paleomagnetism of coastal california and baja california alternatives to large scale northward transport paleomagnetic data from the santa lucia orocopia sloa and baja borderland bba allochthons of coastal california and baja california have been interpreted to indicate up to 2500 km of post mid cretaceous northward transport of these regions with respect to interior north america however with neogene strike slip offsets taken into account geological interpretations correlate basement rocks of the coastal allochthons with continental basement rocks directly across the san andreas and related fault systems we have examined paleomagnetic data from sloa and bba and conclude that apparent discordances can be explained without large scale pre neogene tectonic transport three major observations are fundamental to this analysis 1 paleolatitudes derived from volcanic rocks of the jurassic eugenia formation of bba and coast range ophiolite of sloa are concordant when compared to revised jurassic reference paleomagnetic poles from interior north america 2 isotopic and paleobarometric data from the peninsula ranges batholith in southern california indicate that the batholith has been tilted northeast side up by an amount that can account for discordant paleomagnetic directions observed in plutonic rocks of the batholith without large scale northward transport 3 literal interpretation of the paleolatitudes determined from paleomagnetic directions in upper cretaceous and paleogene marine sedimentary rocks of sloa and bba requires north then south then north transport and a complex motion history between the two allochthons however concordant paleolatitudes are indicated by some sedimentary rocks while coeval or younger sedimentary rocks of the same allochthon have discordant paleolatitudes coupled with recent documentations of compaction shallowing of paleomagnetic inclination in other marine sedimentary rocks these inconsistencies suggest that paleolatitudes derived from most of the marine sedimentary rocks of sloa and bba are biased towards low paleolatitudes by compaction shallowing

experimental calibration of the aluminum in hornblende geobarometer with application to long valley caldera california volcanic rocks a new geobarometer based on the al content of igneous hornblendes in equilibrium with melt fluid biotite quartz sanidine plagioclase sphene and magnetite or ilmenite has been calibrated experimentally the calibration was performed by equilibrating the required phase assemblage over the pressure range 2 8 kbar at 740 780c and then analyzing euhedral hornblendes in equilibrium with glass melt experiments were performed on natural samples of both volcanic and plutonic rocks earlier empirical calibrations of this geobarometer relied on analyzing natural hornblendes from plutons with the required phase assemblage and inferring pressure from nearby metamorphic country rocks the experimental calibration differs from the empirical calibrations especially above 5 kbar and shows that the al content of hornblendes in equilibrium with the required phase assemblage is greater for a given total pressure than previously thought the geobarometers uncertainty is dramatically reduced the derived equation is p plus minus 0 5 kbar 3 minus 3 46 plus minus 0 24 4 23 plus minus 0 13 al sup t the geobarometer is applied to post bishop tuff volcanic rocks from long valley caldera california and reveals that most rhyodacites in this complex erupted from depths of about 6 km these eruptions occurred over 500 000 yr suggesting that the rhyodacitic magma reservoir beneath longmore valley had reached a steady p depth t state less

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

global earthquake forecasts summary we have constructed daily worldwide long and short term earthquake forecasts these forecasts specify the earthquake rate per unit area time and magnitude on a 0 5 degree grid for a global zone region between 75n and 75s latitude 301 by 720 grid cells we use both the global centroid moment tensor gcmt and preliminary determinations of epicenters pde catalogues like our previous forecasts the new forecasts are based largely on smoothed maps of past seismicity and assume spatial and temporal clustering the forecast based on the gcmt catalogue with the magnitude completeness threshold 5 8 includes an estimate of focal mechanisms of future earthquakes and of the mechanism uncertainty the forecasted tensor focal mechanism makes it possible in principle to calculate an ensemble of seismograms for each point of interest on the earth s surface we also introduce a new approach that circumvents the need for focal mechanisms this permits the use of the pde catalogue that reliably documents many smaller quakes with a higher location accuracy the result is a forecast at a higher spatial resolution and down to a magnitude threshold below 5 0 such new forecasts can be prospectively tested within a relatively short time such as a few years because smaller events occur with greater frequency the forecast s efficiency can be measured by its average probability gains per earthquake compared to the spatially or temporally uniform poisson distribution for the short term forecast the gain is about 2 0 for the gcmt catalogue and 3 7 for the pde catalogue relative to a temporally random but spatially localized null hypothesis preliminary tests indicate that for the long term global spatial forecast the gain is of the order 20 25 compared to the uniform event distribution over the earth s surface we can also prospectively test the long term forecast to check whether it can be improved

error analysis for the determination of tectonic rotation from paleomagnetic data appendix b is available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document b83 001 2 50 payment must accompany order recent determinations of tectonic rotation and flattening from paleomagnetic data have exaggerated the size of the confidence limits or error bars by about 25 this has been caused by the misuse of conventional error propagation formulas to derive one degree of freedom error bars from a two dimensional cone of confidence 95 an analytical calculation which is valid when error bars are small shows that the correct error bars are 75 to 80 of the values derived in previous studies i have used numerical integration to check on the applicability of the analytical solution and to calculate error bars when the analytical approximation cannot be used the analytical approximation may be used whenever 95 is less than 10 and the mean inclination is not too close to vertical confidence limits given for tectonic rotation and flattening in recent literature are too large and should be reduced by 20 25 narrowing the error bars in this way permits a more accurate interpretation of paleomagnetic data

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

compaction corrected inclinations from southern california cretaceous marine sedimentary rocks indicate no paleolatitudinal offset for the peninsular ranges terrane paleomagnetic data have been used extensively to delineate the terrane displacement and accretion history of the western margin of north america however the anomalously shallow paleomagnetic inclinations used to indicate large scale northward translation might be alternatively interpreted as due to postmagnetization tilting of batholithic rocks and compaction of marine sediments to understand the magnitude of burial compaction effects on the post cretaceous motion history of the peninsular ranges baja borderlands terrane a rock magnetic compaction and paleomagnetic study of the ladd formation and the point loma formation from southern california was conducted the anhysteretic anisotropy of remanence of the characteristic remanence carrying grains and individual magnetic grain anisotropy were used to correct the inclinations of each formation individual magnetic grain anisotropy was determined by both compaction experiments and redeposition of a magnetic separate in a dc magnetic field standard paleomagnetic studies of the units indicated that previous ladd formation results could be reproduced and a correction was made at the sample level we were unable to adequately reproduce earlier results of the point loma formation so the average remanence anisotropy was used to correct the previously reported mean direction the mean inclination of the ladd formation was conected from 46 95 8 to 58 95 4 and the mean inclination of the point loma formation was conected from 39 5 5 4 normal and 36 4 16 6 reversed to 56 0 5 1 normal and 53 0 16 7 reversed these results suggest that the peninsular ranges baja borderland terrane has been part of the western north america since the late cretaceous and that clay containing sedimentary rocks may typically experience from 10 to 15 of inclination shallowing due to burial compaction

1 8 1 5 ga links between the north and south australian cratons and the early middle proterozoic configuration of australia abstract the archaean and early middle proterozoic 1 8 1 5 ga terranes of the north australian craton and the south australian craton are separated by 400 km of ca 1 33 1 10 ga orogenic belts and phanerozoic sediments however there is a diverse range of geological phenomena that correlate between the component terranes of the two cratons and provide evidence for a shared tectonic evolution between approximately 1 8 and 1 5 ga in order to honour these correlations we propose a reconstruction in which the south australian craton is rotated 52 counterclockwise about a pole located at 136 e and 25 s present day coordinates relative to its current position this reconstruction aligns the ca 1 8 1 6 ga orogenic belts preserved in the arunta inlier and the gawler craton and the ca 1 6 1 5 ga orogenic belts preserved in the mount isa block and the curnamona province before 1 5 ga the south australian craton was not a separate entity but part of a greater proto australian continent which was characterised by accretion along a southward migrating convergent margin ca 1 8 1 6 ga followed by convergence along the eastern margin ca 1 6 1 5 ga after 1 5 ga the south australian craton broke away from the north australian craton only to be reattached in its current position during the ca 1 33 1 10 ga albany fraser and musgrave orogenies

paleomagnetism magnetic anisotropy and mid cretaceous paleolatitude of the duke island alaska ultramafic complex we report paleomagnetic results from layered igneous rocks that imply substantial post mid cretaceous poleward motion of the insular superterrane western canadian cordillera and southeast alaska relative to north america the samples studied are from the stratiform zoned ultramafic body at duke island which intruded rocks of the alexander terrane at the south end of the southeastern alaska archipelago at about 110 ma thermal and alternating field demagnetization experiments show that the characteristic remanence of the ultramafic rocks has high coercivity and a narrow unblocking temperature range just below the curie temperature of magnetite this remanence is likely carried by low ti titanomagnetite exsolved within clinopyroxene and perhaps other silicate hosts the duke island intrusion exhibits a well developed gravitational layering that was deformed during initial cooling but below 540 c into folds that plunge moderately to the west southwest the characteristic remanence clearly predates this early folding and is therefore primary the fisher parameter describing the concentration of the overall mean remanence direction improves from 3 to 32 when the site mean directions are corrected by restoring the layering to estimated paleohorizontal all samples exhibit a magnetic anisotropy that is strong but nonuniform in orientation across the intrusion and we show that it has no significant or systematic effect on the site mean directions of remanence at least some of the anisotropy derives from secondary magnetite formed during partial serpentinization the mean paleomagnetic inclination 56 10 corroborates paleomagnetic results from five coeval silicic plutons of the canadian coast plutonic complex to the south and southeast and implies 3000 km 1300 km of poleward transport relative to the north american craton between mid cretaceous and middle eocene time the insular superterrane and coast plutonic complex shared a common paleolatitude history with more poleward transport than coeval inboard terranes

