tertiary flexural evolution of the beaufort mackenzie basin canada abstract seismic reflection data indicate that more than 14 16 km of clastic materials are preserved in the beaufort mackenzie basin these correspond to tectonic activity and sediment loading from the upper cretaceous to the present day to understand better how the basement movement responds to the thick sediment loading an inverse flexural model has been used to simulate the evolutionary process the results of the inverse flexural model simulation show that the basin subsidence developed dominantly as an elastic flexural response to sediment loading with a minor component due to lateral compressive stress the forward model results show that the late eocene to pleistocene subsidence of the basin included three stages with different rates of subsidence the koponoar kugmallit and iperk sequences represent products of two rapid subsidence stages whereas the mackenzie bay and akpak sequences reflect the products of a more stable and slower subsidence stage

new hypothesis for formation of lengguru foldbelt irian jaya indonesia the lengguru foldbelt an area 300 km 180 mi long with a maximum width of 100 km 60 mi is near the western end of the island of new guinea sedimentary rocks of the belt include mesozoic marine sandstone and shale tertiary deep water limestone tertiary shelf limestone and upper miocene to pleistocene detritus the slab of folded platform sedimentary rocks making up the lengguru foldbelt was originally at the northern margin of the australian continent and was thrust southwestward over the undeformed continental crust of the western part of new guinea the slab was also rotated clockwise by about 30 about a pivot at its northern end during rotation thrusting and decollement within the foldbelt caused a repetition by stacking of the stratigraphic section and the belt was dragged along transcurrent faults to the south this foldbelt is of interest for oil exploration because of proximity to the salawati and bintuni oil fields on the westernmost tip of the island

geochronology and tectonic implications of magmatism and metamorphism southern kootenay arc and neighbouring regions southeastern british columbia part i jurassic to mid cretaceous k ar dates and u pb zircon dates define three periods of igneous activity in the southern kootenay arc 1 emplacement of late synkinematic to post kinematic granodioritic plutons in mid jurassic time 170 165 ma accompanying amphibolite facies regional metamorphism 2 emplacement of post kinematic granitic plutons in mid cretaceous time 100 ma and 3 emplacement of small bodies of syenite in eocene time 50 ma in the western part of the area micas from mid jurassic plutons that yield the oldest k ar dates 158 166 ma also yield plateau shaped 40ar 39ar age spectra age spectra for biotites younger than these but older than 125 ma reflect thermal overprinting in southeastern british columbia the kootenay arc marks the transition from the north american rocks of the cordilleran miogeocline to the tectonic collage of allochthonous terranes that have been accreted to it deformation metamorphism and plutonism recorded in rocks of the southern kootenay arc commenced in mid jurassic time as a co

geology and petroleum potential of upper cretaceous and tertiary strata beaufort mackenzie area northwest canada 1 upper cretaceous to holocene strata on the beaufort sea continental margin were deposited as a series of northward prograding delta complexes totaling 12 16 km thick the succession contains eleven regionally extensive transgressive regressive sequences that were deposited during four large scale tectonostratigraphic phases each phase terminated by a major tectonic event during the cenomanian to middle maastrichtian sedimentation was limited to relatively thin organic rich muds on an outer shelf to basinal environment from the late maastrichtian to middle eocene deltaic depocenters were located along the southwestern margin of the canadian beaufort sea during the third depositional phase middle eocene to late miocene sedimentation was concentrated in the central canadian beaufort sea depocenters shifted to the eastern beaufort sea during the fourth depositional phase pliocene to early pleistocene the modern mackenzie delta may represent a new phase of deposition considerable volumes of oil and gas have been discovered in tertiary rocks principally in eocene and oligocene delta front strata with lesser volumes in paleocene and miocene strata three families of oils have been recognized in tertiary reservoirs the most important of which appears to have been derived from the eocene richards sequence in general tertiary strata have modest toc total organic carbon values 1 2 and low thermal maturity to drilled depths 4000 4500 m in the more extensively explored central beaufort mackenzie area however thermal and subsidence modeling of tertiary strata suggest that maturity rapidly increases between 5000 and 6000 m

sedimentation and tectonics of a diffuse plate boundary the canadian arctic islands from 80 ma b p to the present abstract use of a revised magnetic anomaly time scale provides a more accurate chronology of sea floor spreading events in labrador sea baffin bay new stratigraphic data from meighen and remus basins in the eastern arctic islands shows that sedimentary and tectonic events there can be correlated with relative movements of greenland between 80 and 36 ma b p caused by labrador sea baffin bay spreading within the eastern arctic islands these movements generated the eurekan orogeny across the diffuse greenland canada plate boundary subsequently the arctic islands were affected by uplift and erosion and then by extensional faulting and renewed clastic sedimentation between 15 ma b p and the present

age and significance of sequence boundaries on jurassic and early cretaceous rifted continental margins the age and significance of sequence boundaries on jurassic to early cretaceous rifted continental margins in three ocean basins have been documented the margins are the santos basin in the south atlantic the grand banks in the north atlantic and the beaufort sea in the arctic ocean large industry data bases were used for the interpretation of each area megasequence boundaries separate the major phases of basin evolution for example syn rift and post rift boundaries developed with an average periodicity of 49 m y sequence boundaries define the component parts of each megasequence and developed with a modal periodicity of 10 15 m y out of 27 total boundary ages most 16 are developed on just one margin only two possible age ranges overlap on all three margins ighty percent of the megasequence boundaries and 50 of the sequence boundaries show a direct causal connection with coeval faulting and or folding the rest of the boundaries appear as unstructured surfaces separating transgressive and or regressive sedimentary wedges and are interpreted to result from changes in the rate of basin subsidence sediment input and long term eustatic sea level these data do not support theories advocating synchronous worldwide boundary development resulting from periodic short term falls in global eustatic sea level only in like basins of the same age with identical subsidence and sediment input rates are boundaries likely to develop synchronously hence the concept of global synchroneity of sequence boundary development may well be an illusion creat d by the similarity in age of the majority of basins studied as a result of this study it seems wise discard the global approach to basin analysis

stratigraphy age and paleogeography of the eocene chuckanut formation northwest washington the eocene chuckanut formation of washington s north cascades comprises as much as 6000 m of alluvial strata and is one of the thickest nonmarine sequences in north america it is exposed in several disconnected outcrop belts that are remnants of what was probably an extensive fluvial system in western washington in this study seven stratigraphic members are defined in the main outcrop belt of the chuckanut formation near the town of bellingham their ages based on fission track zircon dates palynologic studies and correlation by mapping extend from the early to the late eocene three types of fluvial systems contributed to the chuckanut formation and are distinguished on the basis of their lithology sedimentology and petrology the first comprises fine load meandering river deposits of the lower eocene bellingham bay member and the middle eocene slide member sandstones are arkosic and had their main source in rapidly uplifted high grade metamorphic terranes in eastern washington the second type

fractal structure of spatial distribution of microfracturing in rock summary a constant stress fracture experiment of oshima granite was carried out at the confining pressure of 40mpa hypocentres of 2064 acoustic emissions were located during the experiment using the correlation integral we found that the spatial distribution of hypocentres of acoustic emission is a fractal and that the fractal dimension decreases with the evolution of rock fracturing the spatial distribution of earthquake s hypocentres reveals fractals ranging from regional to worldwide distribution if we extrapolate from laboratory measurements it is possible to predict the occurrence of large earthquakes by the decrease in the fractal dimension

