impact of active faulting on the post lgm infill of le bourget lake western alps france we have used high resolution seismic imaging to detect and characterize the recent deformation recorded by the quaternary sediments of le bourget lake the last glacial episodes mis 6a and 2 i e riss and wurm scoured out an elongated over deepened basin to more than 300 m below the present lake level and the basin accumulated 150 m of post lgm to holocene sediments the well stratified character of the infill is locally disturbed by tectonic deformations and gravity reworking a northern fault zone in continuation with the left lateral strike slip culoz fault is imaged within the holocene and late glacial accumulations a southern fault zone is also detected which can be related to the sublacustrine continuation of a much smaller fault affecting the jura alpine foreland the col du chat left lateral strike slip fault different generations of fractures have been identified in the lake allowing correlation and mapping in pre quaternary substratum the culoz fault has a n 160 orientation within the post lgm sediments fractures related to the culoz fault have an orientation between n135 and 95 a cloos model 1932 is thus proposed to explain the observed pattern of lacustrine deformations the calculated horizontal slip rate for culoz fault during holocene is about 1 3 mm yr 1 and for the col du chat fault is around 0 6 mm yr 1

crack fusion dynamics a model for large earthquakes the physical processes of the fusion of small cracks into larger ones are nonlinear in character a study of the nonlinear properties of fusion may lead to an understanding of the instabilities that give rise to clustering of large earthquakes we have investigated the properties of simple versions of fusion processes to see if instabilities culminating in repetitive massive earthquakes are possible we have taken into account such diverse phenomena as the production of aftershocks the rapid extension of large cracks to overwhelm and absorb smaller cracks the influence of anelastic creep induced time delays healing the genesis of juvenile cracks due to plate motions and others a preliminary conclusion is that the time delays introduced by anelastic creep may be responsible for producing catastrophic instabilities characteristic of large earthquakes as well as aftershock sequences however it seems that nonlocal influences i e the spatial diffusion of cracks may play a dominant role in producing episodes of seismicity and clustering

fractal reconstruction of sea floor topography sea floor bathymetric profiles exhibit features at many different scales of length this suggests that they could be described as fractals an algorithm interpolating a fractal line between points has been used to reconstruct bathymetric profiles from a few data points in general this fractal line has the same fourier amplitude spectrum as real bathymetry and if the parameters of the interpolation are suitably chosen it has a very similar appearance the success of this fractal reconstruction algorithm for the sea floor raises the possibility that it could be used to extrapolate from data collected at one scale the properties of the sea floor at finer scales and that similar techniques could be used to interpolate a surface between bathymetric profiles the fractal character is a sign that the processes that shape the sea floor are scale invariant and suggests that the renormalization group technique could be used to model these processes

the nature and genesis of gold silver tellurium mineralization in the metaliferi mountains of western romania precious metal au ag and base metal pb zn deposits in the metaliferi mountains of western romania occur in steeply clipping quartz ca mn carbonate veins which are hosted by miocene andesitic stocks and lava flows and surrounding sedimentary rocks the deposits consist predominantly of sulfides pyrite chalcopyrite sphalerite galena sulfosalts of as and sb and a diverse range of au ag tellurides the igneous host rocks have undergone mild pervasive propylitic alteration whereas immediately adjacent to the veins the wall rock alteration assemblages consist of quartz sericite k feldspar calcite and pyrite fluid inclusion stable isotope and thermodynamic data suggest that the majority of the mineralization and hydrothermal alteration in these deposits was caused by loci salinity 0 5 wt nacl equiv medium temperature 200 degrees 300 degrees c near neutral ph 5 6 fluids which underwent occasional boiling the fluid inclusion and stable isotope data support a model in which a metal bearing magmatic fluid was exsolved from a crystallizing calc alkaline melt and ascended to higher levels in the crust undergoing some isotopic exchange with surrounding sedimentary rocks but limited mixing with ground waters although the deposits in this part of the romanian carpathians exhibit many of the geologic characteristics of classic low sulfidation volcanic hosted au ag epithermal deposits they seem to have formed from essentially magmatic waters and there is little evidence for the incorporation of meteoric fluids into the hydrothermal system

a model for repetitive cycles of large earthquakes the theory of the fusion of small cracks into large ones reproduces certain features also observed in the clustering of earthquake sequences by modifying our earlier model to take into account the stress release associated with the occurrence of large earthquakes we obtain repetitive periodic cycles of large earthquakes a preliminary conclusion is that a combination of the stress release or elastic rebound mechanism plus time delays in the fusion process are sufficient to destabilize the crack populations and ultimately give rise to repetitive episodes of seismicity

the statistical mechanics of earthquakes abstract we review recent theoretical developments on the physics of earthquakes in particular we focus on the rise of the statistical mechanical view of earthquakes as a kind of phase transition this view is appealing in light of the well known scaling relations such as the gutenberg richter magnitude frequency and omori s law of aftershock decay scaling relations such as these which are in reality power laws are known to be associated with dynamical systems residing near a critical point in the state space of the system these second order critical points are associated with second order transitions which are a result of gradual changes of the controlling parameters at the same time characteristic earthquakes which involve the entire fault segment sliding nearly at once are more reminiscent of a first order transition which is characterized by sudden widespread changes in the physical state of the system in this paper we review these ideas and show how recent developments are leading to a view of earthquake fault systems based on modern statistical mechanics

premonitory transformation of steel fracturing and seismicity abstract transformation of microfracturing preceding the break up of steel and rock samples is similar to transformation of earthquakes flow prior to strong earthquakes in southern california the break up in a sample is preceded by transition from formation of new microcracks to coalescence or expansion of existing cracks this is reflected in the relation between the length and the number of the cracks similar transformation of seismicity precedes southern california earthquakes with magnitude m 6 6 1935 1994 specifically magnitude frequency relation bends downward for magnitudes from 3 to 4 5 and upward for magnitudes from about 4 5 to 6 in the usual notations the b value becomes larger in the first interval and smaller in the second one this transformation is accompanied by the increased share of aftershocks in the earthquakes flow in such a way the approach of a strong earthquake is reflected in both major traits of seismicity magnitude frequency relation and earthquake clustering imprecision of the earthquake catalog and reasonable variations in its analysis do not change our conclusions this phenomenon explains so far qualitatively a wide set of premonitory seismicity patterns we give it a formal definition allowing to test whether it takes place in other seismic regions

premonitory seismicity changes prior to the parkfield and coalinga earthquakes in southern california abstract in this work we apply the pattern informatics technique for evaluating one surface expression of the underlying stress field the seismicity in order to study the parkfield coalinga interaction over the years preceding the 1983 coalinga earthquake we find that significant anomalous seismicity changes occur during the mid 1970s in this region prior to the coalinga earthquake that illustrate a reduction in the probability of an event at parkfield while the probability of an event at coalinga is seen to increase this suggests that the one event did not trigger or hinder the other rather that the dynamics of the earthquake system are a function of stress field changes on a larger spatial and temporal scale

