dehydration melting of amphibolite at 10 kbar the effects of temperature and time we have simulated the dehydration melting of a natural low k calcic amphibolite 67 4 hornblende 32 5 anorthite in piston cylinder experiments at 10 kbar and 750 1000 c for 1 9 days the solidus temperature is lower than 750 c garnet appears at 850 c the overall reaction is hb p l cpx al hb ca hb ga opx three stages of reaction are 1 melting dominated by the growth of clinopyroxene and garnet with little change in composition of liquid or garnet 2 a reversal of this reaction between 875 c and 900 c with decreases in the amounts of liquid and garnet and 3 a large increase in liquid along with the loss of hornblende and decrease of plagioclase while clinopyroxene and garnet increase garnet is enriched in pyrope and zoned from fe cores to mg edges range 3 mol pyrope liquid composition is enriched first in an to 950 c and then in ab the liquids are more calcic and aluminous than natural tonalites which is attributed to the plagioclase composition an90 the formation of peraluminous liquid from the metaluminous amphibolite is caused by anorthite not h2o saturated conditions the results are consistent with an amphibolite phase diagram with relatively high solidus temperatures in the garnet absent field 900 1000 c but with a solidus backbend at 7 9 kbar coincident with the garnet in boundary hornblende breakdown due to garnet formation in a closed system must make h2o available for h2o undersaturated melting right down to the h2o saturated solidus below 700 c which defines a large low temperature pt area where hydrous granitoid melts can be generated with residual garnet and hornblende

the nars deep project the nars deep project involves the deployment of broadband seismological stations in russia belarus and the ukraine six stations were installed in 1995 two in 1997 and more stations were to be installed from 1998 onwards the nars deep project was initiated as a temporary deployment but funding from the european community enabled the stations to become permanent in this paper we present first results of the nars deep project a surface waveform inversion for the upper mantle structure along a profile from egypt to spitsbergen shows evidence for strong variations in the shear velocity structure for the different tectonic units the most striking features of the model comprise strong lithospheric anisotropy beneath the eastern mediterranean and a lithospheric thickness of approximately 200 km beneath the shield areas the crustal structure beneath the seismic station in st petersburg was investigated using the receiver function method the results of a monte carlo inversion for the receiver functions of this station show evidence for a sedimentary layer with a thickness of less than 1 km overlying an upper crustal layer extending to a depth of approximately 16 km the moho depth cannot be resolved from the receiver functions of this station

is hydrology kinematic a wide range of phenomena natural as well as man made in physical chemical and biological hydrology exhibit characteristics similar to those of kinematic waves the question we ask is can these phenomena be described using the theory of kinematic waves since the range of phenomena is wide another question we ask is how prevalent are kinematic waves if they are widely pervasive does that mean hydrology is kinematic or close to it this paper addresses these issues which are perceived to be fundamental to advancing the state of the art of water science and engineering copyright 2002 john wiley sons ltd

do cenozoic analogues support a plate tectonic origin for earth s earliest continental crust archean continental crust largely comprises the trondhjemite tonalite and granodiorite dacite ttg d suite of igneous rocks formation of the earliest archean 3 5 ga ttg ds is controversial being attributed to either subduction zone processes with active plate tectonics or thermochemical mantle convection with no plate tectonic processes a suite of cenozoic adakite like lavas in jamaica has geochemical compositions comparable to early archean ttg d the data indicate that the adakites were generated by underthrusting or subducting and partial melting of oceanic plateau crust beneath jamaica this setting is analogous to proposed plate tectonic processes in the early archean where hot thick and more buoyant archean oceanic crust underthrusts adjacent plates the new adakite data imply that earliest archean ttg d continental crust could have formed above primitive subduction zones

