist zone the nature of the present day continental lower crust and the characteristics of the electrical asthenosphere beneath europe

the stress shadow induced by the 1975 1984 krafla rifting episode 1 it has been posited that the 1975 1984 krafla rifting episode in northern iceland was responsible for a significant drop in the rate of earthquakes along the husavik flatey fault hff a transform fault that had previously been the source of several magnitude 6 7 earthquakes this compelling case of the existence of a stress shadow has never been studied in detail and the implications of such a stress shadow remain an open question according to rate state models intense stress shadows cause tens of years of low seismicity rate followed by a faster recovery phase of rate increase here we compare the long term predictions from a coulomb stress model of the rifting episode with seismological observations from the sil catalog 1995 2011 in northern iceland in the analyzed time frame we find that the rift induced stress shadow coincides with the eastern half of the fault where the observed seismicity rates are found to be significantly lower than expected given the historical earthquake activity there we also find that the seismicity rates on the central part of the hff increased significantly in the last 17 years with the seismicity progressively recovering from west to east our observations confirm that rate state theory successfully describes the long term seismic rate variation during the reloading phase of a fault invested by a negative coulomb stress coincident with this recovery we find that the b value of the frequency magnitude distribution changed significantly over time we conclude that the rift induced stress shadow not only decreased the seismic rate on the eastern part of the hff but also temporarily modified how the system releases seismic energy with more large magnitude events in proportion to small ones this behavior is currently being overturned as rift induced locking is now being compensated by tectonic forcing

aftershock triggering by complete coulomb stress changes 1 we examine the correlation between seismicity rate change following the 1992 m7 3 landers california earthquake and characteristics of the complete coulomb failure stress cfs changes cfs t that this earthquake generated at close distances the time varying dynamic portion of the stress change depends on how the rupture develops temporally and spatially and arises from radiated seismic waves and from permanent coseismic fault displacement the permanent static portion cfs depends only on the final coseismic displacement cfs diminishes much more rapidly with distance than the transient dynamic stress changes a common interpretation of the strong correlation between cfs and aftershocks is that load changes can advance or delay failure stress changes may also promote failure by physically altering properties of the fault or its environs because it is transient cfs t can alter the failure rate only by the latter means we calculate both cfs and the maximum positive value of cfs t peak cfs t using a reflectivity program input parameters are constrained by modeling landers displacement seismograms we quantify the correlation between maps of seismicity rate changes and maps of modeled cfs and peak cfs t and find agreement for both models however rupture directivity which does not affect cfs creates larger peak cfs t values northwest of the main shock this asymmetry is also observed in seismicity rate changes but not in cfs this result implies that dynamic stress changes are as effective as static stress changes in triggering aftershocks and may trigger earthquakes long after the waves have passed