the transition from temperate phases to stadials in the long upper pleistocene sequence from les echets france abstract from two sections of the long sequence of les echets corresponding to the end of the eemian and to the end of st germain ii interstadial respectively detailed pollen diagrams have been established which provide information about the climatic conditions prevailing during the transitions from very temperate periods to the following cold stadials

chloritization of the hydrothermally altered bedrock at the igarape bahia gold deposit carajas brazil the igarape bahia gold deposit has developed from weathering of a near vertical hydrothermal cu au mineralization zone the unweathered bedrock composed of chlorite schists is mainly metamorphosed basalts pyroclastic and clastic sedimentary rocks and iron formation contents and fe fe mg ratios of chlorites increase from distal country rock towards the mineralization zone which can be attributed to different water rock ratios and locations in a hydrothermal system in the hydrothermal system high salinity fluids convected through basin floor rocks stripping metals from the recharge zones with precipitation in discharge zones the chlorite with lower fe fe mg ratios indicates alteration by relatively unreacted mg rich fluids occurring within recharge zones by contrast the chlorite with higher fe fe mg ratios in the mineralization zone formed from solutions rich in fe mn au cu h2s and sio2 within a discharge zone the iron formation could also be formed within the discharge zone or on the basin floor from the fe rich fluids the distal country rock with less chlorite content is a hydrothermal product at low water rock ratios whereas the proximal country rock and the host rock with more chlorite content formed at high water rock ratio conditions the al iv contents of chlorites indicate that the formation temperatures of these rocks range from 204 to 266 c with temperatures slightly increasing from distal country rock towards the mineralization zone

earthquake recurrence models and historical seismicity in the mexicali imperial valley abstract we have examined the historical seismicity of the mexicali imperial valley since about 1850 the largest observed earthquake in the area has been the magnitude m w 7 1 december 1934 event the magnitude distribution for large plate boundary rupturing earthquakes m 5 8 is not well fit by the gutenberg richter type b value model models which better fit the observed magnitude distribution are derived from a lognormal distribution of stress drops on faults of constant size and from an exponential distribution of rupture lengths as might be expected from randomly distributed rupture stopping asperities along the length of the fault this may be among the best data in the world for testing earthquake recurrence models e g time predictability slip predictability on a strike slip fault but the uncertainties are still too great to permit a unique interpretation

an observational test of the origin of accelerating moment release before large earthquakes 1 a progressive increase of seismic activity distributed over a wide region around a future earthquake epicenter is termed accelerating moment release amr this phenomenon has been observed in several studies over the last 15 years although there is no consensus about the physical origin of the effect in a recent hypothesis known as the stress accumulation sa model the amr is thought to result from the last stage of loading in the earthquake cycle in this view the increasing seismicity is due to minor stress release as the whole region becomes sufficiently stressed for the major event to occur the stress accumulation model makes specific predictions about the distribution of events in an amr sequence because the amr is predicted to be a result of loading on the main fault the precursory activity should be concentrated in the positive lobes of the far field stresses calculated by a backslip dislocation model of the main shock to test this model amr is first found in optimal circular regions around the epicenters of each of the m w 6 5 earthquakes in central and southern california since 1950 a backslip dislocation model is then used to determine which of the precursory events occur in the regions predicted by stress accumulation amr is shown to occur preferentially in the lobes of the backslip stress field predicted by the stress accumulation model

towards a new view of earthquake phenomena recent advances in the theory of fracture and fragmentation are reviewed empirical laws in seismology are interpreted from a fractal perspective and earthquakes are viewed as a self organized critical phenomenon soc earthquakes occur as an energy dissipation process in the earth s crust to which the tectonic energy is continuously input the crust self organizes into the critical state and the temporal and spatial fractal structure emerges naturally power law relations known in seismology are the expression of the critical state of the crust an soc model for earthquakes which explains the gutenberg richter relation the omori s formula of aftershocks and the fractal distribution of hypocenters is presented a new view of earthquake phenomena shares a common standpoint with other disciplines to study natural complex phenomena with a unified theory

evidence for chaotic fault interactions in the seismicity of the san andreas fault and nankai trough interactions between fault segments are one of the main sources of complexity in the seismicity of active tectonic regions such interactions are likely to influence the spatial and temporal patterns of earthquakes here we examine the dynamical behaviour introduced by fault interactions using a simple spring loaded slider block model with velocity weakening friction the model consists of two slider blocks coupled to each other and to a constant velocity driver by elastic springs for an asymmetric system in which the frictional forces on the two blocks are not equal the solutions exhibit chaotic behaviour the system s behaviour over a range of parameter values seems to be generally analogous to that of weakly coupled segments of an active fault we see similarities between our model simulations and observed patterns of seismicity on the south central san andreas fault in california and in the nankai trough along the coast of southwestern japan

feldspar composition as an efficient tool for tephra identification a case study from holocene and lateglacial lacustrine sequences jura france four volcanic ash layers have been identified in lateglacial and holocene sediments from three lakes in the jura mountains the vasset tephra and the nugere tephra chaine des puys the vedde ash icelandic and the laacher see tephra lst eifel some of these are invisible to the naked eye and have been detected by magnetic susceptibility measurements and x ray fluorescence analysis these layers are composed of rare glass shards in association with feldspars and pyroxenes in lacustrine carbonated sediment formations where glass shards are scarce and altered the geochemical analysis of feldspar composition appears to be an effective substitute tool for characterization of the tephra the identification of the middle lst c phase in our sites modifies the currently known spatial distribution of the lst eifel germany the identification of two tephras from the chaine des puys volcanic sources in jurassian sites the trachytic vasset tephra and the trachy andesitic nugere tephra provides new time markers for the early holocene and late allerod respectively thereby enhancing our knowledge of their distribution throughout western europe more generally these results confirm the major scientific value of lacustrine sequences from the jura region for cryptotephra research especially within late quaternary palaeoenvironmental studies

weathering processes in superficial deposits regolith and their influence on pedogenesis a case study in the swiss jura mountains abstract the last glacial period left a mantle of freshly reworked sediments covering the european landscape glacial periglacial fluvio glacial and aeolian dynamics enhanced transportation and mixing of materials generating new superficial deposits in which holocene soils developed these assorted surface sediments often differed from the underlying bedrock in their lithological composition and texture and were delimited by lithological discontinuities in the swiss jura mountains the mesozoic limestone bedrocks are covered by various superficial deposits moraines cover beds loess deposits cryoclasts etc which reduce or even suppress the influence of limestone on present day soil development in this context soils and their underlying bedrock no longer present a genetic continuity the nature and relationships between these deposits is studied within a toposequence of soils in terms of their mineralogical and geochemical compositions three main superficial deposits limestone bedrock clasts loess and non carbonate moraine are used as reference materials in order to characterize the complex mixing of sediments through the toposequence soils with limestone clasts undergo decarbonation and decalcification processes iron rich alpine loess deposits composed of fine silicate particles enhance brunification process in soils a non carbonate alpine moraine displays the most acidic conditions within the toposequence due to enhanced leaching clay and ions processes consequently the reworked surface sediments including limestone cryoclasts moraines and cover beds have a prevailing influence on pedogenesis compared to the hard underlying bedrock