mesozoic paleomagnetism and northward translation of the baja california peninsula paleomagnetic data from cretaceous igneous and sedimentary rocks of the peninsular ranges and continental borderland of the baja california peninsula yield an average pole position of 83 n 344 e a95 3 4 suggesting that the peninsula as a whole has moved northward 11 and rotated 32 clockwise with respect to the north american craton since cretaceous time only a small portion of this movement is due to the neogene opening of the gulf of california results from stratified rocks giving both positive and negative fold tests are included in the average cretaceous pole the rocks that fail fold tests have been deformed and remagnetized by nearby intrusives that are only slightly younger unconnected directions from these sites closely match corrected directions from sites where the fold tests are positive oceanic rocks were also sampled in the continental borderland from upper triassic and upper jurassic tectonostratigraphic terranes which are apparently allochthonous with respect to the western baja peninsula and each other these oceanic rocks show magnetizations indicating low paleolatitudes although the hemisphere of origin is presently unknown the cretaceous rocks of the baja california peninsula may have originally formed adjacent to the now truncated continental margin along the northern middle america trench northward transport of the peninsula probably occurred by transcurrent faulting associated with oblique subduction of the farallon plate beneath western north america between late cretaceous and late miocene time

measurements of the cretaceous paleolatitude of vancouver island consistent with the baja british columbia hypothesis a previously unsampled outcrop of gently dipping or flat lying upper cretaceous sedimentary strata in the vancouver island region which contains unaltered aragonitic mollusk fossils yielded a stable remanent magnetization that is biostratigraphically consistent with cretaceous magnetochrons 33r 33n and 32r these results characterized by shallow inclinations indicate an upper cretaceous paleolatitude of about 25 3 degrees north which is equivalent to that of modern day baja california these findings are consistent with the baja british columbia hypothesis which puts the insular superterrane well south of the oregon california border in the late cretaceous

geophysical and isotopic mapping of preexisting crustal structures that influenced the location and development of the san jacinto fault zone southern california we examine the role of preexisting crustal structure within the peninsular ranges batholith on determining the location of the san jacinto fault zone by analysis of geophysical anomalies and initial strontium ratio data a 1000 km long boundary within the peninsular ranges batholith separating relatively mafic dense and magnetic rocks of the western peninsular ranges batholith from the more felsic less dense and weakly magnetic rocks of the eastern peninsular ranges batholith strikes north northwest toward the san jacinto fault zone modeling of the gravity and magnetic field anomalies caused by this boundary indicates that it extends to depths of at least 20 km the anomalies do not cross the san jacinto fault zone but instead trend northwesterly and coincide with the fault zone a 75 km long gradient in initial strontium ratios sr i in the eastern peninsular ranges batholith coincides with the san jacinto fault zone here rocks east of the fault are characterized by sr i greater than 0 706 indicating a source of largely continental crust sedimentary materials or different lithosphere we argue that the physical property contrast produced by the peninsular ranges batholith boundary provided a mechanically favorable path for the san jacinto fault zone bypassing the san gorgonio structural knot as slip was transferred from the san andreas fault 1 0 1 5 ma two historical m6 7 earthquakes may have nucleated along the peninsular ranges batholith discontinuity in san jacinto valley suggesting that peninsular ranges batholith crustal structure may continue to affect how strain is accommodated along the san jacinto fault zone

regional crustal thickness variations of the peninsular ranges southern california we used the teleseismic receiver function technique to obtain a profile of the crustal thickness of the northern peninsular ranges california depth to the moho varies from 37 km beneath the western peninsular ranges batholith to 27 km at the western edge of the salton trough an average apparent dip of 10 to the west over a lateral distance of 60 km we previously obtained a similar result for a profile 100 km to the south a moho dip of 20 over 30 km lateral distance in both cases the moho depth variations do not correlate with topography of the eastern batholith but rather appear to parallel the trend of a boundary that separates compositionally distinct eastern and western terranes these observations suggest that a steeply dipping moho is a regional feature beneath the eastern peninsular ranges and that compensation is through lateral variations in crustal or upper mantle density rather than through an airy root

time variable factors in earthquake hazard abstract the development of a model for time variable hazard estimation involves both subjective and objective elements in eight identifiable stages the final stage adoption of the model for practical use is reached only after the conclusion of a successful performance test at the present state of knowledge such a test consists in measuring the performance of the time variable model against that of the present static model i e seismic zoning precursory phenomena provide a basis for the quantification of the time variable hazard provided the data are sufficient to allow certain intermediate quantities the probability distributions for location magnitude and time of occurrence the valid alarm rate and the failure rate to be evaluated similar quantification should also be attainable on the basis of various types of regularity which have been suggested in the occurrence of large earthquakes but the details of these models have yet to be fully ascertained

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

high and low k granites and adakites at a palaeoproterozoic plate boundary in northwestern australia the lamboo complex is one of several palaeoproterozoic terrains in northern australia that is intruded by high k i type granites the oldest granites in the complex consist of the high k 1865 1850 ma paperbark supersuite with initial e nd values between 2 7 and 4 0 tonalite sheets of the c 1850 ma dougalls suite have high al 2 o 3 na 2 o sr sr y and la yb and low y and hree and initial e nd values between 1 4 and 0 7 the rocks have compositions similar to adakites that form by melting of mafic rocks in the deep crust with garnet in the residue granites of the 1835 1805 ma sally downs supersuite range from high k types through to crustally derived adakites all with initial e nd values between 0 1 and 1 2 the two supersuites and the dougalls suite were intruded into different tectonic settings previously all of the granites in the lamboo complex were interpreted as partial melts of a chemically and isotopically uniform underplate beneath a rifted archaean craton however their spatial and temporal distribution and their varied compositions are best explained by large scale horizontal plate motions and subduction of oceanic crust

tectonic implications of palaeoproterozoic post collisional high k felsic igneous rocks from the kimberley region of northwestern australia abstract palaeoproterozoic high k i type granites high level porphyry intrusions and felsic volcanic rocks of the whitewater volcanics dominate the hooper and lamboo complexes in the kimberley region of northwestern australia the granites porphyries and volcanic rocks are gradational into each other in the field and they have the same mineralogy similar major and trace element abundances and indistinguishable shrimp u pb zircon ages of 1865 1850 ma there is evidence of widespread mingling between the granites and coeval gabbros magma mixing may be important in the formation of some of the mafic granites but most of the rocks probably formed from felsic parent magmas that underwent variable degrees of fractional crystallization the felsic igneous rocks may have formed by partial melting of intermediate to felsic calc alkaline rocks along the southern and eastern margins of the kimberley craton following accretion of various earlier palaeoproterozoic terranes to the craton therefore models for palaeoproterozoic high k granites in northern australia that invoke intracratonic rifting of a stable archaean craton may need to be revised

long range earthquake forecasting allowing for aftershocks summary an earthquake occurrence model aimed at forecasting main shocks can be adjusted to allow for the occurrence of aftershocks conforming to well known empirical relations describing their temporal decay magnitude distribution and spatial extent modifications are proposed to the every earthquake a precursor according to scale eepas long range forecasting model to allow for the occurrence of aftershocks of predicted events using earthquake catalogues of california and the kanto region central japan versions of the modified and original eepas model are fitted to a period of about 10 yr and independently tested on a later period of about 10 yr of each catalogue for the testing period the increase in the log likelihood per earthquake of the modified models over their original counterparts is about 0 1 on average this gives preliminary confirmation of the efficacy of the modifications versions of the modified model will be submitted to regional testing centres of the collaboratory for the study of earthquake predictability for further independent performance testing in real time

mesoscale and regional kinematics of the northwestern yalakom fault system major paleogene dextral faulting in british columbia canada the northwestern yalakom fault system yfs lies on the eastern margin of the coast belt in southwestern british columbia the yalakom fault is the most significant structure in the fault system with at least 115 km of dextral slip mostly of early tertiary age the nw yfs is up to 25 km wide and is bounded on the southwest by the tchaikazan fault zone which had 5 km or more of dextral slip kinematic and paleostress analysis of mesofaults and map scale structures shows that secondary faults within the nw yfs had both dextral and sinistral oblique slip three large synclines had increasing amounts of clockwise vertical axis rotation from southeast to northwest block rotation between two synthetic strike slip faults with large offset yalakom and moderate offset tchaikazan is similar to current kinematics between the san andreas and san jacinto faults in southern california the nw yfs was active from latest cretaceous to mainly eocene time and postdates early late cretaceous thrust faulting to the southwest early stage mesofaults are compatible with the thrust belt and suggest that open folds developed in the foreland of the thrust belt before strike slip faulting commenced the abrupt northwest termination of the yfs may be related to extension within the adjacent tatla lake metamorphic complex some dextral slip may have been transferred farther northwest through the coast belt but these structures have not been documented in west central british columbia most of the 120 km of dextral slip on the yfs was transferred to the north via a mosaic of normal and strike slip faults in central british columbia thus the yfs forms the southwestern margin of a broad zone of transtensional structures that extends to the tintina rocky mountain trench fault zone these structures accommodated northwestward displacement of the northwestern cordillera in paleogene time

