finite fault source study of the great 1994 deep bolivia earthquake we apply an empirical green s function method to recordings of teleseismic body waves from the june 9 1994 deep focus bolivia earthquake the far field source time functions reveal that rupture occurred on a sub horizontal fault plane the main rupture began some 25 km to the east of the hypocenter consists of three large subevents and covers a total area of about 60 40 km the static stress drop is quite large more than 150 mpa and the obtained rupture velocity is less than 2 km sec while the total dimensions of the earthquake are large compared to estimates of the width of a metastable olivine wedge at this depth the moment release is confined largely to a narrow band along an ew axis and may be compatible with phase transitions within a thickened slab core

estimation of source rupture process and strong ground motion simulation of the 2002 denali alaska earthquake a m w 7 9 inland crustal earthquake occurred in the denali fault system alaska on 3 november 2002 at 22 12 utc in this study we estimated the source process of the 2002 denali earthquake by a multiple time window linear kinematic waveform inversion using strong motion and global positioning system gps measured static displacement data the obtained source model could explain both the observed strong motion waveforms and gps measured static displacements large slips on the fault plane are observed at approximately 80 90 km and 150 200 km east from the hypocenter these features are consistent with the observed surface rupture distribution and the other inversion results obtained using teleseismic body waves we also observed some portions of the whole fault with a local rupture propagation velocity of more than 4 0 km sec that exceeded the shear wave velocity of the source region the relation between the rupture area and seismic moment of this earthquake seems to follow the bilinear l model scaling rather than the self similar source scaling model the combined area of asperities is somewhat smaller than that expected from the empirical scaling relationship with seismic moments developed by compiling inverted source models finally we conducted a forward ground motion simulation using the finite difference method to estimate the influence of the heterogeneous source process obtained here on the spatial distribution of strong ground motions the calculated ground motions are relatively large above and around the large slip areas and also in the region east of the fault area because of the forward directivity effect of unilateral rupture propagation

controls of tor formation cairngorm mountains scotland tors occur in many granitic landscapes and provide opportunities to better understand differential weathering we assess tor formation in the cairngorm mountains scotland by examining correlation

stochastic simulation of radionuclide migration in discretely fractured rock near the aspo hard rock laboratory we study the migration of sorbing tracers through crystalline rock by combining relatively simple transport measures with particle tracking in a discrete fracture network the rock volume is on a 1

rupture characteristics of the deep bolivian earthquake of 9 june 1994 and the mechanism of deep focus earthquakes the m w 8 3 deep 636 kilometers bolivian earthquake of 9 june 1994 was the largest deep focus earthquake ever recorded seismic data from permanent stations plus portable instruments in south america show that rupture occurred on a horizontal plane and extended at least 30 by 50 kilometers rupture proceeded at 1 to 3 kilometers per second along the down dip azimuth of the slab and penetrated through more than a third of the slab thickness this extent is more than three times that expected for a metastable wedge of olivine at the core of the slab and thus appears to be incompatible with an origin by transformational faulting these large events may instead represent slip on preserved zones of weakness established in oceanic lithosphere at the earth s surface

source parameters for small events associated with the 1986 north palm springs california earthquake determined using empirical green functions using small events as empirical green functions which include path site and instrument effects on the p waveforms source parameters were estimated for 25 ml 3 4 to 4 4 events associated with the 1986 north palm springs earthquake the static stress drops ranged from 3 to 80 bars for moments of 0 7 to 11 1021 dyne cm there was a spatial pattern to the stress drops of the aftershocks which showed increasing values along the fault plane toward the northwest compared to relatively low values near the hypocenter of the mainshock the highest values were outside the main area of slip and are believed to reflect a loaded area of the fault that still has an higher level of stress which was not released during the main shock the relatively high stress drop of a preshock in 1983 located close to the hypocenter of the main shock is also interpreted as evidence that stress drops of magnitude 3 and 4 events can be used as indicators of the stress level in a particular area

sorbing tracer experiments in a crystalline rock fracture at aspo sweden 3 effect of microscale heterogeneity we study the impact of microscale 10 3 10 2 m heterogeneity in material and structural properties on sorbing tracer transport in a single crystalline fracture of the true 1 tests mesoscale

source characteristics of large deep earthquakes constraint on the faulting mechanism at great depths 1 source parameters for eight large deep earthquakes are inferred from broadband data of the global seismograph network we completed an unprecedented data set composed of 14 largest deep earthquakes mw ranging from 7 0 to 8 3 from six different subduction zones studied with identical source parameter inversion methods the study confirms earlier findings that deep earthquake source properties vary with the temperature of the subducting plate events in cold slabs show high aftershock activity high rupture velocity and high seismic efficiency in contrast earthquakes in warm slabs generally have low aftershock productivity low rupture velocity and low seismic efficiency however the 23 june 1991 argentina event has source properties that are rather characteristic for earthquakes in cold slabs and that differ from those of other large south american events we suggest that two types of deep earthquakes occur in south america and we interpret these results in the context of the shear instability model for the mechanism of deep earthquakes in this model shear failure occurs through a thermal runaway mechanism within a shear zone at great depth and low seismic efficiency might indicate significant energy dissipation due to heating and possible melt production the 1991 argentina event located in a pocket of deep seismicity within the slab core may represent a shear instability with little melting as would be the case for large deep earthquakes in cold subduction zones whereas the other known south american large deep events such as 1963 peru 1970 colombia and 1994 bolivia are located in relatively aseismic regions and may involve significant melting within warmer regions of the slab

thermal elastic stresses and the criticality of the continental crust 1 heating or cooling can lead to high stresses in rocks due to the different thermal elastic properties of minerals in the upper 4 km of the crust such internal stresses might cause fracturing yet it is unclear if thermal elasticity contributes significantly to critical stresses and failure deeper in earth s continental crust where ductile creep causes stress relaxation we combined a heating experiment conducted in a synchrotron microtomograph advanced photon source usa with numerical simulations to calculate the grain scale stress field in granite generated by slow burial we find that deviatoric stresses 100 mpa can be stored during burial with relaxation times from 100 s to 1000 s ka even in the ductile crust hence grain scale thermal elastic stresses may serve as nuclei for instabilities thus rendering the continental crust close to criticality

the 1996 june 17 flores sea and 1994 march 9 fiji tonga earthquakes source processes and deep earthquake mechanisms summary source parameters of the 1996 flores sea and 1994 fiji tonga deep earthquakes are derived from teleseismic body waves recorded by the global seismic network of broad band seismograph stations both events consisted of several subevents models to approximate the spatial and temporal extent of the source process include point sources propagating point sources and a combination of these for the flores sea event rupture lasted about 23 s and terminated some 70 km east of the nucleation point as inferred from the duration of p wave pulses in agreement with the findings reported by other investigators our preferred model suggests bilateral rupture propagation it consists of four point sources that have variable double couple radiation patterns and source time histories and explains well the large compensated linear vector dipole clvd component inferred from the harvard centroid moment tensor cmt solution the main moment release in the fiji tonga event lasted only about 15 s our best model consists of two point sources with a total moment release of 2 8 1020 n m rupture propagated subhorizontally from the nucleation point to the north the termination of rupture was located about 40 km to the north of rupture initiation the inferred velocity of moment release in the flores sea and fiji tonga events was 3 5 km s 1 a value which is higher than that inferred for the great bolivian earthquake of june 1994 other derived source parameters static stress drop radiated seismic energy and maximum seismic efficiency are also significantly different from those inferred for the 1994 bolivian event suggesting that deep earthquake processes do not follow an easily detectable common mechanism

comparison between connected and overall porosity of thermally stressed granites abstract the structural evolution of four granites heated from 20 to 700 c was examined after cooling the granites have four typical initial structures which can be sub divided into two groups rocks with high connected porosity comprising cracks with low aspect ratio and alteration pores type a pores and a few cracks type b or cracks type c and rocks with low connected porosity with cracks type d the connected porosity was measured by mercury injection and the total porosity by x ray computerized tomography at low temperature t the connected porosity decreases with increasing temperature particularly for the material with high crack density and connected porosity a and b the total porosity increases for b c and d and decreases for the material with low aspect ratio cracks a above 300 c both porosities increase the data show that the thermal history of a granite can be decomposed into two phases in the first stage the connected porosity decreases with increasing temperature cracks are initiated at low temperature and they form unconnected networks in the second stage the connected and total porosities increase the previously initiated cracks form a connected network by opening and they interact with newly created cracks

changes in compressional and shear wave velocities and dynamic moduli during operation of a hot dry rock geothermal system compressional and shear wave velocities measured during cross well seismic surveys are found to decrease during operation of a hot dry rock geothermal system the relative p and s wave velocity decrease is very close to values predicted by o connell and budiansky 1974 who modeled velocities in rocks containing fluid saturated and dry cracks because our data fit their model quite well we attribute the velocity decrease to an increased density of fluid filled fractures in the reservoir fracture density parameters of o connell and budiansky range as high as 0 365 near the main heat transfer areas of the geothermal reservoir the dynamic shear and young s modulus are significantly lower near the principal heat transfer surfaces but the bulk modulus is largely unaffected these observations suggest that the velocity differences are caused by fully saturated fractures we demonstrate that the fractures inferred by this survey may have lengths as large as 70 cm these fractures may have been caused by shear failure microcracking associated with thermal drawdown or thermal stress cracking