tectonic history of northern alaska canadian arctic and spitsbergen regions since early cretaceous the correlation of interregional unconformities structures and magmatic activity suggests tectonic events in the arctic were controlled by the early cretaceous collision and combined interaction of the eurasian and north american plates in northeastern ussr the late mesozoic cenozoic accretion of exotic terranes in the north pacific and north atlantic arctic sea floor spreading contemporaneous with the accretion of exotic terranes in northeastern ussr and interior alaska the brooks range developed as a cordilleran mountain belt at the same time during the cretaceous between 125 and 85 ma the canada basin spread north of alaska about a pole of rotation located southeast of the mackenzie delta the alaskan plate was first a part of the northwestern nose of the north american plate when the canada basin spreading ceased the basin was severed by movement along the kaltag and associated strike slip faults and became a part of the northeasterly moving eurasian plate the kaltag fault system is inferred to extend from the western bering sea at the northern end of the kuril arc through alaska and along the outer margin of the arctic islands to the north of greenland it is postulated to have formed the transform boundary between the north american and eurasian plates with the alaskan plate bonded to the latter since the late cretaceous the late eocene change in the direction of pacific spreading terminated the subduction related laramide orogeny as well as the right lateral displacements of major cordilleran faults such as the tintina and denali faults changing eurasian plate movement may have caused most of the strong middle eocene right lateral displacement along the kaltag fault zone continuing displacement from the southwest caused the development of a late cenozoic foldbelt in coastal northeastern alaska herein named the romanzof disturbance coeval with balancing right lateral movement along the kaltag fault zone the huge undrilled marsh creek anticline is a part of this foldbelt seismic data show evidence of middle eocene compression followed by weak extension east of the kaltag fault zone in the beaufort sea the same activity is evident at the northeastern end of the north american plate at nares strait located between the arctic islands and greenland eocene fault movement along the kaltag nares strait and de geer separating greenland and spitsbergen transforms is regarded as complementary the presence of eocene thrust zones located on the western side of nares strait and in western spitsbergen suggests that northward movement of the greenland plate formed both the transforms and the thrust belts

depositional relations of cretaceous and lower tertiary rocks northeastern alaska analysis of depositional environments new paleontologic data and analogy with depositional patterns observed in areas to the west all indicate the need for revision of cretaceous and lower tertiary stratigraphy in northeastern alaska in the sadlerochit mountains area of the arctic national wildlife refuge the northern derived ellesmerian late neocomian kemik sandstone member and organic rich pebble shale member of the kongakut formation unconformably overlie jurassic and triassic rocks the unconformity which is of mid neocomian age is present throughout northernmost alaska and passes southward into a conformable shelf sequence after pebble shale deposition the depositional pattern is simply one of progradational basin filling from a southern brookian provena ce this pattern is represented in vertical sequence initially by deep marine basinal deposits succeeded by prodelta slope shales and ultimately by deltaic deposits that prograded to the east or northeast in a predictable fashion over most of the area the better known thick shallow marine and nonmarine units in the central north slope grade to thin prodelta or basinal turbidites some units are entirely missing owing to nondeposition on the south dipping flank of the basin no evidence exists for subaerial erosion to explain these marked stratigraphic changes in the sadlerochit mountains area which may be an extension of the barrow arch the pebble shale neocomian is overlain by about 1 600 ft 500 m of deep water deposits of late cretaceous age aptian and albian rocks are either absent by nondeposition or are represented by a thin condensed section here the upper cretaceous to lower tertiary section consists of basinal shale bentonite and thin bedded prodelta turbidites two noteworthy features in this sequence are an interval of organic rich shale of probable turonian to coniacian age just above the pebble shale and the placement of the cretaceous tertiary boundary within deep marine deposits unlike the western part of the north slope where deltaic deposition occurred in the early cretaceous prograding deltaic deposition d d not reach the western part of the wildlife refuge until early in the tertiary the consistent pattern of easterly deltaic progradation is complicated at igilatvik sabbath creek in the north central wildlife refuge by the occurrence of thick regressive dominantly nonmarine deposits of early tertiary age which apparently prograded into the basin from the south or southeast

devonian mississippian sinistral transcurrent faulting along the cratonic margin of western north america a hypothesis in the northern canadian cordillera three major proterozoic assemblages show a distinct sinistral separation along the long lived richardson hess fault zone it is suggested that this separation resulted from displacements along a mid paleozoic sinistral fault system connecting the devonian mississippian ellesmerian orogen of the arctic with the antler orogen of the western united states composite displacement of possibly hundreds of kilometres along this fault system created transpressional and transtensional deformation along the western outer margin of the north american craton deformation was accompanied by eastward progradation of turbiditic chert quartz arenites local igneous activity and exhalative ore deposition extensive late mesozoic and cenozoic compression and extension probably greatly modified mid paleozoic fault related deformation patterns

tectonic evolution of gulf of anadyr and formation of anadyr and navarin basins the gulf of anadyr is underlain by two major sedimentary basins kresta basin and east anadyr trough that trend east to southeast and contain in places more than 9 km 29 500 ft of fill the basins are flanked on the east and north by the okhotsk chukotsk volcanic belt a broad bedrock high composed of plutonic and volcanic rocks that extends from eastern siberia along the inner bering sea shelf at least to st matthew island the east anadyr trough extends onshore and connects with the larger anadyr basin which underlies the lowlands between the koryak range and okhotsk chukotsk volcanic belt of eastern siberia new seismic reflection and refraction data reveal that anadyr basin is separated from navarin basin by anadyr ridge a southeast northwest trending bedrock high that is characterized by high amplitude short wavelength magnetic anomalies anadyr ridge may be an offshore extension of the melange belt underlying the koryak range sonobuoy refraction data indicate that the velocity profile of strata in east anadyr trough is similar to that in navarin basin structurally the basins are different navarin basin is complex and contains both compressional and extensional elements whereas anadyr basin is a simple broad crustal sag semicircular in outline correlation of our reflection data from the offshore part of the anadyr basin including the east anadyr trough and kresta basin with d illing data onshore allows us to differentiate three distinct sequences in the offshore portion of the basin these sequences are separated by two strong reflectors agr and s and are tentatively identified with increasing depth as boundaries separating the neogene and paleogene and paleogene and mesozoic respectively in the northeastern corner of the gulf of anadyr across the anaut uplift shallow beds are folded and broken by faults that commonly offset the sea floor furthermore earthquake epicenters recorded landward of anadyr basin from cape navarin to the southwest and around the chukotsk peninsula to the northeast suggest recent tectonic movement in the gulf of anadyr near cape navarin and near kresta bay we believe that anadyr basin originally formed as a fore arc basin during the cretaceous as a result of underthrusting of the kula plate beneath siberia the collision of the kula plate with siberia resulted in the formation of the okhotsk chukotsk volcanic arc north of anadyr basin and the koryak melange belt south of the basin anadyr basin continued to subside during the cenozoic and ajor uplift in the koryak range occurred in the late miocene to pliocene

stochastic synthesis of earthquake catalogs a model of earthquake occurrence is proposed that is based on results of statistical studies of earthquake catalogs we assume that each earthquake generates additional a probability that depends on time as t 1 this assumption together with one regarding the independence of branching events on adjacent branches of the event tree is sufficient to permit the generation of complete catalogs of earthquakes that have the same time magnitude statistical properties as real earthquake catalogs if is about 0 5 the process generates sequences that have statistical properties similar to those for shallow earthquakes many well known relations are reproduced including the magnitude frequency law omori s law of the rate of aftershock and foreshock occurrence the duration of a recorded seismic event versus its magnitude the self similarity or lack of scale of rate of earthquake occurrence in different magnitude ranges etc a value of closer to 0 8 or 0 9 seems to simulate the statistical properties of intermediate and deep shocks a formula for seismic risk prediction is proposed and the implications of the model for risk evaluation are outlined the possibilities of the determination of long term risk from real or synthetic catalogs that have the property of self similarity are dim

