guided wave propagation in laterally varying media ii lg waves in north western europe summary lg wave observations at norsar from a sequence of explosions straddling the central graben in the north sea show that the phase is almost extinguished by passing through this structure for models of the graben structure based on seismic refraction experiments with crustal thinning beneath a zone of thickened sediments numerical modelling of lg propagation shows very poor transmission the inclusion of attenuation simulating the effects of scattering from faults and other complex structures further diminishes the transmittivity the theoretical effect of a crustal pinch is to redistribute s energy over a wide range of groups velocities a pattern that fits well with the observations three components recordings at norsar of explosive charges fired in water covering a wide range of azimuths show significant transverse components to the seismograms the transverse energy builds up with travel time and for lg is of the same order as the vertical component these results are consistent with the theoretical prediction of progressive net transfer of energy from rayleigh to love modes as the wavetrain propagates through a three dimensionally heterogeneous medium

upper mantle structure under western europe from fundamental and higher mode surface waves using the nars array summary a generalized inversion of a new data set consisting of surface wave phase velocities and sn traveltimes has resulted in a new shear velocity and density model for the west european platform wepl 2 the surface wave phase velocity data set consists of fundamental and higher mode mode 1 6 measurements from 25 to 70mhz using the network of autonomously recording stations nars array which was specifically designed for higher mode surface wave measurements the sn traveltime data set consists of isc readings for selected european events major features of wepl 2 are a high velocity lid of 80 140 km depth underlain by a pronounced low velocity zone between 160 and 220 km depth the transition zone 400 650 km depth is characterized by high shear velocities with respect to prem the density shows a positive gradient from 60 to 140 km depth followed by an approximately constant value down to 400 km depth a model for the baltic shield scsh 2 is obtained by combination of nolet s 1977 higher mode phase velocity data set for western europe including the baltic shield and the present phase velocities for the platform this shield model shows an absence of the low velocity layer and low shear velocities in the top of the transition layer with respect to wepl 2 density although less well resolved shows lower values for the shield structure between 200 and 350 km depth

theoretical study of the excitation spectral characteristics and geometrical attenuation of regional seismic phases abstract we present a theoretical study of the generation and geometrical attenuation of regional crustal phases we do this through the computation of seismograms in the epicentral distance range from 60 to 500 km the geometrical attenuation of lg waves with epicentral distance is of the form r 0 83 pg wave amplitudes display a much stronger decay of the form r 1 5 the spectral density of the crustal transfer function for pg waves is relatively flat for frequencies between 0 1 and 5 hz while lg wave spectra strongly fall off beyond 2 to 3 hz the excitation of pg wave is insensitive to the depth of the source within the crust while the lg amplitude is about 50 per cent higher for a source in the upper and middle crust than in the lower crust the amplitudes of these two phases drastically decrease when the source is below the moho these results illustrate the important role of wave guide played by the crust for the propagation of lg and pg we find that the geometrical attenuation of pg and lg waves is independent of source mechanisms in the case of an explosion the excitation of pg is insensitive to the source depth the lg wave amplitude is small in comparison to pg and rayleigh waves and depends on the closeness of the source to an interface or to the free surface

mapping of crustal heterogeneity in the north sea basin via the propagation of lg waves summary the propagation of lg waves within the continental area in and around the north sea basin shows strong dependence on the path between source and receiver paths lying within the british isles and norway show very clear lg phases but paths which cross the graben zone lying in the middle of the north sea basin have very weak lg over 150 paths have now been studied across the region and the character of the lg wave has been described by comparison with the size of the sn phase for shallow events this gives a stable measure of the efficiency of lg propagation the regions which appear to block the transmission of lg are quite localized in the middle of the north sea in the region with graben structures and extend on into the netherlands a weak zone of poor transmission appears to be associated with the oslo graben with the relatively dense areal coverage provided by paths crossing the basin with a wide range of azimuths it is possible to attempt to invert for the pattern of crustal heterogeneity which gives rise to the observed character of the lg propagation an interative scheme has been devised to find the propagation properties in cells of a 1 x 1 grid and a well defined map of the heterogeneity is obtained the strongest heterogeneities correlate very well with the major tectonic features of the viking and central grabens running north south through the basin where the path coverage is greatest the position of the heterogeneity can be tightly constrained and lies within a rather narrow zone around 100 km wide despite the number of paths employed it is not possible to obtain this level of resolution over the whole region seen in the light of theoretical studies of lg wave transmission the heterogeneity map gives an indication of the strength of horizontal gradients in seismic properties in the crust these are most likely to be associated with crustal thinning beneath the graben structures

the complete synthesis of seismic crustal phases at regional distances using a new method to evaluate green s functions for elastic layered media we compute complete synthetic seismograms at regional distances for an earthquake in the earth crust we choose as source parameters the ones inferred for an earthquake in central france and compare the computed seismograms to the ones recorded at several short period stations of the french seismic network the major features of the records including complexity and duration are well reproduced by the synthetics lg waves which are the prominant phase are shown to be guided waves made up of sh and sv waves incident on the moho at angles of incidence more grazing than the critical angle and multiply reflected within the crust the length of the computed lg wave coda extends between group velocities of 3 5 and 2 8 km s and is in good agreement with the data

origin and petrogenetic implications of tourmaline rich rocks in the sierra nevada betic cordillera southeastern spain tourmaline rich rocks up to 60 tourmaline associated with low medium grade metamorphic assemblages occur in the sierra nevada area betic cordillera southeastern spain tourmaline appears in a variety of forms 1 stratiform tourmalinites 2 quartz tourmaline nodules 3 porphyroclasts in felsic orthogneisses and 4 disseminations in psammopelitic metasediments and gneisses tourmaline within these lithologic groups exhibits textural and chemical variations that reflect complex premetamorphic growth under open system conditions and subsequent changes due to alpine regional metamorphism microprobe analyses of the tourmalines reveal a wide compositional variation between schorl and dravite end members with variable contents of x site vacancies av 0 084 0 225 apfu ca av 0 095 0 269 apfu and excess of al up to 6 588 apfu compared with the theoretical value of 6 in ideal schorl and dravite the amount of ca may be significant in porphyroclasts from the gneisses fe fe mg ratios for tourmalines in tourmalinites metasediments and gneisses range from 0 34 to 0 95 0 16 to 0 92 and 0 28 to 0 97 respectively na na ca ratios are also variable mostly ranging from 0 5 to 0 9 many of the tourmalines have complex chemical and colour zoning patterns including significant fluctuations in al fe mg na ca ti and f based on petrographic and chemical data three generations of tourmaline have been established the first generation corresponds to magmatic postmagmatic tourmaline that is represented by tourmaline porphyroclasts within the orthogneisses the second generation of tourmaline formed during tourmalinization of psammopelitic rocks giving rise to tourmalinites the third generation of tourmaline is represented by cellular textures pale reaction rims and overgrowths developed during the alpine regional metamorphic overprint d 2002 elsevier science b v all rights reserved