parallelepiped cooling joint and anisotropy of p wave velocity in the takidani granitoid japan alps correlations between anisotropy of joint systems and physical rock properties particularly p wave velocities were investigated characterization of fracture networks in the takidani granitoid japan alps was obtained by field observation and laboratory measurement of p wave velocities three preferred joint sets with no shear displacement were identified and their directions change and spacing progressively increases from the margin to the center of the pluton the azimuthal variation of p wave velocity vp is minimal perpendicular to one of the preferred joint orientations the orientation of microcracks observed at grain scale and joints at outcrop scale show a good correlation vp and the preferred orientation of microcracks are in harmony with anisotropy of the joint system allowing reconstruction of the joint structure in the takidani granitoid thus we were able to evaluate joint anisotropy in terms of vp anisotropy

granitic magma transport by fracture propagation granitic magmas commonly ascend tens of kilometres from their source terranes to upper crustal emplacement levels or to the earth s surface apart from its obvious bearing on the interpretation of the geology and geochemistry of felsic igneous rocks the magma ascent mechanism critically affects any modelling of the metamorphic evolution of the upper lithosphere as well as its rheology we propose that in general granitic magmas ascend via propagating fractures as dykes in extremely short time periods long distance diapiric transport of granitoid magmas through crustal sections is not viable on thermal or mechanical grounds and there is an apparent total absence of field evidence for diapiric rise of such magmas even in supposed type localities neither the shapes nor internal or external characteristics of granitic plutons necessarily reveal anything about the transport of their precursor magmas these are purely arrival phenomena dictated by local structure kinematics and stress states based on existing numerical treatments of the problem we show that granitic magmas are apparently sufficiently inviscid to travel through fractures to high crustal levels without suffering thermal death by freezing for example a 2000 km3 granitic batholith can be inflated by a 1 km 3m 20 km deep dyke system in less than 900 years the model proposed has numerous far reaching petrological and rheological consequences some of which are outlined

the opening of the gulf of california near loreto baja california mexico from basin and range extension to transtensional tectonics abstract detailed structural field analyses of faults and fractures have led to the reconstruction of the tectonic evolution of the loreto region baja california mexico during the opening of the gulf of california three main tectonic events have been recognized i formation of large scale radial structures along the future main gulf escarpment here interpreted as associated with emplacement of magmatic bodies at shallow levels during the beginning of extension processes in early middle miocene ii ne sw extension basin and range event active since 15 ma producing nw se normal dip slip faults in the oligo miocene volcaniclastic basement and indicating high extension rates iii transtensional tectonics recorded especially in the plio quaternary sediments and associated with the activation of nw se dextral strike slip faults and n s normal faults the tectonic structures related to the basin and range extension are sealed by the plio quaternary sediments of the loreto basin and by the volcanics of the mencenares volcanic complex a huge volcanic field interfingering with the sedimentary succession of the basin

a regionalized upper mantle rum seismic model seismic velocity heterogeneity in the earth s mantle is strongly concentrated near its top the shallow heterogeneity of the mantle correlates strongly with surface tectonics we use these observations as constraints of a tomographic experiment aimed at building a regionalized upper mantle rum reference model we use a select set of teleseismic travel times to minimize the mapping of mislocation into structure the data selection emphasizes the robustness of individual picks the form of the rum model is a set of velocity profiles as functions of depth through the upper mantle for each of the different tectonic provinces of earth together the profiles constitute a three dimensional model which incorporates considerable structural detail but is described by only 90 parameters and has only about 22 degrees of freedom this is achieved by irregularly sampling a detailed regionalization of the globe by detailed mapping of subducted lithosphere in the mantle as defined by seismicity and by combining these structures in an irregular grid in which bookkeeping is efficiently handled the resulting rum model includes subducting slabs as sharp fast features in the upper mantle old continents are fast young oceans are slow models have been derived for both compressional and shear velocity the rum model is designed to represent as much of upper mantle heterogeneity as seen by body wave travel times as possible with a simple model it can be useful as a reference model for individual tectonic regions travel times are efficiently generated for the rum model mislocations of explosions of known location are significantly reduced when corrections for the rum model are applied to travel time residuals for a spherically symmetrical earth model

deep earthquake rupture histories determined by global stacking of broadband p waveforms 1 we conduct a systematic investigation of time histories of moment release in deep earthquakes whose physical mechanism remains unknown we have constructed source time functions stfs of 111 large deep earthquakes depth 100 km and mw 6 4 by stacking p waveforms from broadband seismograms recorded by the global seismographic network aligning and stacking waveforms cancels noise and allows us to identify the rupture initiation and termination times accurately each stf is scaled to a reference moment of 1019 n m using the duration moment relation m01 3 in order to investigate depth dependence of the stfs we bin them into three depth ranges 100 350 km 350 550 km and deeper than 550 km based on physical properties of the mantle and the distribution of the data we infer a change in character near 550 km earthquakes deeper than about 550 km are shorter have simpler time functions and are more uniform in their characteristics further we find longer than expected scaled durations and greater complexity in the 350 550 km depth range the scaled durations of the 350 550 km earthquakes do not decrease with depth as 1 vs instead possessing a slightly longer average scaled duration than those 100 350 km deep we further categorize the earthquakes by subduction zone and find a similar depth dependence within individual zones finally the events that have achieved highest moment rate in the first 1 2 s after initiation tend to be deeper and or larger events the latter suggesting that dynamic rupture propagation affects the final size of the earthquake the depth dependence of duration and complexity suggests more complicated rupture histories between 350 and 550 km and a possible change in the physical mechanism of rupture at about 550 km

thermal stress evolution in cooling pluton environments of different geometries thermoelastic displacement potentials and fast fourier transforms can be combined to rapidly calculate the thermal stresses in 2 d for plutons that cool by conduction first temperature distributions over time are computed by solving the diffusion equation thermal stresses are then obtained using thermoelastic stress potentials this method can be applied to a broad range of pluton geometries and initial conditions and requires far less computation time than finite difference or finite element analyses results of 2 d analyses show that pluton geometry strongly influences the thermal stresses that occur in a cooling pluton thermal stresses of several tens of mpa arise during cooling and are highest at the corners or where the intrusion is thin the most tensile stress is greater inside a pluton than in the host rock moreover the orientation of the most tensile stress in a cooling pluton generally changes over time this could result in multiple fracture sets which would significantly affect the mechanical and hydraulic behavior of a pluton

thermal stress cracking in granite we have developed a comprehensive experimental capability to study thermally induced microfractures in rock we count acoustic emissions and measure compressional wave velocities while a sample is heated to a maximum temperature of 300 c under confining pressures up to 55 mpa after a heating cycle we measure crack porosity and crack compressibility we count the cracks under an sem sorting them by grain boundary and intragranular types and by mineral pair occurrence our observations reveal that 1 significant thermal cracking occurs in granites heated above 200 or 250 c under 28 and 55 mpa and above 100 c in granites heated under 7 mpa 2 most newly created thermal cracks close at pressures below 40 mpa 1 5 km depth 3 grain boundaries between quartz grains or between quartz and another mineral are preferentially cracked 4 the threshold temperature for acoustic emissions is a positive linear function of pressure 5 total acoustic emission counts in westerly granite heated to 300 c are slightly lower under 55 than 28 mpa confining pressure and are substantially lower under 28 than 7 mpa 6 the compressional velocity decreases 22 as westerly granite is heated to 300 c at 7 mpa 15 at 28 mpa and 10 at 55 mpa and 7 greater hysteresis in compressional velocities occurs in samples heated at lower pressures the acoustic emission counts in westerly granite during heating show one or more peaks of activity as a function of temperature with more peaks at lower pressures we interpret this result to mean that additional crack populations are able to open at lower confining pressures the curves of acoustic emission count rates can be fit by summing one to three gaussian density functions

stress enhanced tensile fractures in elliptical clast in conglomerate abstract mode i fractures within the elliptical clasts from archaean age chitradurga schist belt dharwar craton south india are analyzed to decipher the paleostress condition these fractures are characterized as systematic steeply dipping and parallel to each other the analysis is performed in three steps 1 fixing and transforming of the coordinate systems to describe the elliptic domain under far field stress 2 proposing suitable complex potentials for inclusion and matrix followed by the plane strain solution for elliptical domain to fractured clasts 3 obtaining the state of stresses readily inside the inclusion we conclude that the mode i fractures in elliptical clasts are developed due to far field stress enhancement inside the rigid clasts at shallow depth the deduced paleostress conditions also fit very well with the orientation and sense of previously revealed regional tectonics we infer that the amplification of stresses in the rigid inclusions is function of elastic moduli of the clast and matrix ellipticity of the clasts and remote stresses we interpret that the enhanced intra clast differential stresses are more for the clast with higher aspect ratio thus is more susceptible for tensile fracturing than the lower one for a constant applied far field stresses we also estimate the minimum breakage loads as well as minimum depths required for the clasts of different aspect ratio to develop tensile fractures in them we imply that fractured elliptical clasts can be regarded as an important paleostress indicator