ellesmere greenland fold belt structural evidence for left lateral shearing abstract regardless of whether they were passive or active markers of the eurekan deformation fold axial traces in the ellesmere greenland fold belt define a regional pattern typical of left lateral ductile shear zones it is therefore postulated that a left lateral mega shear zone spanned the entire east west width of ellesmere island plus adjacent northern greenland and that the shear direction was subparallel to nares strait a left lateral motion along nares strait is required by the plate tectonic models of j t wilson and e c bullard to explain the opening of the labrador sea and baffin bay by sea floor spreading these models involve a left lateral displacement between greenland and north america of 200 400 km because of the lack of lithological and structural offsets across nares strait the models have been controversial the mega shear zone proposed herein reconciles all the conflicting evidence accordingly the ductile behaviour of the sedimentary strata on ellesmere island permitted a large left lateral displacement of greenland relative to north america without a large offset of geological features across nares strait

a two stage model of fracture of rocks in this paper we propose a two stage model of rock fracture in the first stage cracks or local regions of failure are uncorrelated and occur randomly throughout the rock in response to loading of pre existing flaws as damage accumulates in the rock there is a gradual increase in the probability that large clusters of closely spaced cracks or local failure sites will develop based on statistical arguments a critical density of damage will occur where clusters of flaws become large enough to lead to larger scale failure of the rock stage two while crack interaction and cooperative failure is expected to occur within clusters of closely spaced cracks the initial development of clusters is predicted based on the random variation in pre existing flaw populations thus the onset of the unstable second stage in the model can be computed from the generation of random uncorrelated damage the proposed model incorporates notions of the kinetic and therefore time dependent nature of the strength of solids as well as the discrete hierarchic structure of rocks and the flaw populations that lead to damage accumulation the advantage offered by this model is that its salient features are valid for fracture processes occurring over a wide range of scales including earthquake processes a notion of the rank of fracture fracture size is introduced and criteria are presented for both fracture nucleation and the transition of the failure process from one scale to another

geopressure evolution hydrocarbon generation and migration in the beaufort mackenzie basin canada results from two dimensional quantitative modelling abstract three cross sections of onshore and offshore areas of the beaufort mackenzie basin were used to simulate geopressure evolution hydrocarbon generation and migration processes of the tertiary section using a two dimensional model two analytical approaches were used 1 adjusting geological geophysical and geochemical parameters to obtain the best fit between the model results and regional geological data in a one dimensional manner and 2 reconstructing the basin evolutionary history in a two dimensional manner the model results indicate that the present day distributions of geopressure and maturity levels at different locations have been modified by late miocene uplift and erosion followed by rapid deposition of the late miocene pleistocene lperk sediments although the occurrence of oil and gas has no obvious relationship to geopressure at the present day the evolution of geopressure in strata older than the mackenzie sequence plays an important part in the maturation of tertiary source rocks geopressure in these older formations caused an increase in thermal gradient and porosity in the deep formations the analysis indicates that the timing of hydrocarbon generation and the evolution of geopressure are critical factors in the development of horizontal migration reindeer reservoirs versus vertical migration kugmallit reservoirs

tectonic evolution of northeastern siberia and adjacent regions abstract previous models for the tectonic evolution of northeastern siberia have proposed the existence of a kolyma plate composed of the kolyma and omolon massifs of presumed precambrian age lithologic similarities between the siberian platform and the cherskiy mountains and the presence of oceanic and island arc type deposits in the kolyma indigirka interfluve suggest that no such plate exists the eastern margin of the siberian plate is suggested to lie along a line between the ulakhan sis range the alazeya uplift and the arga tas range the cherskiy mountains and the verkhoyansk fold belt are parts of the siberian plate the paleozoic deposits of the omolon massif are unlike those found in the cherskiys or siberia paleomagnetic data from the omolon massif are discordant from data from siberia it is suggested that the omolon massif represents a microplate which accreted onto siberia in the jurassic ophiolites in central chukotka are of the same emplacement age as in the western brooks range and may have been emplaced at the initiation of the rotation of arctic alaska geometric and limited stratigraphic data suggest that the east siberian sea may be floored by oceanic crust left by an incomplete closure between arctic alaska siberia and omolon the tectonic position of the prikolymsk massif remains ambiguous

the nares strait problem a re evaluation of the geological evidence in terms of a diffuse oblique slip plate boundary between greenland and the canadian arctic islands abstract geophysical models of sea floor spreading in baffin bay labrador sea require that greenland was displaced sinistrally relative to the canadian arctic islands by 200 300 km it has usually been assumed that this movement took place along nares strait but onshore geological evidence recently compiled by dawes and kerr appears to rule out any displacement in excess of 50 km twenty different structural and stratigraphic markers cross the strait without significant displacement a new approach is suggested here which spreads the displacement across a diffuse oblique slip plate boundary 1 1 south of bache peninsula displacement of up to about 150 km may have occurred along nares strait bache peninsula arch probably did not cross the strait but is a north south feature extending south from bache peninsula 2 2 revisions of proterozoic stratigraphy show that the arch cannot have marked the limit of thule basin as formerly assumed thule basin isopach data can readily be accommodated to a 150 km sinistral displacement 3 3 cambrian ordovician strata in bache peninsula area may have occupied a north south embayment similar to others along the southern border of franklinian geosyncline 4 4 north of bache peninsula most of the strike slip displacement probably took place along strike faults within central ellesmere and north greenland fold belts paleozoic stratigraphic markers which cross nares strait without strike slip displacement would not be displaced by these faults either because stratigraphic and structural trends are parallel within the fold belts the structural style of the ellesmere fold belt is probably one of transpressive oblique slip with local counterclockwise block rotations 5 5 up to 50 km of displacement may have occurred along northern nares strait itself probably as a late phase of movement a detailed palinspastic reconstruction must await further detailed groundwork this should include the following which would also serve as independent tests of the hypothesis detailed basin analysis of thule basin and cambro ordovician strata immediately to the north analysis of small scale structural features joints cleavage slickenside and map patterns of faults within the central ellesmere and north greenland fold belts deep reflection seismic and paleomagnetic analysis of the fold belts

seismic imaging of the 2001 bhuj mw7 7 earthquake source zone b value fractal dimension and seismic velocity tomography studies abstract we use precisely located aftershocks of the 2001 mw7 7 bhuj earthquake 2001 2009 to explore the structure of the kachchh seismic zone by mapping the 3 d distributions of b value fractal dimension d and seismic velocities from frequency magnitude analysis we find that the catalog is complete above mw 3 0 thus we analyze 2159 aftershocks with mw 3 0 to estimate the 3 d distribution of b value and fractal dimensions using maximum likelihood and spatial correlation dimension approaches respectively our results show an area of high b d and vp vs ratio values at 15 35 km depth in the main rupture zone mrz while relatively low b and d values characterize the surrounding rigid regions and gedi fault gf zone we propose that higher material heterogeneities in the vicinity of the mrz and or circulation of deep aqueous fluid volatile co2 is the main cause of the increased b d and vp vs ratio values at 15 35 km depth seismic velocity images also show some low velocity zones continuing in to the deep lower crust supporting the existence of circulation of deep aqueous fluid volatile co2 in the region probably released from the eclogitasation of olivine rich lower crustal rocks the presence of number of high and low velocity patches further reveals the heterogeneous and fractured nature of the mrz interestingly we observe that aki 1981 s relation d 2b is not valid for the spatial b d correlation of the events in the gf d2 1 2b zone however the events in the mrz d2 1 7b show a fair agreement with the d 2b relationship while the earthquakes associated with the remaining parts of the aftershock zone d2 1 95b show a strong correlation with the aki 1981 s relationship thus we infer that the remaining parts of the aftershock zone are probably behaving like locked un ruptured zones where larger stresses accumulate we also propose that deep fluid involvement may play a key role in generating seismic activity in the mrz therefore a similar episode of deep fluid inflow could play a crucial role in causing the next strong earthquakes in the surrounding blocks of nwf