palaeogeographical relationships between alpine and jura glaciers during the two last pleistocene glaciations abstract two main moraine complexes are usually defined in the northwestern alpine piedmont the external moraine complex emc dated to the penultimate glaciation riss sensu lato and the internal moraine complex imc dated to the last glaciation wurm until recently the prevalent concept was that these two complexes had been built by glaciers originating in the central alpine zone this paper presents a new palaeogeographical diagram based on mapping and petrographical studies of these two moraine complexes and especially on the relationships between alpine and jura tills we reach the following conclusions 1 1 the jura glaciers were independent of the alpine glaciers during the two last pleistocene glaciations 2 2 the jura mountains formed a topographical barrier blocking and modifying the alpine glacier advance towards the northwest with the result that during the wurmian glaciation the maximum elevation 1200 m a s l of the alpine glaciers on the eastern margin of the jura was too low to allow alpine ice to enter the jura and during the rissian glaciation the greater thickness of the alpine glaciers resulted in their penetration only into the lower marginal zone of the jura 3 3 thus in the studied area the central alps were not the only centre of ice dispersal during the two last pleistocene glaciations on the northwestern jura slopes the corresponding moraine complexes were mainly built by glaciers emanating from the central jura

geology mineralogy and genesis of the world class mahd adh dhahab epithermal au ag telluride deposit kingdom of saudi arabia abstract mahd adh dhahab polymetallic au telluride mine in kingdom of saudi arabia is a world class deposit the mineralization is hosted by subalkaline bimodal rhyolite basalt arc succession part of the late proterozoic mahd group the mineralized quartz veins mostly occupy fractures that formed in response to local folding of the mahd volcanic sedimentary sequence the ore predominantly consists of massive sulfides sphalerite chalcopyrite pyrite and galena and a diverse range of au ag tellurides sylvanite petzite hessite tetradymite tellurobismuthite and altaite gangue mineral assemblage comprises chlorite epidote sassurite and quartz tellurides occur as subhedral grains dispersed within chalcopyrite sphalerite and fe rich chlorite geological structural and mineralogical observations support a model invoking a multi stage process of mixed magmatic meteoric fluids and boiling as a cause of telluride precipitation the metal bearing magmatic fluid was exsolved from a crystallizing arc alkaline melt produced by partial melting of a subducted slab containing ocean floor sediments precipitation from solution occurs as a result of the condensation of te rich vapor phase and mixing of auriferous fluids with cooled oxygenated meteoric water at a shallow depth

phase relations among tellurides sulfides and oxides pt ii applications to telluride bearing ore deposits data on telluride bearing mineral assemblages from various types of ore deposits are compiled and interpreted in terms of the prevailing fugacities of te 2 s 2 and the temperature during deposition in the majority of hydrothermal deposits the appearance of tellurides after initial deposition of sulfides reflects an increase in the f sub te 2 f sub s 2 ratio most likely due to input of h 2 te from a magmatic source in some vein deposits such as boulder county colorado initial deposition of native tellurium is followed by deposition of minerals with progressively lower tellurium content indicating a decrease in f sub te 2 over the course of telluride deposition this trend may reflect local isolation of early formed minerals from the hydrothermal fluids and or progressive depletion of tellurium at the source ore minerals in other deposits such as mahd adh dhahab saudi arabia reveal systematic temporal or spatial variations in mineralogy that are attributed to introduction of a tellurium rich fluid into a preexisting sulfide assemblage and subsequent buffering of f sub te 2 and f sub s 2 by reactions such as 2pbs te 2 2pbte s 2 this buffering may exert considerable control on vein minerals such as the presence and relative abundance of gold and calaverite and the presence or absence of native tellurium

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

statistical model for the stick slip behaviour of faults summary inspired by an earlier work by smalley turcotte solla 1985 in this paper we consider a fault consisting of large sets of asperities with a statistical distribution of strength it is argued that the principle of equal load sharing between asperities inside a segment is necessary to account for the stick slip behaviour this principle is responsible for amplifying or damping the effective probability for the displacement of crustal blocks the antecedents of this idea in the seismological literature are commented on

petrological mineralogical fluid inclusion and stable isotope studies of the gies gold silver telluride deposit judith mountains montana the gies gold silver telluride deposit judith mountains montana occurs in steeply dipping quartz veins near the contact of late cretaceous to paleocene alkaline porphyritic intrusions quartz monzonite and syenite stocks and tinguaite dikes and sedimentary rocks shale sandstone conglomerate limestone and dolomite of middle cambrian to late paleocene age trace element geochemistry suggests that these intrusions were possibly derived from the shallowly dipping subducting farallon plate lithosphere or the overlying asthenospheric mantle vein related alteration is variable and does not extend more than 100 m away from veins potassic alteration and silicification are most closely associated with telluride mineralization the vein mineralogy is complex and consists of at least 36 minerals including two unknown possibly new minerals and six tellurides four stages of vein mineralization are recognized in the gies deposit the dominant mineral assemblages are i quartz pyrite roscoelite carbonates ii quartz pyrite base metal sulfides carbonates minor tellurides roscoelite iii quartz tellurides pyrite roscoelite base metal sulfides sulfosalts and iv sulfides sulfosalts native gold fluid inclusion studies of quartz from stages i ii and iii yield homogenization temperatures of 270 degrees to 319 degrees c mean 293 degrees or 10 degrees c 222 degrees to 282 degrees c mean 256 degrees or 9 degrees c and 195 degrees to 250 degrees c mean 220 degrees or 13 degrees c respectively assuming hydrostatic pressure a 5 degrees c correction due to pressure yields mean trapping temperatures of approximately 300 degrees 260 degrees and 225 degrees c respectively for stages i ii and iii salinities of primary fluid inclusions in all three quartz stages range from 5 7 to 8 0 wt percent nacl equiv isotopic studies show that delta 34 s values between 1 0 to 3 1 per mil for vein sulfides are most consistent with a magmatic origin oxygen isotope values of quartz in stages i ii and iii range from 13 1 to 18 1 per mil whereas values for feldspar in unaltered alkaline intrusions range from 7 1 to 9 8 per mil feldspar in altered alkaline intrusions from 7 3 to 9 8 per mil and a single sample of stage iii kaolinite is 7 9 per mil values of delta 18 o water computed from quartz and fluid inclusion trapping temperatures for stage i ii and iii fluids are 5 9 to 9 4 per mil 6 4 to 8 7 per mil and 3 6 to 6 2 per mil respectively a delta 18 o value of 3 3 per mil for fluid in equilibrium with stage iii kaolinite agrees well with values derived from fluids in equilibrium with stage iii quartz hydrogen isotope values of stage ii roscoelite stage iii kaolinite and fluid inclusions in stage i ii and iii quartz range from 115 to 78 per mil whereas fluids in equilibrium with these minerals range from 115 to 88 per mil oxygen and hydrogen isotope evidence suggests that gold telluride mineralization precipitated by conductive cooling in response to increased mixing of evolved meteoric water with magmatic fluids concomitant with a decrease in temperature from stage i through stage iv are decreases in ph f sub s 2 and f sub o 2 and increases in f sub te 2 and vanadium content of the ore fluid geologic and mass balance calculations are consistent with a low water rock ratio 0 1 and indicate that magmatic fluids and many of the ore forming components e g au ag te v s have possibly been derived from a buried intrusion e g tinguaite or carbonatite at approximately 59 ma