granite tectonics revisited insights from comparison of k feldspar shape fabric anisotropy of magnetic susceptibility ams and brittle fractures in the jizera granite bohemian massif in the jizera granite of the krkonose jizera plutonic complex northern bohemian massif contrasting patterns of magmatic k feldspar fabrics and brittle fractures characterize different structural levels of the pluton the uppermost exposed level at 800 1 100 m above sea level is dominated by flat foliation that overprints two steep foliations in contrast k feldspar shape fabric in an underground tunnel 660 m above sea level shows complex variations in orientation and intensity magnetic fabric carried by coaxial contributions of biotite magnetite and maghemite is homogeneous along the examined section of the tunnel and is decoupled from the k feldspar fabric the jizera granite is crosscut by two regional sets of subvertical fractures ne sw and nw se and by near surface exfoliation joints the multiple fabrics are inferred to reflect a complex magmatic strain history at different structural levels of the pluton bearing little or no relationship to the fracture network in contrast to the original concept of hans cloos granite tectonics we conclude that no simple genetic relationship exists between fabrics and fractures in plutons an alternative classification of fractures in plutons thus should avoid relationships to magmatic fabrics and should instead consist of cooling syntectonic uplift and post uplift fractures

body wave inversion of the 1970 and 1963 south american large deep focus earthquakes a comprehensive set of teleseismic waveforms from two south american deep focus earthquakes of the predigital era the 1970 colombia mw 8 1 and 1963 peru bolivia mw 7 7 events are inverted for source mechanism seismic moment rupture history and centroid depth the p and sh wave inversion of the colombia event confirms previous work indicating that rupture occurred on a plane that dips steeply west rupture direction paralleled the trend of the wadati benioff zone we decompose the source into subevents based on a source time function which shows two major moment release pulses separated by 20 s the first subevent is located near the initiation point at a depth of 630 km the main moment release was located 70 km to the southeast and 20 km shallower rupture subsequently propagated farther southeast the source time function has an initial subevent accounting for 30 of the moment release of the entire event whereas the long period centroid moment tensor cmt analysis russakoff et al 1997 has the initial subevent yielding 50 the high angle nodal plane rotated 15 clockwise during the rupture explaining the large compensated linear vector dipole clvd component inferred from cmt solutions individual subevents have large clvd and compressive isotropic components a full moment tensor inversion of the colombia and 1994 bolivia events suggests that the initial subevents might contain a large non double couple ndc component for the 1963 peru bolivia event using p waves rupture propagated nnw for a distance of 70 km parallel to the high angle nodal plane and the trend of the wadati benioff zone the focal mechanism changed dramatically after the second subevent causing a very large ndc component both events together with the 1994 bolivia earthquake have a precursor separated in space and time from the main rupture and show rupture velocities varying between 3 and 4 km s between subevents with 2 0 km s on average for the entire event low seismic efficiencies and rupture velocities support a highly dissipative temperature dependent rupture mechanism for large deep focus south american earthquakes compared with events in cold subducting slabs

contaminant advection and spreading in a fractured permeable formation part 2 numerical simulation abstract in a companion paper referred to as paper i the transport of contaminants in a fractured permeable formation was characterized and formulated it was shown that advective movements in the fracture flow and the permeable block flow as well as mixing between these two types of flow are the most significant factors affecting contaminant transport and spreading in such formations the basic formulation and the closed form analytical solution developed in paper i invite the use of numerical schemes for a further analysis of the contaminant transport processes in the framework of the present paper this target is achieved a numerical solution scheme stemming from the conceptual model of paper i is developed simulations are performed by considering the various properties of the discrete fracture flow and the permeable block flow the results of the present study indicate that fractured permeable formations can be represented by single continuum models provided that a sufficiently large number of sectors is included in the representative elementary volume rev the minimum number of sectors depends on the ratio between the specific discharge of the permeable block flow and that imposed by the fracture presence this ratio is named the mobility number the larger the mobility number the smaller the number of sectors which should be incorporated in the rev equivalent properties of the continuum representing the fractured permeable formation such as the equivalent porosity and dispersivity are determined and evaluated

low radiation efficiency of the intermediate depth earthquakes in the japan subduction zone robust determination of earthquake source parameters over a continuous depth range is central to inferring rupture mechanisms dominant at different depths we employed a cluster event method to constrain the source parameters as well as along path attenuation for earthquakes over 0 150 km depths and 4 orders of seismic moments in the japan subduction zone we found that corner frequency and stress drop increase with depth whereas the radiated energy scaled by seismic moment declines with depth slightly as a result the radiation efficiency exhibits a notable deficit for events deeper than 60 km together these suggest an increased energy dissipation during faulting in ductile deformation regime consistent with shear heating instability as an important faulting mechanism for intermediate depth earthquakes

structural setting of the candelaria fe oxide cu au deposit chilean andes 27 30 s the candelaria fe oxide cu au ore deposit lies within the thermal aureole of the lower cretaceous magmatic arc plutonic suite in the candelaria punta del cobre district atacama region northern chile 27 30 s economic mineralization is present within a synplutonic ductile shear zone candelaria shear zone containing foliated and potassically altered volcanic and volcaniclastic rocks of the punta del cobre formation in the candelaria shear zone there was a complex interplay in space and time between ductile and brittle deformation during mineralization at high structural levels brittle moderately to steeply dipping extensional faults curve downward into gently dipping ductilely deformed rocks in the shear zone textural and structural characteristics of the ore and the deformed rocks indicate that the dilation of the sulfide bearing vein systems occurred at the same time as ductile deformation and implies that ductile brittle cycling occurred in a cooling hydrothermal system in the thermal aureole of the arc plutonic rocks the la brea and the san gregorio plutonic complexes are exposed in the plutonic arc immediately adjacent to the candelaria orebody the intrusions are interpreted to be flat lying tabular bodies emplaced by roof uplift floor depression mechanisms during regional extensional deformation an 40 ar 39 ar age of 119 6 1 2 ma and five k ar ages between 123 and 117 ma were obtained for the la brea pluton and an 40 ar 39 ar age of 111 5 0 4 ma was obtained for the san gregorio plutonic complex 40 ar 39 ar ages of 111 0 1 4 and 110 7 1 6 ma obtained from syntectonic biotite from the candelaria shear zone are interpreted to be the age of the mineralization these are indistinguishable from the age of the san gregorio plutonic complex and therefore heat from this pluton could have promoted ductile deformation during emplacement of the orebody this result together with known isotopic similarities between candelaria ore and the plutonic rocks implies that the san gregorio plutonic complex was the most probable source of the mineralizing fluids at candelaria although the critical intrusive unit may not be exposed the ore deposit is located where a roof uplift fold in the side wall of the san gregorio plutonic complex provided a dilatational site which may have drawn hydrothermal fluids out of the adjacent fractionating magmas into a structural trap in the punta del cobre formation below the carbonate rocks of the chanarcillo group

a broadband p wave analysis of the large deep fiji island and bolivia earthquakes of 1994 the complex broadband p wave displacement recordings of the 570 km deep march 9 1994 mw 7 6 fiji island and the 660 km deep june 9 1994 mw 8 2 bolivia earthquakes are analyzed to estimate the spatial and temporal characteristics of their ruptures we model relative arrival times and amplitudes of coherent subevents in p waveforms and perform waveform analyses we resolve 1 short rupture durations relative to their seismic moments 12 and 40 s for the fiji and bolivia earthquakes respectively 2 small areas of main moment release for both earthquakes 30 40 km 3 high stress drops compared to shallow earthquakes with the stress drop of the bolivia event 283 mpa being significantly higher than the stress drop of the fiji event 26 mpa 4 small changes in mechanism up to 10 changes in fault plane orientation and 5 a steeply dipping rupture plane for the fiji earthquake and a shallowly dipping rupture plane for the bolivia earthquake details of the ruptures are difficult to resolve using teleseismic p waveforms

prediction of elastic moduli via crack density in pressurized and thermally stressed rock the elastic moduli of crystalline rocks show marked reductions when heated to high temperatures t even when subjected to confining pressure p this degradation of moduli has been attributed to the creation of new microcracks or opening of preexisting microcracks from thermal stresses due to differential thermal expansion between mineral grains a similar lowering of moduli is observed on depressurization of crystalline rock and is also thought to be due to microcrack opening a spherical inclusion model has been used to predict whether a given change in t or p will introduce a tensile crack between a mineral constituent and the rock matrix by using the principal thermal expansions and compressibilities of individual minerals and simplifying assumptions we are able to predict crack densities as a model rock is subjected to changes of p and t experimental crack densities for three granitic rocks a gabbro and two basalts are calculated from high temperature high pressure young s modulus data the predicted and inferred crack densities are then compared for these six rocks the results are dependent upon the p t path to which the rock is subjected and comparisons are for the case in which the rocks are heated only at maximum p and then decompressed isothermally considering the simplicity of the model we believe the comparisons are quite close for the three granitic rocks the model underestimates the crack densities of the quartz free gabbro and basalts