mesozoic evolution of exotic terranes and marginal seas western north america abstract regional terrane analysis has been combined with a global evaluation of plate kinematics to produce a new tectonic model for the mesozoic evolution of western north america and its associated marginal seas the model employs a two tiered data reliability ranking system to resolve conflicts within data sets the lower tier of the ranking system involves the assignment of a numerical rank to paleomagnetic and or paleobiogeographic data based on each data set s reliability the upper tier of the ranking system places the paleomagnetic and paleobiogeographic data in perspective by assigning a relative order of importance to different types of data the most reliable data are considered to be departure rift and arrival collision times that are tightly constrained by independent data sets evidence of subduction and or strike slip motion also ranks high in the master ranking system paleomagnetic and vertebrate paleobiogeographic data come next in the hierarchy followed by invertebrate and floral paleobiogeographic data application of this approach to a case study the baja british columbia controversy has resulted in a coherent model for the entire region results derived from the application of this modelling approach to the problem of the mesozoic assembly of western north america suggest that its evolution may be modeled using a minimum of 57 large terranes oblique convergence may have been the dominant tectonic process along the western north american margin during the mesozoic causing large scale latitudinal transport of many exotic terranes the motions of the terranes produced a number of marginal seas yukonia etc that were short lived but important components of western margin tectonics a combination of collision events side swiping episodes and changes in plate kinematics led to the initiation of several regional tectonic upheavals including the nevadan and sevier orogenies

unified scaling theory for distributions of temporal and spatial characteristics in seismology abstract the paper describes the unified scaling theory for distribution functions of temporal and spatial characteristics in seismology it is based on the scaling of seismological characteristics calculated for various energy spatial temporal intervals the common mathematical methods for the scaling of distribution functions are developed the means to test possibility of such scaling are found as well the relationship between the unified scaling theory and other present scaling approaches is determined the theory is applied to two characteristics of different seismoactive regions the first characteristic is the waiting time between earthquakes t the second one is a new space parameter d min which is the minimum distance of a current seismic event to the nearest in space neighbor in an energy spatial temporal interval the distribution of the characteristics t and d min allows estimating the time interval to the next earthquake and the distance of the following earthquake from previous earthquakes thus these characteristics are very important for seismic hazard estimations scaling of distributions functions is proven to be successful for d min in all energy spatial temporal intervals and for t with variations of energy magnitude range the distribution function of t for various time domains was stable in only 60 of the cases and near to unstable for spatial variations

effects of rifting and subsidence on thermal evolution of sediments in canada s east coast basins regional maps of lithospheric deformation and thermal history have been derived for the eastern continental margin of canada subsidence associated with the rifting and cooling stages of rifted margin formation was calculated from gridded maps of sediment thickness and bathymetry along the labrador grand banks and nova scotian margins a two layer lithospheric extension model was used to compute the deformation and thermal evolution of each region deformation results show that the crust and lower lithosphere have generally stretched by different amounts and that either crustal or subcrustal lithospheric stretching dominates beneath the various basins thermal modelling results for the older nova scotian and grand banks margins show a strong correlation between thermal gradient crustal stretching and sediment thickness and the predicted thermal gradient pattern for the younger labrador margin correlates extremely well with predicted stretching of the still cooling subcrustal lithosphere predictions

earthquakes as self organized critical phenomena a cellular automation model with threshold elements previously proposed by bak et al 1988 which generates 1 f noise and self organizes into a critical state is studied as a model for earthquake occurrence the model explains some of fractal features of earthquakes such as the power law distribution of the size of the earthquake the model is modified so that every earthquake may trigger aftershocks the modified trigger model explains other fractal features of earthquakes such as the power law decay of aftershock frequency and the power law decay of aftershock frequency and the power law correlation of the hypocenter distribution

the western svalbard margin 74 80 n abstract a regional study of the continental margin between the senja and molloy spitsbergen fracture zones reveals that the transition from continental to oceanic crust occurs in a narrow zone beneath the outer shelf and uppermost slope the postulated continent ocean boundary appears to be fault related consisting of sheared and rifted segments the marginal structures are compatible with a plate tectonic model in which the southern greenland sea opened along a northeasterly propagating plate boundary in the eocene whereas the northern greenland sea started opening in the early oligocene the main structure at the margin is the hornsund fault zone which probably reflects an old zone of weakness rejuvenated in the tertiary first by shear and later by extensional movements in the early tertiary local transpressional and transtensional components along the plate boundary are associated with the spitsbergen orogeny emplacement of belts of high density oceanic crust and tectonism in the western barents sea a complex volcanic rifted margin characterized by the bjornoya marginal high links the predominantly sheared margin segments on either side the main ridge like segment of the hovgaard fracture zone was originally part of the spitsbergen margin in a regional sense the hornsund fault zone demarcates the eastern boundary of the tertiary sedimentary wedge which reaches a total thickness of more than 7 km there appears to have been a considerable increase in deposition of sediments the last 5 6 my depocentres located seaward of the east west fjord systems and submarine depressions indicate a relationship between late cenozoic glaciations and high sedimentation rates

late cretaceous age of the hutshi mount nansen and carmacks groups southwestern yukon territory and northwestern british columbia volcanic rocks of the hutshi mount nansen and carmacks groups occur in the southwestern yukon where they unconformably overlie the yukon crystalline terrane and deformed strata of the whitehorse trough the volcanic rocks are faulted and tilted locally altered and largely postorogenic the more basic carmacks volcanics locally overlie intermediate to acid rocks of the mount nansen group but are mostly in isolated exposures northwest of the hutshi and mount nansen volcanics hutshi mount nansen volcanics of the miners range are porphyritic partly vesicular calc alkaline andesite flows and flow breccias intruded by calc alkaline alkali rich rhyolite and two feldspar andesite dikes a low greenschist metamorphic overprint affects most rocks carmacks volcanics near carmacks are flows epiclastic breccias and sintered tuffs interbedded with immature volcanic sandstone one analysed breccia clast is calc alkaline andesite but the flows are potassic basalt trachybasalt and tristanite recent assignme

spatial and temporal patterns of earthquake distribution in soviet central asia application of pair analysis statistics we have examined the soviet regional earthquake catalog for central asia for the period 1962 to 1983 to characterize the spatial and temporal structure of the earthquake process in this highly active continental collision zone three areas of apparently homogeneous earthquake distribution were identified as characteristic of distinct seismic regimes 1 a segment of the range bounding gissar kokshal fault zone 2 the interior of the crystalline massif of the tien shan mountain range and 3 the tadjik depression fold thrust belt the pair analysis technique applied in our study compares the spatial and temporal distribution of pairs of earthquakes with those determined by uniformly distributed events in the same area and time interval we have found the earthquake distribution in this region to be dominated by significant nonrandomness in both space and time the spatial nonrandomness is manifested in two major ways spatial clustering appears to characterize the overall structure of the earthquake process in the region as it is observed regardless of the scale considered and even upon removal of foreshocks aftershocks and swarms from the catalog anomalies at larger distances could also be distinguished suggesting the existence of a regular spatial alternation of subareas of higher and lower levels of seismic activity the nonrandomness in temporal distribution of earthquakes is also characterized by clustering at short time intervals in contrast with the spatial patterns earthquakes appear to be randomly distributed in time after removal of foreshocks aftershocks and swarms