snowmelt infiltration and storage within a karstic environment vers chez le brandt switzerland summary even though karstic aquifers are important freshwater resources and frequently occur in mountainous areas recharge processes related to snowmelt have received little attention thus far given the context of climate change where alterations to seasonal snow patterns are anticipated and the often strong coupling between recharge and discharge in karst aquifers this research area is of great importance therefore we investigated how snowmelt water transits through the vadose and phreatic zone of a karst aquifer this was accomplished by evaluating the relationships between meteorological data soil water content vadose zone flow in a cave 53 m below ground and aquifer discharge time series data indicate that the quantity and duration of meltwater input at the soil surface influences flow and storage within the soil and epikarst prolonged periods of snowmelt promote perched storage in surficial soils and encourage surficial lateral flow to preferential flow paths thus in karstic watersheds overlain by crystalline loess a typical pedologic and lithologic pairing in central europe and parts of north america soils can serve as the dominant mechanism impeding infiltration and promoting shallow lateral flow further hydrograph analysis of vadose zone flow and aquifer discharge suggests that storage associated with shallow soils is the dominant source of discharge at time scales of up to several weeks after melt events while phreatic storage becomes import during prolonged periods without input soils can moderate karst aquifer dynamics and play a more governing role on karst aquifer storage and discharge than previously credited overall this signifies that a fundamental understanding of soil structure and distribution is critical when assessing recharge to karstic aquifers particularly in cold regions

sliding with cavity formation we present a model for the determination of a sliding law in the presence of sub glacial cavitation this law determines the basal stress at a clean ice bedrock interf ace in terms of the velocity and effective pressure the method is based on an exact solut ion of the nye kamb linearly viscous sliding problem with cavities and uses ideas of lliboutry 979 to construct via re norma lization methods an approximate law for gene ral bedrock form we show that for a bedrock whose spectrum has a power law behaviour one obtains a sliding law which gives the basal shear stress proportional to a power of the velocity and to a power of the effective pressure the effect of subgl acial cavitation on the drainage system is exam ined using recent ideas of kamb for sufficiently high velocities drainage through a r6thlisberger tunnel system is unstable and drai nage takes place through the linked system of cavities this leads to a reduction of the effective pressure and by taking account of this one can rewrite the sliding law in terms of st ress and velocity only this sliding law can be multi v alued and it is suggested that this unde rlies the dynamic phenomenon of surges

a model of propagating brittle failure in heterogeneous media i consider a nonelastodynamic model for the propagation of brittle failure in a heterogeneously stressed medium numerical simulation shows a power law distribution of failure sizes with a slope not far different from the size distribution of seismic events the time history of calculated failure activity is not consistent with observed seismic behavior and some explanations and implications are discussed

some metallogenic features of gold and copper deposits related to alkaline rocks and consequences for exploration porphyry copper gold skarn copper gold sediment hosted carlin style gold breccia pipe low sulphidation epithermal gold pluton related mesothermal or orogenic gold vein and volcanogenic massive sulphide deposits associated with alkaline rocks are commonly broadly similar to those hosted by their calc alkaline counterparts in contrast porphyry molybdenum gold deposits are confined to alkaline igneous centres alkaline suites are notably deficient in high sulphidation epithermal gold deposits and even in the advanced argillic lithocaps which host them this is surprising given that the required oxidised sulphur species are seemingly more abundant than in calc alkaline igneous centres highly efficient buffering of acidic fluid by metasomatised alkaline rocks may offer a viable explanation all types of intrusion related zinc deposits also appear to be poorly developed in alkaline provinces the characteristics of several gold and copper deposits associated with alkaline rocks including the giant porgera cripple creek ladolam olympic dam and phalaborwa examples are judged to diverge appreciably from their most closely related deposit types rendering them arguably unique most of these aberrant mineralisation styles may be due to variations in magmatic fluid compositional and liberation characteristics consequent upon the extreme diversity of ore related alkaline magmas most types of gold and copper deposits developed in calc alkaline provinces also constitute exploration targets in and around alkaline igneous centres although porphyry copper gold and low sulphidation epithermal gold deposits are considered to possess the greatest potential perhaps of even greater interest however is the possibility of encountering unconventional giant gold and copper deposits which lack closely analogous examples if already defined aberrant deposits are truly unique then exploration designed specifically to detect additional examples is pointless furthermore exploration for new unique deposits is difficult because their defining geological parameters are unknown alkaline rocks within or behind calc alkaline arcs at convergent plate boundaries probably offer the greatest exploration potential although anorogenic intracontinental extensional settings should not be ignored

the interpretation of the b and the b0 values and its implications on the regional deformation of the crust summary after reviewing the model and the interpretation of the negative power laws which represent the statistical distributions of the linear dimension of faults l and of the stress drops p of the earthquakes it is seen that the coefficient of the law log m0 m increases with m for smaller m it is verified that the parameters l and p of california earthquakes are independent and also it is suggested that one may consider a fractal dimension of earthquakes associated with p it is shown how these statistical distributions may allow distribution of slips in the seismic regions to be inferred where all the slips occur approximately in the same horizontal direction from the density distribution of the length of the faults it is found that in california 50 per cent of the regional displacement is due to the faults with linear lengths larger than 63 per cent of the maximum linear length of the faults similar results are obtained using the seismic moment m0 or the magnitude m instead of l in these cases however the density distribution of p is also needed for the exact computation of the displacement assuming that in california the regional displacement has been 5 cm yr 1 as measured with ground observations and space techniques it is tentatively estimated that the displacement due to earthquakes with m0 larger than 1027 1 may be as large as 4 2 cm yr 1 and that a cumulative displacement of at least 170 cm due to earthquakes with m0 larger than 1027 1 may have not been released since the great 1906 san francisco earthquake it is finally discussed how the variation in the density distribution of stress drops may be a precursor to earthquakes

the 2009 l aquila central italy seismic sequence as a chaotic process abstract in this paper we demonstrate that the seismic sequence of foreshocks culminating with the recent m w 6 3 main shock on april 6 2009 in l aquila central italy evolved as a chaotic process to do this we apply a nonlinear retrospective prediction to this seismic sequence and look at the temporal behaviour of the error between predicted and actual occurrence of the main shock when gradually increasing parts of the sequence are considered this is a generalisation of the typical nonlinear approach which is quite powerful to detect chaos in relatively short time series the method of prediction is based on the accelerated strain release asr analysis in time and on the nonlinear forecasting approach in a reconstructed phase space we find that i the temporal decay of the prediction error is consistent with an exponential function with a time constant of about 10 days and ii at around 6 days before the main shock asr analysis is quite powerful for anticipating the time of occurrence with an uncertainty of about a day due to its retrospective characteristics the latter result could be affected by changes on some a priori parameters used in the application of the asr technique however we consider these findings together with those obtained from the phase space analysis to be strong evidence that the studied sequence of foreshocks was produced by a physical process dominated by a significant chaotic component characterised by a k entropy 1 of about 0 1 day 1 this result could have important implications for the predictability of the possible main shock for those seismic sequences showing analogous nonlinear chaotic properties