on regional s the character of regional s wave trains is quite complex and consists of two major elements sn waves which principally travel in the upper mantle and lg waves guided in the earth s crust the effect of lateral heterogeneity is to modify the signals for these phases compared with the predictions for horizontally stratified models however complete synthetic seismogram calculations for simple stratified crustal models for a suite of distances out to 950 km including both sn and lg provide a range of insights into the nature of the s wave train in particular late picks of sn arrivals are likely to arise because the actual s onset has been missed in the p coda and a higher amplitude surface multiple phase with an extra crustal delay has been picked instead such a effect was first recognized by lapwood 1955 in a study of the iss readings for a sequence of japanese events recorded at regional distances but has usually not been taken into consideration in studies using regional networks lateral heterogeneity along the propagation path has the effect of inducing interconversion between sn and lg energy and thus alters the character of the s wave train the lower attenuation for s in the uppermost mantle compared with the crust frequently leaves sn as the most prominent phase at ranges greater than 1000 km long range propagation of high frequency lg requires a relatively undisturbed crust

density versus depth models from multimode surface waves multimode love and rayleigh wave data related to the pacific ocean and to north america are inverted using two sets of parameters 1 the isotropic p and s velocities plus the density and 2 five elastic parameters describing a transversely isotropic medium plus the density it is found that the assumption of isotropy leads to very unrealistic upper mantle models while much more realistic models are obtained under the assumption of transverse isotropy the lateral variations in density between the pacific ocean and north america are then less than 1 5 and in both regions a large density gradient is well resolved at a depth near 360 km

seismic wavefield calculation for laterally heterogeneous earth models ii the influence of upper mantle heterogeneity summary there is increasing evidence that the earth s mantle is laterally heterogeneous on a broad range of scales but the character of smaller scale heterogeneity has to be deduced indirectly the aim of the present paper is to examine the influence of a variety of stochastic representations of heterogeneity on seismic wave behaviour to help constrain the nature of the variations in seismic properties in the upper mantle for each of the models the seismic wavefield is simulated using a pseudospectral method in a 2 d cylindrical coordinate system the presence of stochastic heterogeneity is particularly important for those parts of the seismic wavefield where a significant portion of the propagation path in the upper mantle is close to horizontal such as the pp and ss phases and fundamental mode and higher mode surface waves the effects are noticeable traveltime anomalies and waveform changes for the body waves particularly associated with phase triplications and significant phase shifts for rayleigh waves a variety of styles of stochastic heterogeneity models are compared for the same source and station configurations using wavefield snapshots and the character of the calculated seismograms the influence of heterogeneity on body waves and on longer period rayleigh waves increases as the scale length increases compared to the wavelength of the seismic waves the aspect ratio of the heterogeneity has a pronounced effect on the coherence and amplitude of traveltime fluctuations and waveform changes across stations at the surface which depend on the structures encountered along the propagation paths to the specific receivers the effect of nearly isotropic heterogeneity is to induce small short scale variations in traveltime fluctuations and waveform changes as the heterogeneity becomes more plate like the fluctuations are on a broader scale and of larger amplitude because the individual patches of heterogeneity have a stronger influence the effects of broad scale and stochastic heterogeneity are compared for a model built from a slice through a tomographic model derived from delay time inversion for the himalayan region as would be expected the influence of the deterministic heterogeneity derived from the tomography study has the result of introducing systematic traveltime variations for body waves and noticeable phase shifts for surface waves when compared with the results for the background reference model the addition of a moderate level of small scale stochastic heterogeneity which could not be resolved in the tomography study has a limited effect on the seismic wavefield at longer periods but is much more significant for periods of less than 4 s when the heterogeneity scale is of the order of 40 km

propagation of regional seismic phases in the indian shield constraints on crustal and upper mantle velocity models the regional seismic wave field in the central indian shield is studied including propagation characteristics of various prominent phases well recorded in the broadband seismograms of the 21 may 1997 jabalpur deep crustal focal depth 36 km earthquake m w 5 8 the seismograms covering a distance range out to about 1650 km although limited in number seem to well reveal the prominent phases including the p bar and lg as well as the high frequency pn and sn and their coda by detailed numerical simulations the generation and propagation characteristics of the p bar phase from earthquake sources at shallow and deep crustal depths are examined it is found that the p bar phase propagates efficiently at regional distances even for a deep crustal source depth the p bar phase is nevertheless very sensitive to the surface layer velocity structure extremely weak in the absence of a low velocity surface layer and also slightly weak in the presence of a relatively high velocity surface layer analyses of the jabalpur earthquake seismograms and the synthetics reveal that the p bar phase is well generated and propagates efficiently in the deccan traps v p 4 8 4 9 km sec covered regions i e even without a lower velocity surface layer surrounding the earthquake epicenter and the recording stations further the anatomy of the p bar phase is revealed by several computational models its time window composed of several multiple pmp reflections as well as pms conversions the principal boundaries being the moho and the free surface the first observations of high frequency pn and sn phases in the indian shield are recognized from the jabalpur earthquake seismograms by numerical simulations consistent with these observations including the coda a lamellae model with alternating high and low velocity layers for the structure of the indian continental uppermost mantle is inferred a complete synthesis of the regional seismograms is obtained based on the inferred models of the p and s wave velocity structure of the crust and upper mantle in the central indian shield comparison of the synthetics with the jabalpur earthquake seismograms reveals a consistent fit to various observations including the lg phase group velocity window 3 6 3 2 km sec the low pass filtered seismograms at the regional distances are further found to reveal coherent phases consistent with predicted reflection times from discontinuities in the upper mantle a plausible p velocity model inferred from these observations reveals velocity discontinuities at average depths of 230 320 430 and 680 km suggesting significant stratification of the upper mantle b region in the indian shield