new constraints on the rupture process of the 1999 august 17 izmit earthquake deduced from estimates of stress glut rate moments summary this paper illustrates the use of integral estimates given by the stress glut rate moments of total degree 2 for constraining the rupture scenario of a large earthquake in the particular case of the 1999 izmit mainshock we determine the integral estimates of the geometry source duration and rupture propagation given by the stress glut rate moments of total degree 2 by inverting long period surface wave lpsw amplitude spectra kinematic and static models of the izmit earthquake published in the literature are quite different from one another in order to extract the characteristic features of this event we calculate the same integral estimates directly from those models and compare them with those deduced from our inversion while the equivalent rupture zone and the eastward directivity are consistent among all models the lpsw solution displays a strong unilateral character of the rupture associated with a short rupture duration that is not compatible with the solutions deduced from the published models with the aim of understand this discrepancy we use simple equivalent kinematic models to reproduce the integral estimates of the considered rupture processes including ours by adjusting a few free parameters controlling the western and eastern parts of the rupture we show that the joint analysis of the lpsw solution and source tomographies allows us to elucidate the scattering of source processes published for this earthquake and to discriminate between the models our results strongly suggest that 1 there was significant moment released on the eastern segment of the activated fault system during the izmit earthquake 2 the apparent rupture velocity decreases on this segment

a study of the barisakho georgia earthquake of 1992 october 23 from broad band surface and body waves summary we study the 1992 october georgian earthquake located in the centra part of the great caucasus this is the last strong ms 6 5 shallow earthquake of a series of three that struck this region in the two year period of 1991 1992 in order to determine the source parameters we analysed surface and body waves from the iris and geoscope very broad band digital networks the fundamental mode of surface waves was retrieved using frequency time analysis ftan a technique that makes inversion more stable and enables the measurement of the spectral features from the signal in the presence of stationary noise we used long period surface waves 60 150 s to obtain the seismic moment mo 4 8 10 n m and the focal mechanism strike 8 300 dip 6 15 and rake a 135 the space time distribution of the source moment density tensor was determined from intermediate period 35 60 s surface waves we found the following results duration 6 s rupture velocity 3 2 km s i major and minor axes of the fault surface i 32 km and zmin 20 km respectively for the inversion of body waves we performed a shape waveform modelling using the gradient method of nabelek we considered the source as a point source of 6 s duration the results of body wave inversion mo 3 0 10 n m 8 300 6 17 and 1 137 are in good agreement with estimates from surface waves one of the nodal planes of the fault plane solution corresponds to a thrust fault which agrees with the general seismotectonic features of the region of the kartli and kokheti ridges in the central part of the great caucasus the southern slope of the great caucasus strikes wnw ese and the underlying crystalline basement plunges towards the nne under the main axial zone the source plane coincides with the location of the contact between the crystalline basement and the upper block overthrust

higher degree moment tensor inversion using far field broad band recordings theory and evaluation of the method with application to the 1994 bolivia deep earthquake summary we present a method to estimate parameters of the extended earthquake source using higher degree moment tensors at 27 centroid locations we show that a taylor series expansion of green s functions around a single centroid is not accurate enough when working with seismic wave periods and wavelengths in the range of the rupture duration and spatial extent of the fault respectively introducing a grid of 27 centroid locations on the fault and using higher degree moment tensors we are able to model adequately body and surface waves with periods and wavelengths smaller than the rupture duration and fault dimensions under simplifying assumptions an iterative inversion scheme is coded to estimate parameters of planar haskell type faults realistic inversion examples for deep and shallow earthquakes show that uni and bidirectional rupture models rupture direction fault and auxiliary plane and kinematic source dimensions and can be constrained with teleseismic body and or surface waves the application to the deep bolivia event indicates a subhorizontal fault plane unidirectional rupture to the north is slightly preferred the rupture duration of 25 s and fault dimensions of 47 25 km agree well with the estimates for the main pulse moment release given in other studies

secular changes in tonalite trondhjemite granodiorite composition as markers of the progressive cooling of earth archean tonalite trondhjemite granodiorite associations ttg are classically thought to generate through partial melting of hydrous metabasalts however the chemical composition of the least differentiated ttg parental magmas evolved from 4 0 to 2 5 ga during this interval the mg as well as the ni and cr contents increased which is interpreted as reflecting increased interactions between felsic melts generated by metabasalt melting and mantle peridotite similarly cao na2o and sr also increased over time thus reflecting an increase in the abundance of plagioclase in the melt residue the presence or absence of residual plagioclase is interpreted in terms of melting depth the demonstrated interaction between ttg parental magmas and the mantle rules out their genesis by fusion of previously underplated metabasalt and favors the melting of subducted slab material at 4 0 ga earth s geothermal gradient was sufficiently high to allow slab melting at shallow depths where plagioclase was stable consequently due to the small thickness of the overlying mantle wedge felsic magmas interacted little with the mantle at 2 5 ga however owing to lower geothermal gradients the melting depth was greater and plagioclase became no longer stable in the thick mantle wedge overlying the subducted slab as a result felsic magmas reacted strongly with the mantle peridotite the changes of ttg composition during archean time can be thus interpreted as reflecting the progressive cooling of earth