dispersion of regional body waves at 100 150 km depth beneath alaska in situ constraints on metamorphism of subducted crust phase delays at high frequencies are observed in body waves that travel in the alaska slab along its strike at 100 150 km depth the delays between 2 6 hz energy and the direct 0 5 1 hz arrival are 0 5 1 5 s for p waves and 1 5 4 s for s waves such dispersion suggests a waveguide structure that parallels the slab perhaps near its top a channel that is 2 6 km thick and 2 5 5 slower than surrounding mantle can explain the observations the thickness of the layer is comparable to that of subducted oceanic crust or somewhat thinner the layer may be crust that is slow at these depths the required velocity anomaly is too small to be due to a continuous layer of metastable gabbro yet too large to represent an eclogite layer it may indicate a mixture of the two or persistence of hydrated mineral assemblages to depth

analysis of some laboratory tracer runs in natural fissures tracer tests in natural fissures performed in the laboratory are analyzed by means of fitting two different models in the experiments sorbing and nonsorbing tracers were injected into a natural fissure running parallel to the axis of a drill core the models take into account advection dispersion diffusion into the rock matrix and sorption onto the surface of the fissure and on the microfissures inside the matrix for the second mechanism one of the models considers hydrodynamic dispersion while the other model assumes channeling dispersion the models take into account time delays in the inlet and outlet channels the dispersion characteristics and water residence time were determined from the experiments with nonsorbing tracers surface and volume sorption coefficients and data on diffusion into the rock matrix were determined for the sorbing tracers the results are compared with values independently determined in the laboratory good agreement was obtained using either model when these models are used for prediction of tracer transport over larger distances the results will depend on the model the model with channeling dispersion will show a greater dispersion than the model with hydrodynamic dispersion assuming constant dispersivity

an analysis of the influence of fracture geometry on mass transport in fractured media a stochastic modeling technique has been developed to investigate mass transport within a network of discrete fractures the fracture network is composed of two orthogonal fracture sets with fracture length location and aperture characterized by appropriate probability distributions emphasis is placed on understanding how fracture geometry influences mass transport within a network of discontinuous fractures the network is aligned in such a manner that one fracture set set one forms the dominant pathway for transport the primary role of the second fracture set is to provide connecting pathways between the discontinuous fractures of set one results suggest that mass transport can be described in terms of the directness of the connection between the upstream and downstream boundaries variations in fracture geometry which have the effect of increasing the probability that a relatively indirect or circuitous pathway exists through the network generally lead to an increase in both the mean and the standard deviation in the arrival time of various breakthrough fractions examples include a reduction in the number of fractures forming the set aligned with the direction of the hydraulic gradient or a decrease in the average length of fractures forming that set variations in fracture geometry which have the effect of increasing the probability that a relatively direct pathway will exist through the network have the opposite effect transport is sensitive to the variability in fracture aperture the connectivity of the fracture network is also shown to influence the magnitude of dispersive effects

a variable aperture fracture network model for flow and transport in fractured rocks a three dimensional variable aperture fracture network model for flow and transport in fractured rocks was developed the model generates both the network of fractures and the variable aperture distribution of individual fractures in the network before solving for the flow and transport of the whole network a library of single fracture permeabilities and particle transport residence time spectra is first established the spatially varying aperture field within an individual fracture plane is constructed by geostatistical methods then the flow pattern the fracture transmissivity and the residence times for transport of particles through each fracture are calculated the library of transmissivities and frequency distributions of residence times is used for all fractures in the network by a random selection procedure the solution of flow through the fracture network and the particle tracking calculation of solute transport for the whole network are derived from one side of the network to the other the model thus developed can handle flow and transport from the single fracture scale to the multiple fracture scale the single fracture part of the model is consistent with earlier laboratory tests and field observations the multiple fracture aspect of the model was verified in the constant aperture fracture limit with an earlier code the simulated breakthrough curves obtained from the model display dispersion on two different scales as has been reported from field experiments

linear response concept combining advection and limited rock matrix diffusion in a fracture network transport model this paper presents the conceptual and mathematical basis of a model for transport of nuclides in the geosphere between the near field of a radioactive waste repository and high conductivity fractures that are assumed to be closely connected to the biosphere the geosphere is modeled as a network of fractures that are mapped onto a network of channels the balance equations and boundary conditions on the scale of a single rectangular channel are given the effects of one dimensional matrix diffusion in addition to advection linear sorption in the fractures and the rock matrix and radioactive decay are considered a hierarchical linear response concept using laplace transformation techniques is developed for solution of the balance equations 1 on the scale of a channel network 2 in the individual channels and 3 in the rock matrix adjacent to the channels examples with unlimited and limited matrix diffusion and for additional rock layers are discussed

fractured micro granitoid enclaves a stress marker abstract systematic parallel and steeply dipping tensile fractures within rounded to sub rounded micro granitoid enclaves are analyzed to decipher the stress condition at chitradurga granite dharwar craton south india the study is performed in two steps 1 assessing the fracturing condition through thermo mechanical model as fractures in granite may be related to thermal stresses during its cooling or to tectonics stresses 2 performing the plane strain mechanical solution for circular rigid inclusions to fractured enclaves where rock mechanics concepts of fracturing are integrated with kinematic analysis we interpret that the parallel systematic fractures in the micro granitoid enclaves developed due to the stress amplification inside enclaves when the host pluton was at shallow depth of 2 4 km the derived paleostress orientation fits well with the orientation and sense of movement to the adjacent chitradurga shear zone the deduced paleostress conditions from fractured micro granitoid enclaves are also in a good agreement with the previously revealed regional tectonics we conclude that the fractured micro granitoid enclaves are reliable stress indicator

directivity analysis of the deep bolivian earthquake of june 9 1994 the june 9 1994 deep bolivian earthquake m w 8 3 d 636 km occurred on a nearly horizontal rupture plane with an approximate area of 2000 km 2 the rupture plane is constrained by directivity analysis of the p wave displacement pulses recorded at local regional and teleseismic distances the fact that there are local recordings of the displacement provides a strong constraint on the vertical extent of faulting which is less than 10 km the moment release had at least four distinct episodes or subevents the best overall explanation for the subevents is rupture which initiates on the western margin of the fault plane propagates to the east and then continues bilaterally along a 350 azimuth with most of the moment release occurring to the north the apparent rupture velocity between subevents is very low approximately 1 2 km s

fracture accommodated strain in the diamond joe stock arizona fractures filled with hydrothermal minerals form a dominantly radial pattern in the diamond joe stock these fractures record a portion of the deformation experienced by the pluton from the time that it was emplaced until it cooled to ambient conditions in individual outcrops fracture orientations are very consistant to within 10 where fractures cross k feldspar phenocrysts no shear offset is observed indicating that the fractures have opened by dilation we have measured the apertures of these veins and define a two dimensional deformation gradient matrix to characterize the uniaxial strain accommodated by each fracture we assume that each fracture represents one increment of strain and superimpose all increments in an individual outcrop to compute the fracture accommodated strain for that outcrop we calculate the orientation and magnitude of the principal strains for each outcrop as well as the area change accommodated by the fractures all of the outcrops have experienced a decrease in area that ranges from 5 a portion of this area change is interpreted as thermal contraction however in the central part of the pluton additional contraction is present in this portion of the pluton the amount of strain and area change correlates well with fracture abundance we interpret this additional contraction to result from volume changes associated with crystallization and or vapor exsolution during crystallization of the pluton

frictional melting during the rupture of the 1994 bolivian earthquake the source parameters of the 1994 bolivian earthquake magnitude m w 8 3 suggest that the maximum seismic efficiency was 0 036 and the minimum frictional stress was 550 bars thus the source process was dissipative which is consistent with the observed slow rupture speed only 20 of the locals wave velocity the amount of nonradiated energy produced during the bolivian rupture was comparable to or larger than the thermal energy of the 1980 mount st helens eruption and was sufficient to have melted a layer as thick as 31 centimeters once rupture was initiated melting could occur which reduces friction and promotes fault slip