spectral analysis of seismic waves in the northern indian ocean region abstract attenuation of ground motion amplitudes away from the seismic source is recognized as a significant issue by researchers of particular interest is the attenuation or propagation of seismic waves from long distance sources regions like sri lanka have experienced tremors from events as far as 1500 km a recently identified diffusing plate boundary just around 300 km away from the southern tip of sri lanka poses significant seismic risk however a comprehensive study of the region with respect to the propagation or attenuation of seismic waves has generally been lacking with the availability of new archival data of 71 events recorded at three digital broadband stations we have estimated q value for the northern indian ocean region surrounding sri lanka multiple linear regression analysis of recorded vertical component fourier acceleration amplitudes yields a relatively higher q 0 value of about 389 2 35 for the subject region furthermore the combined effect of upper crustal amplification and attenuation has been assessed using the standard horizontal to vertical ratio method the negligible upper crustal modifications obtained from the analysis imply the presence of an older crustal rock stratigraphy at near source depths around the subject region source spectra of recorded events have also been derived by correcting the observed amplitudes for geometric and anelastic attenuation the source spectra analysis resulted in a typical stress drop value of about 50 bars which is consistent with brune s source spectra models stochastic modeling of a recent m w 8 6 event that occurred in the region was undertaken based on the parameters derived from the analysis and compared with the real recorded spectra results show a reliable match between the simulations and the recorded spectra which supports the validity of the estimated parameters seismological parameters derived from this study can provide reliable estimates of seismic hazard of sri lanka

tourmalines from appalachian caledonian massive sulfide deposits textural chemical and isotopic relationships tourmaline is a common gangue mineral in several strata bound massive sulfide deposits of the appalachian caledonian orogen most of the tourmaline rich deposits occur in dominantly metasedimentary terranes such as bleikvassli norway black hawk maine ore knob north carolina and elizabeth vermont minor amounts of tourmaline are also known in association with volcanic hosted deposits in the appalachians and in the trondheim district of norway the tourmaline forms isolated euhedral crystals or crystal aggregates in massive sulfide and adjacent wall rocks in a few areas it is found in conformable tourmaline rich layers tourmalinites associated minerals may include quartz plagioclase phlogopite and dolomite with pyrrhotite chalcopyrite galena and sphalerite many of the tourmaline crystals are optically zoned in which brown zones concentrically alternate with pale yellow or green zones a few specimens of tourmaline intergrown with massive sulfide e g ore knob display fine delicate growth lamellae similar to those commonly observed in hydrothermal vein sphalerites skarn garnets and sphalerites from the massive sulfide deposits of the kuroko district japan detailed geochemical studies indicate that the tourmalines have characteristic major and trace element compositions electron microprobe analyses show that with rare exception the tourmalines are mg rich dravites avg feo feo mgo 0 21 abrupt transitions between color zones within some tourmaline are accompanied by relative variations in feo feo mgo of as much as 30 percent yellow brown zones are more mg rich than blue or green zones in contrast the fine growth lamellae are not characterized by such variations in chemistry spectrographic analyses of pure mineral separates indicate that the tourmalines also contain high average contents of cr 78 ppm cu 77 ppm pb 114 ppm sr 98 ppm and v 195 ppm while uniformly low in li 7 ppm and mn 382 ppm in all analyzed samples fluorine is much more abundant than chlorine the average f cl ratio is 33 tourmalines from tourmalinites and massive sulfide deposits are typically characterized by heavier delta 18 o values 9 5 15 5ppm and less variable heavier delta d values generally 45 to 60ppm than tourmalines from unmetamorphosed igneous pegmatites the latter typically have delta 18 o 9 5 per mil and delta d or 60 per mil oxygen isotope fractionations between quartz and tourmaline delta 1 27 4 01 do not correlate directly with inferred grade of subsequent metamorphism although in areas of high metamorphic grade the delta values approach those of igneous quartz tourmaline pairs the delta 18 o values of quartz and tourmaline are believed to reflect variation in the oxygen isotope compositions of the host lithologies the similar narrow range in hydrogen isotope composition for tourmaline in all studied deposits is compatible with a modified seawater origin for the tourmaline and sulfide forming fluids the distinctive textural and chemical characteristics of the tourmalines reported here have both exploration and genetic significance though it may have undergone recrystallization and some accompanying chemical and isotopic exchange during regional metamorphism tourmaline in the massive sulfide deposits is an early formed perhaps diagenetic mineral in which fine lameliar zoning may be a preserved premetamorphic feature in any case the tourmalines from the massive sulfide deposits are mg rich dravites with trace element and stable isotope compositions substantially different from those of the fe rich schorls typical of most granitic rocks these geochemical and isotopic signatures are attributed to the original environment of formation of the associated sulfide deposits and suggest that mg rich tourmaline may be a valuable prospecting guide in the search for massive sulfide deposits

geological fluid inclusion and isotopic studies of the yinshan cu au pb zn ag deposit south china implications for ore genesis and exploration abstract the yinshan cu au pb zn ag deposit is located in dexing south china ore bodies are primarily hosted in low grade phyllite of the neoproterozoic shuangqiaoshan group along ew and nnw striking fault zones pb zn ag mineralization is dictated by jurassic rhyolitic quartz porphyries ca 172 ma whereas cu au mineralization is associated with jurassic dacite porphyries ca 170 ma the main ore minerals are pyrite chalcopyrite galena sphalerite tetrahedrite tennatite gold silver and silver sulphosalt and the principal gangue minerals are quartz sericite calcite and chlorite two phase liquid rich type i two phase vapor rich type ii and halite bearing type iii fluid inclusions can be observed in the hydrothermal quartz sulfides veins type i inclusions are widespread and have homogenization temperatures of 187 303 c and salinities of 4 2 9 5 wt nacl equivalent in the pb zn ag mineralization and homogenization temperatures of 196 362 c and salinities of 3 5 9 9 wt nacl equivalent in the cu au mineralization the pervasive occurrence of type i fluid inclusions with low moderate temperatures and salinities implies that the mineralizing fluids formed in epithermal environments the type ii and coexisting type iii inclusions from deeper levels below the cu au ore bodies share similar homogenization temperatures of 317 448 c and contrasting salinities of 0 2 4 2 and 30 9 36 8 wt nacl equivalent respectively which indicates that boiling processes occurred the sulfur isotopic compositions of sulfides 34 s 1 7 to 3 2 suggest a homogeneous magmatic sulfur source the lead isotopes of sulfides 206 pb 204 pb 18 01 18 07 207 pb 204 pb 15 55 15 57 and 208 pb 204 pb 38 03 38 12 are consistent with those of volcanic subvolcanic rocks 206 pb 204 pb 18 03 18 10 207 pb 204 pb 15 56 15 57 and 208 pb 204 pb 38 02 38 21 indicating a magmatic origin for lead in the ore the oxygen and hydrogen isotope compositions 18 o 7 8 to 10 5 d 66 to 42 of inclusion water in quartz imply that ore forming fluids were mainly derived from magmatic sources the local boiling process beneath the epithermal cu au ore forming system indicates the possibility that porphyry style ore bodies may exist at even deeper zones

