constitution of the moon 2 composition and seismic properties of the lower mantle abstract to constrain the composition of the moon we have calculated the stable phase assemblages and their seismic properties by the method of minimization of gibbs free energy to determine whether various compositional models are consistent with the seismic observations for the lunar lower mantle at depths between 500 and 1000 km p wave and s wave velocities have been calculated for a series of proposed bulk composition models compositional models for the moon impactor composition orgueil composition etc and earth like compositions lherzolite and pyrolite have been considered it is found that impactor and orgueil models are unlikely for the lower mantle within reasonable temperature adjustment in the temperature profile all of the terrestrial compositional models come close to the seismic data below the 500 km discontinuity it is found that a composition enriched in al 2 o 3 up to about 6 wt and having pyrolite content of the other major oxides lunar pyrolite is adequate to describe the seismic properties of the lunar lower mantle within the uncertainty of calculations and resolution of seismic data an al rich model with a terrestrial ol px ratio and unusually enriched in garnet gives the best fit to the lunar lower mantle seismic properties despite the uncertainty of the seismic data it is shown that none of the analysed compositional models satisfies the seismic constraints simultaneously in the middle and lower mantle phase changes in any model considered are not able to explain the nature of the 500 km discontinuity it is concluded that the lunar mantle is chemically stratified

long range earthquake forecasting with every earthquake a precursor according to scale scaling relations previously derived from examples of the precursory scale increase before major earthquakes show that the precursor is a long term predictor of the time magnitude and location of the major earthquake these relations are here taken as the basis of a stochastic forecasting model in which every earthquake is regarded as a precursor the problem of identifying those earthquakes that are actually precursory is thus set aside at the cost of limiting the strength of the resulting forecast the contribution of an individual earthquake to the future distribution of hazard in time magnitude and location is on a scale determined through the scaling relations by its magnitude provision is made for a contribution to be affected by other earthquakes close in time and location e g an aftershock may be given low weight using the new zealand catalogue the model has been fitted to the forecasting of shallow earthquakes exceeding magnitude 5 75 over the period 1965 2000 it fits the data much better than a baseline poisson model with a location distribution based on proximity to the epicenters of past earthquakes further the model has been applied with unchanged parameters to the california region over the period 1975 2001 there also it performs much better than the baseline model fitted to the same region over the period 1951 1974 the likelihood ratio is 1015 in favor of the present model these results lend credence to the precursory scale increase phenomenon and show that the scaling relations are pervasive in earthquake catalogues the forecasting model provides a new baseline model against which future refinements and other proposed models can be tested it may also prove to be useful in practice its applicability to other regions has still to be established

refinements for footwall red bed diagenesis in the sediment hosted stratiform copper deposits model the emplacement of copper in sediment hosted stratiform copper deposits requires the circulation of a low temperature chloride rich brine in rift filling footwall red beds probably driven by meteoric recharge in adjacent highlands the descending oxygen rich meteoric water may become saline probably by leaching of footwall evaporites or possibly by mixing with brines draining down from contemporaneous evaporite pans and evolve toward a moderately oxidized brine as oxygen is consumed during the diagenetic reddening of the initially nonred coarse grained clastic rift sediments under these conditions the pore solution attains its maximum ability to leach and transport trace amounts of copper from the red beds sediment hosted stratiform copper deposits may form where the brine crosses a redox boundary into reduced sulfide rich gray beds with further consumption of oxygen during reddening the brine may become highly reduced and able to take iron into solution possibly explaining synsediment hosted stratiform copper iron oxide alterations and deposits the timing of copper deposition is clearly linked to the diagenetic reddening of immature footwall sediments in rift basins a process considered to extend over millions of years

the sediment hosted stratiform copper ore system sediment hosted stratiform copper deposits comprise disseminated to veinlet cu and cu fe sulfides in siliciclastic or dolomitic sedimentary rocks sediment hosted stratiform copper deposits are extremely common though economically significant deposits are rare they account for approximately 23 percent of the world s cu production and known reserves in addition to being significant sources of co and ag three sedimentary basins the paleoproterozoic kodaro udokan in siberia the neoproterozoic katangan in central africa and the permian basin of central europe contain supergiant 24 million metric tons mt contained cu deposits sediment hosted stratiform copper deposits are the products of evolving basin scale fluid flow systems that include source s of metal and s source s of metal and s transporting fluids the transport paths of these fluids a thermal and or hydraulic pump to collect and drive the fluids and the chemical and physical processes which result in precipitation of the sulfides metal sources are undoubtedly red bed sedimentary rocks containing fe oxyhydroxides capable of weakly binding metals sulfur may be derived from marine or lacustrine evaporites reduced seawater or hydrogen sulfide bearing petroleum metals appear to have been transported at low to moderate temperatures in moderately to highly saline aqueous fluids with the temperature of the fluid largely dependent on the time of fluid migration in the basin s burial history these basinal fluids were focused to potential metal precipitation sites by thinning of the red bed sequence at basin margins by faults by differentially permeable sedimentary units by paleotopography within the basin or along the margins of salt diapirs fluid movement produced widespread basin scale alteration that has commonly been overlooked but can form an important exploration guide sulfide precipitation occurred due to reduction typically caused by reaction with carbonaceous rocks or petroleum the amount of sulfides present at any deposit may be either metals or sulfide limited or could have been controlled by the amount of available reductant e g petroleum while understanding of sediment hosted stratiform copper ore genesis at the deposit scale is relatively robust there are still significant questions in regards its position in terms of basin evolution a wide variety of basin architectures and processes can lead to the formation of sediment hosted stratiform copper deposits despite general agreement that sulfides postdate sedimentation the absolute age of mineralization in many deposits has been difficult to document and the available evidence suggests that deposits can form throughout a basin s evolution from early diagenesis of ore host sediments to basin inversion and metamorphism supergiant and giant deposits formed in basins which underwent prolonged periods of fluid flow and in which unique conditions allowed for the accumulation of large amounts of metal bearing fluid sufficient reduced s and large amounts of reductants

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

constitution of the moon 3 composition of middle mantle from seismic data abstract the constitution of the lunar middle mantle which is located between two prominent discontinuities at depths of 270 and 500 km has been investigated by a method of thermodynamic modeling on the basis of the thermoseism data base self consistent phase equilibrium assemblages and synthetic seismic profiles have been calculated for various geochemical models with different contents of the major petrogenic oxides it is shown that none of the analyzed compositional models satisfies the seismic velocity profiles simulataneously in the middle and lower mantle phase changes in any petrological model considered do not explain the nature of the 500 km discontinuity pyroxenite models having 50 52 sio2 and 15 16 feo mg number 74 76 have the best fit to the middle mantle mean velocities of nakamura j geophys res 88 677 686 1983 and satisfy the mean density and lower mantle density constraints these results and the calculations of kuskov and fabrichnaya phys earth planet inter 83 197 216 1994 strongly reinforce the case for a chemically stratified moon interior

mixture models for improved earthquake forecasting with short to medium time horizons abstract optimal mixtures of three space time magnitude earthquake likelihood models are found for forecasting earthquakes with magnitudes of 5 0 and greater in the new zealand and california catalogs with forecasting time horizons ranging from 0 to 3000 days the models are the epidemic type aftershock etas short term clustering model the every earthquake a precursor according to scale eepas medium term clustering model and the proximity to past earthquakes ppe quasi time invariant smoothed seismicity model the etas model is by far the most informative of these models for short time horizons of a few days but even with a zero time horizon an optimal mixture of the three models here called the janus model outperforms it with an information gain per earthquake igpe of about 0 1 for time horizons of 10 3000 days the janus model outperforms the most informative of its component models with igpes ranging from 0 2 to 0 5 as the time horizon lengthens beyond six months in new zealand and two years in california the eepas model becomes the most informative of the individual models and the major component of the optimal mixture changes in the janus model parameters with the forecasting time horizon reveal features of time and area scaling of precursory seismicity the results suggest that both cascades of triggering and the precursory scale increase phenomenon contribute to earthquake predictability and that these contributions are largely independent