calcic amphibole equilibria and a new amphibole plagioclase geothermometer reply to the comments of hammarstrom and zen and rutherford and johnson we reaffirm the barometric potential of our amphibole plagioclase thermometer for rocks where and only where the final equilibration temperature is very well constrained in the advantageous case of granitoids with simple thermal histories this temperature may be the wet granitoid solidus at the pressure of interest we emphasise the need for careful petrographic assessment of equilibrium between plagioclase and amphibole before attempting total al barometry and recommend that a relatively large number of pairs are analysed for each sample in rocks with complex post consolidation or fluid flow histories such barometry requires an independent means of determining amphibole equilibration temperature

p wave image of the peninsular ranges batholith southern california we invert earthquake p wave arrival times to image the 3d distribution of p wave velocities in the mesozoic peninsular ranges batholith and nearby areas in southern california there is a 3 velocity contrast between the eastern and western peninsular ranges at 4 and 20 km depth west side faster and a 1 to 1 5 velocity contrast across the san andreas fault zone south side faster in the san bernardino region at 4 to 14 km depth the san andreas velocity contrast is due to the juxtaposition of different rock types by slip along the fault zone the peninsular ranges batholith velocity contrast is due to a difference in rock composition across the batholith the maximum gradient in the crustal velocities is coincident with a compositional boundary within the batholith that reflects emplacement of the batholith across juxtaposed oceanic and continental crust quaternary fault development has been in part concentrated at this boundary

mid cretaceous paleomagnetic reference field for north america restudy of 100 ma intrusive rocks from arkansas we have obtained new paleomagnetic data from three middle cretaceous alkalic intrusive complexes in central arkansas magnet cove and potash sulfur springs intrusions about 100 ma 20 sites and granite mountain stock about 88 ma 6 sites out of 254 specimens measured 147 from 20 sites were accepted the remainders have scattered magnetization directions which experiments indicate were caused by lightning occurring during frequent electrical storms in this region the geologic evidence indicates that the intrusions have not been tilted since emplacement the directions of magnetization calculated with respect to present day horizontal yield a mean paleopole at 192 5 e 74 1 n n 20 k 34 a95 5 7 this does not differ at 95 confidence from that determined previously by scharon and hsu but the error is diminished by half the angular dispersion sd of site virtual geomagnetic poles vgps is 13 6 similar to the value of sd about 15 predicted by current paleosecular variation models the revised arkansas paleopole is combined with four other cratonic north american paleopoles of mid cretaceous age to yield a revised middle cretaceous reference pole at 196 e 71 n a95 4 9 the mean of nine paleopoles derived from overprints in rock units from the craton and craton margin which range in age from proterozoic to jura cretaceous is 202 e 68 n a95 8 2 this is not different from the reference paleopole indicating that overprinting was very widespread across north america in mid cretaceous time

prediction probabilities from foreshocks when any earthquake occurs the possibility that it might be a foreshock increases the probability that a larger earthquake will occur nearby within the next few days clearly the probability of a very large earthquake ought to be higher if the candidate foreshock were on or near a fault capable of producing that very large mainshock especially if the fault is towards the end of its seismic cycle we derive an expression for the probability of a major earthquake characteristic to a particular fault segment given the occurrence of a potential foreshock near the fault to evaluate this expression we need 1 the rate of background seismic activity in the area 2 the long term probability of a large earthquake on the fault and 3 the rate at which foreshocks precede large earthquakes as a function of time magnitude and spatial location for this last function we assume the average properties of foreshocks to moderate earthquakes in california 1 the rate of mainshock occurrence after foreshocks decays roughly as t 1 so that most foreshocks are within three days of their mainshock 2 foreshocks and mainshocks occur within 10 km of each other and 3 the fraction of mainshocks with foreshocks increases linearly as the magnitude threshold for foreshocks decreases with 50 of the mainshocks having foreshocks with magnitudes within three units of the mainshock magnitude within three days we apply our results to the san andreas hayward san jacinto and imperial faults using the probabilities of large earthquakes from the report of the working group on california earthquake probabilities 1988 the magnitude of candidate event required to produce a 1 probability of a large earthquake on the san andreas fault within three days ranges from a high of 5 3 for the segment in san gorgonio pass to a low of 3 6 for the carrizo plain

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

the eepas forecasting model and the probability of moderate to large earthquakes in central japan abstract the eepas every earthquake a precursor according to scale model is a space time point process model based on the precursory scale increase phenomenon and associated predictive scaling relations it has previously been fitted to the new zealand earthquake catalogue and applied successfully in quasi prospective tests on the cnss catalogue for california for forecasting earthquakes with magnitudes above 5 75 and on the jma catalogue of japan for magnitudes above 6 75 here we test whether the scaling relations extend to lower magnitudes by applying eepas to depth restricted subsets of the nied catalogue of the kanto area central japan for magnitudes above 4 75 as in previous studies the eepas model is found to be more informative than a quasi static baseline model based on proximity to past earthquakes and much more informative than the stationary uniform poisson model the information that it provides is illustrated by maps of the earthquake occurrence rate density covering magnitudes from 5 0 to 8 0 for the central japan region as at the beginning of year 2004 using the nied and jma catalogues to mid 2003

geological framework of the archean and paleoproterozoic tanami region northern territory the tanami region a poorly exposed mostly paleoproterozoic province within the north australian craton hosts a number of significant gold deposits in diverse settings rare exposures of 2 520 2 500 ma amphibolite facies archean gneiss and metasedimentary rocks form basement to the thick overlying metasedimentary succession of the 1 880 1 830 ma tanami group the basal unit of the tanami group is the dead bullock formation a fining upward deep water succession dominated by siltstone carbonaceous siltstone iron rich siltstone and mafic sills carbonaceous and iron rich lithologies in the upper dead bullock formation represent important hosts for gold mineralization the conformably overlying killi killi formation represents turbiditic sedimentary rocks that are correlated with the widespread lander rock beds of the arunta region sedimentation of the tanami group was terminated by regional deformation and greenschist to amphibolite facies metamorphism during the tanami event d1 m1 at around 1 830 ma the tanami group is unconformably overlain by rhyolite siliciclastic sedimentary rocks and felsic ignimbrite of the ware group that were deposited at about 1 825 1 810 ma subsequent ese wnw to se nw directed shortening d2 followed by ne sw to e w directed shortening d3 has resulted in open ne f2 and nw f3 trending folds in both the tanami and ware groups voluminous granitoids dominated by i type biotite granodiorite and monzogranite were intruded in the interval 1 825 1 790 ma and have been subdivided using geochemical criteria into the birthday frederick and grimwade suites basalt and immature sedimentary rocks of the mount charles formation are restricted in extent to the tanami mine corridor and are interpreted to reflect a continental rift succession that was deposited around 1 800 ma with an early archean sedimentary provenance steep s to se dipping f4 fold structures of tanami and ware group metasedimentary rocks many spatially associated with 1 825 1 790 ma granitoid intrusions indicate a period of sse directed regional shortening d4 syn to post the regional granitoid intrusive phase a network of n to nw striking faults several of which are interpreted as oblique thrusts with a component of left lateral movement indicates a period of d5 convergence during wsw ene to e w directed shortening the tanami mine corridor fault system comprises a network of n ne to ene striking d5 faults that merge with n to nw striking faults and probably accommodated movement between granite core domains d5 faulting is associated with the main phase of gold mineralization in suitable structural lithological traps the paleoproterozoic basement of the tanami region is unconformably overlain by quartz sandstone lithic arenite and conglomerate of the pargee sandstone pargee sandstone may represent syn tectonic sedimentation related to the 1 730 ma strangways orogeny and is unconformably overlain by the late paleoproterozoic platform cover succession of the birrindudu group the paleoproterozoic basement and cover sequences have subsequently undergone several episodes of faulting collectively termed d6 the paleoproterozoic evolution of the tanami region is interpreted to have occurred in an intracratonic setting but was fundamentally influenced by tectonic events in the adjacent halls creek orogen 1 835 1 805 ma halls creek orogeny and arunta region 1 815 1 800 ma stafford event the boundaries between the tanami region and kimberley region to the northwest and the arunta region to the southeast are transitional and are largely defined by the presence or absence of identifiable dead bullock formation

is the southeast coast plutonic complex the consequence of accretion of the insular superterrane evidence from u pb zircon geochronometry in the northern washington cascades zircon u pb geochronometry of orthogneisses and plutons in the southwestern crystalline core of the north cascades coupled with fabric and textural studies of the orthogneisses plutons and their metamorphic host rocks indicates extensive synmetamorphic plutonism at 89 96 ma metamorphic mineral assemblages define a culmination composed of an axial kyanite sillimanite zone rimmed by lower grade zones high grade index minerals are typically syntectonic to posttectonic metamorphic fabrics are characterized by an orogen parallel northwest striking steep foliation that contains a subhorizontal stretching and mineral lineation interpreted to be the product of ductile strike slip deformation this fabric is crosscut by 96 92 ma plutons yet is imprinted on 92 89 ma orthogneisses suggesting spatially diachronous fabric development during orogeny documentation of the spatial and temporal coincidence of magmatism with the peak of orogeny together with the kinematic significance of the metamorphic fabric precludes generation of the metamorphic fabric and plutons in response to thrust loading the authors suggest that this part of the coast plutonic complex evolved as a transpressional magmatic arc