s wave attenuation in the marmara region northwestern turkey the frequency dependent attenuation of shear waves in the crust is estimated by using two different methods based on the rate of time decay of coda wave amplitude qc 1 and the rate of decay of the s wave to coda wave amplitude ratio with distance qs 1 the epicentral distances of selected earthquakes range between 20 and 110 km and magnitudes are around 3 the quality factors qc are calculated at frequencies of 1 5 3 6 12 and 24 hz and lapse times of 40 50 60 and 70 s estimated qc values show a dependence on frequency and lapse time we observed the similarity in the frequency dependency of qc 41 1 07 f1 08 0 03 and qs 50 1 7 f1 09 0 05 for a lapse time of 50 s indicating that the attenuation mechanism for coda waves is similar to that of the direct s waves

lg wave attenuation in the australian crust abstract we estimate the lg wave quality factor q across the australian continent from vertical component lg waveforms a tomographic inversion is performed to construct an lg attenuation model for 58 frequencies between 0 05 and 10 0 hz the available spatial resolution is approximately 1 5 1 5 for the 0 5 2 0 hz band at 1 0 hz the lg wave q over the whole island continent varies from 50 to 1250 with an average value of 850 significant regional variations in the lg wave q images tie well with many geological features and boundaries in australia the cratons in western northern and southern parts of australia usually have higher q values 700 1250 while the volcanic regions sedimentary basins and orogenic areas in eastern australia are characterized by increased attenuation lower q values 50 650 we determine the frequency dependent q of lg waves for different blocks across australia and find the frequency dependence of q is much more complex than the traditional single power law representation when combined with the assumed geometrical spreading relation the lg q maps provide a new way of assessing potential ground motion across the continent for any event location

amplitude tomography of lg waves in xinjiang and its adjacent regions amplitude tomography of lg waves at frequencies from 1 to 5 hz are investigated in this work to reveal the lateral attenuation heterogeneities of the study area the xinjiang uygur autonomous region of china and its adjacent regions by using a large set of broadband seismic waveform data first we inverted the average q lg at each of 10 frequencies from 0 5 to 5 hz then the study area was divided into evenly spaced 1 1 grid cells after conducting both a checkerboard test and a resolution test finally the high resolution q lg tomographic images at the 10 frequencies were obtained the moment magnitudes of the events and the site terms of the stations we used were obtained simultaneously the attenuation pattern of q lg at each frequency shows obvious lateral heterogeneities in xinjiang and its adjacent regions which are coincident with the geological features of the area the tarim basin and the middle and the eastern part of the southern tian shan belong to high q regions the northeastern margin of the pamir plateau the northwestern margin of the tibetan plateau the western part of the southern tian shan and northern tian shan are prominent low q areas the attenuation pattern of lg waves shows that large scale tectonic boundaries zones with rapid topographic or crustal thickness gradient are in good accordance with the boundaries of the high and low q lg most of the historical strong earthquakes occurred on the interior or edge of low q lg areas

on the nature of regional seismic phases i phase representations for pn pg sn lg summary an operator development of the seismic wavefield is used to generate descriptions of the propagation processes contributing to the main regional seismic phases pn pg sn lg these operator forms are valid for laterally heterogeneous crust and mantle models and include the major processes of interconversion between wavetypes these representations of the regional phases are used to examine the theoretical basis for discriminants between earthquakes and underground explosions based on the relative amplitudes of p and s phases the ratio of sn to pn amplitude looks promising as a high frequency discriminant however the ratio of lg to pn amplitudes is not as useful because of the complex nature of the propagation characteristics of lg

petrogenesis of the mafic igneous rocks of the betic cordilleras a field petrological and geochemical study mafic igneous rocks are widespread in the nevado filabride complex the lowermost metamorphic unit of the internal zones of the betic cordilleras they form intrusive small discontinuous bodies predominantly dikes with subordinate small lava flows the entire complex underwent alpine compressional metamorphism during the paleogene continental collision resulting in eclogites and blueschists in the mafic bodies and high pressure assemblages in the intruded metasediments locally weakly metamorphosed or completely unmetamorphosed igneous rocks with the same textural features occur as patches surrounded by eclogitized igneous rocks the bulk rock chemistry of unmetamorphosed and completely metamorphosed mafic igneous rocks is consistent with an alkaline to transitional tholeiitic magmatism with typical within plate geochemical characteristics all but a few samples are nepheline normative and display ree and trace element characteristics typical of continental rift related magmatism this conclusion is strongly supported by the mineral chemistry of the major constituents in particular the calcic ti rich character of clinopyroxene the lack of orthopyroxene and the occurrence of kaersutitic amphibole incompatible trace element abundances and sr and nd isotopes support the provenance of these magmas from a variably metasomatized previously depleted sub continental lithospheric mantle source

regional wave propagation in china and its surrounding regions a comprehensive study of the gross characteristics of high frequency seismic wave propagation in china and its surrounding regions was accomplished to learn more about how regional geology affects high frequency phases amplitudes of the regional seismic waves sn and lg relative to p coda were used to map lateral variations of shear wave attenuation in the crust and upper mantle over 7000 digital seismograms from 13 broadband stations of the chinese digital seismic network and global seismic network in the frequency range 0 5 to 5 0 hz were visually examined propagation efficiencies of sn and lg were qualitatively analyzed by ranking their amplitudes relative to the p wave coda efficient sn propagation is observed in the tien shan tarim platform southern tibet yangzi paraplatform and sino korean platform we have confirmed results of previous studies by finding a lack of sn transmission in north central tibet the ryukyu and japan arcs burma and the baikal rift an important observation which has not been previously reported is that sn does not propagate across mongolia the elimination of sn and the occurrence of recent volcanism in north central tibet and mongolia suggest that there is partial melt in the uppermost mantle beneath those regions high frequency lg waves propagate efficiently for most of china indochina and mongolia lg signals are attenuated within central tibet as well as along its southern boundary crustal structure variations along with an anomalously low q crust are primarily responsible for weakened lg amplitudes in tibet propagation paths across oceanic crust in the sea of japan and the andaman sea show blockage of the lg phase as well this investigation has relevance to comprehensive test ban treaty monitoring by showing where certain regional phases will or will not propagate efficiently