mode of strong earthquake recurrence in the central ionian islands greece possible triggering due to coulomb stress changes generated by the occurrence of previous strong shocks the spatiotemporal distribution of shallow strong m 6 3 earthquakes occurring in the area of central ionian islands is analyzed these shocks are generated on two adjacent fault segments with different strike but both segments are associated with strike slip faulting constituting the boundary between continental collision to the north and oceanic subduction to the south seismic activity is concentrated in short time intervals alternating with much longer relatively quiescent periods each active period consists of a relatively large event or series two to four of events occurring closely both in space and time this alteration was observed to happen four times since 1867 the period when complete data exist for the study area since the phenomenon is not strictly periodic and during each active period multiple events occurred i attempted to interpret the seismic behavior on the basis of possible trig gering i then investigated how changes in coulomb failure function dcff asso ciated with one or more earthquakes may trigger subsequent events both the co seismic slip due to the generation of the strong earthquakes and stress buildup associated with the two major fault segments were taken into account for the dcff calculation earthquakes can be modeled as static dislocations in elastic half space and the stress pattern has been calculated according to the geometry and slip of each of the faults that ruptured in the chain of events these calculations show that 13 out of 14 earthquakes of m 6 3 were preceded by a static stress change that encouraged failure the magnitude of the stress increases transferred from one earthquake to another ranged from 0 01 mpa 0 1 bar to over 0 1 mpa 1 bar showing that stress transfer adequately explains the occurrence pattern of these events maps of current dcff provide additional information to long term earthquake prediction areas of positive dcff have been identified at two sites in kefalonia and lefkada faults respectively where the next strong events are expected to occur a fact that will substantiate the hypothesis elaborated in this article

kalahari valley calcretes their nature origins and environmental significance abstract calcretes that form in non pedogenic settings have been widely reported in the geomorphological and geological literature yet they are still poorly understood in comparison with pedogenic varieties this may be because there are assorted types of non pedogenic calcretes often loosely referred to as groundwater calcretes but encompassing groundwater phreatic open valley or confined channel calcrete types forming within vadose and phreatic environments in different geomorphological settings relatively few studies have described the detailed petrological characteristics of such calcretes leading wright and tucker calcretes international association of sedimentologists reprint series 1991 vol 2 blackwell scientific publications oxford p 10 to suggest that much more work is needed to define the groundwater calcrete facies and to devise criteria for its recognition so that the various non pedogenic calcretes can be identified within the quaternary as well as further back in the geological record most descriptions of groundwater calcretes are highly generalistic and do not take into account the variability that may occur as a result of calcretes forming in different positions within a landscape and affected by separate controls thus the range of groundwater calcretes that exists now needs to be studied individually to identify patterns within the distinct types as a step towards expanding our knowledge of the variety of non pedogenic calcretes this paper describes the petrology micromorphology and mode of development of one of these types of calcrete namely that which forms within valley locations but not in definite fluvial channels late quaternary to holocene valley calcretes are described from various dry valleys mekgacha across the kalahari region of central botswana with the majority of samples collected from trunk and tributary valleys of the okwa samples have been analysed in thin section and under scanning electron microscope in order to determine the carbonate matrix type and calcrete micromorphology in general most samples consist of grains of quartzose kalahari sand cemented by fine crystalline often glaebular grain coating and pore filling micrite cement types are fairly consistent and not as micromorphologically variable as has been noted for other kalahari calcretes biological inputs are prevalent in many samples and include networks of calcified rootlets these characteristics reflect the fact that the calcretes formed in a relatively near surface environment with relatively high rates of evaporation

evolution of the stress field in the northern aegean sea greece summary the evolution of the stress field in the area of the northern aegean sea during the 20th century has been studied the area is dominated by dextral strike slip faulting and is characterized by frequent strong earthquakes coulomb stress changes dcff were calculated assuming that earthquakes can be modelled as static dislocations in an elastic half space and taking into account both the coseismic slip in large mi7 0 earthquakes and the slow tectonic stress build up along the major fault segments the stress change calculations were performed for strike slip faults of strike dip and rake appropriate to the large events we evaluate whether these stress changes brought a given large earthquake closer to or farther from failure it was found that each of the large events occurred in regions of increased calculated coulomb stress moreover the majority of smaller events for which reliable fault plane solutions are available were also located in areas of positive dcff by extending the calculations to 2020 and assuming that no additional large mi7 0 earthquake occurs between 1999 and 2020 possible sites of future large earthquakes are identified

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

demarcation and scaling of long term seismogenesis a space time envelope of minor seismicity related to major shallow earthquakes is identified from observations of the long term precursory scale increase phenomenon which quantifies the three stage faulting model of seismogenesis the envelope which includes the source area of the major earthquake is here demarcated for 47 earthquakes from four regions with tectonic regimes ranging from subduction to continental collision and continental transform the earthquakes range in magnitude from 5 8 to 8 2 and include the 24 most recent mainshocks of magnitude 6 4 and larger in the san andreas system of california the hellenic arc region of greece and the new zealand region together with the six most recent mainshocks of magnitude 7 4 and larger in the pacific arc region of japan also included are the destructive earthquakes that occurred at kobe japan 1995 magnitude 7 2 izmit turkey 1999 magnitude 7 4 and w tottori japan 2000 magnitude 7 3 the space a p in the space time envelope is optimised with respect to the scale increase while the time t p is the interval between the onset of the scale increase and the occurrence of the earthquake a strong correlation is found between the envelope a p t p and the magnitude of the earthquake hence the conclusion that the set of precursory earthquakes contained in the envelope is intrinsic to the seismogenic process yet a p and t p are correlated only weakly with each other suggesting that a p is affected by differences in statical conditions such as geological structure and lithology and t p by differences in dynamical conditions such as plate velocity among other scaling relations predictive regressions are found between on the one hand the magnitude level of the precursory seismicity and on the other hand both t p and the major earthquake magnitude hence the method as here applied to retrospective analysis is potentially adaptable to long range forecasting of the place time and magnitude of major earthquakes

an assessment of source parameters of earthquakes in the cordillera of the western united states abstract source parameters for 50 earthquakes occurring between 1915 and 1988 have been used to examine the faulting characteristics of magnitude 5 5 to 7 8 earthquakes within the western u s cordillera an area extending from the eastern sierra nevada to the great plains and from northwestern montana to trans pecos texas source parameters used in this study include seismic information from first motion analyses body and surface waveform modeling geodetic studies and geological studies of surface faulting the principal results of this analysis include 1 all earthquakes occurred on faults dipping 38 or more and no evidence for listric of low angle planar faulting was found 2 all m 7 0 earthquakes occurred at depths 12 km and were composed of multiple subevents 3 most earthquakes 70 per cent had unilateral ruptures and 4 no individual subevent had a rupture length 21 km