the importance of early crustal architecture for subsequent basin forming magmatic and fluid flow events the granites tanami orogen example abstract the paleoproterozoic granites tanami orogen gto consists of tightly folded predominantly greenschist facies rocks the orogen a component of the north australian craton includes a ca 1864 ma succession of turbiditic and pelagic sedimentary rocks interbedded with volcanic rocks and abundant dolerite sills in a back arc basin setting which is intruded by collision related ca 1800 ma granitic rocks integrated 4d interpretation of deep seismic profiles gravity and magnetic field observations associated with available surface geology and igneous isotope geochemistry suggest that the gto forms an imbricated crust developed on a partially inverted s dipping rifted archean basement the rifting took place in the paleoproterozoic around 1864 ma and was followed by e w orientated compressional deformation ca 1850 ma with the development of northerly trending isoclinal folds and associated faults orthogonal collisional tectonics followed at ca 1800 ma which is associated with s verging kilometre scale folds faults and orogenic lode gold deposits in the region recognition of the preserved early rift architecture in the gto has major implications for the subsequent evolution of the orogen the early architecture has influenced all subsequent deposition deformation magmatic and fluid events including spatial control of the ca 1864 ma rock succession to the location of intrusive bodies and fluid transfer during formation of ca 1800 ma orogenic gold mineralization

northward translation of baja british columbia along the late cretaceous to paleocene margin of western north america paleomagnetic data suggest that a large part of british columbia and southern alaska was at the latitude of baja california mexico in early late cretaceous time this allochthonous block baja bc includes the insular talkeetna in alaska and intermontane composite terranes the miniterranes between them and possibly part of the omineca metamorphic belt assuming that baja bc was adjacent to north america by middle cretaceous an analysis using plate kinematics of the pacific basin produces a model of northward movement of baja bc which is compatible with the known geology of the reconstructed margin of western north america baja bc moved north 2400 km as part of the kuia plate along a transform margin with north america from 85 to 66 ma this time interval is marked by the cessation of igneous activity in the sierra nevada development of wrench faults and basins along coastal california and initiation of laramide style tectonics to the east within baja bc diminished igneous activity to the west was coeval with possible wrench tectonic basins along its eastern margin by the end of the cretaceous baja bc was positioned from oregon to northern british columbia between 66 and 56 ma baja bc became attached to north america in a dextral transpressive stage during which the kula north america plate boundary expanded to encompass the whole block with a series of northwest trending strike slip faults a fold and thrust belt in the east and large scale uplifts and the formation of an incipient volcanic arc on the west southern alaska was the site of convergence during the whole of the period of northward translation of baja bc a late cretaceous subduction zone in alaska evolved into a major compressional belt as the basin and miniterranes on the northern margin of baja bc collided with interior alaska the collision culminated in the paleocene with formation of the mckinley granites and coeval dextral slip on the denali fault system

discordant paleomagnetic poles from the canadian coast plutonic complex regional tilt rather than large scale displacement stratigraphic petrologic and isotopic data indicate that parts of the coast plutonic complex and the north cascade range have been tilted northeast side up by angles of approximately 30 degree about north northwest trending axes these tilts can account for discordant paleomagnetic directions observed in mid cretaceous plutons from these regions without large scale displacement relative to north america

shrimp u pb analyses of detrital zircon a window to understanding the paleoproterozoic development of the tanami region northern australia poorly exposed paleoproterozoic turbiditic to shallow marine sedimentary rocks of the tanami basin nt australia are largely the erosional products of either the 1 87 1 85 hooper orogeny and or magmatism associated with the 1 87 ga nimbuwah event dating of detrital zircon from six of the principal sedimentary units shows that deposition spanned at least the period 1 84 1 77 ga collectively the detrital zircon ages reveal a progression in provenance that is a record of the development of the orogen the basal dead bullock formation contains only zircon derived from archean basement and no contemporaneous products of orogeny its deposition age is inferred to be 1 87 1 84 ga orogenic 1 86 ga zircon appears in the overlying killi killi formation deposited between 1 84 1 82 ga and persists probably due to recycling in all overlying units except one the mount charles formation the accepted stratigraphic position of this unit might be incorrect

lessons and questions from thirty years of testing the precursory swarm hypothesis in 1976 frank evison identified the first examples of earthquake swarms as long term precursors of main shock events and thereby discovered the predictive scaling relations of long term seismogenesis from this time on forecasting became the main focus of his research after learning from an early attempt to communicate forecasts confidentially to government he recognised the importance of hypothesis testing and the precursory swarm hypothesis was cast in a form similar to a regional likelihood model tests of its performance relative to a stationary poisson model at m 5 8 in new zealand were begun in 1977 the initial hypothesis was that of a 1 1 relation between swarms and main shock events following a study of the japan catalogue the generalised swarm hypothesis in which multiple swarms were precursory to multiple main shock events was formulated tests of this form of the hypothesis at m 6 8 were initiated in a region of surveillance east of japan in 1983 eventually the generalised hypothesis was adopted in new zealand also in 1999 tests were begun in a region of greece in 1994 1995 several main shock events favourable to the swarm hypothesis occurred however four main shock events near arthur s pass new zealand occurred without precursory swarms subsequent analysis showed that events called quarms which were similar to swarms but more protracted in time had preceded these events this led to the proposal of a qualitative physical process to account for swarms quarms and the predictive relations a three stage faulting process in which a major crack induces aftercracks in its neighbourhood just as a main shock induces aftershocks an inference from this process was that the most general long term precursor should be an increase of seismicity at similar magnitudes to the eventual aftershocks it turned out that such a precursory scale increase nearly always occurs before major earthquakes and conforms to the predictive scaling relations setting aside the problem of identifying the scale increase before the major earthquake the eepas every earthquake a precursor according to scale forecasting model was formulated the success of this relatively weak model in forecasting major events in new zealand california japan and greece shows that the predictive scaling relations are ubiquitous in earthquake catalogues although none of the formal tests of the swarm hypothesis were successful in their own terms they were beneficial in identifying shortcomings in its formulation thereby leading to improved understanding of long term seismogenesis and a better forecasting model some puzzling aspects of the scaling relations are whether they vary regionally and why the precursor area and aftershock area scale differently with magnitude a more practical question is whether the eepas model can be strengthened by making use of the clustering of some precursors in swarms and quarms to bring us nearer to the original goal of forecasting individual major earthquakes

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

geochemical and nd isotopic systematics of granites from the arunta inlier central australia implications for proterozoic crustal evolution geochemical and sm nd isotopic results are reported for granites from the proterozoic arunta inlier of central australia these combined with new geochronological data for the granites zhao and bennett 1995 allow important constraints to be placed on proterozoic tectonic and crustal evolution in central australia granites from the arunta inlier can be divided into three major geochemical groups a calcalkaline trondhjemitic group cat a high heat production group hhp and a volumetrically significant main group the cat group which occurs only in the southern margin of the inlier is characterised by high na2o nak sr krb and sry and relatively low k2o rb rbsr th u ree nb and y analogous to calc alkaline suites occurring in modern convergent plate margins the hhp group which occurs mainly in the interior of the arunta inlier and is spatially associated with the main group is characterised by high k rb th u rbsr and rbzr and relatively low sr ba nak krb barb mgo cr and ni the main group which occurs throughout the arunta inlier is geochemically intermediate between the cat and hhp groups it is geochemically analogous to the 1880 1850 ma old barramundi igneous association recognised in other proterozoic terrains of central australia and can be further subdivided into four age subgroups 1820 1780 1750 1650 and 1615 1600 ma respectively all three groups show similar negative nb anomalies on the trace element normalized diagrams despite the geochemical diversity of the arunta granites no correlations between the nd isotopic and geochemical signatures are observed the ranges of initial nd values and nd depleted mantle model ages tnddm for the three groups of granites overlap with each other overall there are two groups of tnddm ages the most common ranging from 2 33 to 1 96 ga and the other from 1 83 to 1 72 ga although initial nd values of the granites show large variations there is a general trend for the nd values to increase i e become less negative with decreasing crystallization ages the large geochemical and isotopic variations of the arunta granites reflect considerable heterogeneity in the sources of the granites and do not support a uniform 2 3 2 1 ga old barramundi type underplate source for the origin of the granites the combined geochemical and nd isotopic data suggest the sources of the granites contain at least two main components an palaeoproterozoic mantle derived component and an older crustal component the older crustal component was incorporated into the source region of the granites either through magma assimilation of crustal materials at lower crustal levels or more probably via sediment subduction and mantle wedge metasomatism the increasing nd values with decreasing crystallization ages may be a result of progressively increasing proportions of newly accreted island arc materials being incorporated in the subducted sediments alternatively a juvenile mantle derived component may have been added to the source region of the younger granites it is apparent that the nd isotopic signatures in the granites has resulted from complex processes and neither simple mixing nor simple two stage protolith models can as yet satisfactorily explain the observations the petrogenesis of the three geochemical groups of granites can be interpreted in a plate tectonics scenario it is considered that the cat group was formed by fractionation of arc type magmas and or partial melting of arc related intrusions or underplates in a subduction related continental margin setting whilst the formation of the main group may involve partial melting of fractionated and or modified arc related underplates but not necessarily in a subduction environment the younger hhp group was probably generated by remelting of the coexisting main group during subsequent tectonothermal events