determination of stress glut moments of total degree 2 from teleseismic surface wave amplitude spectra abstract a special case of the seismic source where the stress glut tensor can be expressed as a product of a uniform moment tensor and a scalar function of spatial coordinates and time is considered for such a source a technique of determining stress glut moments of total degree 2 from surface wave amplitude spectra is described the results of application of this technique for the estimation of spatio temporal characteristics of the georgian earthquake 29 04 91 are presented

predominance of unilateral rupture for a global catalog of large earthquakes the manner in which an earthquake rupture propagates across a fault reflects both the initial properties of the fault and the dynamical stresses produced by the rupture we quantify the propagation of an earthquake rupture using the second moments of the earthquake space time distribution in particular the second moments provide a simple way to differentiate between approximately bilateral and predominantly unilateral ruptures we determined the second moments for a catalog of m w 7 earthquakes that have occurred since 1994 the results show that approximately 80 of large shallow ruptures are predominantly unilateral our result agrees well with strong motion inversions from previous studies on moderate and large earthquakes the predominance of unilateral propagation in large earthquakes is explained by a simple characteristic earthquake model in which large events rupture an entire structurally defined fault segment and nucleation points are uniformly distributed along the fault the predominance of unilateral rupture may also be enhanced by the dynamic stress field produced by contrasts in the elastic properties between the two sides of plate boundary faults manuscript received 16 november 2001

non linear dynamics of the lithosphere and intermediate term earthquake prediction abstract the lithosphere of the earth is structured as a hierarchical system of volumes of different sizes from about 10 tectonic plates to about 10 25 grains of rock their relative movement against the forces of friction and cohesion is realized to a large extent through earthquakes the movement is controlled by a wide variety of independent processes concentrated in the thin boundary zones between the volumes the boundary zone has a similar hierarchical structure consisting of volumes separated by boundary zones etc altogether this hierarchy of volumes and multitude of processes compose the lithosphere into a large non linear complex system upon coarse graining the integral mesoscale empirical regularities emerge indicating a wide range of similarity collective behavior and the possibility of earthquake prediction this approach led to new paradigms in the dynamics of the lithosphere and on the practical side created a capacity to predict from 70 to 90 of large earthquakes with alarms occupying 10 20 of the time space considered such predictions may be used to undertake earthquake preparedness measures which would prevent a considerable part of the damage although far from the total damage the methodology linking prediction with preparedness was developed it may help a disaster management authority to choose the preparedness measures allowing for the currently realistic accuracy of predictions a large scale experiment in advance prediction of large earthquakes worldwide has been launched to test the prediction algorithms the test is unprecedented in rigor and coverage the forecasts are communicated with due discretion to several dozen leading scientists and administrators in many countries among already predicted earthquakes are all the last eight great ones with magnitude 8 and more the major drawback is the rate of false alarms the possibility is outlined to develop a new generation of prediction methods with fivefold increase in accuracy and the transition to short term prediction the links with prediction of geotechnical and engineering disasters are established scenarios of transitions to a large earthquake happen to share some features with a broader class of catastrophes this experience now opens as yet untapped possibilities for reduction of technological disasters