differences in attenuation of ground motion perpendicular to the mexican subduction zone between colima and guerrero an explanation based on numerical modeling abstract a recent article tejeda jacome and chavez garcia 2007 showed that significant differences in seismic ground motion attenuation perpendicular to the pacific coast exist between guerrero and colima in western mexico for hypocentral distances larger than 100 km larger ground motions are predicted using a model derived from local data in the northern section of the subduction zone colima relative to ground motion models derived using data from the southern section guerrero in this article we consider two possible explanations for the differences the first possible explanation is differences in the geometry of the subducting slab between colima and guerrero the second is the varying shallow structure of the overriding plate due to the presence of the trans mexican volcanic belt tmvb oblique to the middle american trench we use 2d numerical modeling for p sv waves to investigate which of the two factors can explain the differences in the observed attenuation our results show that it is the presence of the tmvb closer to the coast in colima that better explains the differences

generation of the teleseismic p wave coda from aleutian earthquakes summary we investigate large amplitude phases arriving in the p wave coda of broad band seismograms from teleseisms recorded by the grafenberg array the german regional seismic network and the global seismic network the data set consists of all events mb 5 6 from the aleutian arc between 1977 and 1992 earthquakes with large amplitude coda waves correlate with the presence of oceanic crust in the source region the amplitudes sometimes approach those of the p wave much larger than predicted by theory modelling indicates that phases in the p wave coda cannot be p wave multiples beneath the source and receiver or underside reflections which precede pp from upper mantle discontinuities among the events seismograms are very similar where the arrival times of the unusual phases agree approximately with the predicted times of s to p conversions from the upper mantle discontinuities under the source because the large amplitude phases in the p wave coda have little if any dependence on event depth and have predominantly an sv wave radiation pattern towards the receiver we suggest that they originate as sv and or rayleigh waves and are enhanced by lateral heterogeneity and multipathing from the subducting aleutian slab

stochastic prediction of ground motion and spectral response parameters at hard rock sites in eastern north america empirical predictions of ground motions from large eastern north american earthquakes are hampered by a lack of data for such events for this reason most prediction techniques have been based at least in part on data from the seismically active and well instrumented western north america concentrating on the prediction of response spectra on hard rock sites we have used a relatively new theoretical technique that does not require western data to make ground motion predictions for eastern north america this method often referred to as the stochastic model has its origins in the work of hanks and mcguire who treat high frequency motions as filtered random gaussian noise for which the filter parameters are determined by a seismological model of both the source and the wave propagation the model has been successfully applied to the predictions of ground motions in the western united states and to short period magnitudes from large to great earthquakes worldwide for our application the essential parameters of the model are estimated by using existing data from small to moderate eastern north american earthquakes a crucial part of the model is the relation between seismic moment and corner frequency the relation proposed in 1983 by nuttli for mid plate earthquakes leads to predictions of ground motions that are lower than available data by a factor of about 4 on the other hand a constant stress parameter of 100 bars gives model predictions in good accord with the data to aid in applications the ground motion predictions are given in the form of regression equations for earthquakes of magnitude 4 5 to 7 5 at distances within 100 km of the source the explanatory variables are hypocentral distance and moment magnitude m because predictions are often required in terms of m g rather than m we have used the theoretical model to establish a relation between the two magnitudes the predicted relation agrees with the sparse data available although the large uncertainties in the observed magnitudes for the larger events as well as the sensitivity of the theoretical magnitude to the attenuation model make it difficult to discriminate between various source scaling models

lg and rg waves on the california regional networks from the december 23 1985 nahanni earthquake we investigate lg and rg propagation in california using the central and southern california regional networks approximately 550 stations constitute these two short period networks providing a dense coverage of almost the entire state the waveforms recorded from the december 23 1985 nahanni canada earthquake are used to construct three profiles along the propagation path almost n s and three perpendicular to the propagation path almost e w to look at the nature of propagation of these two types of surface waves groups of records from stations in various geological and tectonic provinces in california are also examined in order to establish regional characteristics of the surface waves we find that the propagation characteristics of lg differ from those of rg across california lg waves are apparently more sensitive to crustal heterogeneities the most striking observations are the similarity of coda for both the lg and the rg waves within geologic provinces and the marked difference in coda between regions these differences are seen in the amplitudes coda duration shape of the energy envelope frequency content and sharpness of the phase initiation in general a decrease in the moho depth near the pacific coast is correlated with a decrease in the surface wave amplitude especially at higher frequencies 0 15 0 2 hz most interesting is the association of the san andreas fault with abrupt changes in the wave train amplitudes the surface waves are amplified in the vicinity of the fault zone and then decrease in amplitude after the zone is crossed in the coast ranges amplitudes are low and waveform coherence is poor the rg phase dominates the record in the sierra nevada and both surface waves are amplified by the thick sedimentary sequence of the great valley

source parameters and scaling relationships of earthquakes in israel abstract determination of earthquake dynamic source parameters such as the seismic moment stress drop and rupture area are often based purely on theoretical considerations in reality however some of the corrected coefficients utilized in the computations should preferably be defined empirically in the present study 39 earthquakes of ml between 3 0 and 6 7 are used to define the correction coefficients associated with distance geometric and unelastic attenuation and ratios between zero frequency spectral amplitides of s waves recorded by vertical and horizontal seismographs these are used in turn to determine the seismic moment m0 and the empirical correlation between log m0 and ml magnitudes for that region the validity of using constant stress drop assumption and correlation between moment and corner frequency is also discussed