geology and regional setting of kuparuk oil field alaska the kuparuk oil field is located on the alaskan arctic plain in the colville prudhoe basin 10 to 30 mi 16 to 48 km west of the prudhoe bay field the 24 api crude is similar in type to that in the permo triassic reservoirs in the prudhoe bay field however it is from the lower cretaceous kuparuk formation this reservoir is located in a basin between the colville and prudhoe highs the origin of the oil is believed to be predominantly lower sequence formations with migration occurring possibly via the prudhoe bay field the dominant trapping mechanism is stratigraphic pinch out and truncation of the reservoir at a local unconformity along the southern and western flanks of a southeast plunging antiform structural dip closure exists along the northern and eastern flanks the reservoir sandstones occur within sequences which become cleaner and coarser upward and are thought to be shallow marine in origin with a provenance to the northeast they are interpreted to be infrarift sediments on what is now a passive atlantic type continental margin two of the four major lithostratigraphic units mapped within the kuparuk formation exhibit good reservoir characteristics and extend over an area in excess of 200 mi2 518 km2 the cumulative net pay in the kuparuk field ranges up to 90 ft 27 m and the estimate of movable oil in place is 4 4 billion stock tank bbl there is no gas cap the field exhibits a variable oil water contact ranging from 6 530 ft 1 990 m in the southeast to 6 700 ft 2 042 m in the north after secondary waterflooding the potential recoverable reserves are estimated to be about 1 0 to 1 5 billion stock tank bbl kuparuk field therefore ranks as one of the largest oil fields in the united states

the yermak plateau formed at a triple junction the yermak plateau is an arcuate marginal plateau located seaward of northwestern spitsbergen the plateau is divided into two zones based on bathymetric trends and magnetic characteristics that have roughly coincident boundaries north of latitude 82 n where the bathymetric contours trend ne the magnetic amplitudes are large whereas the southern portion strikes nnw and exhibits a subdued magnetic signature beneath the northern section of the plateau crustal refraction velocities of 5 0 km s 1 underlain by 7 2 km s 1 are recorded while farther south velocities of 4 3 6 0 and 8 0 km s 1 are measured the 6 0 km s 1 velocity is similar to ones reported on the continental shelf south of spitsbergen dredged material gravity heat flow and seismic reflection and refraction data indicate the northern region of the plateau is oceanic and formed in conjunction with the morris jesup rise in contrast the southern section is thinned continental crust formed by the initial rifting process at a triple junction north of greenland plate reconstructions for anomalies 24 and 13 are consistent with this interpretation little space is required for the yermak plateau at anomaly 24 because it is composed of oceanic and thinned continental crust the development of the yermak plateau and the morris jesup rise paired aseismic ridges took place when the north american eurasian and greenland plates were moving independently

geochronology and tectonic implications of magmatism and metamorphism southern kootenay arc and neighbouring regions southeastern british columbia part ii mid cretaceous to eocene a north south trending belt of amphibolite facies regional metamorphism parallels the purcell trench transects the kootenay arc and is in part fault bounded towards the axis of this belt progressively higher pressure metamorphic mineral assemblages are exposed in the contact aureoles of post kinematic mid cretaceous 100 ma plutons and in metapelites contours of k ar biotite dates for plutonic rocks 55 95 ma are regular are broadly conformable with metamorphic isograds appear to cross internal intrusive contacts of post kinematic plutons and young towards the highest pressure and temperature regional metamorphic zones within the sillimanite zone most micas yield k ar dates between 40 and 55 ma rb sr muscovite dates for deformed and undeformed pegmatites and for muscovite bearing monzogranite and granodiorite fall between 53 and 84 ma u pb zircon dates for the kaniksu batholith and nearby gneiss of uncertain origin yield a lower concordia intercept of 94 ma micas from mid jurassic and mid

role of pore fluids in the generation of seismic precursors to shear fracture a systematic study of temporal changes in seismic b values defined as the log linear slope of the earthquake frequency magnitude distribution has shown that large earthquakes are often preceded by an intermediate term increase in b followed by a decrease in the months to weeks before the earthquake1 the onset of the b value increase can precede earthquake occurrence by as much as 7 years a recently proposed fracture mechanics model of the earthquake source2 explains these temporal fluctuations in b in terms of the underlying physical processes of time varying applied stress and crack growth the model predicts two minima in b separated by a short lived maximum here we report the results of controlled laboratory deformation experiments done in simulated upper crustal conditions on both air dried and water saturated rock specimens as found in previous experiments3 5 shear fracture in dry specimens is characterized by a decline in b during anelastic deformation to a single minimum reached just before failure but in water saturated specimens when pore fluid volume is kept constant by servo control we also observe a second intermediate term b value minimum so reproducing the double b value anomaly predicted by the model2

evidence against large scale strike slip separation of paleozoic strata along the richardson hess fault system northern canadian cordillera a review of geologic relationships across the richardson hess fault system demonstrates that large scale strike slip separation did not occur among rocks younger than proterozoic evidence against major lateral separation is 1 structural units of gently dipping paleozoic strata deformed during columbian laramide orogenesis show only 10 to 20 km total generally right lateral separation across the fault system 2 the only notable discontinuity across the fault system occurs along a prominent lineament at its south end this discontinuity is part of a 200 km long transition of thick lower cambrian quartzite and carbonate strata southwestward into argillite and does not need to be explained by strike slip faulting 3 lower paleozoic paleogeography across the richardson hess system features a complex arrangement of arches basins and troughs all strata in and around these features are at present harmoniously juxtaposed

maps of expected earthquakes based on a combination of parameters abstract the technique for compiling maps of expected earthquakes has been developed and tested retrospectively and in real time the conditional probability of future earthquakes was calculated based on geotectonic data geodetic measurements and spatio temporal variations of such seismic parameters as density of seismogenic faults slope of the recurrence curve number of events such as seismic quiescence and activation ratio of s and p wave travel times and seismic energy release the probability of detection the probability of false alarm the mean waiting time the mean waiting area and the prediction efficiency were estimated from the retrospective analysis of earthquakes with magnitudes m 5 0 the map of expected earthquakes for the caucasus in 1986 1990 was sent to local seismological institutes in 1985 three main zones with a high probability of future earthquakes were revealed on that map each of them has a size of about 10 4 km 2 several smaller zones have a mosaic like pattern and are distributed along tectonic faults and their intersections 10 of the territory is covered by areas with an earthquake probability of 3 5 times larger compared with random occurrence six earthquakes with magnitudes m 5 0 occurred in the caucasus in 1986 august 1989 their epicentres were located within 30 km of the corresponding waiting zones the biggest shock occurred in armenia on the 7th of december 1988 m 6 9 it destroyed the cities spitak leninakan and kirovakan a high probability zone appeared in that area in 1983 i e 5 years before the event showing a gradual growth both in amplitude and size up to 1988 in five other cases the anomalies appeared 1 2 years before the corresponding earthquakes this technique is now being tested in other seismic areas of the soviet union

paleomagnetism of the esayoo formation permian of northern ellesmere island possible clue to the solution of the nares strait dilemma abstract the esayoo formation lower permian of northern ellesmere island 81 n 82 w has been sampled at two localities twelve sites 88 cores studied in the early tertiary eurekan orogeny fold and thrust belt of the northern sverdrup basin northern ellesmere island the directions of remanent magnetization at the two localities are in excellent agreement after correction for geological tilt their mean is 126 2 61 8 b sites 12 k 105 95 4 3 and the corresponding paleopole is 48 1 n 159 2 e k 52 a 95 6 1 comparison with early permian reference paleopoles for north america shows that the formation of overthrust sheets has produced no paleomagnetically detectable displacement in a paleolatitudinal sense as would be inferred from the geology but there is a significant anticlockwise rotation of 36 8 this rotation is the first to be observed in the canadian arctic islands geological evidence allows no more than about 50 km of lateral motion along nares strait between ellesmere island and greenland this falls far short of the 300 km of relative motion required by the marine geophysical evidence for the opening of the labrador sea and baffin bay this discrepancy between the geological and geophysical evidence is the nares strait paradox evidently relative motion between greenland and ellesmere island is not restricted to nares strait itself and must be more generally distributed across ellesmere island we suggest that the 36 rotation observed is a manifestation of this distributed strain and therefore provides a clue to the solution of the nares strait paradox