source parameters and tectonic origin of the 1996 june 1 tianzhu mw 5 2 and 1995 july 21 yongden mw 5 6 earthquakes near the haiyuan fault gansu china summary the 1996 june 1 tianzhu mw 5 2 ms 4 9 and the 1995 july 21 yongden mw 5 6 ms 5 4 earthquakes are the two largest events recorded in the last 10 years between the 1990 october 20 ms 5 8 and the recent 2000 june 6 ms 5 6 earthquakes near the tianzhu seismic gap on the haiyuan fault in northeastern tibet we use frequency time analysis ftan to extract the fundamental modes of love and rayleigh waves from digital records a joint inversion of their amplitude spectra and of p wave first motion polarities is then performed to calculate the source parameters focal mechanisms depths and seismic moments of these two ms 5 earthquakes such a joint inversion is tested for the first time we use iris and geoscope network records for period ranges of 20 40 s for the former event and 35 70 s for the latter the inversion of the tianzhu earthquake yields nodal planes with strike dip and slip of 282 72 and 3 and 191 87 and 162 respectively a focal depth around 12 km and a seismic moment of 0 56 1017 n m consistent with the harvard cmt calculation and the alignment and depths of the aftershocks recorded by a local network we propose two possible tectonic interpretations for this off fault event the solution for the yongden earthquake is consistent with a thrust with strike dip and slip of 105 45 and 75 respectively a focal depth around 6 km and a seismic moment of 2 4 1017 n m also in agreement with the harvard cmt mechanism the distribution of the aftershocks recorded by a regional network and the general tectonic setting that we refine

imaging coseismic rupture in far field by slip patches summary since the end of the 1970s teleseismic waves are used routinely to infer the first order characteristics of the event location depth duration focal mechanism but finding the second order kinematic parameters spatial distribution of slip rupture velocity and more basically the discrimination between the fault plane and the other nodal plane of distant events remains a difficult task classically these events are studied by two different methods either they are seen as a succession of subevents each of which is considered as a point source or like in near field as extended sources where the kinematic parameters are retrieved on a grid the first approach is not physically satisfactory and can lead to erroneous interpretations of the

the geochemistry of young volcanism throughout western panama and southeastern costa rica an overview oblique aseismic subduction below western panama and southeastern costa rica has produced recent arc related volcanism the aseismicity is probably related to the subduction of relatively hot oceanic lithosphere the volcanism throughout this region over the past 2 ma has been quite distinct consisting of felsic magmas andesites to rhyolites but mainly dacites with geochemical signatures suggesting a metamorphosed basaltic source it is believed that the subduction of young oceanic crust sets up conditions under which the slab melts rather than the overlying mantle wedge rocks with slab melt geochemistries and associated with young subducted crust have been termed adakites elsewhere the young adakite melts are sometimes associated with a few rare young high nb basalts but there is no obvious genetic link between them through differentiation high nb basalts may also be derived from the partial melting of the subducted oceanic crust high nb basalt migmatites have been found with pegmatites of adakite compositions in the exposed subduction terrain of the catalina schist california alternatively the high nb basalts may be partial melts of phlogopite rich mantle that has previously reacted with adakite magmas eruption of adakites and high nb basalts was preceded by a 2 3 ma period of relative quiescence prior to this there was a 7 ma period of calc alkaline volcanism typical of the present day magmatism associated with a distinct benioff zone found throughout the central american arc the abrupt transition in volcanism with time from an early calc alkaline sequence to a later adakite high nb basalt sequence may record a change in the tectonic setting of western panama and southeastern costa rica over the past 12 ma

directly estimating earthquake rupture area using second moments to reduce the uncertainty in stress drop author posting the author s 2018 this article is posted here by permission of oxford university press for personal use not for redistribution the definitive version was published in geophysical journal international 214 2018 2224 2235 doi 10 1093 gji ggy201

temperatures heat flux and frictional stress near major thrust faults we examine the two dimensional advective and conductive transport of heat in a region of thrust faulting both simple theoretical considerations and numerical experiments show that the steady state temperatures near the fault are reduced by a divisor s 1 b z vsin below what they would be with the same heat sources but in the absence of advection in this expression z is the depth to the fault v is the slip rate is the component of the dip of the fault in the direction of underthrusting is thermal diffusivity and b is a dimensionless factor that is essentially equal to one for most forms of heating initial changes in temperatures near the fault are given by t z t t z 0 12vsin t z 0 z these simple formulae are successful because of the neglible influence of lateral conduction of heat at least for slip rates of a few mm yr or more two time constants govern the transition from the initial change in temperature to steady state t1 u v where u is the distance along the fault in the direction of underthrusting from the surface to the depth in question and t2 z 2 2 where z is the depth to the fault when elapsed times exceed the sum of these two time constants temperatures differ from their steady state values by only about 10 percent the numerical experiments indicate that the simple formulae are sufficiently accurate that sophisticiated numerical modeling of temperatures in specific regions is unwarranted putain an application of these simple formulae to measurements of conductive heat flow at island arcs implies that shear stresses at island arcs approach 100 mpa and are greater than 30 mpa calculations of temperatures appropriate for the himalaya suggest that shear stresses of 100 mpa on the main central thrust probably are required to account for the tertiary granites of the region if melting took place after slip began on the thrust similarly the cut off in seismicity at a depth of about 15 km in the himalaya if due to temperatures exceeding 350 to 450 c implies a deviatoric stress close to 100 mpa