silver and silver bearing minerals at the um samiuki volcanogenic massive sulphide deposit eastern desert egypt the um samiuki zn cu pb ag mineralisation south eastern desert egypt is hosted by felsic volcanic rocks which form part of the 712 ma old east west trending shadli volcanic belt two major occurrences of massive sulphides are present at the top of rhyolitic breccia in the western and eastern mine areas in each occurrence a bornite bearing zone is overlain by a pyrite chalcopyrite bearing zone and underlain by a disseminated cu depleted zone in the massive sulphide ore sphalerite chalcopyrite pyrite galena bornite and tetrahedrite tennantite are major minerals whereas arsenopyrite pyrrhotite molybdenite and magnetite are accessory phases covellite and digenite are common secondary minerals bornite tetrahedrite tennantite and covellite contain high amounts of silver averages of 1 97 1 39 and 1 82 wt respectively based on mineralogical balance calculations bornite and covellite accommodate 80 of silver in the um samiuki deposit ag was incorporated in the crystal structure of the early crystallised copper sulphides and sulphosalts and silver minerals the temperature sequential precipitation of the fluids and the structure of the crystallising phases control the distribution of silver post depositional deformation and metamorphic processes caused liberation remobilisation and redeposition of silver within the massive sulphides

first results of cosmogenic dated pre last glaciation erratics from the montoz area jura mountains switzerland the jura mountains are a perialpine chain bending from the sw to the nw of switzerland alpine ice reached only marginal areas of this chain during the last glacial maximum lgm but remaining erratic boulders of alpine origin indicate older glaciations of unknown age tentatively correlated either with the classical rissian or with the most extensive glaciation presented here are the first results of dating these pre lgm boulders by using cosmogenic radionuclides 10be and noble gases 21ne both data sets are in good agreement within 1 error with radionuclide apparent exposure ages ranging from 60 to 107 ka and noble gas apparent ages from 73 to 123 ka considering the importance of erosion on older boulders the age of the erratics corresponds most probably to marine isotope stage 6 these results are encouraging for further studies on pre lgm erratic boulders in the mid latitudes

premonitory spreading of seismicity over the faults network in southern california precursor accord 1 we establish a connection between geometry of the faults network in a region and seismicity preceding the strong earthquakes in the intermediate term timescale of years previous studies of observed and computer simulated seismicity demonstrated that strong earthquakes are preceded in that timescale by the rise of seismic activity in a lower magnitude range here we explore a complementary phenomenon spreading of activity over the fault network this phenomenon is depicted by the seismicity pattern accord defined as a simultaneous rise of seismicity in a sufficiently large number of fault zones hence its name pattern accord has been found recently in synthetic seismicity generated by the colliding cascades cc model the present study demonstrates this pattern in observed seismicity of southern california we applied to observations a prediction algorithm based on the pattern accord scaled to the target magnitude 7 5 the pattern accord emerges within a few years before each of the three largest earthquakes in southern california kern county 1952 landers 1992 and hector mine 1999 and at no other time scaled to the target magnitude interval from 6 5 to 7 4 the pattern accord precedes six out of nine earthquakes the duration of alarms in both cases is about 30 of the time considered we repeated prediction with different combinations of adjustable numerical parameters of the algorithm summing up the success and error scores on an error diagram this numerical experiment shows that the prediction results are stable under moderate variations of adjustable parameters the final test would be as always an advance prediction the pattern accord has a simple physical explanation connected with equilibrium of the crustal blocks system under the impact of tectonic driving forces at the same time accord is a manifestation of a broader phenomenon premonitory increase of earthquakes correlation range the latter phenomenon was found for the first time in the cc model although it was hypothesized by one of the authors much earlier

estimating present day displacement fields and tectonic deformation in active mountain belts an example from the chartreuse massif and the southern jura mountains western alps abstract determination of relative movements between the alpine foreland and the external crystalline massif is a key point for the understanding of the present day tectonics of the western alps in this study we try to test the continuity of the present day tectonics with the mio pliocene deformation in particular we will test if the present day displacements are localized along the thrusts of the jura mountains or along a blind thrust in the bas dauphine molasse basin definition of relative movements is achieved by several methods including a comparison of two high precision leveling networks to estimate vertical displacements horizontal deformation measurements performed by triangulation triangulation and triangulation gps comparison in situ stress measurements performed in the different tectonic units and geomorphologic observations that constrain the location and the magnitude of the quaternary deformation comparison of leveling data demonstrates 1 an uplift of the southern bas dauphine molasse basin relative to its northern part 0 8 mm year also revealed by geomorphologic analysis 2 a significant uplift of the most external jurassian anticlines 0 8 to 2 mm year also recorded by the deformation of a paleo river bed and 3 an important uplift up to 2 mm year of the subalpine massifs the horizontal strain estimated from comparison of horizontal geodetic data triangulation gps shows 1 a nw se directed shortening between the eastern chartreuse massif and the bas dauphine molasses basin approximately 3 mm year 2 an e w directed shortening in the jura mountains approximately 4 3 mm year and 3 a dextral strike slip motion consistent with focal mechanisms along a nne ssw direction between the eastern chartreuse massif and the eastern belledonne massif these data reveal a present day strain partitioning between the belledonne external crystalline massif and the bas dauphine molasses basin the westward motion of the subalpine massifs is partitioned along two southern jurassian thrust folds and a dextral nne ssw strike slip shear zone between the chartreuse massif and the belledonne massif this strain partitioning is also accompanied by a stress partitioning between the alpine foreland and the external crystalline massifs

high resolution seismic stratigraphy of late quaternary fill of lake annecy northwestern alps evolution from glacial to interglacial sedimentary processes abstract lake annecy is a peri alpine lake of glacial origin remnant of the last glaciation the lake basin accumulated over 150 m of sediment since the last glacial maximum a dense grid of high resolution seismic data acquired during a 1993 sparker survey revealed the glacial and post glacial sedimentary infill the depth and morphology of the wurm erosion surface and penetrated the riss wurm interglacial deposits as deep as the underlying riss erosion surface this paper focuses on the interpretation of the high resolution seismic facies of the infilling sediments of the lake basin in correlation with the results of the annecy core the quality and density of the seismic data allow in this case detailed analysis of the seismic facies in their three dimensional organisation and permit reliable interpretation in terms of depositional process and palaeo environmental setting the study reveals that the geometry and seismic facies of the infilling deposits are controlled essentially by the basin morphology and the characteristics of the sediment supply the sediment supply to the lake changes throughout the deglaciation from subglacial drainage to proglacial meltwater streams to alluvial streams and finally to the present day interglacial condition where authigenic sedimentation prevails the depositional patterns change accordingly from chaotic outwash deposits and glacio lacustrine muds at the base over axially aggrading lacustrine fans prograding alluvial fan deltas at the lake margins to finally a drape of lacustrine chalk and marl the interpreted sedimentary environment and deduced character of the sediment source are used to reconstruct the changing palaeo environment in the catchment area