source complexity of the 1988 armenian earthquake evidence for a slow after slip event we analyzed teleseismic p and s waves using a multiple event deconvolution method to investigate the source process of the spitak armenia earthquake of december 7 1988 teleseismic long period body waves exhibit complex waveforms significantly more complex than those normally seen for an event of this size we identified two groups of subevents one is a group of strike slip events during the first 20 s the other is a dip slip event initiating at about 30 s after the initial rupture the tensor sum of all the subevents is essentially strike slip strike 302 dip 59 rake 143 with a scalar moment of 1 47 10 19 n m the seismic moment of the dip slip event strike 89 dip 60 rake 88 is 5 6 10 18 n m nearly 40 of the total and the moment release rate is slower than the other subevents with a strike slip mechanism we call this event a slow after slip event the mechanism of the after sup event is consistent with the present day deformation pattern in the caucasus where north south compression is predominant due to the continental collision between the arabian plate and the russian platform this result suggests that in a region where both strike slip motion and crustal shortening are taking place like southern california a large strike slip event may accompany large thrust events and vice versa in order to determine the total coseismic deformation pattern it is essential to resolve these multiple events in time space and mechanism

broadband study of the 1989 loma prieta earthquake we determined the source characteristics of the oct 18 1989 loma prieta california earthquake using teleseismic data the solution from body waves gives a mechanism with dip 70 rake 138 and strike 128 and a seismic moment of 3 10 26 dyne cm m w 6 9 this solution is similar to those obtained from long period rayleigh and love waves p nl waves and first motion data the body wave form suggests a depth of about 15 km the effective duration of the source is 6 sec which suggests a fault length of 30 km and 15 km for bilateral and unilateral faulting respectively considering the extent of the aftershock area we used 35 km as an estimate of the total rupture length the strike slip and the thrust components of the coseismic slip are 177 and 159 cm respectively the large thrust component raises an important question regarding the recurrence pattern if the loma prieta earthquake is a characteristic earthquake with a recurrence interval of about 100 years the 159 cm displacement implies a long term uplift rate of about 1 cm year which appears too large for this region three hypotheses for reconciling this apparent conflict are 1 the geometry of plate motion along the santa cruz mountain segment changes over a time scale of several thousand years so that the coseismic displacement has not accumulated enough to produce high topographic relief 2 the coseismic shp direction varies from event to event 3 the slip plane of the 1989 loma prieta earthquake is different from the major boundary between the pacific and the north american plates if this is the case the loma prieta earthquake is a rather rare non characteristic event the surface slip of about l m for the 1906 san francisco earthquake is one of the key data in long term forecasting no surface slip was observed for the 1989 loma prieta earthquake even if the horizontal slip at depth is as large as 1 8 m this points to a risk of relying too heavily on surface observations for long term seismic risk analysis

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

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

source mechanisms of three moderate california earthquakes of july 1986 abstract we studied the source processes of three moderate size earthquakes in california the m s 6 0 event of july 8 1986 near palm springs the m s 5 8 shock of july 13 1986 offshore of oceanside and the m s 6 2 event of july 21 1986 in the chalfant valley on the east side of the sierra nevada the centroidal source parameters are estimated by inversion of long period p and sh waves recorded at teleseismic distances by seismographs of worldwide networks a more detailed description of the source is then obtained by analyzing broadband seismograms the north palm springs earthquake had a simple rupture process most of the seismic moment was released in the first 3 sec in a single step the strike of the source fault plane follows the average trend of the banning fault and its dip agrees with the dip of the fault plane delineated by the aftershocks the faulting mechanism of the main shock is right lateral strike slip with a sizable reverse component that is consistent with uplift north of the banning fault the earthquake offshore of oceanside had a slightly more complex rupture process the far field source time function consists of two pulses that represent the release of most of the moment in the first 3 sec the source mechanism indicates reverse faulting with the compressional axis trending northeast almost perpendicular to the trend of mapped faults offshore the event does not appear to be associated with major mapped faults in the area but the strike of one of the nodal planes agrees with the trend of the major mapped faults offshore and its mechanism is consistent with the missing component of plate convergence not taken up by the onshore strike slip fault systems and the idea of a weak san andreas fault system the rupture process of the chalfant valley earthquake was yet more complicated the source time function indicates that in a 4 sec time window three asperities were broken the source mechanism indicates right lateral strike slip faulting with a small normal faulting component on a fault that dips approximately 50 southwest earthquake activity suggests that presently the deformation in the northern part of the owens valley which includes the chalfant valley is dominated by conjugate strike slip faults which strike obliquely to the main range bounding normal faults the waveforms indicate the presence of a low velocity zone at a depth of about 20 km in the crust in the chalfant valley a synthesis of information from waveform modeling first motion fault plane solutions and aftershock distributions indicates that the nucleation and or termination of rupture for the north palm springs and the chalfant valley events were controlled by preexisting fault geometry

centroid moment tensor solutions for 35 earthquakes in western north america 1977 1983 abstract seismic records from the gdsn sro asro dwwssn rstn and ida networks were used to obtain long period t 45 sec focal mechanisms for 35 earthquakes in western north america longitude 140 to 110 latitude 30 to 60 employing the centroid moment tensor method of dziewonski et al 1981 and dziewonski and woodhouse 1983 the same algorithm was applied to all events the smallest m 0 6 4 10 23 dyne cm being an aftershock to the 1979 imperial valley california earthquake and the largest m 0 8 5 10 26 dyne cm the 1980 eureka california earthquake all events were analyzed with and without the constraint m r m r 0 on the moment tensor an ad hoc criterion on the relative variance reduction was employed to determine a favored solution our solutions show general agreement with other published results as well as with tectonic structures agreement with results obtained using the abundant local and regional data confirms the adequacy of the method in determining long period source parameters and verifies its applicability in regions where local and regional data are scarce or nonexistent in some cases disagreement between our solution and results from first motion studies appears to be related to source complexities our moment tensor represents the total stress release of the composite event a consistent westward movement of the centroid locations reflects lateral heterogeneities in the crust and mantle

the transfiguration continental red bed cu pb zn ag deposit quebec appalachians canada the transfiguration cu pb zn ag deposit enclosed within reduced grey sandstone is associated with continental red beds of the lower silurian robitaille formation in the quebec appalachians canada the robitaille formation rests unconformably on foliated cambro ordovician rocks the unconformity is locally cut by barite veins the basal unit of the robitaille formation comprises green wacke and pebble conglomerate which locally contain calcite nodules the latter have microstructures characteristic of alpha type calcretes such as floating fabrics calcite filled fractures crystallaria and circumgranular cracks massive grey sandstone overlies the basal green wacke and pebble conglomerate unit which is overlain in turn by red fine grained sandstone mineralisation occurred underneath the red sandstone unit chiefly in the grey sandstone unit as disseminated and veinlet sulphides chalcopyrite the most abundant cu sulphide replaced early pyrite calcrete disseminated carbonate and vein carbonate have stable isotope ratios varying from 7 5 to 1 1 13c and from 14 7 to 21 3 18o the negative 13c values indicate the oxidation of organic matter in a continental environment sulphur isotope ratios for pyrite chalcopyrite and galena vary from 19 to 25 34s as measured on mineral concentrates by a conventional so2 technique laser assisted microanalyses by fluorination of s isotopes in pyrite show an analogous range in 34s values from 21 to 25 negative and positive 34s values are compatible with bacterial sulphate reduction bsr in systems open and closed with respect to sulphate we interpret similarly high 34s values for sulphide concentrates 25 1 and for vein barite 26 2 to result from rapid and complete thermochemical reduction of pore water sulphate two early to late diagenetic stages of mineralisation best explain the origin of the transfiguration deposit the first stage was characterised by the ponding of groundwater over the taconian unconformity recorded by calcrete and early pyrite formation via bsr in grey sandstone early pyrite contains up to 2 wt pb which is consistent with pb fixation by sulphate reducing bacteria the second stage ii is defined by the replacement of early pyrite by chalcopyrite as well as by sulphide precipitation via either bsr or thermochemical sulphate reduction tsr in grey sandstone this event resulted from the synsedimentary fault controlled percolation and mixing of 1 an oxidising sulphate bearing cupriferous fluid migrating per descensum from the red bed sequence and 2 a hydrocarbon bearing fluid migrating per ascensum from the cambro ordovician basement mixing between the two fluids led to sulphate reduction causing cu sulphide precipitation the positive correlation between cu and fe3 fe2 bulk rock values suggests that fe acted as a redox agent during sulphate reduction stage ii diagenetic fluid migration is tentatively attributed to the late silurian salinic extensional event