evolution and regional stratigraphy of the northeastern canadian polar margin seismic refraction data from the northeastern canadian polar margin were compared to sonic logs and other refraction data in the area to develop a regional stratigraphy for the continental shelf north of the sverdrup rim a schematic geological cross section derived from these data showed 12 km of sedimentary rocks north of the rim based on seismic correlations the section near the edge of the shelf was predicted to consist of 4 km of upper cretaceous to tertiary postrift strata with an initial velocity of 2 1 km s 1 and a high gradient of 0 5 s overlying about 8 km of lower mesozoic to palaeozoic synrift strata with an initial velocity of 4 4 km s 1 and a lower gradient of 0 1 0 15 s all resting on a crystalline basement with a velocity of about 6 2 km s 1 mantle was measured at a depth of 25 km on the outer shelf the geological interpretation of the margin was examined in terms of circum arctic geology and was shown to be consistent with it when the arctic ocean was reconstructed to its predrift position during mississippian to early cretaceous the close spatial relationship of the canadian polar margin basin to the brooks mackenzie basin of alaska which has a mississippian to hauterivian sequence supported the geological interpretation of the margin described here

geology of norton basin and continental shelf beneath northwestern bering sea alaska the rocks that floor the norton basin and the northwestern bering sea are most likely of precambrian and paleozoic age like those rocks that crop out around the basin a maximum of 6 5 km of mainly cenozoic strata lie over basement in the basin on the basis of the geometry of reflections in seismic data we believe alluvial fans to be present deep in the basin and to border major basement fault blocks these fans are the lowest units of the basin fill in many areas and consist of uppermost cretaceous or lower paleogene possibly coal and volcanic rich rocks mainly clastic nonmarine sedimentary rocks overlie the fan deposits the neogene and quaternary basin rocks apparently were deposited in a marine environment the basement of the northwestern bering sea west of norton basin is 1 km below sea level for the most part but local structural lows are filled with at most 2 km of strata of probable late neogene and quaternary age the continental shelf in this area is separated structurally from the seward peninsula by a zone of small basement antiforms over which relatively high gravity values have been measured the norton basin comprises two structural areas that are separated by a major northwest striking horst the first structural area lies west of this horst where major normal faults strike northwest to form local areas where the basin is as deep as 5 km the second area east of the horst includes major normal faults that strike east and northeast the deepest part of the norton basin 6 5 km lies there during the late jurassic and early cretaceous basement rocks now beneath the norton basin were affected by the orogeny that formed the brooks range these basement rocks were metamorphosed and thrust and then eroded deeply nearly 50 m y before the basin began to form in the middle late cretaceous the area of the eastern seward peninsula and eastern norton sound was subjected to east west compression and consequent eastward thrusting the strike slip kaltag fault probably formed at this time if norton basin formed as a pull apart basin along this fault then the basin may be as old as middle late cretaceous however during the latest cretaceous and early paleogene the compression gave way to regional extension that formed northeast trending grabens onshore east of norton basin we believe that the extensional norton basin most likely formed in response to this regional extension initial deepening of the basin was controlled by major normal faults and occurred rapidly whereas subsidence was slower and more regional in scale

subsidence and thermal history of queen charlotte basin a tectonic model for the formation subsidence and thermal history of queen charlotte basin is developed based upon regional geological and geophysical data subsidence data from offshore wells in hecate strait and queen charlotte sound and thermal criteria derived from present heat flow and vitrinite reflectance information queen charlotte basin is seen to have resulted from two distinct mechanisms 1 during a period of broad regional uplift rifting and crustal extension occurred in queen charlotte sound up to about 17 ma ago and the queen charlotte islands were displaced northwards toward their present position by transcurrent motion along the louscoone inlet sandspit fault system the rifting generated a significant thermal anomaly and a restricted deep basin as a consequence of crustal thinning and subsequent thermal cooling 2 beginning about 6 ma ago oblique underthrusting commenced along the margin resulting in flexural uplift of the western part of the queen charlotte islands and comp

rock damage evolution as failure process of hierarchical structure abstract the present study is devoted to evolution of rocks in the fracture process initially the rock is considered as an ideal medium with no cracks rock formation is assumed in the form of a nested self similar hierarchical structure the hierarchical structure scheme is chosen in accordance with the experimentally verified criterion of fracture the failure probability of the lowest structure level represents a function of time temperature material parameters and loading conditions knowing the failure probabilities of each structure level allows one to calculate the stress dynamics in a rock material failure volumes for each hierarchy level energy release etc the influence of temperature type of the hierarchical structure rock material stress rate on the fracture dynamics is considered the results of calculations of the rock fracture dynamics are compared with the results of experiments this study can be seen as an attempt to explain the stability of the gutenberg richter law

permian and triassic sedimentation in the northeastern brooks range alaska deposition of the sadlerochit group permian and triassic rocks of the sadlerochit group crop out extensively in the northeastern brooks range adjacent to the coastal plain of the arctic national wildlife refuge terrigenous clastic rocks of the sadlerochit group are separated from underlying carbonates of the lisburne group by a regional unconformity marking the pennsylvanian permian systemic boundary lithologic and diagenetic patterns of rocks above and below the sub sadlerochit unconformity vary systematically with substantial paleotopography along the erosional surface within the sadlerochit group nonmarine conglomerate of the basal echooka formation fills erosional channels and valleys and grades upsection into a retrogradational succession of tempestites deposited during episodic storm surge in shal ow marine environments the overlying ivishak formation records an abrupt reversal of environmental migration pattern and the beginning of southerly progradation of a broad suite of deltaic environments depositional units in the ivishak are strongly progradational and cyclic at a variety of scales reflecting alternating episodes of progradation and transgression inherent in delta construction the basal kavik member of the ivishak formation is an upward coarsening depositional assemblage recording initial migration of prodelta environments and evolution of an extensive subaqueous delta platform the overlying ledge sandstone member is organized into three depositional assemblages recording the evolution of delta fringe distributary channel and crevasse splay environments of the lower delta plain the fire creek siltstone member is an aggradational and transgressive assemblage deposited in shallow marine environments that reworked sediment originally deposited on the lower delta plain the depositional assemblage records the final large scale subsidence and drowning of the ivishak delta platform the most favorable reservoir strata are developed immediately above and below the sub sadlerochit unconformity and in distributary mouth bar and distributary channel deposits of the ledge sandstone member

relationships between plate motions and late cretaceous to paleogene magmatism in southwestern alaska four major late cretaceous to paleogene magmatic belts have been recognized in southwestern alaska and tentative boundaries have been drawn for each the belts indicate minimum ages by which the tectonostratigraphic terranes they overprint must have been linked together though there has been significant postmagmatic tectonism the kuskokwim mountains belt 73 60 m y b p the alaska range belt 74 55 m y b p and the gulf of alaska belt 62 57 m y b p all may have been related to a period of rapid north northeastward motion of the kuia plate from about 74 to 56 m y b p the angle of convergence was low with respect to the present orientation of the belts suggesting the possibility of postmagmatic rotation of the belts a higher angle of convergence may have existed with respect to the alaska range belt a probable arc if postmagmatic rotation resulted from 300 400 km of right lateral displacement on the denali fault the gulf of alaska belt is in an anomalous forearc position with respect to the alaska range belt but probably formed by a convergence related mechanism the kuskokwim mountains belt is in an apparent back arc position but the mechanism of its origin is uncertain it may have been part of an unusually broad alaska range arc or less likely it may have been a separate arc magmatic quiescence occurred throughout south western alaska during a period of plate reorganization from about 56 to 43 m y b p a period which began with extremely rapid northward motion of the kuia plate magmatism resumed when the present period of rather slow northwestward pacific plate motion began at about 43 m y b p the aleutian arc probably formed at this time and has been episodically active in about the same location ever since