variations in architecture and cyclicity in fault bounded carbonate platforms early miocene red sea rift nw saudi arabia abstract the early miocene was a period of active rifting and carbonate platform development in the midyan peninsula nw saudi arabia however there is no published literature available dealing with the detailed characterization of the different carbonate platforms in this study area therefore this study aims to present new stratigraphic architectural models that illustrate the formation of different carbonate platforms in the region and the forcing mechanisms that likely drove their formation this study identified the following features formed during active rifting a a late aquitanian n4 fault block hangingwall dipslope carbonate ramp b a late burdigalian n7 n8 isolated normal fault controlled carbonate platform with associated slope deposits and c a late burdigalian n7 n8 attached fault bounded platform with reef buildups rimmed shelf developed on a footwall fault tip within a basin margin structural relay zone that formed coinciding with the second stage of rifting variations in cyclicity have been observed within the internal stratigraphic architecture of each platform and also between platforms high resolution sequence stratigraphic analysis shows to be parasequences the smallest depositional packages metre scale cycles within the platforms the hangingwall dipslope carbonate ramp and the attached platform demonstrate aggradational progradational parasequence stacking patterns these locations appear to have been more sensitive to eustatic cyclicities despite the active tectonic setting the isolated fault controlled carbonate platform reveals disorganized stratal geometries in both platform top and slope facies suggesting a more complex interplay of rates of tectonic uplift and subsidence variation in carbonate productivity and resedimentation of carbonates such that any sea level cyclicity is obscure this study explores the interplay between different forcing mechanisms in the evolution of carbonate platforms in active extensional tectonic regions characterization of detailed parasequence scale internal architecture allows the spatial variation in syn depositional relative base level changes to be inferred and is critical for understanding the development of rift basin carbonate platforms such concepts may be useful for the prediction of subsurface facies relationships beyond interwell areas in hydrocarbon exploration and reservoir modeling activities

fractal dimension of fault systems in japan fractal structure in rock fracture geometry at various scales based on fault maps whether or not the fracture geometry of rocks is self similar was examined by using a box counting algorithm the statistical self similarity fractal structure of the fault fracture systems holds well at the scale of about 2 to 20 km the fractal dimension in japan varied from 1 05 to 1 60 the fractal dimension is about 1 5 1 6 at the central part of the japan arc and decreases with distance from the center at a smaller scale the fractal structure also holds well in the rock fracture geometry the fractal dimension of the north izu peninsula fault system branching faults is 1 49 at the scale of 0 625 to 10 km the fractal dimension of rock fracture geometry at the scale order of 10 1 to 10 2 meters is about 1 49 1 61 the upper limit of the fractal dimension of rock fracture geometry is about 1 6 judging from the estimation of fractal dimension on actual fracture geometry of rocks this value may impose a restraint on modeling of faulting and the fracture process of rocks

asperity distribution and percolation as fundamentals of an earthquake cycle abstract a seismic cycle model is proposed based on the existence of an asperity space strength distribution along the fault plane and the applicability of the percolation theory to earthquakes as suggested by vrancea seismotectonic data two seismic regions somewhat decoupled are emphasized in the lower lithosphere roughly between 80 and 110 km and between 120 and 170 km depth and an asperity magnitude quasi independent dimension of 0 3 0 4 km is determined for small to moderate earthquakes accordingly two concepts are introduced 1 the active zone a distinct fault region able to generate a major earthquake by percolation and characterized by a specific background seismicity total area and maximum possible magnitude 2 the asperity cell an elementary local stress inhomogeneity of an active zone generating weak to moderate events percolation requires the presence of a critical stress free surface 44 of the active zone area the model explains the non linearity of the frequency magnitude relationship and enables the estimation of the major earthquake magnitude domain in each zone the computed maximum possible magnitudes are mw 7 6 and mw 7 8 respectively in agreement with historical data a complex form of the recurrence period of earthquakes in the major magnitude domain is determined ranging from about 40 to 100 years irrespective of the seismic zone it follows that the seismic activity per unit area is invariant in both zones this result is considered to be a consequence of an intrinsic material property the scale invariance of the fragmentation process in the lithospheric material different aspects related to the discrete structure of the active zone and the fractal dimension of faulting are also discussed from the point of view of this model

high resolution seismic stratigraphy of glacial to interglacial fill of a deep glacigenic lake lake le bourget northwestern alps france abstract lake le bourget is a deep peri alpine glacial lake originating from the last glacial the wurm the lake has amassed over 250 m of sediment since the last glacial maximum two seismic sparker surveys on the lake revealed the glacial and post glacial sedimentary infill the depth and the morphology of the wurm erosion surface and penetrated the riss wurm interglacial deposits as deep as the underlying riss erosion surface the density of the seismic grid and the high resolution of the data even at greater depths allowed a detailed study of the sedimentary processes and of their evolution throughout the deglaciation five main seismic facies characterise the basin fill they are interpreted as glacial deposits glacio lacustrine sediments proglacial lacustrine fans alluvial fan deltas and authigenic lacustrine drape these occur as a suite of deposits associated with the major lake tributaries and are the result of major changes in sediment supply and style of discharge into the lake the three dimensional facies associations within the basin fill document the history of the basin and its catchment area since the onset of the deglaciation

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

first evidence of in situ eemian sediments on the high plateau of evian northern alps france implications for the chronology of the last glaciation a 2 m profile of organic sediments interbedded between two tills was taken from the evian high plateau at hameau de maravant 860 m a s l haute savoie western alps france pollen plant macrofossils and insect remains were used to reconstruct the local palaeoenvironment which consisted of a moss and carex mire surrounded by a dense abies and picea mixed forest pollen and macrofossil data indicate that this peat layer was deposited at the end of the eemian interglacial the lower till should therefore be assigned to the penultimate glaciation and the upper till to the maximum extent of the rhone glacier during the wurm a comparison of the results with previous studies carried out in the geneva area and other alpine valleys has yielded a detailed reconstruction of the past fluctuations of the rhone glacier 1 a first early lower wurmian advance reaching the region around lyon 2 a subsequent retreat of ice 3 a second moderate readvance restricted to the surroundings of geneva followed by a final deglaciation a continuous lacustrine sequence has been obtained from the nearby roseire peat bog 890 m a s l pollen and radiometric results show the establishment of a former palaeolake during the upper pleniglacial probably before ca 22 450 850 cal years bp thus implying that the high plateau was ice free from that time these new data appear to suggest that the maximal extension of the rhone glacier occurred prior to the last glacial maximum ois 2 and according to a well documented geomorphological context probably during the lower wurmian pleniglacial