origin of the nchanga copper cobalt deposits of the zambian copperbelt the zambian copperbelt forms the southeastern part of the 900 km long neoproterozoic lufilian arc and contains one of the world s largest accumulations of sediment hosted stratiform copper mineralization the nchanga deposit is one of the most significant ore systems in the zambian copperbelt and contains two major economic concentrations of copper and cobalt hosted within the lower roan group of the katangan supergroup a lower orebody copper only and upper orebody copper and cobalt occur towards the top of arkosic units and within the base of overlying shales the sulfide mineralogy includes pyrite bornite chalcopyrite and chalcocite although in the lower orebody sulfide phases are partially or completely replaced by malachite and copper oxides carrollite is the major cobalt bearing phase and is restricted to fault propagation fold zones within a feldspathic arenite hydrothermal alteration minerals include dolomite phlogophite sericite rutile quartz tourmaline and chlorite quartz veins from the mine sequence show halite saturated fluid inclusions ranging from 31 to 38 wt equivalent nacl with homogenisation temperatures thtot ranging between 140 and 180 c diagenetic pyrites in the lower orebody show distinct relatively low 34s ranging from 1 to 17 whereas arenite and shale hosted copper and cobalt sulfides reveal distinctly different 34s from 1 to 12 for the lower orebody and 5 to 18 for the upper orebody there is also a clear distinction between the 34s mean of 12 1 3 3 n 65 for the upper orebody compared with 5 2 3 6 n 23 for the lower orebody the 13c of dolomites from units above the upper orebody give 13c values of 1 4 to 2 5 consistent with marine carbon however dolomite from the shear zones and the alteration assemblages within the upper orebody show more negative 13c values 2 9 to 4 0 and 5 6 to 8 3 respectively similarly shear zone and upper orebody dolomites give a 18o of 11 7 to 16 9 compared to lower roan dolomites which show 18o of 22 4 to 23 0 two distinct structural regimes are recognized in the nchanga area a weakly deformed zone consisting of basement and overlying footwall siliciclastics and a moderate to tightly folded zone of meta sediments of the katangan succession the fold geometry of the lower roan package is controlled by internal thrust fault propagation folds which detach at the top of the lowermost arkose or within the base of the overlying stratigraphy and show vergence towards the ne faulting and folding are considered to be synchronous as folding predominantly occurred at the tips of propagating thrust faults with local thrust breakthrough the data from nchanga suggests a strong link between ore formation and the development of structures during basin inversion as part of the lufilian orogeny sulfides tend to be concentrated within arenites or coarser grained layers within shale units suggesting that host rock porosity and possibly permeability played a role in ore formation however sulfides are also commonly orientated along but not deformed by a tectonic fabric or hosted within small fractures that suggest a significant role for deformation in the development of the mineralization the ore mineralogy hydrothermal alteration and stable isotope data lend support to models consistent with the thermochemical reduction of a sulfate and metal enriched hydrothermal fluid at the site of mineralization there is no evidence at nchanga for a contribution of bacteriogenic sulfide produced during sedimentation or early diagenesis to the ores

metastable growth of corundum adjacent to quartz in a spinel bearing quartzite from the archaean napier complex antarctica in a granulite facies spinel bearing quartzite corundum orthopyroxene and sapphirine and rarely cordierite and sillimanite form partial rims separating spinel from quartz textures indicate the reactions spinel quartz orthopyroxene corundum and spinel quartz orthopyroxene sapphirine thus corundum and sapphirine are produced by reactions involving quartz the low al content of the orthopyroxene 0 5 2 8 wt and low values for mg fe distribution coefficient for spinel sapphirine and spinel orthopyroxene reflect low temperature conditions during formation of the reaction products absence of zoning in spinel and a constant mg fe distribution coefficient for spinel sapphirine and spinel orthopyroxene over a compositional range indicate mg fe equilibration it is suggested that stable reactions such as spinel quartz cordierite or spinel quartz garnet sillimanite were over stepped and that metastable reactions give rise to the anomalous juxtaposition of corundum quartz

early silurian carbonate platforms in the appalachian orogenic belt the sayabec la vieille formations of the gaspe matapedia basin quebec the coeval early silurian late llandoverian to late wenlockian sayabec and la vieille formations represent the first occurrence of shallow water platformal limestones and reefs in the paleozoic sequence of the gaspe belt of the northern appalachians both units display very similar fades representing laterally well zoned south dipping carbonate platforms with four parallel depositional belts these from nearshore to offshore are i a peritidal mud flat dominated by microbial communities laminites stromatolites thrombolites oncolites ii a low knob reef rim built by skeletal metazoans corals bryozoans stromatoporoids skeletal calcareous algae and microbial communities iii a well sorted lime sand belt and iv a deeper water nodular lime mud belt supporting a tabulate and rugose coral stromatoporoid skeletal algae and large shelled brachiopod biota the two platforms developed at the margin of the quebec reentrant and st lawrence promontory in the gaspe belt of the northern appal

comparative performance of time invariant long range and short range forecasting models on the earthquake catalogue of greece 1 time invariant long range and short range forecasting models were fitted to the earthquake catalogue of greece for magnitudes 4 0 and greater to optimize their ability to forecast events of magnitude 6 0 and greater in the period 1966 1980 the models considered were stationary spatially uniform and spatially varying poisson models a long range forecasting model based on the precursory scale increase phenomenon with every earthquake regarded as a precursor according to scale and epidemic type short range forecasting models with spatially uniform and spatially varying spontaneous seismicity each of the models was then applied to the catalogue for 1981 2002 and their forecasting performance was compared using the log likelihood statistic the long range forecasting model performed substantially better than the time invariant models and the short range forecasting models performed substantially better again the results show that the information value to be gained from modeling temporal and spatial variation of earthquake occurrence rate at both long and short range is much greater than can be gained from modeling spatial variation alone

in the shadow of 1857 the effect of the great ft tejon earthquake on subsequent earthquakes in southern california the great 1857 fort tejon earthquake is the largest earthquake to have hit southern california during the historic period we investigated if seismicity patterns following 1857 could be due to static stress changes generated by the 1857 earthquake when post 1857 earthquakes with unknown focal mechanisms were assigned strike slip mechanisms with strike and rake determined by the nearest active fault 13 of the 13 southern california m 5 5 earthquakes between 1857 and 1907 were encouraged by the 1857 rupture when post 1857 earthquakes in the transverse ranges with unknown focal mechanisms were assigned reverse mechanisms and all other events were assumed strike slip 11 of the 13 earthquakes were encouraged by the 1857 earthquake these results show significant correlations between static stress changes and seismicity patterns the correlation disappears around 1907 suggesting that tectonic loading began to overwhelm the effect of the 1857 earthquake early in the 20th century