hierarchy in earthquake size distribution abstract we propose a fault model in which there are a finite number of characteristic lengths between the smallest and the largest scales e g between a grain size and a size of great earthquakes a fault plane in one scale is segmented into blocks of statistically similar sizes by the barriers of statistically similar heights rupture expands by successively climbing the barriers the average barrier height is proportional to the average block size which defines the characteristic length of the relevant scale stresses before and after rupturing are assumed to be independent of earthquake size with these assumptions the probability for rupture to grow further is shown to be independent of the scale of barrier structure the rupture in one scale however tends to grow more easily as it grows so that once the rupture exceeds some critical size it no longer stops until it encounters the barriers in the next larger scale rupture grows by repeating this cycle which starts with rupturing of a unit block in one scale and ends with one in the next larger scale our model involves two parameters which must be determined empirically one is the length ratio r between two successive scales the other is the critical number of blocks n c which defines the critical size for unstable rupture growth in one scale we suggest values of 5 for both r and n c with these values our model explains a diversity of earthquake phenomena such as the magnitude frequency relation the seismic gap and the magnitude gap the magnitude difference between a main shock and its largest aftershock the occurrence of multiplet earthquakes the generation of high frequency seismic waves the incoherency of the near field acceleration and the recent observation by furumoto and nakanishi that the main rupture is often preceded by a precursory rupture whose time duration in general scales with seismic moment

geometry segmentation and stress regime of the spitak armenia earthquake from the analysis of the aftershock sequence summary the aftershock sequence of the spitak earthquake as recorded by a dense portable network deployed around the source region is analysed in order to obtain a precise description of the mechanics of the rupture a collection of 708 well recorded events corresponding to a period of about two weeks is studied their hypocentres are accurately located and their focal mechanisms are calculated individually as well as by a joint procedure that permits us to estimate the stress regime the epicentral distribution of these aftershocks indicates that the fault at depth extends well beyond the surface rupture towards the west and northwest neotectonic and seismic observations permit us to identify five segments broken during the earthquake the southeastern one oriented n140 corresponds to the surface ruptures along the alavar right lateral shear fault the main surface ruptures between spitak and gekhasar correlate well with aftershocks showing a n120 trending fault surface dipping 50 to the ne and acting as a thrust with a right lateral component two similar segments towards the west are offset and hidden under active folds a fifth segment towards the nw corresponds to a right lateral blind shear fault buried in depth in the vicinity of the large pambak sevan fault 14 vertical sections across the fault including focal mechanisms illustrate these features a relocation of the main shock and aftershocks for the period before the installation of the portable network confirms the spatial extent of the seismicity the foreshock the main shock and the strongest aftershock 4min 20s after the main shock have approximately the same epicentre thus the rupture started at the crossing of the pambak sevan and alavar faults and propagated bilateraly from there although the seismic moment associated to the alavar branch is only about one sixth of the total moment the stress regime is one of triaxial compression with a a axis oriented n344 the same orientation is given by the microtectonic observations made on the central segment of the surface ruptures a result that agrees with previous estimates for the georgian caucasus

a self exciting process of acoustic emission occurrence in steady creep of granite under uniaxial stress clustering of acoustic emissions ae in space and time was found in a laboratory experiment to investigate the stochastic process of ae occurrence event times of ae were measured during steady creep phases under different stress levels oshima granite was continuously subjected to constant uniaxial stress of different intensity the occurrence time of ae event was analyzed as a combination of a poisson process and a self exciting part in the latter events are excited by preceding events the self exciting character was more enhanced under higher crack density in accordance with a stronger concentration in hypocenter distribution at higher stress

sediment thickness in the southern canada basin abstract multichannel seismic reflection data are used in conjunction with deep crustal seismic refraction data to estimate the thickness of sediments in the southern canada basin of the arctic ocean north of alaska the sediments are interpreted to be of hauterivian mid early cretaceous to holocene age comparison of the seismic reflection character of seismic reflections in the study area with that in other basins indicates that a base of sediment top of oceanic layer 2 reflection is not present above the depth at which the water bottom multiple obscures all deeper arrivals which is in conflict with the conclusions drawn from aeromagnetic refraction and other reflection studies seismic velocity structure determined from the reflection data indicates that the reflections above the multiple are from sedimentary strata in the absence of seismic reflection evidence for the top of layer 2 above the multiple we estimate total sediment thickness by using the layer 3 refractions and subtracting an average assumed layer 2 thickness from the top of layer 3 assuming that an average thickness of oceanic layer 2 1 4 km overlies layer 3 in the southern canada basin sediment thickness in the study area is estimated to range between 6 5 km where water depth is 3 8 km to greater than 11 km where the water depth is 2 km this is nearly double that of any previous estimates and should have a significant effect on calculations such as the age of canada basin regional heat flow and long term sedimentation rates

dynamics of shallow lateral shear layers experimental study in a river with a sandy bed shallow lateral shear layers forming between flows with different velocities though essential for mixing processes in natural streams have been examined only in laboratory settings using smooth fixed bed channels this paper reports the results of an experimental study of a shear layer in a straight reach of a natural river where the layer in contrast to the two dimensional structure observed in the laboratory is highly three dimensional the study included pronounced transverse pressure gradients which influenced shear layer structure compared to flume experiments it also introduces an analysis that complements conventional theory on mixing layers the lateral velocity gradient between the flows downstream from a splitter plate placed in the river the principal controlling factor was adjusted for three experimental runs to determine the influence of different gradients on shear layer dynamics in each run detailed three dimensional measurements of mean and turbulent characteristics were obtained at five cross sections downstream from the splitter plate although experimental results agreed with conventional mixing layer theories with respect to turbulence the dynamics of the shear layers were dominated by the mean lateral fluxes of momentum after re examining the governing equations we developed a parabolic equation describing the shear layer evolution and several scaling relations for essential terms of the energy budget mean and turbulent lateral fluxes of momentum turbulent kinetic energy and dissipation rates the study also provides insight into the spectral dynamics of turbulence in the shear layer and clarifies previous observations reported for confluences in natural streams

structural setting and validation of direct hydrocarbon indicators for amauligak oil field canadian beaufort sea the recent discovery of a giant oil field in the southeastern beaufort mackenzie basin has brought this frontier area closer to oil production despite severe environmental conditions the amauligak field is a fault bounded growth structure developed in the kugmallit trough within deltaic deposits of the beaufort sea shelf shelf construction occurred during the late cretaceous tertiary by repeated progradation of the mackenzie river delta in response to rift induced opening of the canada basin and extension of the kugmallit trough the amauligak field contains oil and gas in multiple sandstone reservoirs of the oligocene kugmallit sequence the upper sandstones are truncated by an unconformity and sealed by the overlying shales of the miocene mackenzie bay sequence based on two dimensional seismic coverage the field was initially described as structurally simple interactive interpretation on landmark and sidis workstations of a three dimensional seismic program revealed the local structural complications spatial configuration and detailed structural elements of the field direct hydrocarbon indicators dhis including amplitude anomaly phase change flat spot and low frequency zone associated with a large gas cap were investigated using full amplitude range and attribute extraction methods interpretation of seismic data and correlation with well results suggest that a combination of structural stratigraphic and hydrodynamic factors are responsible for the appearance and distribution of amauligak dhis on the amplitude displays a flui contact is seismically mappable over the field clearly separating the gas cap from the wet reservoir