earthquake size frequency relations from an analytical stochastic rupture model an analytical stochastic model of earthquake rupture is presented although the general formulation makes no a priori self similarity assumption scale independent earthquake size frequency esf statistics emerge from the interaction between fault strength heterogeneity and rupture mechanics the model also gives theoretical derivations for scale dependent esf statistics including gradual frequency saturation for small earthquakes and a continuum of possible transitions in the statistics of large earthquakes a model fault is characterized as a surface composed of a large number of asperities defined as small discrete contact surfaces of finite strength an earthquake rupture grows via successive asperity breaking subevents the probability of rupture to a certain size earthquake or greater is the total product of incremental rupture growth probabilities these are governed by a new asperity failure probability distribution derived as a mixture of weibull distributions by including fracture mechanics the resulting mixture distribution characterized by the scale and shape parameters and is written in terms of the rupture size the important difference between the mixture distribution and the weibull distribution is that the mixture results in power law esf statistics self similarity occurs when material heterogeneity and rupture mechanics are mutually tuned to give 1 frequency saturation for small earthquakes is shown to be a simple consequence of a general aseismic nucleation process the nucleation magnitude m defines the roll off point in esf statistics that occurs when the area of seismic rupture equals the area of precursory aseismic rupture growth by fitting the model to the parkfield earthquake data set m 0 9 is obtained the change in esf scaling for the transition from moderate to large earthquakes depends on the changes in stress at the growing rupture front the northern california earthquake data center seismicity data set is fitted for a transition at magnitude m 5 with 0 4 and 0 75 this result indicates that the change in the esf relation associated with the transition from moderate to large earthquakes in california and nevada is caused by surface rupture accompanied by partial width and slip saturation

physical and chemical properties of the epidote minerals an introduction epidote minerals are known since the 18th century but at that time the greenish to dark colored varieties were termed actinolite or schorl and not distinguished from the minerals to which these names apply today hauy defined the mineral species and introduced the name epidote in 1801 whereas werner in 1805 used the term pistacite quoted from hintze 1897 epidote is derived from greek epidosis to increase because the base of the rhombohedral prism has one side larger than the other and pistacite refers to its green color all references for names after luschen 1979 blackburn and dennen 1997 weinschenk 1896 proposed the name clinozoisite from its monoclinic symmetry and zoisite like composition for those monoclinic members of the epidote family that are fe poor optically positive and have low refractive indices and birefringence zoisite was probably confused with tremolite until the beginning of the 19th century in 1804 siegmund zois baron von edelstein 1747 1819 an austrian sponsor of mineral collections found and described a new mineral in a handspecimen from the saualpe mountains in carinthia that was named zoisite by werner hauy 1822 interpreted zoisite as a variety of epidote and included it in his epidote spezies weiss 1820 presented a theory of the epidote system and also discussed crystal morphological features of the epidote minerals weiss 1828 rammelsberg 1856 studied the relationship between epidote and zoisite and presented a compilation of chemical analyses of zoisite he already noticed that the relative concentrations of di tri and tetravalent cations are identical in zoisite and epidote but that the fe content in zoisite about 2 3 5 wt fe2o3 is generally less than in epidote about 9 12 wt fe2o3 piemontite see bonazzi and menchetti 2004 was probably first described in 1758 by cronstedt

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

a chlorite solid solution geothermometer the los azufres mexico geothermal system chlorite constitutes a major hydrothermal alteration product of metamorphism of andesites in the active geothermal system of los azufres mexico electron microprobe analyses performed on a set of crystals from each sample show wide variations in composition correlation coefficients among chemical constituents were calculated it is shown that the tetrahedral charge is positively correlated with the octahedral vacancy and negatively with the iron content and there is almost no correlation with the octahedral aluminium and magnesium content a procedure is proposed to select end members and substitution vectors and to give a general formula for these chlorites

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

fractal geometry in the san andreas fault system it has been noted that the spatial distribution of earthquakes and the mode of strain release in the san andreas fault system is related to the complexity of fault geometry because of their rough appearance over many length scales faults can be regarded as fractal surfaces direct estimates of fractal dimension d of portions of the san andreas fault system between the northern gabilan range and the salton sea including the postulated extent of the great 1857 fort tejon earthquake are obtained from measured fault lengths analogous to the lengths of coastlines as discussed by mandelbrot regions characterized by complicated fault geometry are associated with larger values of d based on fault traces mapped at a scale of 1 750 000 d is 1 3 for this reach of the fault defined as a 30 km wide band about a main fault trace for that part near parkfield which could be associated with the nucleation of the 1857 earthquake d is 1 1 at this same scale d is 1 4 for the san andreas and related faults near san bernardino where the 1857 rupture stopped compared to 1 2 for the san andreas san juan fault segments near the point of arrest of the 1966 parkfield earthquake at finer map scales 1 24 000 and 1 62 500 critical lengths of 500 m and 1 km are identified which might relate to the extent of off san andreas fault offsets the critical lengths also suggest that fault geometry is not self similar if this fractal geometry persists through the seismic cycle it may be possible to use a quantitative measure of complexity to explain the occurrence of great and characteristic earthquakes along a given reach of fault

the timing of glacier advances in the northern european alps based on surface exposure dating with cosmogenic 10be 26al 36cl and 21ne

a renormalization group approach to the stick slip behavior of faults we treat a fault as an array of asperities with a prescribed statistical distribution of strengths when an asperity fails the stress on the failed asperity is transferred to one or more adjacent asperities for a linear array the stress is transferred to a single adjacent asperity and for a two dimensional array to three adjacent asperities using a renormalization group rg method we investigate the properties of a scale invariant hierarchical model for the stochastic growth of fault breaks through induced failure by stress transfer an extrapolation to arbitrarily large scales shows the existence of a critical applied stress at which the solutions bifurcate at stresses less than the critical stress virtually no asperities fail on a large scale and the fault is locked above the critical stress asperity failure cascades away from the nucleus of failure we interpret this catastrophic failure as an earthquake and it corresponds to the transition from stick to slip behavior on the fault thus the stick slip behavior of most faults can be attributed to the distribution of asperities on the fault we propose our stochastic mechanism as an alternative to the traditional hypotheses for the stick slip behavior of faults a major advantage of our approach is the inclusion of scale invariance thus the observed frequency magnitude relation for seismicity is a natural consequence of our basic hypothesis

aseismic slip in earthquake nucleation and self similarity evidence from parkfield california aseismic slip microearthquakes and moderate earthquakes all take place along the san andreas fault at parkfield california in this letter we discuss the relationship of these slip mechanisms by establishing and modelling the local microearthquake size frequency distribution by examining the effect of background noise on earthquake event detection we show that the distribution is complete for m 0 3 unlike the gutenberg richter law the distribution begins with a relatively small number of very small events further the scaling relation of the distribution changes continuously with event size noting that many parkfield aseismic slip or creep events have moments equivalent to the smaller microearthquakes we show that the nucleation of microearthquakes by this type of slip can account for the size frequency distribution such a model does not require a lower limit to either earthquake or creep event size rather it suggests that at parkfield a transition from creep dominated slip to earthquake dominated slip takes place in the range of moments equivalent to magnitudes close to m 0 9 this is well above the m 0 3 detection limit of the seismic network but right at the limit of current near surface strain instruments