mineralogy geochemistry and geological significance of tourmaline rich rocks from the paleozoic cinco villas massif western pyrenees spain tourmaline rich rocks associated with clastic metasedimentary rocks of carboniferous age occur in the cinco villas massif western pyrenees three types of tourmaline rich rocks were distinguished 1 fine grained stratiform tourmaline rich rocks which are associated with carbonaceous metapelites tr1 2 stratabound tourmaline rich rocks associated with metapelites in the contact aureole of the aya granitoid pluton tr2 3 stratabound to massive tourmaline rich rocks associated with psammopelites in contact with granites and pegmatites tr3 tourmalines belong to the schorl dravite solid solution series and have a wide compositional range from nearly end member dravite for tr1 tourmalines to schorl for tr3 tourmalines tr2 tourmalines have intermediate compositions the fe fe mg typically varies between 0 02 and 0 55 increasing from tr1 to tr3 the tr1 tourmalines commonly display a discontinuous chemical zoning with fe rich green cores 8 8 5 feo and mg rich colorless rims 10 11 mgo in contrast crystals that exhibit fine growth lamellae appear to lack significant chemical zoning oxygen and hydrogen isotope compositions also reveal major differences between tr1 and tr3 tourmalines the former displaying heavier 18o values 17 7 19 and d values 35 to 42 than tr3 tourmalines 11 to 13 and 47 to 76 respectively the tr2 tourmalines show intermediate values of 11 3 to 14 6 for 18o and 40 to 55 for d linear and continuous chemical variations obtained for major and trace elements of the whole rocks reflect mixing between clay rich and quartz rich end members indicative that some tourmaline rich rocks contain a significant detrital component chondrite normalized ree rare earth element patterns of tourmaline rich rocks are similar to those of surrounding unaltered clastic metasediments except for some tr1 rocks which are characterized by low contents of ree mass balance calculations show that tourmaline forming processes plus metamorphism led to mass and volume changes at mesoscopic scales 10 for the tr1 tourmalinites silicon fe mn and ree elements were partially lost from sedimentary rocks whereas mg and particularly b were added to pelitic sediments available data nevertheless do not allow an assessment of the boron source formation of the tr1 tourmaline rich rocks probably was the net result of several processes including direct precipitation from b rich hydrothermal fluids or colloids early diagenetic reactions of carbonaceous pelitic sediments with these fluids and subsequent recrystallization during regional metamorphism the tr2 tourmaline rich rocks mainly developed by metamorphic recrystallization of tr1 tourmaline rich rocks and veins adjacent to pegmatites and granitic rocks tr3 are the result of boron metasomatism the primary boron having been recycled from stratiform tourmalinites during regional metamorphism and magmatism

hypocenter constraint with regional seismic data a theoretical analysis for the natural resources defense council network in kazakhstan ussr source depth and epicenter determination remains a simple but key method for discrimination between earthquakes and nuclear explosions at near regional distances a variety of secondary body wave arrivals can be observed that may be useful for constraining source depth and epicenter in this paper we study the source location problem using regional arrival time and arrival azimuth data from a sparse seismic network a theoretical analysis of the source location inverse problem provides estimates of the stability and uncertainty of the solution for a particular suite of data as a function of epicenter and depth as well as evaluating the importance of each datum to the solution an empirical analysis with actual data complements the theoretical analysis our approach is applied to the three station natural resources defense council soviet academy of sciences network in kazakhstan the theoretical analysis indicates that reasonable constraint on depth and epicenter is possible whenever three distinct phases p pn pg pzp and pmp or equivalent s phases are observed at two or three stations our theoretical analysis for two station locations shows that the epicenter constraints are extremely poor for sources along the line passing through the two observing stations the use of arrival azimuth in two station locations results in improvement in epicenter constraint for events occurring in the vicinity of the line connecting the two stations but there is no significant improvement elsewhere an empirical analysis of data from two of the september 1987 chemical explosions and data from an explosion in an active mining area supports the theoretical analysis showing that two station locations both epicenter and depth are quite reliable furthermore the theoretical analysis also indicates that even with data from a single observing station satisfactory results are obtained if three or more phases plus arrival azimuth are available

attenuation of high frequency shear waves in the crust measurements from new york state south africa and southern california we compare the attenuation of high frequency 3 30 hz shear waves for crustal paths in new york state south africa and southern california over source receiver distances of about 10 400 km the data consist of digital recordings of s waves 5 100 km and lg waves 100 400 km produced by earthquakes we use a coda normalization method to remove the effects of site amplification and source excitation from the amplitudes of the s and lg waves over the entire distance range studied 10 400 km the amplitude decay of 3 hz shear wave energy is considerably less for the tectonicaily stable areas of new york and south africa than for the tectonicaily active region of southern california high frequency 30 hz s wave attenuation is significantly less for new york and south africa than for southern california for distances between 15 and 90 km we parameterize the decay with distance r of coda normalized shear wave amplitudes with a frequency independent q and geometrical spreading exponent where geometrical spreading is proportional to r for new york state the s wave amplitude decay 3 30 hz is well described by a frequency independent q of 2100 330 490 and of 1 3 0 1 the decay of lg wave amplitudes from 3 to 15 hz in the new york state region is fit with a frequency independent q of 1600 280 330 of 0 70 0 2 the s wave amplitudes 3 30hz in south africa yield a q of 1500 190 380 and of 1 3 0 1 fixing the geometrical spreading at r 0 5 produces an lg wave q estimate at 3 hz in south africa of 360 50 80 this lg wave q is low considering that south africa is a cratonic tectonicaily stable area the s wave amplitudes from southern california are described with a frequency independent q of 800 150 240 and a large geometrical spreading exponent of of 1 9 0 2 we find an lg wave q at 3 hz of 260 30 for southern california after constraining the geometrical spreading at r 0 5

frequency dependent lg attenuation in the indian platform we use seismograms from regional earthquakes recorded on digital seismographs in peninsular india to determine the frequency dependent q of lg for the indian platform we measure lg attenuation by determining the decay of spectral amplitudes with distance the available data suggest some spatial variation in attenuation but a much denser ray path coverage would be required to validate such observations we therefore combine all the measurements of overlapping regions that span both the shield and intervening terranes to obtain an average value of attenuation for the indian platform lg q 665 10 with the frequency exponent n 0 67 0 03 this average value of lg attenuation for the indian platform is similar to the average for other stable regions of the globe

regional phases in continental and oceanic environments summary the very different crustal thicknesses between continental and oceanic crust lead to the establishment of distinct styles of regional seismic wavefield observations and numerical simulations of events near subduction zones in japan allow a direct comparison of seismic wave propagation in oceanic and continental structures the thick zone of lower seismic velocities in the continental crust acts to trap s wave energy in particular and generates crustally guided phases such as pg lg in the oceanic environment there is no efficient s wave trapping and crustal energy progressively leaks into the mantle reverberations in the crust and the water above help to sustain the amplitude of the mantle arrivals pn sn to large distances

regional wave propagation from mexican subduction zone earthquakes the attenuation functions for interplate and inslab events the seismic waves from subduction zone earthquakes are significantly affected by the presence of 3d variation in crust and upper mantle structure around the source area these heterogeneous structures also profoundly modify the character of seismic waves as they propagate from the source area to regional distances this is illustrated by studying shallow interplate earthquakes along the mexican subduction zone and deeper inslab normal faulting earthquakes in the subducted cocos plate beneath mexican mainland the strong motion recordings of these earthquakes are used to evaluate the character of wave propagation along the path between the source region and mexico city we compare the wavefield from two large earthquakes of different source type during the shallow h 17 km interplate 1995 guerrero earthquake m w 7 3 the lg phase is the most prominent feature at regional distances of about 150 to a few hundred kilometers from the source the presence of a lateral velocity gradient in the crust caused by the subduction of the cocos plate enhances the lg wave amplitude which is then amplified further in the mexican volcanic belt by amplification in the low velocity volcanic rocks both effects lead to very large ground motions along the path from the coast to the mexican inland in the frequency band from 0 2 to 4 hz however for the deeper h 40 km inslab normal faulting 1999 oaxaca earthquake m w 7 5 the amplitude of the lg phase is too small to produce the abnormal wave propagation and the direct s wave and its multiple sms reflections between the free surface and moho show a simple attenuation with increasing distance we compare these observations with numerical simulations of seismic wave propagation using the fourier spectral method the results provide a key to the understanding of seismic wave field generated by shallow interplate and deeper inslab earthquakes in a realistic 3d heterogeneous structure