crustal tilting and differential exhumation of gangdese batholith in southern tibet revealed by bedrock pressures abstract the exhumation history of the gangdese batholith southern tibet bears on how magmatism and tectonism interact with surface processes in a long lived magmatic orogen in this study we applied al in hornblende barometry across the eastern gangdese batholith to obtain pluton emplacement pressures our results together with existing bedrock pressure data reveal the regional paleo depth pattern across the gangdese batholith the western part of the batholith near lhasa exposes plutons emplaced at 1 2 kbar whereas the eastern part near nyingchi exposes crust recording pressures typically of 6 12 kbar we coupled pressure data with new and published u pb zircon ages to constrain the exhumation history of the gangdese batholith the results show that since 100 ma the upper crust experienced limited exhumation except a pronounced oligocene miocene pulse in contrast the middle lower crust experienced a complex exhumation and burial history reflecting major tectonic events including the development of continental arc and continent continent collision since ca 10 ma the eastern nyingchi sector experienced fast exhumation total exhumation 40 km which was likely related to the exhumation of the eastern himalayan syntaxis the lhasa sector experienced comparatively limited exhumation total exhumation

mixture models for improved short term earthquake forecasting abstract the short term earthquake probability step forecasting model applies the omori utsu aftershock decay relation and the gutenberg richter frequency magnitude relation to clusters of earthquakes it is mainly intended to forecast aftershock activity and depends on a time invariant background model to forecast most of the major earthquakes on the other hand the long range earthquake forecasting model eepas every earthquake a precursor according to scale exploits the precursory scale increase phenomenon and associated predictive scaling relations to forecast the major earthquakes months years or decades in advance depending on magnitude both models are shown to be more informative than time invariant models of seismicity by forming a mixture of the two we aim to create an even more informative short term forecasting model using the advanced national seismic system catalog of california over the period 1984 2004 the optimal mixture model for forecasting earthquakes with m 5 0 is a convex linear combination consisting of 0 42 of the eepas forecast and 0 58 of the step forecast this mixture gives an average probability gain of more than 2 compared to each of the individual models several different mixture models will be submitted to the csep testing center at the southern california earthquake center to ascertain whether or not this result is borne out by real time tests of the models against future earthquakes

paleomagnetic evidence for displacement from the south of the coast plutonic complex british columbia the mid cretaceous spuzzum and porteau plutons of the coast plutonic complex of british columbia have two magnetizations a and b the a magnetization eight sites 83 specimens d 30 3 i 56 7 95 4 9 paleolatitude 37 5 n paleopole 65 0 n 14 9 w a95 6 2 is considered to have been acquired in the age range 105 90 ma this result differs from the field established for cratonic north america in this time range the difference could be caused either by previously undetected tilting about a horizontal axis of the plutons or by their rotation about a vertical axis and lateral displacement relative to the craton previously observed mid cretaceous magnetizations from other rock units from the western canadian cordillera and the cascades of washington united states are similarly discordant with respect to the craton this similarity over such a large area indicates that although local undetected tilting could be partly responsible it is unlikely to be the prime cause and we argue ther

earthquake forecasting in diverse tectonic zones of the globe we present a simple method for long and short term earthquake forecasting estimating earthquake rate per unit area time and magnitude for illustration we apply the method to the pacific plate boundary region and the mediterranean area surrounding italy and greece our ultimate goal is to develop forecasting and testing methods to validate or falsify common assumptions regarding earthquake potential our immediate purpose is to extend the forecasts we made starting in 1999 for the northwest and southwest pacific to include somewhat smaller earthquakes and then adapt the methods to apply in other areas the previous forecasts used the cmt earthquake catalog to forecast magnitude 5 8 and larger earthquakes like our previous forecasts the new ones here are based on smoothed maps of past seismicity and assume spatial clustering our short term forecasts also assume temporal clustering an important adaptation in the new forecasts is to abandon the use of tensor focal mechanisms this permits use of earthquake catalogs that reliably report many smaller quakes with no such mechanism estimates the result is that we can forecast earthquakes at higher spatial resolution and down to a magnitude threshold of 4 7 the new forecasts can be tested far more quickly because smaller events are considerably more frequent also our previous method used the focal mechanisms of past earthquakes to estimate the preferred directions of earthquake clustering however the method made assumptions that generally hold in subduction zones only the new approach escapes those assumptions in the northwest pacific the new method gives estimated earthquake rate density very similar to that of the previous forecast

paleomagnetism of the mount stuart batholith revisited again what has been learned since 1972 we have collected 20 new paleomagnetic sites from the mount stuart batholith and the adjacent beckler peak stock using thermal and low temperature demagnetization and rock magnetic tests we have found that the remanence in most of the batholith is carried by single domain magnetite the mean of the new mount stuart batholith sites is d 354 2 i 46 2 k 87 2 a95 4 6 n 11 and is similar to those of the beck and noson 1972 and beck and others 1981 studies examination of ar geochronology of hornblende and biotite from the mount stuart batholith finds that the southern part of the batholith cooled through the blocking temperature of magnetite at 91 ma the northern part cooled through the blocking temperature of magnetite at 86 ma and of pyrrhotite at 83 ma from these combined results we conclude that the paleomagnetic directions from the southern part of the batholith were acquired within 0 5 to 1 0 ma of the time at which the ah barometers cooled below their closure temperature use of the ah barometry to establish paleohorizontal for these rocks is thus well justified correcting the mount stuart direction for the tilt indicated by the aluminum in hornblende ah barometry the mean becomes d 355 9 i 50 6 this result places the mount stuart batholith at a latitude of 31 3 3 8 3 4 n at 91 ma by identifying the carrier of remanence in the mount stuart batholith as being single domain sd magnetite we have removed the major remaining uncertainty in interpreting the paleomagnetism of these rocks the characteristic magnetization repeatedly found in the mount stuart rocks clearly supports the microplate tectonic model of beck and noson 1972 presently manifest as the baja british columbia baja bc hypothesis

tilt and northward offset of cordilleran batholiths resolved using igneous barometry considerable controversy surrounds the suggestion based on palaeomagnetic evidence that large segments of the north american cordillera travelled long distances parallel to the coast during the latest cretaceous and early tertiary periods well after the amalgamation of exotic terranes discordant palaeomagnetic data from mid cretaceous plutonic rocks of the peninsular ranges batholith of coastal southern california and baja and the mount stuart batholith of the cascade range in washington play a pivotal role in the controversy the discordant data were originally interpreted to reflect northward transport of 1 000 km relative to cratonal north america after the batholiths cooled through their magnetic blocking temperatures1 5 more recently it has been argued that the discordances arise from local tilting of batholiths rather than northward offset6 7 here we present and implement new methods based on hornblende barometry8 for determining the palaeohorizontal in granitic batholiths and correcting palaeomagnetic data for tilting our results indicate that the peninsular ranges and mount stuart batholiths have undergone northward offsets of 1 000 450 and 2 900 700 km respectively and also significant tilting

tectonic evolution of proterozoic australia proterozoic australia has long been interpreted as a single intact continent in which all tectonic and magmatic activity was intracratonic this paper proposes an alternative hypothesis in which numerous fragments of continental crust were assembled by plate tectonic processes the assembly was completed between 1300 and 1100 ma when the crustal fragments were combined as an early component of the rodinian supercontinent rifting and fragmentation of archaean continents began in the late archaean and continued into the proterozoic passive margin deposits such as those of the hamersley basin accumulated on isolated fragments of archaean crust these numerous fragments were subsequently assembled into three cratons by 1830 ma a west australian craton was established by collision of the archaean pilbara and yilgarn cratons which were joined along the capricorn orogen similarly a south australian craton developed by amalgamation of the proto gawler and proto curnamona cratons along the kimban orogen a north australian craton appears to have formed by accretion of numerous crustal fragments including the kimberley pine creek lucas and altjawarra cratons with sutures marked by the king leopold halls creek tennant creek and proto isan orogens the southern margin of the north australian craton was the site of repeated terrane accretion and orogenic activity between 1880 ma and 1400 ma this included an orogenic event at 1880 1850 ma the strangways 1780 1730 ma argilke 1680 1650 ma and chewings 1620 1580 ma orogenies and the intracratonic anmatjira uplift 1500 1400 ma intracratonic rifting at 1750 to 1710 ma and 1640 to 1600 ma produced the mcarthur basin and related minor basins parts of which were deformed by the isan orogeny at 1600 and 1530 ma rifting along the line of the capricorn orogen led to deposition in the overlying intracratonic bangemall basin between 1630 and 1300 ma along the eastern margin of the south australian craton the 1670 to 1600 ma olarian orogeny marks interaction with now obscured continental crust to the east tectonic activity between 1300 and 1100 ma led to the assembly of proterozoic australia as an early component of the supercontinent of rodinia this first involved the amalgamation of the west australian and north australian cratons followed by collision with the south australian craton the centralian superbasin developed over the junction of the north south and west australian cratons between 830 and 750 ma rifting to the east formed the adelaide geosyncline at 830 ma this was followed by the breakup of rodinia with the rifting apart of laurentia and gondwanaland along the eastern margin of proterozoic australia at 750 ma and the subsequent formation of the palaeo pacific ocean after the breakup of rodinia a series of northeast southwest compressional events followed by periods of relaxation reflect the assembly of a new supercontinent old lines of weakness were reactivated culminating in the intracratonic king leopold paterson petermann ranges and pinjarra orogenies between 620 and 540 ma subsequent reactivation continued into the phanerozoic with the widespread eruption of continental flood basalts and the formation of intracratonic basins 540 530 ma