a physical model predicting instability of rock slopes with locked segments along a potential slip surface abstract better understanding the evolutionary mechanism of landslides is very important to predict their occurrence based on firm scientific grounds the stability of a rock slope is often dominated by one or more locked segments along a potential slip surface with a large bearing capacity to resist instability we propose three preliminary categories for locked segments and develop a physical model for predicting the instability of rock slopes with locked segments by coupling a one dimensional renormalization group model with a strain softening constitutive model based on the weibull distribution we found that the ratio of the strain at the peak strength point of a locked segment to the strain at its volume dilation point is exclusively dependent on the weibull shape parameter m and is approximately constant at 1 48 the accelerating displacement of the slope can be observed from the volume dilation point of the locked segment due to unstable fracture propagation the physical model for slopes with multiple locked segments is only related to the displacement corresponding to the volume dilation point of the first locked segment and the number of locked segments applying this model to two typical cases the yanchihe rockslide in china and the wedge rockslide in libby dam usa the results are in agreement with field records this work will help to better understand the failure mechanism of slopes with locked segments and may provide guidelines for disaster mitigation and prevention

strong motion seismology strong motion seismology is concerned with earthquake ground motion in the amplitude range that poses the threat of human injury or property damage because the occurrence of strong motion cannot be predicted in advance and because the time between significant events at any one place may range from tens to thousands of years strong motion data is recorded on triggered instruments that typically must be maintained in readiness for years between periods of significant recording as a consequence the strong motion data set is sparse because of the engineering need for estimates of future ground motion the scope of the field of strong motion seismology encompasses seismic source theory and any other aspect of seismology that can provide insights helpful in making the best possible estimates given the limited data this relationship with the rest of seismology is a reciprocal one in that strong motion data gives perhaps the best information available on earthquake source processes

introduction to special section on physical processes in geodynamics on may 16 and 17 1992 a meeting was held at cornell university as part of activities to honor donald l turcotte on the occasion of his 60th birthday which actually occurred on april 22 1992 the papers in the following special section are a result of that meeting which included invited presentations and posters representing the diverse areas of geology and geophysics to which donald turcotte has contributed three of the papers deal with aspects of mantle convection a c fowler addresses the problem of initiation of subduction by extending boundary layer theory to a viscoplastic rheology turcotte and oxburgh 1967 pioneered such studies by showing how boundary layer theory could be used to describe the dependence of geophysical observables such as heat flux on distance from a midocean ridge or age of the oceanic crust d w sparks et al use a model of three dimensional convection beneath a segmented ridge to explore how buoyancy effects and melt production beneath a spreading center influence ridge parallel variations in crustal thickness and gravity magma migration and the dynamics of midocean ridges have been major focuses of donald turcotte s research in papers dating back to 1978 e g turcotte and ahern 1978 ahern and turcotte 1979 turcotte 1982a kenyon and turcotte 1987 g a glatzmaier and g schubert calculate models of three dimensional two layer mantle convection in a spherical shell and compare with whole layer spherical shell three dimensional convection models these models represent the end member states of a spectrum of possible modes of mantle convection turcotte and oxburgh 1972 oxburgh and turcotte 1978 turcotte 1979a silver et al 1988

stable isotope evidence for a magmatic component in fumarole condensates from augustine volcano cook inlet alaska u s a abstract d h and 18 o 16 o ratios have been determined for fumarole condensates from augustine volcano an active calc alkaline stratovolcano in lower cook inlet alaska the isotopic data for the condensates form a linear d 18 o array from low temperature fluids d 150 18 o 19 to high temperature 450 c fluids collected at the volcano summit which are enriched in both d and 18 o d 35 18 o 3 5 several lines of evidence suggest that the d and 18 o rich condensates likely are magmatic fluids released into the hydrothermal system during and immediately after the 1976 eruption prior to 1976 the augustine hydrothermal system was dominated completely by local meteoric waters between 1976 and 1982 fumarole condensates were observed to be variable mixtures of the magmatic fluid and meteoric water with the proportion of the former systematically decreasing as the hydrothermal system cooled following the 1976 eruption

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

a geodetic sign of the critical point of stress strain state at a plate boundary i found a curious oscillating behavior in secular variations of relative ground level in the tokai district central japan the period of the oscillation is becoming shorter acceleratedly with time which thereby predicts the existence of a critical point in near future the data variations can successfully be expressed by the general equation describing the near critical point behavior based on the discrete scale invariance theory the critical point may be interpreted as the occurrence of the maximum sized fracture i e the biggest earthquake in a given tectonic environment the time predicted is 2004 7 1 7 year

new quantitative displacement criteria for slope deformation process from the onset of the accelerating creep to brittle rupture and final failure abstract two quantitative displacement criteria for slope deformation were deduced through the combination of a one dimensional renormalization group model and the strain softening constitutive model of geological materials the criteria can be used to understand the mechanical process from the onset of the accelerating creep on a slope through brittle rupture to the final failure and landslides the study showed that according to the first criterion the displacement ratio between the brittle rupture and the onset of the accelerating creep is approximately 1 48 which can be used to predict the brittle rupture of a slope with continuous progressive deformation the second displacement criterion shows that the displacement ratio between the final failure and the onset of the accelerating creep is approximately 2 59 which can be used to predict the occurrence of the ultimate disaster thus the critical displacement prior to the failure of the slope can be predicted using a time series of monitoring displacement data the methodology proposed in this study was validated using data from two well known landslides the vajont landslide in italy and the xintan landslide in china the results verify the applicability of this method

search for direct empirical spatial correlation signatures of the critical triggering earthquake model summary we propose a new test of the critical earthquake model based on the hypothesis that precursory earthquakes are actors that create fluctuations in the stress field which exhibit an increasing correlation length as the critical large event becomes imminent our approach constitutes an attempt to build a more physically based time dependent indicator cumulative scalar stress function in the spirit of but improving on the cumulative benioff strain used in previous works documenting the phenomenon of accelerating seismicity using a simplified scalar space and time dependent viscoelastic green s function in a two layer model of the earth s lithosphere we compute spatiotemporal pseudo stress fluctuations induced by a series of events before four of the largest recent shocks in southern california through an appropriate spatial wavelet transform we then estimate the contribution of each event in the series to the correlation properties of the simplified pseudo stress field around the location of the mainshock at different scales this allows us to define a cumulative scalar pseudo stress function which reveals neither an acceleration of stress storage at the epicentre of the mainshock nor an increase of the spatial stress stress correlation length similar to those observed previously for the cumulative benioff strain the earthquakes we studied are thus either simple witnesses of a large scale tectonic organization or are simply unrelated and or the green s function describing interactions between earthquakes has a significantly longer range than predicted for standard viscoelastic media used here