stress coupling between earthquakes in northwest turkey and the north aegean sea we have investigated the coulomb stress interactions of 29 earthquakes m s greater than or equal to 6 0 that have occurred in the region of northwest turkey and north aegean sea since 1912 of these events 23 may be related to earlier events and 16 are clearly related to earlier events all events after 1967 are related to previous events events in the early part of our time interval that show no correlation could be related to historical events as yet unidentified in some cases faults that have received a stress reduction from earlier events are prepared for an event by an earthquake occurring a few years before that creates a local coulomb stress rise thus regions of coulomb stress shadow can become regions where a damaging earthquake may occur the relation between smaller events and the coulomb stress distribution is less clear but may be related to poor data quality and practical limitations of our modeling technique nonetheless there are 4 times as many events per unit area in regions of enhanced stress than where stress is reduced we discuss the contemporary distribution of coulomb stress and argue that it is possible to identify the likely locations of future damaging earthquakes including identifying the most likely candidate faults

paleogeography of the matapedia basin in the gaspe appalachians initiation of the gaspe belt successor basin the matapedia basin consists of the uppermost ordovician lowermost silurian deep water fine grained carbonate siliciclastic rocks of the honorat garin formation and matapedia groups pabos and white head formations the lower rock assemblage of the gaspe belt in the gaspe appalachians paleogeographic maps of eight time slices from the caradocian to the llandoverian are presented to better understand the tectonosedimentary evolution of the matapedia basin deposition evolved from siliciclastic garin fm to argillaceous limestones pabos fm to limestones white head fm the overall change from terrigenous garin fm to limestone facies white head fm reflects a change in the source area paleocurrent directions and composition of sandstones indicate an orogenic source area to the south for the garin formation which is believed to be the inliers of the humber and dunnage zones in the southern gaspe and new brunswick appalachians lime muds deposited by turbidity currents coming from the nor

microscopic sulfur isotope variations in ore minerals from the viburnum trend southeast missouri a shrimp study mississippi valley type ore samples from two mines in the viburnum trend of southeast missouri have been examined with the shrimp ion microprobe to determine the extent of their microscopic sulfur isotope variations approximately 140 shrimp delta 34 s values were obtained microscopic delta 34 s variations within and among the intergrown fe cu pb zn sulfides are very large 10 to 25 and indicate an extremely complex history of mineral deposition textures record the general paragenesis fe sulfide galena and sphalerite chalcopyrite and bornite and covellite early fes 2 delta 34 s 10 to 10 is generally much more depleted in 34 s than later galena or chalcopyrite delta 34 s 0 25 both early fes 2 and late chalcopyrite growth sequences exhibit large zonations in delta 34 s typically from light to heavy values over a 15 per mil range isotopic zoning in galena crystals is comparatively negligible but variations among different galena crystals encompass a large total range in delta 34 s values 0 25 that is similar in magnitude to the total ranges observed in early fes 2 and late chalcopyrite where later sulifides crosscut and replace earlier sulfides the shrimp data indicate that there has been negligible local recycling of s from earlier sulfides in the ore forming zone each generation of metal appears to have brought in its own isotopically distinct and evolving batch of sulfur during successive deposition of each metal generation the observed delta 34 s variations require mixing among two or more isotopically distinct distal source fluids feeding already reduced sulfur to the ore forming zone and or the existence of in situ sulfur isotope fractionation mechanisms producing reduced sulfur whose isotopic composition varied progressively with time in the ore forming zone

the 1971 san fernando earthquake a double event evidence is presented which suggest that the 1971 san fernando earthquake may have been a double event that occurred on two separate subparallel thrust faults it is postulated that the initial event took place at depth on the sierra madre fault zone which runs along the base of the san gabriel mountains rupture is postulated to have occurred from a depth of about 15 km to a depth of about 3 km a second event is thought to have initiated about 4 sec later on another steeply dipping thrust fault which is located about 4 km south of the sierra madre fault zone the surface trace of this fault coincides with the san fernando fault zone which was the principal fault associated with surface rupture it is postulated that rupture propagated from a depth of 8 km to the free surface the moments of the first and second events are approximately 0 7 10 26 dyne cm and 1 0 10 26 dyne cm respectively this model is found to explain the combined data sets of strong ground motions teleseismic p and s waveforms and static offsets better than previous models which consist of either a single fault plane or a plane having a dip angle which shallows with decreasing depth nevertheless many features of the observed motions remain unexplained and considerable uncertainty still exists regarding the faulting history of the san fernando earthquake

biogenic and thermogenic sulfate reduction in the sullivan pb zn ag deposit british columbia canada evidence from micro isotopic analysis of carbonate and sulfide in bedded ores abstract the layered clastic hosted sedex type proterozoic ca 1475 ma sullivan pb zn ag deposit was metamorphosed by several episodes of metamorphic recrystallization that have extensively modified or erased primary grain to grain textural relationships yet genetically significant variations of sulfur and carbon isotope ratios have been preserved at the millimeter and greater scale whereas sulfur isotope fractionations on a grain to grain scale cannot distinguish between likely formation temperatures and post peak metamorphic cooling the preserved fine scale and deposit scale stratigraphic variations of 34 s and 13 c bear on the origin and formational history of this deposit high spatial resolution documentation of accurate grain to grain and stratigraphic sulfur isotope variations in selected portions of bedded ore from the sullivan deposit was made possible by use of a cold stage during in situ laser assisted isotopic analysis pyrrhotite formed from biogenic sulfate reduction in the water column can be distinguished from sulfides e g sphalerite with higher 34 s values that formed in response to hydrothermal fluids in a brine pool isotopic analysis of carbonates in the presence of abundant sulfides was facilitated by development of a gas chromatographic carbonate extraction system with a high efficiency cryogenic trap calcite present in interlayered massive sulfide and siliciclastic layers in the bedded ore zone in trace amounts to a few weight percent records a carbon isotopic stratigraphy that suggests variable thermogenic sulfate reduction stratigraphic curves illustrating the variation in carbon and sulfur isotopes from the base of the main band to above the hu bands mine stratigraphic names in the bedded ore zone are similar in shape values of 13 c decrease abruptly at the base of the main band decrease slightly to the c band then increase to pre ore values the values of 34 s decrease from the base of the main band to the c band and then increase to pre ore values this similarity suggests some linkage between carbon and sulfur isotopic systematics and a sulfur budget dominated in the early stages of massive sulfide precipitation by hydrothermal processes involving thermogenic sulfate reduction giving way to bacteriogenic sulfate reduction in a closed then finally open marine basin

link between long lasting evaporitic basins and the development of thick and massive phreatic calcrete hardpans in the mississippian windsor and perce groups of eastern canada part of the visean upper mississippian succession in the upper paleozoic maritimes basin of eastern canada is overprinted by massive phreatic calcrete hardpans that can exceed 10 m in thickness and that are characterized by the thorough mineral replacement of most of their host sediment by calcite similar to those that are currently forming around salt lakes in quaternary sediments of central australia the precise timing and paleogeography of this carboniferous event was until now poorly known but lateral correlations over a large study area indicate that phreatic calcretization occurred in the vicinity of large evaporitic basins following a marine transgression and regression cycle in chadian to holkerian times this relation confirms that the previously proposed model for modern analogs in central australia which states a genetic link between the salt lakes and the thick and massive phreatic calcrete hardpans can be applied to ancient environments and that such occurrences may be used to infer the former presence of an evaporitic basin in their vicinity finally our relatively large dataset indicates that the stable isotopes of carbon and oxygen are successful in differentiating ancient marine carbonates from ancient phreatic calcretes 2007 elsevier b v all rights reserved