seismological constraints on the mechanism of deep earthquakes temperature dependence of deep earthquake source properties abstract seismological observations are of vital importance for understanding the mechanism of deep earthquakes most of the seismological observables for earthquakes deeper than 300 km are similar to shallow earthquakes deep earthquakes clearly represent shear failure on a planar surface as shown by their double couple mechanisms deep earthquake aftershock sequences show temporal decay rates and magnitude frequency relations b values that are similar to shallow earthquakes with the aftershocks occurring preferentially along the mainshock fault planes in addition deep earthquake rupture velocities are similar to those of shallow earthquakes however there are also some observations that are clearly distinctive relative to shallow earthquakes stress drops of deep earthquakes show a large variation but are larger on average than shallow earthquakes different deep seismic zones show very different b values in contrast to shallow earthquakes which show similar b values worldwide in addition deep earthquakes show fewer aftershocks than shallow earthquakes a variety of observations suggest that deep earthquakes are highly sensitive to the temperature of the slab both deep earthquake b values and the rate of deep earthquake aftershock occurrence are inversely correlated with the temperature of the deep slabs suggesting that these factors are temperature controlled to an extent much greater than with shallow earthquakes large deep earthquakes in warm slabs show slower rupture velocities larger stress drops and lower seismic efficiencies than similar earthquakes in cold slabs the width of deep seismic zones is also probably temperature controlled but deep earthquake rupture can propagate outside the normal limits of benioff zone seismicity simple thermal models for the tonga slab near the 1994 deep earthquake suggest that the temperature at the rupture termination point was at least 200 c warmer than the temperature that limits smaller earthquakes in the slab these observations can be used to evaluate physical models for deep earthquakes including brittle slip along fluid weakened faults transformational faulting and thermal and perhaps melt lubricated shear instabilities it is difficult to explain the large fault widths of some deep earthquakes using a fluid weakening model since hydrated materials are expected in only a narrow depth zone at the top of the slab and the fault planes do not have the expected orientations for reactivated faults the lateral extent of the largest deep earthquakes cast doubt on the transformational faulting model in which events should be confined within a narrow metastable wedge seismological studies have also failed to find evidence for the existence of metastable olivine in slabs the temperature dependence of deep earthquakes argues in favor of a temperature activated phenomenon such as thermal shear instabilities and perhaps fault zone melting

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

rupture of the large mw 7 8 deep earthquake of 1973 beneath the japan sea with implications for seismogenesis the earthquake of 29 september 1973 beneath the western edge of japan sea is the largest deep earthquake along the western pacific m w 7 8 focal depth 575 km the source region is near the tip of the japan wadati benioff zone where a continuous belt of seismicity clearly defines a unique shallow dipping 30 slab down to depths about 600 km this unique geometry of slab predicts a limited vertical extent available for earthquake rupture in direct conflict with previous reports of a large subvertical fault for the 1973 earthquake using a comprehensive data set of nearly 20 p and sh waveforms recorded at teleseismic distances we investigate rupture associated with this event in some detail by inversion of waveforms in particular we use wave trains with all relevant depth phases pp sp and ss that are crucial for resolving the vertical extent of rupture in addition to a northward component of rupture as in previous reports we find clear evidence for a significant component of eastward rupture propagation that cannot fit within a subvertical north south striking nodal plane meanwhile all regions of major slip are at essentially the same depth thus the true fault plane appears subhorizontal with the entire region of slip extending only about 15 6 km across the slab9s thickness the spatio temporal distribution of slip is well explained by a simple circular rupture front propagating at a speed of 3 4 km sec a comparison among the largest deep earthquakes shows that most rupture planes are more or less dimensionally equal with high aspect ratios ranging approximately from 0 5 to 1 while some events have fairly restricted source regions others seem to extend more than 30 km into the thickness of the slabs

rupture characteristics of the 2005 tarapaca northern chile intermediate depth earthquake evidence for heterogeneous fluid distribution across the subducting oceanic plate 1 we examined the rupture of the 2005 tarapaca northern chile earthquake at about 110 km depth with respect to both kinematic and dynamic characteristics by using regional and teleseismic waveforms the earthquake has a downdip tensional focal mechanism the subhorizontal rupture is characterized by two patches of large slip and high stress drop which are aligned nearly in the east west direction being perpendicular to the direction of the chile trench rupture initiated in the eastern patch and then propagated to the western patch between the two patches there exists a region of nonpositive stress drop and high strength excess which can cause subshear rupture to propagate from the eastern to the western patches but radiates little seismic waves seismic radiation energy from this earthquake tends to be low which is consistent with the nonpositive stress drop and high strength excess between the two patches while the physical mechanism of intermediate depth earthquakes is still controversial current leading hypotheses are associated with dehydration within subducting plates the rupture characteristics of the tarapaca earthquake can be related to heterogeneous fluid distribution due to the dehydration the spatial separation and dominant stress of the two large slip patches agree with the characteristics of the previously reported double seismic zone beneath chile the two patches may be the manifestation of the double seismic zone where dehydration reactions can release fluid using a numerical simulation of 3 d dynamic rupture we have shown that weakening due to fluid can account for the rupture characteristics of the tarapaca earthquake

influence of temperature on the distribution of stress and displacement in a volcano a numerical approach a previously published geological model and numerical finite element simulation of a basaltic vollano is extended by introducing temperature dependent elastic parameters the geological model is composed of a shield with a central volcanic cone resting on oceanic crust the magma system consists of a 3 km deep upper reservoir from which rises a central column the model of the temperature field inside the volcano is based on geological observations and comprises 1 a hot zone 200 300 m thick around the magma system where temperature drops rapidly by conduction and 2 a cooler zone where temperature gently decreases by convection of circulating fluids the temperature dependent parameters the young modulus e the poisson coefficient v and the coefficient of linear thermal expansion of which the first two show a non linear variation with temperature introduce heterogeneity in the medium three zones with different mechanical behaviour are distinguished in the volcanic edifice shearing and strong deformation processes are prominent next to the magma system in the less rigid hot confined zone radial cracks are likely to be initiated in the central part of the volcano where tiffness increases and finally concentric vertical or outward dipping fissures are associated with horizontal extension towards the surface with cold and stiff matenal and a low state of thermal stress the results are used to propose a revised model of the internal structure of basaltic oceanic intraplate volcanoes

thermoelastic stresses with reference to scale and morphology of the earth s surface the variability of thermoelastic stresses at the earth s surface is investigated on different scales with a three dimensional numerical model energy transfer by heat conduction and radiation of sun atmosphere and earth s surface is regarded it is shown that thermoelastic stresses are considerably high so that they are able to assist faulting and thus force weathering of rocks their morphological distribution strongly depends on the spatial scale of the relief on large scales it is governed by the temperature distribution on small scales below a few meters the surface morphology plays the dominant part

rupture velocity estimation of large deep focus earthquakes surrounding japan 1 rupture velocity is an important source parameter which is often difficult to determine especially for deep focus earthquakes where there is usually limited near source information to help overcome this problem we developed a new method to estimate rupture velocities of deep focus earthquakes with better resolution we first carry out teleseismic p waveform inversions to determine slip distributions for a range of rupture velocities on the two nodal planes then forward modeling of regional data is performed using the slip distributions determined in the teleseismic inversions to estimate the rupture velocity using this method we attempted to determine the rupture velocities of large deep focus earthquakes surrounding japan which are well recorded on teleseismic and regional networks empirical green functions are used for both the teleseismic and regional analyses although it is difficult to determine the rupture velocity from only the teleseismic data the analyses including regional data show clear difference which can resolve the rupture velocity and fault geometry for three deep earthquakes we obtained rupture velocities of about 1 2 km s which correspond to 20 40 of the shear wave velocity and are much slower than typical values for shallow earthquakes

rupture process of the 1999 kocaeli turkey earthquake estimated from strong motion waveforms the multiple time window linear waveform inversion is applied to study the source process of the 1999 kocaeli turkey earthquake using strong motion data two peculiar observations characterize this event the first one is a conflicting observation of the long surface ruptures and short source duration resulting from the observed strong motion waveforms the second is an anomalously short s p time observed at a station skr considering its hypocentral distance a supershear rupture propagation ellsworth and celebi 1999 and the p wave triggering of an asperity anderson et al 2000 were both proposed to explain the record at skr our waveform inversion study is aimed to examine these possibilities in order to clarify the relation between the spatial distribution of the surface ruptures and coseismic slips we divide the assumed fault plane into three parts and look for the first time window front propagation velocity propagation velocity of triggering front of the first time window at each subfault in each part by performing numerous inversions changing the first time window front propagation velocity separately in each part and selecting the best first time window propagation velocities that give largest variance reduction at the same time appropriate smoothness of spatiotemporal slip distribution is searched for by performing inversions with different strength of smoothing constraints against the observational equations and judging the relative appropriateness of inversion results in terms of the akaike s bayesian information criterion the best source model is characterized by an asperity that is about 35 km east of the epicenter and near a segment boundary at sapanca lake triggered by the first time window front with 5 8 km sec close to p wave velocity the time progression of the rupture suggests a scenario where a p wave arriving from the hypocenter or somewhere around the hypocenter triggered the second largest asperity near the junction of the segments at sapanca lake which is a preferable interpretation the first time window propagation velocities west of the hypocenter and east of skr are expected to be 3 0 km sec manuscript received 20 august 2000