a kinematic model for surface irrigation verification by experimental data a kinematic model for surface irrigation is verified by experimental data obtained for 31 borders these borders are of varied characteristics calculated values of advance times water surface profiles when water reaches the end of the border and recession times are compared with their observations the prediction error in most cases remains below 20 for the advance time and below 15 for the recession time the water surface profiles computed by the model agree with observed profiles reasonably well for the data analyzed here the kinematic wave model is found to be sufficiently accurate for modeling the entire irrigation cycle except for the vertical recession

modification of an oceanic plateau aruba dutch caribbean implications for the generation of continental crust the generation of the continental crust may be connected to mantle plume activity however the nature of this link and the processes involved are not well constrained an obstacle to understanding relationships between plume related mafic material and associated silicic rocks is that later tectonic movements are liable to obscure the original relationships particularly in ancient greenstone belts studies of younger analogous regions may help to clarify these relationships on the island of aruba in the southern caribbean a sequence of partly deformed mafic volcanic rocks intruded by a predominantly tonalitic batholith is exposed the mafic lavas show geochemical and isotopic affinities with other basaltic picritic and komatiitic rocks that crop out elsewhere in the caribbean these are well documented as belonging to an 88 91 ma plume related oceanic plateau which is allochthonous with respect to the americas and is thought to have been formed in the pacific region the 85 to 82 ma tonalitic rocks share some geochemical characteristics high sr and ba low nb and y with archaean tonalite trondhjemite granodiorite ttg suites field relationships suggest that deformation of the plateau sequence possibly related to collision with a subduction zone was synchronous with intrusion of the aruba batholith new incremental heating 40ar 39ar dates combined with existing palaeontological evidence show that cooling of the batholith occurred shortly after eruption of the plateau basalt sequence sr nd isotopic data for both rock suites are uniform 87sr 86sri 0 7035 endi 7 whereas pb isotopes are more variable plateau sequence 206pb 204pb 18 6 19 1 207pb 204pb 15 54 15 60 208pb 204pb 38 3 38 75 aruba batholith 206pb 204pb 18 4 18 9 207pb 204pb 15 51 15 56 208pb 204pb 38 0 38 5 this suggests that there has been a minor sedimentary input into the source region of the batholith however the limited time interval between basaltic and tonalitic magmatism makes a normal subduction related origin for the tonalites improbable instead models involving derivation of tonalite from partial melting of the plateau sequence or alternatively genesis in an unusual subduction zone environment are investigated

dynamic inversion of the 2000 tottori earthquake based on elliptical subfault approximations 1 we propose a simplified nonlinear method for the kinematic and dynamic inversion of near field strong motion data at low frequencies using a few elliptical patches we reduce the number of independent parameters of the inverse problem we apply this method to the dynamic inversion of the western tottori japan earthquake mw 6 6 6 8 of 6 october 2000 using unfiltered records we relocated the hypocenter close to 14 km in depth fifteen records obtained by the kik net and k net accelerometer networks were then filtered to the 0 1 0 5 hz frequency range and integrated to displacement we compare observed and synthetic records using the 2 norm a nonlinear kinematic inversion for the elliptical subfaults is first computed using the neighborhood algorithm na inversion converges to a slip distribution modeled by just two elliptical patches we then propose a dynamic inversion method based on the same simple geometrical ideas dynamic rupture propagation is computed by finite differences on a coarse numerical grid rupture propagation is controlled by a classical slip weakening friction law inversion is implemented with the na for a barrier model in this model prestress is uniform and rupture propagation is arrested by a simple distribution of barriers inversion converges to a model with two elliptical barriers synthetics computed for the dynamic inversion fit the observed data reducing the variance by nearly 60 by making different assumptions about the rupture process we illustrate the nonuniqueness of the solution to dynamic inversion