nonlinear strain buildup and the earthquake cycle on the san andreas fault two contrasting models of the earthquake deformation cycle on strike slip faults predict significant temporal declines in shear strain rate near the fault accompanied by a progressive broadening of the zone of deformation adjacent to it in the thin lithosphere model transient deformation results from flow in the asthenosphere due to stress relaxation following faulting through most or all of the lithosphere for an earth model with a thick elastic lithosphere plate thickness depth of seismic slip transient motions are due to postearthquake aseisrnic slip below the coseismic fault plane data from the san andreas fault indicate a long term temporal decrease in strain rate that persists for at least 30 years and may extend through the entire earthquake cycle observations support a cycle long rate decrease and a temporal spreading of the deformation profile only if movement cycles on the northern and southern locked sections of the fault are basically similar if so the usually lower strain rates and broader deformation zone currently observed on the southern san andreas represent a later evolutionary stage of the northern locked section where a great earthquake is a more recent occurrence although the data allow some extreme models to be discarded no sufficiently strong constraints exist to decide between the thin and thick lithosphere models regardless of the appropriate model the geodetic observations themselves indicate that strain buildup is sufficiently nonlinear to cause significant departures from recurrence estimates based on linear strain accumulation and the time predictable model

application of an iterative least squares waveform inversion of strong motion and teleseismic records to the 1978 tabas iran earthquake an iterative least squares technique is used to simultaneously invert the strong motion records and teleseismic p waveforms for the 1978 tabas iran earthquake to deduce the rupture history the method solves for both slip amplitudes and rupture times on a finite fault several inversions of the data are done to determine the best fitting hypocenter average rupture velocity and source time function within the range of our parameter search the effects of using different data sets and different parametrizations of the problem linear versus nonlinear are also considered teleseismic body waves are shown to be essential to obtain a reliable solution due to the sparse coverage of the fault plane by strong motion stations a simple triangular source time function is compared with a modified kostrov source time function for a circular rupture and a constant propagating stress drop although the waveforms used in the inversions can not resolve between these two time functions the kostrov source time function gives a moment estimate and maximum fault displacement more consistent with long period surface waves and field observations the results of the iterative inversion for slip amplitudes and rupture times are compared with the results of a linear inversion for slip amplitudes in which the rupture velocity is fixed flexibility in the sequence of faulting for the linear inversion is obtained by allowing multiple rupture intervals a consensus of all the inversion runs indicates a complex multiple source for the tabas earthquake with four main source regions over a fault length of 90 km and an average rupture velocity of 2 5 km sec

the july 1986 oceanside ml 5 3 earthquake sequence in the continental borderland southern california an earthquake of m l 5 3 occurred at 32 58 7 n 117 51 5 w southwest of oceanside in san diego county at 13 47 13 july 1986 ut this main shock was followed by an extensive aftershock sequence with 55 events of m l 3 0 during july 1986 the epicenters of the main shock and aftershocks are located at the northern end of the san diego trough bahia soledad fault zone sdt bs where it changes strike from northwest to a more westerly direction through a left offset or a bend in the fault the northwest striking sdt bs is one of three strike slip fault systems that constitute the offshore agua blanca fault system the spatial distribution of the aftershocks indicates a unilateral 7 to 9 km long rupture to the east southeast away from the epicenter of the main shock the focal mechanism of the main shock also has an east southeast striking and south dipping plane with mostly reverse movement on it focal mechanisms of the m l 3 0 aftershocks show both reverse and strike slip movement the reverse focal mechanisms indicate that this sequence may have occurred on a thrust fault that provides for a left stepping offset or a bend in the san diego trough fault as movement is transferred to the west along the santa cruz catalina island escarpment some of the aftershocks that are located to the southeast of the main shock and have strike slip focal mechanisms suggest activation of the northwest trending san diego trough fault a stress inversion of the focal mechanism data shows that the maximum principal stress determined from the focal mechanisms of the main shock and 22 aftershocks that occurred within 36 hours of the main shock has an azimuth of s30 w plunging 18 the maximum principal stress determined from 30 aftershocks that occurred from 15 july to 2 october 1986 has an azimuth of s20 w plunging 18 the values the measure of the relative sizes of the principal stresses are approximately 0 07 and 0 1 respectively indicating that the intermediate and minimum principal stress are of similar magnitude the results of the stress inversion and the focal mechanisms that showed reverse faulting suggest that the inner continental borderland offshore from oceanside is not currently a pure strike slip tectonic regime but rather a strike slip mixed with reverse faulting regime when the 52 aftershock focal mechanisms are divided into four groups and the stress inversion is repeated the change in stress can be described as a progressive counter clockwise rotation of 14 of the orientation of the maximum principal stress to a more southerly direction with the greatest change in stress orientation observed shortly after the main shock the abundance of aftershocks may be related to the large temporal variation in stress orientation that in turn may have resulted from the small stress drop of the main shock

long term seismogenic process for major earthquakes in subduction zones abstract a qualitative physical process for the long term seismogenesis of major earthquakes in subduction zones is proposed on the basis of quantitative empirical evidence that swarms mainshocks and aftershocks are closely related phenomena the relations which have been identified in the comprehensive long term catalogues of new zealand and japan represent swarms as predictors of mainshocks with respect to location time and magnitude clustering of swarms and of mainshock aftershock events is allowed for with a database of 15 sequences of swarms mainshocks and aftershocks tests are being conducted with the object of refining the relations and evaluating them as a possible means of practical synoptic forecasting three sequences have culminated in major earthquakes since the tests began and the systematic study now relates a total of 36 swarms with 29 mainshock aftershock events these empirical results strengthen and quantify the connection between swarms and major earthquakes which several authors have demonstrated by means of numerical physical modelling the proposed seismogenic process includes swarms mainshocks and aftershocks as separate event stages which are related by predictability interevent conditions are specified according to the mogi criteria for the medium cracks at which fractures subsequently occur constitute nonuniformity in the mogi sense and post earthquake healing restores uniformity where the gutenberg richter relation occurs it is accepted as possible evidence of deterministic chaos and unpredictability as a corollary the process is noncyclical the principle of scaling is held to apply except when modified by large scale boundaries in the medium subduction zones and some other localities where water is abundant are indicated by the main empirical studies as favourable to the occurrence of swarms fluid overpressuring is therefore proposed as a mechanism for the self triggering of swarms and this is supported by additional examples of the predictive relations occurring in conditions of high fluid pressure including the vicinity of large man made reservoirs the process can be tested by systematic studies in other subduction regions given adequate catalogues for quantifying the algorithm it also has implications for other tectonic environments with swarms replaced by cognate more protracted seismicity precursors

field study of a highly active fault zone the xianshuihe fault of southwestern china the xianshuihe fault of western sichuan province china is one of the world s most active faults having produced 4 earthquakes during this century of magnitude 7 along a 350 km length of the fault at least 8 such events have occurred since 1725 in the more limited 150 km long segment including luhuo and daofu major earthquakes in 1904 1923 1973 and 1981 m 7 7 7 6 6 9 were associated with overlapping surficial fault ruptures and with individual left lateral displacements as large as 3 6 m field studies indicate that this high degree of activity is typical of the fault s longer term history the holocene left lateral slip rate on the north western segment of the fault has been 15 5 mm yr decreasing to about 5 mm yr on its southeastern segment based on radiometrically dated offset stream channel and terrace deposits and on offset glacial moraines physiographic features of active faulting are fully as diagrammatic as those of california s san andreas fault mainly because of high altitude preservation and the absence of cultural modification on this eastern margin of the tibetan plateau detailed en echelon tensional and pushup features resulting from surface ruptures in 1973 1955 1923 and 1893 can still be recognized today and new data have been collected bearing on the offsets and fault rupture lengths during these and other events the locations and magnitudes of historic earthquakes suggest that the characteristic earthquake model may apply to the xianshuihe fault obvious geometric segmentation of the fault has controlled the initiation and termination of ruptures in some events whereas segmentation control for others remains obscure based on the historic record repeat times estimated from slip rates and current seismic gaps two segments are particularly likely sites for m 7 earthquakes in the near future the 65 km long segment between daofu and qianning and the 135 km long segment bracketing kangding continuing creep has been documented along some segments of the fault and this together with the high degree of activity and other unique attributes makes the xianshuihe fault one of the most promising sites in the world for earthquake prediction and hazard evaluation studies