p wave velocity structure inside the subducting pacific plate beneath the japan region abstract little is known of the internal structure of the subducting pacific plate previous studies suggest the existence of an intermediate boundary within the subducting slab the low density of seismological stations in oceanic regions has prevented high resolution studies recently seismological stations in japan have accumulated digitally recorded seismograms beneath the kanto region central japan the pacific plate is subducting with a high inclination compared with that of the tohoku region northern japan the ray paths from deep earthquakes to seismological stations are expected to penetrate more inner parts of the subducting plate this region is suitable to resolve the velocity structure within the plate in this study travel time residuals and seismograms of the deep focus earthquakes that occurred beneath the kinki region southern japan are used to constrain various parameters related to the velocity structure model within the slab the seismograms of deep focus earthquakes at the geographically restricted stations located in the kanto region central japan show a remarkable high frequency later arrival of the p wave the later arrival was studied and recognized as the reflected wave at the intermediate boundary inside the plate the velocity structure within the plate is also studied our best fit model has a velocity of jeffreys bullen j b model plus 1 5 in the upper layer and j b plus 2 5 in the lower layer

radiation efficiency and apparent stress of small earthquakes in a south african gold mine 1 nine triaxial borehole accelerometers were installed within 200 m along a 2650 m deep haulage tunnel in the mponeng gold mine in south africa we analyzed the high sample rate recordings 15 khz to determine source parameters of small earthquakes in the mine to study the source processes we carried out multiple time window waveform inversions for five larger events 0 8 m 1 4 that occurred within 150 m of the stations from the inversion results we could determine the fault planes for all five events and estimate the range of rupture speed we can conclude that rupture speeds were faster than 2 5 km s 65 of the shear wave velocity the radiation efficiency is written as a function of the rupture speed and becomes greater with increasing rupture speed this study indicates that radiation efficiencies of small earthquakes in the south african gold mine are almost equal to those of larger natural earthquakes we also calculated radiated seismic energies and static stress drops of the five events to investigate their apparent stresses apparent stresses of the five events were from 1 to 10 mpa and static stress drops were 1 to 20 mpa we found that the source parameters rupture speed apparent stress radiation efficiency and static stress drop did not largely differ from values for larger natural earthquakes this suggests that the dynamic rupture processes of these small events were similar to those of the larger natural earthquakes

rapid rupture and complex faulting of the may 12 1990 sakhalin deep earthquake analysis of regional and teleseismic broadband data a large m w 7 1 deep earthquake 606 km occurred beneath sakhalin island about 200 km away from the nearest well defined wadati benioff zone in southwestern kurile moment tensors obtained in various frequency bands using the teleseismic data show that the sakhalin event produced double couple radiation over a very broadband frequency range and the p waveforms appear simple at most teleseismic stations 30 90 o on the other hand many broadband seismometers successfully recorded the seismic waves at regional distances 3 25 o in japan showing two significant arrivals in the p wave seismograms whose time interval is about 3 s

the shift of the α β transition temperature of quartz associated with the thermal expansion of granite at high pressure abstract measurements are presented of volume changes in granite during room temperature compression to 100 200 and 300 mpa confining pressure followed by temperature increase to 900 c comparison with thermal expansion and compressibility data for the constituent minerals allows changes in porosity to be estimated under confining pressure porosity is found to decrease with heating to 200 c through expansion of the minerals into cracks which are thought to be related to the geological cooling history of the rock between 200 c and 840 c porosity increases as a result of differential thermal expansion of the constituent minerals but crack opening is increasingly suppressed at higher confining pressures extrapolation of the results indicates that differential thermal expansion can no longer cause crack opening in dry granite at confining pressures in excess of 450 mpa the quartz transition temperature in granite is marked by a kink in the thermal expansion curve of the rock and it is found to increase by 60 c 70 c per 100 mpa confining pressure as opposed to the published value of 26 c per 100 mpa for single crystals of quartz equations are presented which allow calculation of the effects of confining pressure and temperature on the stresses and displacements in and around a spherical inclusion embedded in a matrix of different elasticity and thermal expansion the theory together with a simple self consistent model for granite accounts semiquantitatively for the observations of thermal expansion and the effect of confining pressure thereon and for the observed transition temperatures for quartz in granite

discrete fracture network interpretation of field tracer migration in sparsely fractured rock field tracer migration in sparsely fractured rock is analyzed with a discrete fracture network model that has been calibrated on fracture and flow data from the stripa 3d experiment in sweden comparison between transport simulations in the flow calibrated discrete model and tracer tests of the field experiment confirms the fracture network parameters obtained from the flow analysis except for the variance of the fracture conductivities which had to be increased the discrete model reproduces the uneven spatial distribution of flow and tracers the complex dispersive behavior and channeling effects that have been observed in the field experiment as a result of flow channeling transport occurs along preferential paths whose transport properties may substantially deviate from the medium average properties for example porosity and wetted fracture surface area available to sorption may be reduced by almost 2 orders of magnitude compared to the medium average values

rupture processes of large deep focus earthquakes from inversion of moment rate functions we determine the source time histories of five recent 1994 1996 large deep focus earthquakes using a method that inverts for fault slip from far field moment rate functions the moment rate functions are obtained through the deconvolution of multiple body wave phases using broadband records from global seismic network gsn and geoscope stations tests of this method on synthetic data indicate that it is successful in determining the low frequency rupture characteristics of deep earthquakes under a variety of complicating conditions we find that source parameters such as average rupture velocity and stress drop are highly variable among the events studied and that some unusual characteristics exhibited by the june 9 1994 great bolivian earthquake are also found for other events comparison of the slip distributions with background seismicity and aftershock locations indicates that most of the moment release for large deep focus earthquakes is probably occurring within the active slab interior this provides further evidence that temperature controlled mechanisms such as transformational faulting play a large role in deep earthquake faulting most of the events studied also show a tendency for horizontal rupture propagation suggesting that isobaric processes may be an important factor in controlling progression of the rupture large gaps in the slip distributions point to possible occurrence on multiple fault planes

analogue modelling of fracturing in cooling plutonic bodies abstract fractures formed when igneous rocks cool below the surface of the earth are of considerable current interest in studies of hydrology mineral systems and radioactive waste disposal however little is known about the geometry and kinematics of such fractures conceptual models suggest that early fractures result from emplacement forces the cloos model while two dimensional numerical modelling suggests that fractures may result from the contraction of cooling bodies we use analogue modelling to investigate the geometry of fractures formed in a cylindrical static contracting body our experiments show that dehydration of buried starch flour is a workable analogue fractures in the analogue material result from drying and contraction of a cylindrical volume which differs from previous experiments in which drying was from a single planar surface and resulted in the formation of columnar joints in buried analogue models two key fracture sets form internally producing sub vertical radial fractures and concentric fractures that curve downwards with depth fracture density decreases towards the centre and bottom of the samples samples that were buried more deeply have fewer and less curved concentric fractures than those with shallow burials radial fractures have similar orientations to those predicted from numerical models and concentric fractures are comparable to marginal fissure orientations of the cloos model the analogue models suggest that both radial and concentric fractures may result from the contraction of plutonic bodies

sliding skis and slipping faults the mechanisms of earthquakes are a matter of debate with different models capable of explaining different aspects of the process in his research commentary wiens discusses work reported in the same issue by kanamori et al 1 in which the authors propose that deep earthquakes occur through melting as the fault ruptures a thin layer of molten rock lubricates the sliding surfaces much as a thin layer of water lubricates ski surfaces on snow wiens suggests that the model is best suited to explaining the deepest quakes including the 1994 bolivia event 1 http www sciencemag org cgi content short 279 5352 839

stress and fracture evolution in a cooling pluton an example from the diamond joe stock western arizona u s a abstract an analytical model of fracturing in a crystallizing cylindrical pluton is applied to the natural fracture distribution in the diamond joe stock western arizona u s a the model accounts for three inputs to the stress during cooling thermal contraction magma pressure and regional tectonics fracture type shear or tensile orientation and density were determined at over 300 locations throughout the 8 km diameter stock a distinct pattern of fractures radiates outward from the center of the stock a deflection of these fracture trends toward the regional maximum principal stress direction provides a constraint on the magnitude and orientation of regional stress at the time of crystallization and cooling a calculated model of the fracture pattern suggests that regional maximum and minimum principal stress were 75 and 15 mpa with the orientation controlled by local tectonism the distribution of fractures appears to be insensitive to variations in magma pressure except near the wall of the chamber hence little constraint on magma pressure could be derived from the model thermal gradients during cooling and regional stress appeared to have a greater effect than magma pressure on the overall fracture distribution larger thermal gradients during the early stages of crystallization led to abundant early tensile fractures assuming that the crystalline portions of the pluton behaved elastically during cooling and that all strain was accommodated by fractures the variation of theoretical strain is similar to the distribution of fracture densities within the stock