magma recharge and reactive bulk assimilation in enclave bearing granitoids tonglu south china national nature science foundation of china 41530211 mlr special funds for public welfare projects 201211013 2 state administration of foreign expert affairs of china b07039 most special funds of the state key laboratory of geological processes and mineral resources msfgpmr01

the proterozoic mount isa fault zone northeastern australia is it really a ca 1 9 ga terrane bounding suture abstract in marked contrast to palaeoproterozoic laurentia the location of sutures and boundaries of discrete crustal fragments amalgamated during palaeoproterozoic formation of the north australian craton remain highly speculative interpretations of suture locations have relied heavily on the analysis of regional geophysical datasets because of sparse exposure of rocks of the appropriate age the mount isa fault zone has been interpreted as one such palaeoproterozoic terrane bounding suture furthermore the coincidence of this fault zone with major shale hosted massive sulphide pb zn ag orebodies has led to speculations that trans lithospheric faults may be an important ingredient for the development of this deposit type this study has integrated geophysical and geochemical data to test the statute of the mount isa fault as a terrane bounding suture forward modelling of gravity data shows that basement rocks on either side of the mount isa fault have similar densities these interpretations are consistent with geochemical observations and sm nd data that suggest that basement lithologies on either side of the mount isa fault are geochemically and isotopically indistinguishable from each other and that the mount isa fault is unlikely to represent a suture zone that separates different palaeoproterozoic terranes our data indicate that the crustal blocks on both sides of the mount isa fault zone must have been in within close proximity of each other since the palaeoproterozoic and that the western fold belt was part of the ancestral north australian craton well before the 1 89 1 87 ga barramundi orogeny it appears that deep crustal variations in density may be related to the boundary between a shallowly west dipping high density mafic to ultramafic plate and low density basement rocks this interpretation in turn impacts on crustal scale models for the development of shale hosted massive sulphide pb zn mineralisation which do not require trans lithospheric faults to tap deep seated metal reservoirs and or mantle plumbing systems the approach applied herein demonstrates the value of multi disciplinary investigations to the critical assessment of long lived proterozoic fault systems which in the absence of methodical analysis are commonly assumed to represent terrane bounding sutures

crustal evolution of southern laurentia during the paleoproterozoic insights from zircon hf isotopic studies of ca 1 75 ga rocks in central colorado lu hf depleted mantle model tdm ages obtained by analysis of zircons previously dated by u pb methods demonstrate that ca 1 75 ga bimodal paleoproterozoic rocks in the gunnison salida region of central colorado and by extension in much of the southwestern u s were formed by partial melting of preexisting crustal rocks the ages of which mostly ages greater than 2 0 ga indicate that range from 1 83 to 1 87 ga some calculated lu hf tdm even older crust was probably involved consistent with the limited presence of ca 2 5 ga xenocrystic zircons in some rocks these results suggest that rocks related to the trans hudson and penokean orogens are cryptically present much farther to the south than previously believed coupled with the bimodality of the volcanic suite in central colorado and indeed in much of the southwestern u s these results indicate that in contrast to current juvenile arc accretion models melting of older crust related to extensional tectonics played an important role in the genesis of many magmatic rocks between 1 6 and 1 8 ga

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

magmatic arc asymmetry and distribution of anomalous plutonic belts in the batholiths of california effects of assimilation crustal thickness and depth of crystallization in order to better understand geologic fac tors controlling pronounced regional variations in whole rock chemistry mineralogy and mineral chemistry in the batholiths of california we calculate the magmatic intensive variables f hf f h 2 o f hf f hcl and f o 2 regional scale west to east increases in f oh in mafic silicates corresponding to the systematic i wc to i mc and i sc progression reflect orders of magnitude increase in f hf f h 2 o attending pluton crystallization low f hf f h 2 o of formation of western i wc types is consistent with their derivation from low fluorine source rocks in subducted oceanic slabs or the upper mantle in contrast higher f hf f h 2 o of crystallization of i mc and i sc types to the east implies the involvement of 1 progressively greater amounts of continental crustal source material such as biotite bearing metamorphic rocks their unweathered sedimentary derivatives retaining f rich mafic minerals or their fusion products and or 2 source materials which become more f rich toward the continental interior the regional distribution of i mc and i sc types suggests that the precambrian craton of western north america or derivative sediments may extend farther north in california and be morphologically more complex than previously thought from seemingly out of place occurrences of i wc plutons on the eastern slopes of the sierra nevada batholith we infer the existence of regions where precambrian basement was thin or absent in mesozoic time which prevented extensive cratonal contamination of subducted slab or upper mantle derived magmas new methods for estimating t f o 2 relations in the magmas demonstrate that i scr granites crystallize at oxygen fugacities as much as five orders of magnitude lower than those of i wc i mc and i sc types under conditions at or below the maximum stability limit of graphite in equilibrium with a c o h s gas phase the local scale formation of i scr granites in plutonic belts within specific wall rock terranes containing highly reducing sediments or metasediments may occur by contamination of i types with graphitic pelite or in some cases by the direct fusion of this reducing pelitic wall rock the spatial distribution of i scr granite provinces therefore is controlled simply by wall rock lithology amphibole geobarometry demonstrates a general west to east decrease in crystallization pressure across the sierra nevada batholith in contrast the peninsular ranges batholith displays a west to east crystallization pressure increase the bulk of the california batholiths crystallized at pressures less than 4 5 kb and depths less than about 15 19 km in the southern sierra nevada batholith the san gabriels and the eastern peninsular ranges however plutons crystallized at pressures exceeding 6 kb at deep crustal levels 23 km reconstruction of the pre erosion top of the batholith shows that in an east west cross section the central sierra nevada batholith was a horizontal tabular body with an aspect ratio of at least five to one

paleomagnetic and geobarometric study of the mid cretaceous whitehorse pluton yukon territory this is the first of several lithoprobe paleomagnetic studies underway to examine geotectonic motions in the northern canadian cordillera except for one controversial study estimates for terranes underlying the intermontane belt in the yukon have been extrapolated from studies in alaska southern british columbia and the northwestern united states the whitehorse pluton is a large unmetamorphosed and undeformed tonalitic body of mid cretaceous age 112 ma that was intruded into sedimentary units of the whitehorse trough in the stikinia terrane geothermobarometric estimates for eight sites around the pluton indicate that postmagnetization tilting has been negligible since cooling through the hornblende crystallization temperature and that the pluton is a high level intrusion paleomagnetic measurements for 22 of 24 sites in the pluton yield a well defined characteristic remanent magnetization chrm direction that is steeply down and northwards the chrm direction gives a paleopole of 285 5 e 81 7 n

statistical model for standard seismicity and detection of anomalies by residual analysis abstract a statistical point process model is derived to describe the standard activity of earthquake occurrences by assuming that general seismicity is given by the superposition of aftershock sequences the parameters are estimated ty the maximum likelihood method using the estimated model the residual point process of the data is defined and used to find the anomalies which are included in the data set but not captured in the considered model for the standard seismicity for instance seismic quiescences can be measured quantitatively by using the residual process some examples are provided to illustrate such analyses furthermore a time series of the magnitudes on the residual point process is considered to investigate its dependence either on the time or on the history of the seismicity by assuming the exponential distribution at each time and modelling of the b value we can examine such dependences and estimate them two practical examples are shown

an isotopic perspective on growth and differentiation of proterozoic orogenic crust from subduction magmatism to cratonization abstract the in situ chemical differentiation of continental crust ultimately leads to the long term stability of the continents this process more commonly known as cratonization is driven by deep crustal melting with the transfer of those melts to shallower regions resulting in a strongly chemically stratified crust with a refractory dehydrated lower portion overlain by a complementary enriched upper portion since the lower to mid portions of continental crust are rarely exposed investigation of the cratonization process must be through indirect methods in this study we use in situ hf and o isotope compositions of both magmatic and inherited zircons from several felsic magmatic suites in the capricorn orogen of western australia to highlight the differentiation history i e cratonization of this portion of late archean to proterozoic orogenic crust the capricorn orogen shows a distinct tectonomagmatic history that evolves from an active continental margin through to intracratonic reworking ultimately leading to thermally stable crust that responds similarly to the bounding archean pilbara and yilgarn cratons the majority of magmatic zircons from the main magmatic cycles have hf isotopic compositions that are generally more evolved than chur forming vertical arrays that extend to moderately radiogenic compositions complimentary o isotope data also show a significant variation in composition however combined these data define not only the source components from which the magmas were derived but also a range of physio chemical processes that operated during magma transport and emplacement these data also identify a previously unknown crustal reservoir in the capricorn orogen

composite basement along the southern margin of the north australian craton evidence from in situ zircon u pb o hf and whole rock nd isotopic compositions abstract hafnium isotope compositions of emplacement age zircon grains are integrated with zircon 18o and whole rock nd isotope data in order to characterise the age and composition of the sources of paleoproterozoic granites along the southern margin of the north australian craton the petrogenesis of the granitic rocks is interpreted in terms of partial melting of distinct crustal components with variable crustal residence ages at different crustal levels reflecting the local paleoproterozoic crustal architecture this finding implies a composite nature of the unexposed deep crust which comprises paleoproterozoic supracrustals and subordinate discontinuous and local neoarchean meta igneous components the limited lateral extension of neoarchean deep crust does not support tectonic models for the paleoproterozoic amalgamation of the craton that consider intracratonic and or continent continent collision settings the composite nature of the basement and the presence of cryptic boundaries are consistent with the accretion of paleoproterozoic supracrustal elements as back arc and island arc to a neoarchean proto craton the dominant paleoproterozoic reworking of archean derived supracrustal materials indicates that accretionary orogenesis was an important setting for crustal reworking and craton stabilisation in the paleoproterozoic