regional pn body wave magnitude scale mb pn for earthquakes along the northern mid atlantic ridge we obtained a robust regional body wave magnitude scale mb pn for earthquakes along the northern mid atlantic ridge by using pn wave recorded at continental stations the new magnitude scale is mb pn log10 a nm 1 86 log10 100 km c 1 62 where a is the zero to peak amplitude of pn wave on the simulated vertical wood anderson seismogram in nanometers is the epicentral distance in kilometers 1 86 represents amplitude attenuation c is the station correction and 1 62 anchors the mb pn to the moment magnitude mw plus amplitude loss in the two crustal legs by using moment magnitude as reference we obtained the event magnitude adjustments ema which represent the difference between the known long period mw and the short period mb pn emas correlate with the source property where ridge events show strong long period waves but poor high frequency signals which lead to mb pn mw and negative adjustment of 0 20 0 24 m u almost all normal faulting events are along spreading ridges whereas strike slip events are along the fracture zones and transform faults hence we developed source specific magnitude adjustments ssma which range from 0 27 m u for earthquakes along the ridges to 0 26 m u for earthquakes along the transform faults using ssma we obtained a regional pn magnitude that is consistent with mw and mb p the regression relationship is mw 0 91 mb pn ssma 0 46 with a standard deviation of 0 15 m u

analysis of short period regional phase path effects associated with topography in eurasia propagation of regional seismic phases is highly dependent on path effects but we have a limited understanding of these effects and no general procedure for accounting for path variation influence on regional waveforms thus there is strong regional variability in the effectiveness of regional wave discriminants used to identify small earthquakes and nuclear explosions motivated by many observations of correlation between surface geology and regional phase behavior we empirically explore the relationship between short period regional and upper mantle distance signal energy and statistics of topography along different travel paths using data for underground nuclear explosions at semipalatinsk kazakhstan we find strong linear correlations of the logarithmic rms amplitude ratio sn lg and to a lesser extent p lg with mean altitude rms roughness rms slope and skewness of topography along the paths to receivers in eurasia this indicates that energy partitioning in the regional wave field is controlled by wave guide structure and attenuation variations that are manifested in surface topography this suggests that it is feasible in many cases to directly calibrate regional discriminants for path effects in terms of observable surface topography as a surrogate for overall path properties the relationships also help to understand the nature of regional phase propagation

seismic anisotropy the state of the art ii summary the theory causes observations and possible applications of seismic anisotropy in the earth have developed considerably since the previous state of the art paper was published in 1977 the behaviour of waves in layered anisotropic media is now much better understood and the evidence for seismic anisotropy indicates that anisotropy is likely to be present throughout much of the crust and upper mantle the top few hundred kilometres of the mantle appears to be anisotropic with the orientations aligned by the present or palaeo stress field the upper part of the crust is frequently anisotropic probably due to cracks differentially aligned by the non lithostatic stresses the possibility of being able to monitor crack geometry by seismic techniques opens a wide range of applications in currently important activities

contrasts in regional seismic wave propagation to station wmq in central asia summary the varying character of regional seismic phase propagation in central asia is well illustrated by the character of the seismograms at the urumqi station wmq in xinjiang china three different classes of behaviour are seen for propagation across the relatively stable platforms to the north along the tien shan chain and across the tarim basin from tibet these paths demonstrate the influences of the variation in crustal structure on the regional phases particularly the tibetan plateau and its north and south boundaries but also the influence of the pamirs on propagation along the tien shan as an interference phase lg is sensitive to changes in crustal structure and can be used to study crustal heterogeneity lg can propagate along the tien shan chain trapped by the gradients in structure on either side but with a progressive loss in amplitude and frequency however once the northern boundary of tibet is crossed the high frequencies in the lg train are lost and there is little recognizable arrival the amplitude ratios of the different crustal phases pn sn and lg can be used to characterize the behaviour and the different classes of propagation can be further separated when account is made of the frequency content in the lg window the influence of the transitions in crustal structure at the northern edge of the tibetan plateau on propagation to wmq is investigated using numerical modelling with the pseudospectral method for models of crustal variations this demonstrates how the crustal pinch at the northern boundary operates to modify the fairly efficient propagation inside tibet with substantial transfer of energy into the mantle

stochastic waveguide in the lithosphere indonesian subduction zone to australian craton summary earthquakes occurring in the indonesian subduction zone recorded in the cratonic regions of northern australia have long high frequency coda associated with both p and s waves similar behaviour is seen for earthquakes within australia on paths within the cratonic regions the complex character of the coda and its rapid spatial variation indicate that the high frequency waves have travelled within a zone of strong multiple scattering with very high intrinsic q there are subtle variations in the nature of the coda that can be described through a coda q the variations in coda are associated with the position along the arc and the nature of the transition from the subduction zone to the continental lithosphere the character of the coda observations can be captured with numerical simulations in models derived from seismic tomography for northern australia and the neighbouring subduction zone incorporating lower crustal and mantle heterogeneity with much longer horizontal than vertical correlation length high frequency calculations to high frequency 16 hz for long propagation distances up to 1500 km have been carried out using finite difference modelling on the earth simulator the variations in coda properties can be associated with the way in which the seismic energy gets ducted into the stochastic waveguide associated with the lithosphere the most efficient transfer occurs where continental lithospheric material is adjacent to the earthquake zone