on the formation of continental silicic melts in thermochemical mantle convection models implications for early earth abstract important constituents of archean cratons formed in the early and hot history of the earth are tonalite trondhjemite granodiorite ttg plutons and greenstone belts the formation of these granite greenstone terrains is often ascribed to plate tectonic processes buoyancy considerations however do not allow plate tectonics to take place in a significantly hotter earth we therefore propose an alternative mechanism for the coeval and proximate production of ttg plutons and greenstone like crustal successions that is when a locally anomalously thick basaltic crust has been produced by continued addition of extrusive or intrusive basalts due to partial melting of the underlying convecting mantle the transition of a sufficient amount of basalt in the lower crust to eclogite may trigger a resurfacing event in which a complete crustal section of over 1000 km long sinks into the mantle in less than 2 million years pressure release partial melting in the complementary upwelling mantle produces large volumes of basaltic material replacing the original crust partial melting at the base of this newly produced crust may generate felsic melts which are added as intrusives and or extrusives to the generally mafic crustal succession adding to what resembles a greenstone belt partial melting of metabasalt in the sinking crustal section produces a significant volume of ttg melt which is added to the crust directly above the location of subduction presumably in the form of a pluton this scenario is self consistently produced by numerical thermochemical mantle convection models presented in this paper including partial melting of mantle peridotite and crustal meta basalt the metamorphic p t conditions under which partial melting of metabasalt takes place in this scenario are consistent with geochemical trace element data for ttgs which indicate melting under amphibolite rather than eclogite facies other geodynamical settings which we have also investigated including partial melting in small scale delaminations of the lower crust at the base of a anomalously thick crust and due to the influx of a lower mantle diapir fail to reproduce this behavior unequivocally and mostly show melting of metabasalt in the eclogite stability field instead

teleseismic inversion for the second degree moments of earthquake space time distributions summary determining detailed descriptions of the space time distribution of an earthquake s rupture using only teleseismic data is often a difficult and non unique process however a description of an earthquake that goes beyond a point source is often needed for many seismotectonic problems we have developed a method that inverts measurements of the shifts in traveltime and amplitude of various seismic phases at global stations for the second degree polynomial moments of an event s space time distribution our values for the second moments of the 1995 mw 8 0 jalisco mexico thrust event correspond to a characteristic rupture length of 121t10 km along strike a characteristic rupture width of 76t11 km downdip a characteristic duration of 29t2 s and a direction of rupture propagation along the strike of the subduction zone to the nw for the 1995 mw 7 2 gulf of aqaba earthquake our estimates of the second moments correspond to a characteristic rupture length of 53t2 km a characteristic duration of 12t1 s and rupture propagation to the ne along the strike of the dead sea transform our estimates of the first and second moments agree well with values from local seismic and geodetic networks for both the jalisco and aqaba events we are able to resolve the fault plane ambiguity associated with the events moment tensors using our estimates of the second spatial moment

self consistent retrieval of source parameters using mantle waves the large number of high quality stations from global networks e g iris geoscope allows for rapid and robust recovery of source parameters of large earthquakes we present a self consistent analysis of surface waves in terms of directivity parameters the boxcar is often used to recover source parameters but is rarely a faithful representation of an event s time function we demonstrate that more reliable estimates of directivity parameters can be obtained when we take into account the source time function stf of the event a low frequency stf is obtained from first r1 and second r2 orbit rayleigh waves in the range 2 to 15 mhz with a spectral synthesis and inversion method we measure the differential amplitudes between data and 3d synthetics we use the r1 r2 ratio of differential amplitudes to invert in a single narrow frequency band for the event s apparent rupture azimuth and velocity for the mw 8 1 chile 1995 event data are consistent with unilateral southward propagation with a velocity of about 2 4 km sec for the mw 7 9 mexico 1995 earthquake the rupture propagated toward the nw at about 2 0 km sec our low frequency estimates agree with broadband studies of both events and can be retrieved rapidly on a routine basis after a large earthquake

investigating microearthquake finite source attributes with iris community wavefield demonstration experiment in oklahoma author posting the authors 2018 this article is posted here by permission of the royal astronomical society for personal use not for redistribution the definitive version was published in geophysical journal international 215 2018 1072 1087 doi 10 1093 gji ggy203