episodic growth of the gondwana supercontinent from hafnium and oxygen isotopes in zircon it is thought that continental crust existed as early as 150 million years after planetary accretion but assessing the rates and processes of subsequent crustal growth requires linking the apparently contradictory information from the igneous and sedimentary rock records for example the striking global peaks in juvenile igneous activity 2 7 1 9 and 1 2 gyr ago imply rapid crustal generation in response to the emplacement of mantle super plumes rather than by the continuous process of subduction yet uncertainties persist over whether these age peaks are artefacts of selective preservation and over how to reconcile episodic crust formation with the smooth crustal evolution curves inferred from neodymium isotope variations of sedimentary rocks detrital zircons encapsulate a more representative record of igneous events than the exposed geology and their hafnium isotope ratios reflect the time since the source of the parental magmas separated from the mantle these model ages are only meaningful if the host magma lacked a mixed or sedimentary source component but the latter can be diagnosed by oxygen isotopes which are strongly fractionated by rock hydrosphere interactions here we report the first study that integrates hafnium and oxygen isotopes all measured in situ on the same precisely dated detrital zircon grains the data reveal that crust generation in part of gondwana was limited to major pulses at 1 9 and 3 3 gyr ago and that the zircons crystallized during repeated reworking of crust formed at these times the implication is that the mechanisms of crust formation differed from those of crustal differentiation in ancient orogenic belts

does the arc accretion model adequately explain the paleoproterozoic evolution of southern laurentia an expanded interpretation a common model for the paleoproterozoic crustal evolution of southern laurentia involves southerly accretion of successively younger island arcs from 1780 to 1650 ma this model may be oversimplified however for although andesite and basaltic andesite major components of modern island arcs occur they are relatively rare and large volumes of rocks are dominantly bimodal metavolcanic assemblages and related granitoids ophiolites occur but they are also rare and only one accretionary melange has been described inherited zircons and common pb and nd isotopic data indicate involvement of older crust in ca 1750 ma rocks of the mojave province of southeastern california and western arizona and the bimodal assemblages of central colorado these data suggest that the bimodal volcanic rocks were derived from pre existing continental crust likely of ca 1850 ma trans hudson penokean age during extension and partial melting associated with the development of transpressional crustal scale shear zones the occurrence of the 1840 1 ma elves chasm pluton in the grand canyon demonstrates that rocks of trans hudson penokean age are present in southwestern laurentia

bulk arc strain crustal thickening magma emplacement and mass balances in the mesozoic sierra nevada arc quantifying crustal deformation is important for evaluating mass balance material transfer and the interplay between tectonism and magmatism in continental arcs we present a dataset of 650 finite strain analyses compiled from published works and our own studies with associated structural geochronologic and geobarometric information in central and southern sierra nevada california to quantify the arc crust deformation our results show that mesozoic tectonism results in 65 arc perpendicular bulk crust shortening under a more or less plane strain condition mesozoic arc magmatism replaced 80 of this actively deforming arc crust with plutons requiring significantly greater crustal thickening we suggest that by 85 ma the arc crust thickness was 80 km with a 30 km thick arc root resulting in a 5 km elevation most tectonic shortening and magma emplacement must be accommodated by downward displacements of crustal materials into growing crustal roots at the estimated downward transfer rate of 2 13 km myr the downward transfer of crustal materials must occur in active magma channels or in escape channels in between solidified plutons that decrease in size with time and depth resulting in an increase in the intensity of constrictional strain with depth we argue that both tectonism and magmatism control the thickness of the crust and surface elevation with slight modification by surface erosion the downward transported crustal materials initially fertilize the mash zone thus enhancing to the generation of additional magmas as the crustal root grows it may potentially pinch out and cool the mantle wedge and thus cause reduction of arc magmatism

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

petrology geochemistry and origin of a major australian 1880 1840 ma felsic volcano plutonic suite a model for intracontinental felsic magma generation in australia a major period of felsic volcanism and granite emplacement occurred between 1880 and 1840 ma towards the end of the early proterozoic these volcanics and granites covering at least 37 000 km2 are compositionally uniform over large areas the felsic magmas are predominantly i type being derived from infracrustal sources which have never been exposed to surficial weathering processes when compared with early archaean and phanerozoic i type granites the 1880 1840 ma suite has distinctively high levels of k2o rb zr la ce th u and low mgo and cao contents even at relatively low sio2 levels of 60 65 the 1880 1840 ma rocks are characterized by low initial 87sr 86sr ratios and negative nd values chemical and isotopic modelling on these volcanics and granites suggest that they formed from mantle derived sources that are around 2300 2000 ma old there is no evidence of a major archaean component in these granites the sources are interpreted to have formed as a result of polygonal small scale mantle convection which led to extensive underplating of archaean crust during this underplating event large volumes of incompatible element enriched mantle derived material accreted to the base of the lower crust and fractionated significantly the more fractionated part of this source was remelted between 1880 1840 ma to produce the voluminous felsic volcanics and comagmatic granites present in nearly every proterozoic domain of australia the actual underplating event between 2300 2000 ma is believed to have triggered the formation of early proterozoic sedimentary basins which occur in a polygonal pattern and appear to wrap around archaean nuclei the composition of these felsic melts and the tectonic setting operating during their emplacement precludes genesis by contemporaneous subduction of oceanic crust all are generated by processes of vertical accretion in an intracontinental environment

geochronological constraints on orogenic events in the arunta inlier a review early workers subdivided the arunta inlier central australia into three major tectonic provinces classified the principal tectonostratigraphic units into three divisions and separated the tectonomagmatic history into five discrete events ranging in age from 1800 ma to 300 ma a review of the evidence for tectonic boundaries within the arunta inlier suggests that no major structural discontinuity exists between the northern and central tectonic provinces but that the redbank thrust zone is at least in part a province boundary the tectonostratigraphic division concept also requires revision as division 3 rocks of the northern and southern arunta cannot be time equivalents division 1 rocks grade into division 2 in the northern region and division 3 of the northern region may be equivalent to division 1 in the central region rocks originally assigned to divisions are better grouped into a larger number of lithological assemblages until better stratigraphic and isotopic correlations can be made compilation of rb sr and 40ar39ar age determinations obtained before 1984 indicate an almost complete age spectrum from 1800 ma to 1000 ma but age clusters exist at 1400 ma 1100 ma and 400 300 ma which have geological significance subdivision of older ages into discrete tectonic events was not justified from this data alone but more recent u pb isotopic analysis of zircons in rocks designated to particular structural metamorphic events has revealed a complex tectonic history in the 1880 1600 ma interval the northern and central provinces underwent major tectonism between 1780 1730 ma but much of the southern province was not deformed until 1600 ma the revised tectonic history nomenclature is proposed for the arunta inlier following deposition of a widespread turbiditic unit at or before 1880 ma possibly on thinned archaean crust the northern and central provinces underwent localized tectonism magmatism at 1880 ma yuendumu tectonic event and 1820 ma stafford tectonic event prior to the widespread strangways orogeny which is subdivided into an early phase at 1780 1770 ma and late phase at 1745 1730 ma it is not clear whether the strangways orogeny is a single arunta wide event or a series of separate short lived smaller scale events although the major deformation in all areas appears to have involved w to sw directed thrusting in the southern province the major events occurred at 1680 ma argilke tectonic event and 1600 ma chewings orogeny the latter involving n directed thrusting that was penecontemporaneous with post tectonic pegmatite intrusion in the northern province suggesting linkage of both regions at this stage the younger history of the inlier is characterised by several stages of uplift and isolated thermal magmatic events major mesoproterozoic crustal exhumation anmatjira uplift phase has been interpreted from widespread 1500 1400 ma ages including regional scale closure of 40ar 39ar systems in hornblende from mafic granulite outcrop scale rb sr total rock isotopic systems in mylonitized granitoids and sm nd garnet hornblende pairs in mylonitized amphibolites a 1150 ma thermal event in the southern part of the inlier teapot magmatic event is recorded by intrusion of granite pegmatites and the alkaline mordor igneous complex and by isotopic resetting of rb sr mineral systems dolerite dyke injection at 1050 ma reflects limited extensional tectonism that may have related to formation of the amadeus basin the second major uplift event was the alice springs orogeny at 400 300 ma an unusual intracratonic thick and thin skinned thrust event that involved limited retrograde amphibolite facies but extensive greenschist facies metamorphism and restricted pegmatite intrusion

syntectonic remagnetization in the southern methow block resolving large displacements in the southern canadian cordillera 1 the upper cretaceous ventura member of the goat wall unit in the southern methow block of southern british columbia and northern washington state holds a syntectonic magnetization eight new sites from manning park in british columbia give a mean direction of d 27 5 i 60 1 k 304 7 95 3 2 after optimal partial tilt correction of five groups of bedded sites from farther south in the basin reported by bazard et al 1990 four have a syntectonic remanence with a direction similar to what we observe the exception is one group which has optimal concentration of remanence directions on 100 untilting and an abherent direction which must be rejected combining the accepted sites the optimal differential syntilting direction is d 11 8 i 61 5 k 39 3 95 3 4 n 47 giving a mean pole of 79 8 n 359 2 e k 19 5 and a95 4 8 the age of the remagnetization is constrained to be between 88 and 80 ma compared to cratonic north america this result indicates that the southern methow block was displaced from the south by 1800 500 km meaning it lay south of the sierra nevada subduction zone but well north of other paleomagnetically constrained cretaceous rock units from the insular superterrane including correlative strata of the mount tatlow area in the northern methow block among several possibilities to reconcile this discrepancy the most plausible has the whole methow block translated coherently but with the southern methow block strata remagnetized during transit