the accommodation of large strains in the upper lithosphere of the earth and other solids by self similar fault systems the geometrical origin of b value plate tectonics has provided a method of visualizing the geometry of the deformation of the earth s lithosphere on a large scale the description is so concise that for many purposes it provides an explanation of geological processes that overshadows the need to understand the driving processes the mechanics of the zones between the plates are less well understood particularly in continental regions where large areas are subject to deformation both continuous and discontinuous models have been tried but both have obvious drawbacks

temporal variations in seismicity during quasi static and dynamic rock failure abstract a comprehensive model is presented which can explain temporal fluctuations in seismic b values in the period leading to mechanical failure in terms of the underlying physical processes of time varying applied stress and stress corrosion enhanced crack growth under conditions of constant strain rate the form of the b value anomaly in the period leading to failure depends on the form of the stress time relationship for the case where dynamic failure occurs at peak stress after a period of strain hardening the model predicts a single cusp like b value anomaly reaching a critically low value of 0 5 at failure for the physically most realistic case where dynamic failure is preceded by a period of precursory strain energy release during strain softening the model predicts two minima in the b value separated by a temporary maximum or inflection point these fluctuations in the b value are consistent with reported intermediate term and short term earthquake precursors separated by a period of seismic quiescence for the case of quasi static cataclastic flow the b value mirrors the stress and never falls to the critical value because there is no critical rupture new results from a series of controlled laboratory experiments are presented in which microseismic event rates and b value were monitored contemporaneously with stress time data for all variants of the stress time relationship recent field observations of temporal changes in seismicity rates and b value preceding major earthquakes are also reported both data sets exhibit b value anomalies which are consistent with the model predictions

shallow mixing layer downstream from a sudden expansion abstractthis study aims at investigating the mixing layer located at the interface between the free stream and recirculation zone downstream from a sudden lateral open channel expansion specific a

analogy in precursors of dynamic events at different scales abstract this paper presents a study of the time space behaviour of certain physical parameters namely the number of pulses of acoustic and seismic emission the density of seismogenic ruptures and the b value in laboratory mine and field experiments during the preparation and development of dynamic events at different scales the preparation stage before failure in rock specimens mine shocks and large earthquakes was studied it was found that in all cases the fault density parameter varies from 3 to 8 before a dynamic event the variance of the number of elastic pulses of acoustic and seismic emission as a rule increases and the b value undergoes changes it is shown that the behaviour of the parameters under study does not qualitatively depend on the linear dimensions of the object being loaded the results obtained strengthen the physical basis for the further development of studies on the prediction of dynamic events

seismicity in north eastern brazil fractal clustering and the evolution of the b value summary we analyse a catalogue of earthquakes recorded near joao camara brazil an intraplate area with a simple velocity structure and low attenuation the evolution of seismicity is characterized by the seismic b value and the fractal dimension of earthquake epicentre locations measured from sliding 100 event windows the events are divided into a number of spatial clusters using a nearest centroid sorting technique and two of these clusters are examined in detail one cluster characterized by intense activity shows a clear negative correlation between b value and fractal dimension of epicentre locations as has been predicted from simple mechanical models a second cluster shows a weak positive correlation and it is suggested that this might be explained in terms of fluid flow in the fault zone

experimental investigation of shallow recirculating flows experiments were conducted to study the bed friction influence in the recirculating zone of a shallow open channel flow velocity measurements were made using a hot film anemometer the recirculating flow rate and the length of the recirculating zone were determined from the measurements and they are related to a horizontal length scale and a bed friction length scale for deep flows the results are independent of the bed friction length scale for shallow flows the results are independent of the horizontal length scale turbulence in the recirculating flows is generated on one hand by the bed friction and on the other hand by the transverse shear the bed generated component is proportional to the bed friction velocity the transverse component is confined to a transverse mixing region in the limit of shallow water depth when the flow is under strong bed friction influence both the transverse mixing region and the recirculating zone have the same length of about one friction length scale

seismicity preceding volcanic eruptions new experimental insights a variety of seismic signals representing different physical mechanisms precedes volcanic eruptions the most meaningful signals are high and low frequency earthquakes and volcanic tremor that have tentatively been related to fracturing and magma transport in the volcanic edifice we provide experimental support for this association by reproducing magma migration while recording seismic signals opening fractures emit high frequency acoustic events while the switch to low frequency and harmonic tremor accompanies the flow of the melt in the fractures discerning between these seismic signals in nature can significantly refine volcanic hazard evaluation

omori s power law aftershock sequences of microfracturing in rock fracture experiment a time series of acoustic emissions ae in basalt was measured under constant uniaxial compression some bursts of ae events considered to be the main shock and aftershock sequences were observed two models describing the aftershock sequences the exponential decay model n t k exp pt and the omori s power law model n t k c t p where n t denotes the occurrence rate of aftershocks at time t were examined with the progress of the fracturing process the bursts changed from the exponential decay type to omori s power law type and the p value of omori s power law aftershock sequences decreased these results indicate that microfracturing gains a longer tail with the evolution of the fracture process the reproduction of omori s power law aftershock sequences of ae events suggests that the self similarity of rock fracturing holds good over a range from microfracturing to large earthquakes

physical modeling of the formation and evolution of seismically active fault zones acoustic emission ae in rocks is studied as a model of natural seismicity a special technique for rock loading has been used to help study the processes that control the development of ae during brittle deformation this technique allows us to extend to hours fault growth which would normally occur very rapidly in this way the period of most intense interaction of acoustic events can be studied in detail characteristics of the acoustic regime ar include the gutenberg richter b value spatial distribution of hypocenters with characteristic fractal correlation dimension d hurst exponent h and crack concentration parameter pc the fractal structure of ar changes with the onset of the drop in differential stress during sample deformation the change results from the active interaction of microcracks this transition of the spatial distribution of ae hypocenters is accompanied by a corresponding change in the temporal correlation of events and in the distribution of event amplitudes as signified by a decrease of b value the characteristic structure that develops in the low energy background ae is similar to the sequence of the strongest microfracture events when the ar fractal structure develops the variations of d and b are synchronous and d 3b this relation which occurs once the fractal structure is formed only holds for average values of d and b time variations of d and b are anticorrelated the degree of temporal correlation of ar has time variations that are similar to d and b variations the observed variations in laboratory ae experiments are compared with natural seismicity parameters the close correspondence between laboratory scale observations and naturally occurring seismicity suggests a possible new approach for understanding the evolution of complex seismicity patterns in nature

temporal variation of multifractal properties of seismicity in the region affected by the mainshock of the october 6 2000 western tottori prefecture japan earthquake m 7 3 1 the temporal variation of multifractal properties in spatial distribution of seismicity in the region affected by the main shock of the western tottori prefecture japan earthquake of october 6 2000 m 7 3 and its aftershock sequence are investigated we use earthquake catalog data from 1985 to 2001 in order to understand the process and mechanism preceding a large shallow earthquake a monotonous decrease of multifractal dimension dq with a wide range of q appeared clearly for about two years prior to this large shallow earthquake dq then increased to a maximum at the time of the main shock during the aftershock sequence dq oscillated between 2 0 and 0 7 the decrease and then increase of dq with respect to the spatial distribution of seismic events indicate clustering and declustering in multifractal structure respectively the temporal variation of dq reflects the accumulation and release of strain energy within the tectonic stress field