evolution of the stress field in southern california and triggering of moderate size earthquakes a 200 year perspective changes in stress in southern california are modeled from 1812 to 2025 using as input 1 stress drops associated with six large 7 0 7 5 earthquakes through 1995 and 2 stress buildup associated with major faults with slip rates 3 mm yr as constrained by geodetic paleoseismic and seismic measurements evolution of stress and the triggering of moderate to large earthquakes are treated in a tensoffal rather than a scalar manner we present snapshots of the cumulative coulomb failure function acff as a function of time for faults of various strike dip and rake throughout southern california we take acff to be zero everywhere just prior to the great shock of 1812 we find that about 95 of those well located m 6 earthquakes whose mechanisms involve either strike slip or reverse faulting are consistent with the coulomb stress evolutionary model that is they occurred in areas of positive acff the interaction between slow moving faults and stresses generated by faster moving faults significantly advanced the occurrence of the 1933 long beach and 1992 landers events in their earthquake cycles coulomb stresses near major thrust faults of the western and central transverse ranges have been accumulating for a long time future great earthquakes along the san andreas fault especially if the san bernardino and coachella valley segments rupture together can trigger moderate to large earthquakes in the transverse ranges as appears to have happened in the santa barbara earthquake that occurred 13 days after the great san andreas shock of 1812 maps of current acff provide additional guides to long term earthquake prediction

correlation of static stress changes and earthquake occurrence in the north aegean region a systematic analysis is made of static coulomb stress changes and earthquake occurrence in the area of the north aegean sea greece in order to assess the prospect of using static stress changes to construct a regional earthquake likelihood model the earthquake data set comprises all events of magnitude m 5 2 which have occurred since 1964 this is compared to the evolving stress field due to constant tectonic loading and perturbations due to coseismic slip associated with major earthquakes m 6 4 over the same period the stress was resolved for sixteen fault orientation classes covering the observed focal mechanisms of all earthquakes in the region analysis using error diagrams shows that earthquake occurrence is better correlated with the constant tectonic loading component of the stress field than with the total stress field changes since 1964 and that little if any information on earthquake occurrence is lost if only the maximum of the tectonic loading over the fault orientation classes is considered moreover the information on earthquake occurrence is actually increased by taking the maximum of the evolving stress field since 1964 and of its coseismic slip component over the fault orientation classes the maximum over fault orientation classes of linear combinations of the tectonic loading and the evolving stress field is insignificantly better correlated with earthquake occurrence than the maximum of the tectonic loading by itself a composite stress change variable is constructed from ordering of the maximum tectonic loading component and the maximum coseismic slip component in order to optimize the correlation with earthquake occurrence the results indicate that it would be difficult to construct a time varying earthquake likelihood model from the evolving stress field that is more informative than a time invariant model based on the constant tectonic loading

long term seismogenesis in greece comparison of the evolving stress field and precursory scale increase approaches 1 recent strong m 6 6 earthquakes in greece are examined from the point of view of two current but disparate approaches to long term seismogenesis these are the evolving stress field esf approach in which earthquakes are considered to be triggered by accumulated stress changes from past earthquakes and tectonic loading on the major faults and the precursory scale increase approach in which a major earthquake is preceded in the long term by an increase in minor earthquake occurrences with the magnitude of the precursory earthquakes and the precursor time and area all scaling with the major earthquake magnitude the strong earthquakes are found to be consistent with both approaches and it is inferred that both approaches have a relevant role to play in the description of the long term generation process of major earthquakes a three stage faulting model proposed previously to explain the phenomenon involves a major crack which eventually fractures in the major earthquake being formed before the onset of precursory seismicity hence we examine whether esf can account for the formation of the major crack by examining the accumulated stress changes at the time of the onset of for each strong earthquake in each case the answer is in the affirmative there is enhanced stress in the vicinity of the main shock at the time of the onset the same is true for most but not all of the locations of precursory earthquakes

slip along the san andreas fault associated with the great 1857 earthquake historical records indicate that several meters of lateral slip along the san andreas fault accompanied the great 1857 earthquake in central and southern california these records together with dendrochronological evidence suggest that the rupture occurred along 360 to 400 km of the fault including several tens of kilometers of the currently creeping reach in central california geomorphic expressions of late holocene right lateral offsets are abundant along the 1857 rupture along 300 kilometers of the 1857 rupture between cholame and wrightwood the youngest discernible offset ranges from 3 to 9 1 2 meters dormancy of the fault since 1857 almost certainly indicates that this latest offset was created in 1857 fault slip apparently associated with the 1857 earthquake varies in a broadly systematic way along the trace of the fault it is relatively uniform along each of several long segments but changes rather abruptly in value between these segments this nonuniform displacement pattern may imply that some segments of the fault rupture more frequently or experience a slower long term slip rate than others the 1857 offsets indicate a seismic moment m o between 5 3 and 8 7 10 27 dyne cm assuming a 10 to 15 km depth of rupture and relatively uniform slip as a function of depth a comparison with the rupture length average slip value and tectonic setting of the california earthquake of 1906 m s 8 1 4 indicates a value of m 8 1 4 for the 1857 event

metallogenic epochs and metallogenic provinces of the estrie beauce region southern quebec appalachians eight distinct metallogenic epochs have been identified within the southern quebec appalachians as follows 1 precambrian early cambrian intracontinental rifting of laurentia is related to the formation of black sand paleoplacer volcanic red bed copper and strata bound cu and zn deposits in dolomite marble and metagraywacke 2 the cambro ordovician opening of the iapetus ocean proto atlantic resulted in the formation of uraniferous phosphorite strata bound zn cu ba deposits and magmatic ni cu deposits on or along the margin of a carbonate platform 3 early ordovician immature island arc formation is related to the initial closure of the proto atlantic ocean and yielded chromitite and cyprus type volcanogenic massive sulfide deposits 4 the middle ordovician taconian orogeny produced disseminated and vein type cu mo u au ag mineralization that formed within the frontal zone of the taconian internal metamorphic domain 5 the middle to late ordovician closure of a marginal basin of the proto atlantic ocean yielded several deposit types the eastward migration of a subduction zone under a small continental rift progressively generated kuroko type massive sulfide porphyry type cu au and then porphyry cu mo deposits in a mature arc setting whereas auriferous black shales and shale hosted sedimentary exhalative deposits were formed in a fore arc basin 6 late ordovician and silurian volcanogenic massive sulfide deposits and associated fe and mn formations were subsequently formed in transtensional rift basins 7 the devonian acadian orogeny yielded hypothermal w mo mesothermal ni cu co zn as and epithermal as sb mineralization 8 niobium and rare earth rich carbonatites granitophile sn or w or mo deposits and diatreme associated au mineralization are related to the opening of the present atlantic ocean and associated jurassic cretaceous alkaline magmatism the eight metallogenic epochs define eight metallogenic provinces in the region which overlap and crosscut one another each province presents inhomogeneities in metal content and in the distribution of the types of contained mineral deposits these inhomogeneities are related to differences such as the tectonic setting during mineral deposition the provenance of the sediments the depth of seawater during mineralization and the relative location of the mineral deposit within hydrothermal convection cells