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

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

the tanami deep seismic reflection experiment an insight into gold mineralization and paleoproterozoic collision in the north australian craton abstract imaging of a major collision zone between the tanami region and aileron province of the arunta orogen in northern australia and recognition that several of the major gold deposits within the tanami region are within near surface antiformal stacks or uplifted and exhumed crustal sections associated with major crustal penetrating shear zones are fundamental results from the 2005 tanami seismic collaborative research project the suture which is interpreted to have resulted from collision separates the northwest dipping structural grain of the aileron province crust in the south from the southeast dipping structural grain of the tanami crust in the northwest the collision between the tanami region and the aileron province is interpreted to have occurred prior to ca 1840 ma the correlation between the surface extension of crustal penetrating shear zones that extend to the moho boundary and the locations of known gold rich mineral fields is significant and has implications for minerals explorers within the tanami region and elsewhere in the near surface where the crustal penetrating structures cut relatively shallow upper crustal tanami group rocks there is a significant increase in the degree of local deformation and results in through going thrust faults associated pop up structures ramp anticlines and antiformal stacking all known ore deposits appear to be located within these more complexly deformed zones and therefore have a direct association with larger scale structures

paleomagnetism and tectonics of the cretaceous mt stuart batholith of washington translation or tilt abstract the mt stuart batholith is a composite pluton of late cretaceous age that intrudes the crystalline north cascades terrane of northwestern washington its paleomagnetic direction d 10 0 i 45 5 95 4 9 is markedly different from the direction expected for cretaceous rocks from northwestern washington d 330 5 i 73 0 which means that the mt stuart batholith either has moved relative to the north american interior or has been tilted through a substantial angle or both since it acquired its magnetism either tilt or translation are possible geometrically but translation is more likely because 1 local geology apparently does not support tilt in the required direction 2 it probably is not possible for a panel of rock the size of the mt stuart batholith to tilt through the necessary angle ca 35 after its deeper parts have cooled sufficiently to retain remanent magnetization 3 the sense of paleomagnetic discordance found in the mt stuart batholith clockwise rotation of declination flattened inclination is identical to that found in nearly every other allochthonous terrane in the western north american cordillera including every other cretaceous batholith studied except the sierra nevada

the duration of the strangways event in central australia evidence for prolonged deep crust processes abstract protoliths of the strangways metamorphic complex smc in the arunta region of central australia are dated to the 1810 1800 ma stafford magmatic event by shrimp u pb dating of relict igneous zircon within granulite facies metamorphic rocks detrital zircons preserved in associated metasediment have a provenance age spectrum similar to that in the lander package sedimentary rocks which are widespread in the region the onset and duration of granulite facies metamorphism is recorded differentially across the smc depending on lithology varying mechanisms of metamorphic zircon crystallisation and the specific p t t paths of individual rocks in different sectors of the complex the earliest recorded thermal process is partial melting in the kanandra granulite at 1734 3 ma zircon ages indicate that melts at edwards creek 1716 3 ma and coles hill 1708 6 ma formed later overgrowths indicate renewed metamorphic zircon precipitation in the kanandra granulite probably from fluids as late as ca 1690 ma a 50 myr continuum of metamorphic zircon ages from ca 1740 to 1690 ma is recorded in a single rock at utnalanama and attributed to prolonged solid state metamorphic zircon formation the strangways event was not a transient and discrete process with a single age there is evidence for prolonged residence at granulite facies conditions with both discrete crystallisation events and prolonged crystallisation responses in different locations termination of the high grade metamorphism coincided with local extension indicated by the intrusion of a dolerite dyke swarm at 1689 8 ma the strangways event coincides with the segment between prominent bends b0 and b1 of the australian palaeomagnetic polar wander path relating the thermal process to major direction changes in the movement of the north australian plate the geographic distribution of high grade metamorphism within the smc shallow crust emplacement of magmas in the tennant region and a low temperature ar isotope record in the tanami region is consistent with effects propagating northwards from a plate boundary south of the smc

national seismic hazard model for new zealand 2010 update a team of earthquake geologists seismologists and engineering seis mologists has collectively produced an update of the national probabilistic seismic hazard psh model for new zealand national seismic hazard model or nshm the new nshm supersedes the earlier nshm published in 2002 and used as the hazard basis for the new zealand loadings standard and numerous other end user applica tions the new nshm incorporates a fault source model that has been updated with over 200 new onshore and offshore fault sources and utilizes new new zealand based and international scaling relationships for the parameterization of the faults the dis tributed seismicity model has also been updated to include post 1997 seismicity data a new seismicity regionalization and improved methodology for calculation of the seismicity parameters probabilistic seismic hazard maps produced from the new nshm show a similar pattern of hazard to the earlier model at the national scale but there are some significant reductions and increases in hazard at the regional scale the national scale differences between the new and earlier nshm appear less than those seen between much earlier national models indicating that some degree of consis tency has been achieved in the national scale pattern of hazard estimates at least for return periods of 475 years and greater online material table of fault source parameters for the 2010 national seismic hazard model

testing earthquake prediction algorithms statistically significant advance prediction of the largest earthquakes in the circum pacific 1992 1997 abstract algorithms m8 and msc i e the mendocino scenario were used in a real time intermediate term research prediction of the strongest earthquakes in the circum pacific seismic belt predictions are made by m8 first then the areas of alarm are reduced by msc at the cost that some earthquakes are missed in the second approximation of prediction in 1992 1997 five earthquakes of magnitude 8 and above occurred in the test area all of them were predicted by m8 and msc identified correctly the locations of four of them the space time volume of the alarms is 36 and 18 correspondingly when estimated with a normalized product measure of empirical distribution of epicenters and uniform time the statistical significance of the achieved results is beyond 99 both for m8 and msc for magnitude 7 5 10 out of 19 earthquakes were predicted by m8 in 40 and five were predicted by m8 msc in 13 of the total volume considered this implies a significance level of 81 for m8 and 92 for m8 msc the lower significance levels might result from a global change in seismic regime in 1993 1996 when the rate of the largest events has doubled and all of them become exclusively normal or reversed faults the predictions are fully reproducible the algorithms m8 and msc in complete formal definitions were published before we started our experiment keilis borok v i kossobokov v g 1990 premonitory activation of seismic flow algorithm m8 phys earth and planet inter 61 73 83 kossobokov v g keilis borok v i smith s w 1990 localization of intermediate term earthquake prediction j geophys res 95 19763 19772 healy j h kossobokov v g dewey j w 1992 a test to evaluate the earthquake prediction algorithm m8 u s geol surv ofr 92 401 m8 is available from the iaspei software library healy j h keilis borok v i lee w h k eds 1997 algorithms for earthquake statistics and prediction vol 6 iaspei software library

zircon provenances provide paleogeographic constraints on models reconstructing the paleoproterozoic columbia supercontinent abstract paleoproterozoic orogens of the north australian craton are related to the assembly of the columbia supercontinent the roles of the distinct orogens in the paleoproterozoic craton amalgamation are poorly understood due to the lack of surface exposure the age and isotopic systematics of detrital zircon grains hosted in paleoproterozoic sedimentary sequences are used to unravel the geological history of the craton in terms of paleogeography and tectonic setting the oldest early paleoproterozoic metasedimentary units are characterised by detrital zircon ages peaking at ca 2500 ma the zircon ehf values show large variations in the different orogens and range from 18 to 6 the overlaying youngest turbiditic units show minor accumulation of archean detritus units from apparently different metasedimentary sequences have a major detrital zircon age population at ca 1865 ma and a relatively restricted range of zircon ehf values between 7 3 and 2 6 the isotopic distinctiveness of the oldest units is attributed to local variations in the depositional environment probably due to horst graben architecture of the early paleoproterozoic basin the youngest turbiditic units blanketed this early horst graben architecture and in part have a local provenance potential detritus sources include south australian craton dharwar craton and aravalli lesser himalayan terrains in india south china and madagascar africa this finding indicates that these regions might have been connected before the columbia supercontinent was formed the ubiquitous ca 2500 ma magmatic event records the assembly of these cratonic fragments in a previous supercontinent called kernorland in addition the data do not support a proximity of the north australian craton with the north china block western laurentia north america and kaapvaal craton africa during columbia amalgamation

revised metamorphic history for the chiwaukum schist north cascades washington a revised metamorphic history for the chiwaukum schist north cascades washington consisting of dynamic contact metamorphism of buchan style associated with the mount stuart batholith followed closely by regional metamorphism of barrovian style is similar to that for rocks adjacent to the sloan creek intrusion 30 km to the north and on the opposite west side of the straight creek fraser river fault system to the settler schist in the vicinity of the spuzzum and scuzzy intrusions 200 270 km north in british columbia the late cretaceous regional increase in lithostatic pressure implied by this history whether caused by tectonic or magmatic processes may be the same as that responsible for the crystallization of magmatic epidote in certain other intrusives in the north cascades such as the tenpeak more radiometric crystallization ages as opposed to cooling ages are needed to resolve this point