mechanisms of seismic attenuation in the crust scattering and anelasticity in new york state south africa and southern california the envelopes of high frequency seismograms from earthquakes in new york state south africa and southern california are analyzed to determine how much of the observed attenuation of shear waves in the crust is caused by anelasticity and how much is produced by scattering from small scale heterogeneities for seismograms from new york and south africa there is a systematic enrichment of high frequency energy that develops in the coda relative to the direct s or l sub g waves the author uses the growth with source receiver distance of the high frequency energy in the coda relative to the direct wave to estimate the scattering attenuation of the crust and the relative time decay of high frequency energy in the coda to determine the anelastic attenuation using the estimate of l sub g wave q as a constraint he finds that the scattering q in the crust of new york is either independent of frequency or increases with frequency f slower than f sup 0 3 a similar analysis for south africa indicates that scattering is the major cause of the observed s wave attenuation of high frequency energy 30 hz at local distances 100 km for southern california the extent of the scattering attenuation is unclear from the data more although the relatively steep coda decay of southern california implies that anelastic attenuation is stronger there than in new york or south africa for southern california and new york state the 3 hz coda q taken from the late coda 50 110 s is comparable to the l sub g wave q however the 3 hz coda q for south africa over these lapse times is about 5 times the estimated l sub g wave q for all three areas the frequency dependence of the coda q does not match the frequency dependence of the s wave q and for new york and south africa it changes with lapse time less

subduction zone guided waves and the heterogeneity structure of the subducted plate intensity anomalies in northern japan 1 the subducting pacific plate acts an efficient waveguide for high frequency signals and often produces anomalously large intensity on the eastern seaboard of northern japan during deep earthquakes the waveform records in the region of high intensity show a low frequency f 2 hz later arrivals with a long coda this behavior is not explained by a simple subduction zone model comprising a high velocity plate with low attenuation from the analysis of observed broadband waveforms and numerical simulation of seismic wave propagation in the pacific subduction zone we demonstrate that the high frequency guided waves traveling in the subducting plate arise from the scattering of seismic waves by heterogeneity in plate structure our preferred model of the heterogeneity has elongated scatterers parallel to the plate margin described by a von karmann function with a downdip correlation length of about 10 km and much shorter correlation length of about 0 5 km in thickness the standard deviation of wave speed fluctuations from the averaged background model is about 2 this new heterogeneous plate model generates significant scattering of seismic waves with wavelengths shorter than correlation distance in thickness but low frequency waves with long wavelengths can easy tunnel through such lamina structure the result is frequency selective propagation characteristics with a faster low frequency phase followed by large and high frequency signals with very long coda a low wave speed channel effect from the former oceanic crust at the top of the subducting slab is not necessary to explain the observed dispersed signals and the very long high frequency coda three dimensional simulations using the earth simulator supercomputer for modeling of high frequency seismic wave propagation in the pacific subduction zone including plate heterogeneity clearly demonstrate the scattering waveguide effects for high frequency seismic waves traveling in the plate the region of large intensity for the heterogeneous model migrates away from the hypocenter into northern japan with an elongated zone along the pacific coast almost comparable to the observations from deep events in the pacific plate

lg wave propagation and crustal structure differences near denmark and the north sea summary recordings of regional earthquakes near denmark and the north sea have been collected in an attempt to find the lg wave propagation properties in the area propagation paths of lengths between 300 and 1100km are investigated the amplitudes of the lg waves and the other seismic phases in the seismograms are compared the propagation paths are classified according to whether the lg wave propagation compared to p and s wave propagation is good intermediate or poor it is noted that there is a distinct regional pattern in the lg wave attenuation the lg wave propagation is poor across the north sea the north sea is surrounded by areas of good continental lg wave propagation except towards the south east in the netherlands and western germany an area in skagerrak is characterized by good but slow propagation of a surface wave similar to lg since this is exactly the area of a cluster of earthquakes in skagerrak it is suggested that the two phenomena are caused by the same structural inhomogeneities in the area just off the coast of north western denmark the lg wave propagation is as good in the northern part of denmark as it is in the fennoscandian shield the extent to which the propagation is poor across the north sea is dependent on the frequency of the lg waves observed with different seismographs the lg waves are more attenuated relative to the other seismic phases the higher the frequency is between 0 25 and 2 hz as the structural differences between the fennoscandian bedrock area and the norwegian danish basin with 8 10 km of sediments has no effect on the lg wave propagation it is suggested that the structural anomalies causing the poor lg wave propagation across the north sea are deep crustal anomalies possibly significant variations in crustal thickness it is likely that such deep crustal differences are located along the most prominent upper crustal differences in the sedimentary grabens in the middle of the north sea the poor propagation across the north sea is similar to that observed across a sedimentary basin in eastern greenland which also developed mainly before seafloor spreading separated greenland from europe the frequency dependent propagation of the lg waves is explainable in terms of surface wave propagation across structural boundaries as well as in terms of anelastic attenuation

modelling short period crustal phases at regional distances for the seismic source parameter inversion abstract waveforms of short period crustal phases observed at regional distances are modelled in an attempt to retrieve the source parameters of small earthquakes for a simple shield type crustal structure the synthetic seismograms calculated for elementary source mechanisms show that the waveforms of crustal phases are quite distinct for different source mechanisms and suggest that these features can be used to constrain the source mechanisms waveforms of the crustal phases are also strongly affected even by small variations in the crustal thickness as well as in the focal depth a generalized linearized waveform inversion technique is used to invert the regional crustal phases for a deviatoric moment tensor source the inversion technique is applied to regional short period records from a small earthquake in central sweden for determining its source parameters the waveform inversion which mainly used lg waves produced a satisfactory fit between the observed and synthetic records suggesting that the source mechanism and focal depth estimates were reasonable the focal depth of 40 km obtained for the event studied suggests the occurrence of a deep crustal earthquake and demonstrates the usefulness of crustal phases in studying small intraplate earthquakes

epigenetic tourmalinite and arsenopyrite in the aureole of the leinster batholith se ireland metasomatic tourmaline quartz hydromuscovite phengite fluorite rocks which locally contain in excess of 40 disseminated arsenopyrite and lesser amounts of pyrrhotite chalcopyrite pyrite molybdenite rutile ilmenite and fe rich chlorite occur near the village of inistioge in se ireland they are developed within lower palaeozoic phyllites close to the northwest margin of the southern termination of the leinster batholith the mineralization occurs within a belt of anomalously high caledonian strain which was active during batholith intrusion and which is essentially a product of heterogeneous shortening tourmaline constitutes up to 60 of the volume of the metasomatic material and although the lithology exhibits bed parallel lamination both detailed field and textural relationships demonstrate its origin to be epigenetic the mineralization is spatially related to pegmatitic k feldspar fluorite and muscovite bearing quartz veins with greisen alteration envelopes composed of coarse grained muscovite fluorite apatite and tourmaline the mineralized rocks were produced during alteration of aluminous metasediments by magmatic and or meteoric fluids which were channelled through the high strain zone during cooling of the batholith