rupture complexity of a moderate sized mb 6 0 earthquake broadband body wave analysis of the north yemen earthquake of 13 december 1982 abstract the occurrence of the north yemen earthquake of 13 december 1982 provides an important opportunity to study source properties of earthquakes in the southern arabian peninsula although moderate in size m b 6 0 this earthquake is the largest to have occurred in the region since the deployment of the global digital seismograph network p waves recorded at teleseismic distances can be obtained from stations of this network and of the graefenberg array that are flat to displacement and velocity in the frequency range from 0 01 to 5 0 hz the broad bandwidth of the data is necessary for deriving a dynamic description of the earthquake as well as the static properties of the source in contrast inversions using only long period data provide much less insight into the complexity of rupture by fitting the displacement pulse shapes with synthetics we find that the yemen earthquake was a complex rupture consisting of two events that occurred about 3 0 sec apart the depth of both hypocenters is estimated to be 7 km the focal mechanisms of the events each have a nodal plane that strikes 340 and dips 60 to the east however the slip directions of the focal mechanisms are in slightly different directions 230 and 300 respectively the total moment of the earthquake is 3 0 10 25 dyne cm with the second event having three times the moment of the initial event by inverting p wave arrival time differences at each station we find the second hypocenter is located 7 5 km from the initial hypocenter in a direction that is nearly colinear with the nnw striking nodal plane of the focal mechanisms of each event the trend of extensional ground cracks in the epicentral region and the predominant strike of composite focal mechanisms of locally recorded aftershocks are also in a nnw direction from the consistency of these observations we infer that the east dipping nnw striking nodal planes are the fault planes the static stress drop of the first and second events are 44 and 31 bars respectively inverting the energy flux in the velocity waveforms we find the energy radiated by the earthquake is 4 8 10 20 dyne cm this implies an average apparent stress of 4 bars at different times during the aftershock sequence seismicity tended to cluster about one or another of two different planes which although having roughly the same strike had conjugate dips one of these planes delineated late in the aftershock sequence coincides with the inferred fault plane for the main shock the complexity of the main shock and of the aftershock sequence suggests that strain accumulated on a system of strongly interdependent faults as the region became critically loaded the effect of a major rupture was to critically stress faults adjacent to the initial nucleation the second event of the main shock represents the rapid release of stress from the fault system while the ensuing aftershock sequence represents the gradual release of stress

faulting associated with large earthquakes and the average rate of deformation in central and eastern asia we determine approximate average rates of deformation in portions of eastern and central asia for the last 80 years these rates are based on estimates of source dimensions average displacements seismic moments and orientations of faults of all large earthquakes m 7 5 and as many other major earthquakes m 7 0 as possible in asia since 1900 a major part of this study is the compilation of these data for separate parts of asia we combine seismic moment tensors to estimate the average rotational strain or deformation tensors for these regions for the last 80 years we estimate that shortening across the tien shan has occurred at 11 mm yr between 5 and 19 mm yr left lateral shear on easterly trending planes in mongolia in northwestern tibet gansu and ningxia and on the xianshuihe fault in western sichuan has been very rapid more than 10 mm yr in each region and apparently as rapid as 40 mm yr in northwestern tibet gansu and ningxia slower rates of a few to 10 mm yr appear to characterize east west extension and conjugate north south shortening of tibet the earthquake history of the himalaya is consistent with rates of underthrusting of more than 10 mm yr but is probably less than the convergence rate of india with eurasia of about 50 mm yr the overall strain field is consistent with a large part of india s penetration into eurasia being absorbed by the extrusion of material out of india s way as a result southeast china moved at about 21 mm yr east southeast with respect to eurasia in the last 80 years with an uncertainty of about a factor of 2 in this estimated rate

the pyrenean earthquake of february 29 1980 an example of complex faulting abstract an m b 5 1 earthquake occurred on february 29 1980 in the western pyrenees near arudy france the telemetred network of the i p g p operating in this area since 1978 allowed a good localization of this earthquake 43 4 21 n 0 24 59 w depth 4km during the two years preceding this earthquake the seismic activity exhibited a gradual decrease a foreshock of magnitude 1 6 was recorded three hours before the main shock a temporary network set up in the epicentral area a few days after the main shock permitted a precise study of the aftershock sequence fifty fault plane solutions for earthquakes ranging from magnitude 1 5 4 were obtained a complex pattern of faulting was revealed with both strike slip and normal faulting however a regional tectonic stress tensor can be proposed from a detailed investigation of the aftershock sequence this stress tensor is in agreement with previous results in this area

can deep seated gravitational slope deformations be activated by regional tectonic strain first insights from displacement measurements in caves from the eastern alps abstract tectonic elastic strain and ground deformations are documented as the most remarkable environmental phenomena occurring prior to local earthquakes in tectonically active areas the question arises if such strain would be able to trigger mass movements we discuss a directly observed fault slip and a subsequent minor activation of a deep seated gravitational slope deformation prior to the m 3 bad fischau earthquake between end of november and early december 2013 in ne austria the data originate from two faults in the emmerberg and eisenstein caves in the transition zone between the eastern alps and the vienna basin monitored in the framework of the fwf speleotect project the fault slips have been observed at the micrometer level by means of an opto mechanical 3d crack gauge tm 71 the discussed event started with the fault activation in the emmerberg cave on 25 november 2013 recorded by measurements of about 2 m shortening and 1 m sinistral parallel slip which was fully in agreement with the macroscopically documented past fault kinematics one day later the mass micro movement activated on the opposite side of the mountain ridge in the eisenstein cave and it continued on three consecutive days further the fault in the emmerberg cave experienced also a subsequent gravitational relaxation on 2 3 december 2013 when the joint opened and the southern block subsided towards the valley while the original sinistral displacement remained irreversible the process was followed by the m 3 earthquake in bad fischau on 11 december 2013 our data suggest that tectonic strain could play a higher role on the activation of slow mass movements in the area than expected although we cannot fully exclude the co activation of the mass movement in the eisenstein cave by water saturation the presented data bring new insight into recent geodynamics of the eastern alps and the vienna basin for better interpretations and conclusions however we need a much longer period of observations

test of the eepas forecasting model on the japan earthquake catalogue the eepas every earthquake a precursor according to scale model is a method of forecasting earthquakes based on the notion that the precursory scale increase phenomenon occurs at all scales in the seismogenic process the rate density of future earthquake occurrence is computed directly from past earthquakes in the catalogue the eepas model has previously been fitted to the new zealand earthquake catalogue and successfully tested on the california catalogue

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

rupture patterns and preshocks of large earthquakes in the southern san jacinto fault zone we relocated the large 1937 1942 and 1954 earthquakes in the san jacinto fault zone the epicenters of the main shocks aftershocks and some preshocks were determined using empirical station corrections from recent small events in the study areas the 1937 ml 5 9 earthquake has an epicenter between the surface traces of the san jacinto and buck ridge faults and aftershocks suggest about 7 km of rupture predominantly to the northwest a significant increase in small earthquake activity occurred about formula yr before this event the 1954 m l 6 2 earthquake is located at the southeast end of the mapped trace of the san jacinto fault and aftershocks suggest about 15 km of rupture further southeast into an area of folded young sediments with no surface fault trace this event was preceded by a cluster of small earthquakes which occurred within an 8 hr period 10 weeks before the main event and in the eventual rupture zone the 1942 m l 6 3 earthquake is located southwest of the southeast end of the coyote creek fault large aftershocks of this event are spread over a 15 by 18 km area southwest of the coyote creek fault and are not associated with any one fault the relation of the 1942 event to the san jacinto fault zone is not simple