fault plane orientations of deep earthquakes in the izu bonin marianas subduction zone 1 we make use of the effects of rupture directivity on waveform shape to analyze the rupture processes of 58 large deep earthquakes in the izu bonin marianas subduction zone for more than half of the analyzed earthquakes we determine a best fitting unilateral rupture direction using teleseismic data for 20 of these earthquakes the constraints on the rupture direction allow the fault plane to be identified where the subducting slab dips at a moderate angle near horizontal fault planes dominate at all studied depths 50 600 km within more steeply dipping slabs fault planes tend to dip toward the south and west rotated into the plane of the slab the poles of the definitively identified faults form a single tight cluster pointing up and toward the surface of the slab identified ruptures have a tendency to propagate away from the top surface of the slab between 100 and 300 km depth but appear to be randomly oriented at greater depths the occurrence of predominantly near horizontal faults at intermediate depths agrees with previous observations in several other subduction zones however at depths 300 km the results from the izu bonin marianas system differ from those previously obtained for tonga kermadec where both horizontal and vertical faults were identified we consider various physical mechanisms to explain our observations and conclude that while pre existing slab structures may be reactivated if they are favorably oriented the observed asymmetry in deep fault orientations may instead result from external forces acting on the slab and resulting changes in slab morphology

en echelon ruptures during the great bolivian earthquake of 1994 rupture during this event has two characteristics first bursts of major moment release subevents have a component of eastward movement from the epicenter second later subevents show northward directivity these observations lead to a model with four subevents the latter three being line sources propagating within approximately 30 of north this model has en echelon regions of moment release over sub horizontal plane s and rupture speeds up to 3 5 0 5 km s within subevents moment release over en echelon regions can accommodate high moment release over a limited seismogenic volume within subducted lithosphere depending on the exact geometry of the wadati benioff zone and the precise direction of rupture propagation lower bounds on the thickness of the seismogenic zone during this event range approximately 10 40 km while several aspects of the en echelon rupture model dovetail with predictions based on the anticrack model for deep focus seismicity one must also allow for the possibility that the rupture zone extended beyond the expected thickness of metastable olivine wedge

paleostress history of the basin and range province in western utah and eastern nevada from healed microfracture orientations in granites healed microfractures in quartz grains in 14 to 169 ma granites from the basin and range province in western utah and eastern nevada record a history of paleostress the microfracture data are in good agreement with the orientations of paleostresses determined for this same region by using orientations of dikes emplaced into only slightly older igneous host rocks samples generally have two or three steeply dipping microfracture sets one set is related to the tectonic stress field at the time of magma emplacement it strikes northeast southwest in 31 169 ma samples and east northeast west southwest in 25 30 ma samples rotates to east west by about 22 ma and strikes northwest southeast in the youngest samples about 14 ma plutons younger than about 14 ma are not exposed at the surface in western utah and eastern nevada other crack sets in the samples could have formed during cooling of the pluton during a post cooling regional thermal or tectonic event or during some local stress event a strong north south trend in these other crack sets may suggest a formation during basin and range extension

position by position cooling paths within the toki granite central japan constraints and the relation with fracture population in a pluton abstract understanding the locational differences of time temperature t t paths within the granite contributes to clarifying the detailed formation history especially the thermal evolution of the entire pluton after the incipient intrusion of the granitic magma into the shallow crust the position by position t t paths of fifteen samples of the toki granitic pluton central japan are reconstructed from thermochronological data including zircon u pb biotite k ar zircon fission track zft and apatite fission track aft ages ft length characterization and ft inverse calculation in case of sample no 1 the t t path consists of zircon u pb ages 74 0 1 1 ma and 72 6 1 7 ma a biotite k ar age 73 0 1 8 ma a zft age 57 2 2 3 ma an aft age 41 5 2 7 ma and the ft inverse calculation the t t paths show position specific characteristics that reflect the history of the pluton after the incipient intrusion of the granitic magma into the shallow crust shallow parts of the western and northeastern margins of the pluton show rapid cooling from the intrusion stage to the zft partial annealing zone paz and thus represent position specific characteristics in relation to crustal assimilation in the intrusion emplacement processes the cooling behavior around the condition of aft paz was interpreted as a reflection of regional tectonic exhumation of the pluton this study also presents useful knowledge to evaluate fracture populations in a granitic pluton the relationship between the position specific t t path and fracture frequency fracture number per unit interval provides a criterion for evaluating the fracture population of the granitic pluton called thermochronological evaluation which is a key insight to investigating fluid flow and mass transfer in the rock mass the t t path shows whether cooling was slow or rapid from thermal conditions of solidification crystallization to the biotite k ar closure temperature parts of the pluton that cooled slowly correspond to parts with high frequencies of fractures and vice versa the absolute value for duration between the zircon u pb age evaluated from the oscillatory zoned area oz age and biotite k ar age shows high correlation with fracture frequency r2 0 89 and thus gives a quantitative indicator for evaluating fracture frequency longer duration accompanies higher frequency a combination of thermochronological evaluation the local cooling indicator and the lithofacies effect can be applied as potential diagnostic tools for detailed evaluation of the fracture population

source characteristics of the 1992 nicaragua tsunami earthquake inferred from teleseismic body waves we analyzed the broadband body waves of the 1992 nicaragua earthquake to determine the nature of rupture the rupture propagation was represented by the distribution of point sources with moment rate functions at 9 grid points with uniform spacing of 20 km along the fault strike the moment rate functions were then parameterized and the parameters were determined with the least squares method with some constraints the centroid times of the individual moment rate functions indicate slow and smooth rupture propagation at a velocity of 1 5 km s toward nw and 1 0 km s toward se including a small initial break which precedes the main rupture by about 10 s we obtained a total source duration of 110 s the total seismic moment is m o 3 4 1020 nm which is consistent with the value determined from long period surface waves m o 3 7 1020 nm the average rise time of dislocation is determined to be 10s the major moment release occurred along a fault length of 160 km with the assumption of a fault width w 50 km we obtained the dislocation d 1 3 m from and d the dislocation velocity is d d 0 1 m s significantly smaller than the typical value for ordinary earthquakes the stress drop 1 1 mpa is also less than the typical value for subduction zone earthquakes by a factor of 2 3 on the other hand the apparent stress defined by 2 e s m o where and e s are respectively the rigidity and the seismic wave energy is 0 037 mpa more than an order of magnitude smaller than the nicaragua tsunami earthquake is characterized by the following three properties 1 slow rupture propagation 2 smooth rupture 3 slow dislocation motion

effect of slab temperature on deep earthquake aftershock productivity and magnitude frequency relations deep earthquakes generally show fewer aftershocks and a larger variability in magnitude frequency relations than shallow earthquakes1 5 these characteristics and the factors that control them may place constraints on the mechanism of deep earthquakes which is still uncertain6 8 here we show that systematic variations in aftershock productivity and magnitude frequency relations are related to the temperature of the downgoing slab as inferred from the vertical velocity and age of the subducting lithosphere deep earthquakes with substantial aftershock sequences are found only in colder slabs and earthquakes in warmer slabs consistently show few aftershocks magnitude frequency relations for deep earthquakes also show systematic variations as a function of slab thermal structure with warmer slabs showing fewer small earthquakes lower b values the statistical properties of deep earthquakes thus appear to be temperature sensitive to an extent not observed for shallow earthquakes and not adequately explained by simple geometrical limitations on fault width

flow through fractures flow through fractures is often idealized as flow between two parallel plates plane poiseuille flow the opening or aperture between parallel plates is unambiguous and its relation to flowrate is well known however fractures in rock have uneven walls and a variable aperture a model for flow in a fracture is proposed wherein the fracture is represented by a set of parallel plate openings with different apertures the model leads to a modified poiseuille equation for flow which includes an aperture frequency distribution for the fracture any arbitrary aperture distribution can be used in order to simplify computation and demonstrate the properties of the model a log normal form of distribution is assumed even when an analytical form of the distribution is assumed two parameters rather than a single value representing aperture size are required to determine flowrate models of aperture change for a fracture undergoing compression fracture walls deforming and extension fracture walls separating are developed which constrain the additional parameter and allow calculation of flowrate as a function of mean aperture the theoretical relationships developed between mean aperture and flowrate can be used to interpret published laboratory data for single fractures

can observations of earthquake scaling constrain slip weakening summary we use observations of earthquake source parameters over a wide magnitude range m w 0 7 to place constraints on constitutive fault weakening the data suggest a scale dependence of apparent stress and stress drop both may increase slightly with earthquake size we show that this scale dependence need not imply any difference in fault zone properties for different sized earthquakes we select 30 earthquakes well recorded at 2 5 km depth at cajon pass california we use individual and empirical green s function spectral analysis to improve the resolution of source parameters including static stress drop and total slip s we also measure radiated energy e s w ecompare the cajon pass results with those from larger california earthquakes including aftershocks of the 1994 northridge earthquake and confirm the results of abercrombie 1995 e s m 0 where rigidity and both e s m 0 and increase as m 0 and s increases uncertainties remain large due to model assumptions and variations between possible models and earthquake scale independence is possible within the resolution assuming that the average trends are real we define a quantity g 2 es m 0 s 2w hich is the total energy dissipation in friction and fracture minus 1 s w here 1 is the final static stress if 1 d the dynamic shear strength during the last increments of seismic slip then g g the fracture energy in a slip weakening interpretation of dissipation

three dimensional fracture distribution in relation to local cooling in a granitic body an example from the toki granitic pluton central japan this paper describes a spatial distribution of fracture frequency fracture number per unit interval in the toki granitic pluton central japan and their evaluation with respect to cooling behavior after solidification of the pluton three dimensional distribution of fracture frequency of all fractures all angle fractures based on borehole television data collected from 19 boreholes shows that 1 the central region of the granite has a high fracture frequency and 2 fracture frequency decreases with decreasing elevation measured from the mean sea level with the exception of the west side of the body the development of sub solidus reaction textures reflects the annealing duration of the pluton after solidification the extent of sub solidus reaction textures was measured at two neighboring positions and the difference was divided by the distance between the two positions the resulting quantity is here defined as a local cooling indicator lci we observed a related pattern between the distribution of fracture frequency and lci the high lci region corresponds to the region with a high frequency of all fractures and vice versa this relation indicates that fracture genesis has been mostly controlled by local cooling after solidification which caused thermal stress thus the three dimensional pattern of lci is a potential diagnostic tool for obtaining the spatial distribution of all fractures

petrographic and physical factors controlling thermal conductivity of granitic rocks in illinois deep holes uph 1 2 and 3 twenty four granitic core samples from the illinois deep drill holes yield thermal conductivity values in the range 29 3 37 6 mw cm c wet bulk densities in the range 2 608 2 960 g cm3 and water accessible porosity in the range 0 12 0 78 thermal conductivity values vary with modal quartz content of the rocks at all depths and both parameters decrease linearly with depth between 673 and 1016 m in drill hole uph 3 below 1070 m there is no systematic variation in modal quartz content with depth and hence no systematic variation in thermal conductivity similarly no systematic variations in modal quartz or physical properties with depth are observed in drill hole uph 2

empirical green function deconvolution of broadband surface waves rupture directivity of the 1992 landers california mw 7 3 earthquake we present a simple method to determine gross temporal and spatial characteristics of faulting that can uniquely define the fault plane for a relatively large earthquake the technique involves deconvolution of teleseismic and regional broadband surface waves and or body waves of a small event an empirical green function from the corresponding signals at the same stations for a large mainshock this deconvolution corrects each mainshock seismic record for propagation and instrument response and if the focal mechanisms and centroid depths are identical deconvolution provides relative source time functions for the mainshock azimuthal variations of source time function width or subevent interference reveal the mainshock rupture directivity changes in the source mechanism during rupture can be evaluated for some classes of events our empirical green function procedure is novel in its application to surface waves and its use for large m 7 earthquakes we perform synthetic tests to establish intrinsic limitations of the method the procedure requires very little data processing and can be applied in near real time with the current distribution of seismic stations that have dial up data retrieval capability it also provides a straightforward procedure for reducing bias in source duration estimates resulting from aspherical heterogeneity and for detecting anomalous long period radiation we apply the procedure to the 28 june 1992 landers california mw 7 3 earthquake the landers earthquake source duration lasted about 25 sec and was dominated by two subevents with predominantly north northwestward rupture extending 60 to 70 km the subevents show counter clockwise rotations of at least 12 in strike that correlate well with mapped surface rupture

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

evidence for a supershear transient during the 2002 denali fault earthquake elastodynamic considerations suggest that the acceleration of ruptures to supershear velocities is accompanied by the release of rayleigh waves along the fault from the stress breakdown zone these waves generate a secondary slip pulse trailing the rupture front but manifest almost entirely in ground motion perpendicular to the fault in the near source region we construct a spontaneously propagating rupture model exhibiting these features and use it to explain ground motions recorded during the 2002 denali fault earthquake at pump station 10 located 3 km from the fault we show that the initial pulses on both the fault normal and fault parallel components are due to the supershear stress release on the fault whereas the later arriving fault normal pulses result from the trailing subshear slip pulse on the fault online material mpeg movies of rupture history and ground motion

supershear rupture in a mw 6 7 aftershock of the 2013 sea of okhotsk earthquake earthquake rupture speeds exceeding the shear wave velocity have been reported for several shallow strike slip events whether supershear rupture also can occur in deep earthquakes is unclear because of their enigmatic faulting mechanism using empirical green s functions in both regional and teleseismic waveforms we observed supershear rupture during the 2013 moment magnitude m w 6 7 deep earthquake beneath the sea of okhotsk an aftershock of the large deep earthquake mw 8 3 the m w 6 7 event ruptured downward along a steeply dipping fault plane at an average speed of 8 kilometers per second suggesting efficient seismic energy generation comparing it to the highly dissipative 1994 m w 8 3 bolivia earthquake the two events represent end members of deep earthquakes in terms of energy partitioning and imply that there is more than one rupture mechanism for deep earthquakes

source description of the 1999 hector mine california earthquake part ii complexity of slip history we present a rupture model of the hector mine earthquake m 7 1 determined from the joint inversion of strong motion records p and sh teleseismic body waves global positioning system gps displacement vectors and measured surface offset we solve for variable local slip rake angle rise time and rupture velocity of a finite fault model involving multiple segments the inversion methodology developed in a companion article ji et al 2002 combines a wavelet transform approach with a nonlinear simulated annealing algorithm the final model is checked by forward simulating the interferometric synthetic aperture radar insar data our estimation to the seismic moment is 6 28 10 19 n m which is distributed along three segments from north to south releasing 37 41 and 22 of the total moment respectively the average slip is 1 5 m with peak amplitudes as high as 7 m the fault rupture has an average rise time of 3 5 sec and a relatively slow average rupture velocity 1 9 km sec resulting in a 14 sec rupture propagation history our approach permits large variation in rupture velocity and rise time and indicates that rise time appears to be roughly proportional to slip and shorter rise times are associated with the initiation of asperity rupture we also find evidence for nearly simultaneous rupture of the two northern branches

source rupture process of the tecoman colima mexico earthquake of 22 january 2003 determined by joint inversion of teleseismic body wave and near source data the spatial and temporal slip distribution of the tecoman colima mexico earthquake is estimated from near source strong motion and teleseismic body wave data to perform a stable inversion we applied smoothing constraints and determined their optimal relative weights on the observed data using an optimized akaike s bayesian information criterion abic the source parameters are as follows strike dip slip 300 20 93 seismic moment m 2 3 1020 n m source duration 30 sec along strike distance 35 km along dip distance 70 km we found that the rupture process can be divided into three stages the rupture nucleated near the hypocenter stage i then it broke the first asperity centering about 15 km southwest from the epicenter stage ii and the rupture propagated to the northeast and the second asperity was broken stage iii we also estimated the shear stress change due to the rupture process of the mainshock on and around the major fault zone it appears that one cluster of aftershocks for the first 5 days which took place in and adjacent to the zones of stress increased due to the fault rupture during the mainshock but overall correlation between the aftershock location and the stress pattern is not clear manuscript received 14 may 2003

formation of joints in cooling plutons abstract the geometry age and mineralogy of steeply dipping joints in the lake edison granodiorite of california indicate that thermal stresses played a key role in the formation of the joints joint traces curve to approach the pluton boundary at high angles at both large and small scales and they generally terminate at or near the contact with an older pluton radiometric dates and the epidote and chlorite fillings of the joints tie jointing to the initial cooling of the pluton a thermo mechanical stress analysis assuming two dimensional conductive cooling predicts thermal stresses of several tens of mpa the same order of magnitude as plausible fluid pressures regional stresses and lateral normal stresses associated with the overburden the orientation of the joints can be accounted for rather well by the stress field formed by superposing a uniform regional stress field on the predicted thermal stresses the large scale pattern of the early joints in many plutons should be predictable based on a pluton s geometry its age relative to the adjacent rock and knowledge of the regional stress at the time of initial cooling these findings bear on issues pertinent to mining petroleum recovery nuclear waste repository siting and ground water flow

stochastic analysis of early tracer arrival in a segmented fracture pathway a stochastic model for transport and retention in fractured rock is proposed as an alternative to more elaborate numerical simulations contaminants are transported by advection through a series of n rock fractures the microscopic processes of matrix diffusion and sorption act together to retain contaminants in the host rock the transport pathway is characterized by large scale fluctuations in the advection velocity caused by spatial variability in the fracture attributes along the pathway the moments of the time of arrival of an initial solute pulse are related in a generic way to the joint distribution of fracture aperture and length these moments are controlled primarily by a dimensionless retention parameter that incorporates all the deterministic model parameters and by correlation between fracture length and aperture the results show that a systematic bias in the predicted contaminant transport can be introduced by neglecting spatial variability in fracture attributes the relative contributions of fracture to fracture variability and within fracture variability are also explored the proposed stochastic methodology can be merged with relatively simple numerical simulations to broaden the applicability