an ensemble approach for improved short to intermediate term seismic potential evaluation pattern informatics pi load unload response ratio lurr state vector sv and accelerating moment release amr are four previously unrelated subjects which are sensitive in varying ways to the earthquake s source previous studies have indicated that the spatial extent of the stress perturbation caused by an earthquake scales with the moment of the event allowing us to combine these methods for seismic hazard evaluation the long range earthquake forecasting method pi is applied to search for the seismic hotspots and identify the areas where large earthquake could be expected and the lurr and sv methods are adopted to assess short to intermediate term seismic potential in each of the critical regions derived from the pi hotspots while the amr method is used to provide us with asymptotic estimates of time and magnitude of the potential earthquakes this new approach by combining the lurr sv and amr methods with the choice of identified area of pi hotspots is devised to augment current techniques for seismic hazard estimation using the approach we tested the strong earthquakes occurred in yunnan sichuan region china between january 1 2013 and december 31 2014 we found that most of the large earthquakes especially the earthquakes with magnitude greater than 6 0 occurred in the seismic hazard regions predicted similar results have been obtained in the prediction of annual earthquake tendency in chinese mainland in 2014 and 2015 the studies evidenced that the ensemble approach could be a useful tool to detect short to intermediate term precursory information of future large earthquakes

an outline of the plate tectonics of china china is principally a part of the eurasian plate but the margins of the indian and philippine sea plates are involved in the himalayas and in the coastal range of taiwan respectively within the eurasian plate the cathaysian paleoplate is separated from the angaraian paleoplate by the junggar hegen suture which contains paleozoic ophiolites and rare blueschists the three microplates of the cathaysian paleoplate consist of precambrian cratons and or phanerozoic accretionary fold belts these coalesced precambrian cratons record at least six stages of intense orogeny before cratonization the paleozoic to cenozoic accretionary fold belts of china can be correlated with similar events now found in west pacific andean and atlantic type active continental margins ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the paleozoic to cenozoic the presence of blueschist in some of these chinese sutures reveals evidence of large scale subduction and tectonic exhumation during consolidation of the eurasian plate cenozoic collision of the eurasian and indian plates produced deformation and uplift of the himalayas strongly influencing the tectonics of western china in contrast mesozoic tertiary evolution of eastern china is typical basin range geology similar to that of the western united states which included development of deep sedimentary basins along with calc alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow the complicated tectonic evolution of china is greatly illuminated by the presence of ophiolites and blueschists in proterozoic to tertiary convergent boundaries these petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in china

spatial and temporal variation of coda wave attenuation in the faryab region southeast of the sanandaj sirjan zone using aftershocks of the tiab earthquake of 28 february 2006 coda quality factor q c estimates for the faryb region in the southeast zagros have been obtained by using aftershock data of the tiab earthquake of 28 february 2006 recorded within an epicentral distance of 100 km more than 394 earthquakes were recorded by a local temporary network consisting of 9 short period stations installed for one month after 28 february 2006 q c was estimated using the single backscattering model in frequency bands of 0 5 24 hz in this research the spatial and temporal variation of q c in the sanandaj sirjan zone is studied to explore the lateral variation q c is calculated for nine stations and in different parts of the covered area the lowest values are derived in kali station in the southern part and the higher value in baga station in the northern part but generally there is an absence of significant lateral variation in coda q c in the faryab region to investigate the attenuation variation with depth q c value was calculated for eight lapse times the average frequency relation for this region is q c 28 1 1 f 1 14 0 01 at 5 s lapse time window length and q c 105 1 3 f 0 98 0 047 at 30 s lapse time window length q c increases with depth however the rate of increase of q c is not uniform with depth in the study area beneath the faryab region the rate of increase of q c is greater at depths less than 49 km compared to larger depths indicating a low attenuation structure at less than 49 km depth which is the moho depth in this region

weak tidal correlation of nw bohemia vogtland earthquake swarms we analyze the possible effect of solid earth tidal stresses upon a vertical strike slip fault in nw bohemia vogtland central europe typical by occurrence of swarm earthquakes the horizontal components of solid earth tidal stresses were found strongly to prevail and to reach the level of 2 kpa we examined tidal triggering as influence of tidal stresses to launching the swarm activity in relative absence of other stress disturbances the onset times of 46 swarms of mostly ml 3 earthquakes that occurred in the period 1991 2005 displayed an increased occurrence near the fortnightly maximum of tidal extensive normal stress the statistical test however did not prove a statistically significant correlation indicating a triggering effect of fault extension due to tidal loading we also examined tidal effects to the already running seismic activity of the prominent 2000 swarm by comparing the tidal stress distribution in the investigated period with the distribution of tidal stresses in the occurrence times of each earthquake the results show that these distributions are almost similar which indicates that individual earthquakes occur independent of tidal stresses the unclear tidal correlation of the swarm seismicity may be interpreted by small amplitudes and rates of tidal stress changes compared to the amplitudes and rates of coseismic stress perturbations and of pressure bursts of deep generated fluids

geology mineralogy and geochemistry of some carbonate hosted lead zinc deposits in kanchanaburi province western thailand during the last years several small to medium sized pb zn deposits have been explored in the western mountain chains of the province of kanchanaburi thailand sulfide mineralization is stratabound and closely related to the development of reeflike algal crinoidal buildups which are incorporated in a thick ordovician limestone sequence fine grained galena sphalerite pyrite ores prevail with accessory fahlore and various sb ag sulfosalts in a gangue of barite silica and carbonate sulfides are usually intimately intergrown grain boundaries of the impingement type sphalerite has a low fe content whereas galena is notably argentiferous sulfide precipitation was mainly controlled by primary porosity and permeability of the host rocks however in some places cavern fillings and collapse breccias of a paleokarst are also mineralized relationships between carbonate cementation and ore structures indicate an ordovician ore emplacement at shallow depth homogenization temperatures of fluid inclusions range from 107 degrees to 174 degrees c the lack of major replacement structures and the fact that carbonate gangue and sulfides have often coprecipitated show that the ore bearing solutions were almost neutral in ph the freezing temperatures of fluid inclusions near 0 degrees c the high contents of ag sb and hg and a zonal pattern of these elements are unusual for most carbonate hosted lead zinc deposits the origin of the metal bearing solutions is uncertain but chemical characteristics and mineralized tuff breccias near the deposits possibly indicate a relationship to an igneous source

attenuation of coda waves in new england abstract seismic wave attenuation was measured in new england from the time domain decay of coda wave amplitudes on narrow bandpass filtered seismograms of local earthquakes the frequency band of interest was 0 75 to 10 hz q c f was found to increase with frequency across this band but there was also a difference between the q c f values for short t t 100 sec lapse times of coda wave propagation for the short lapse time data corresponding to wave paths primarily in the upper crust q c f increases from 400 at 3 hz to 1300 at 10 hz for the large lapse time data corresponding to wave paths in the lower crust and upper mantle q c f was found to vary from 660 at 1 hz to 1500 at 10 hz if we interpret this dataset in terms of a model incorporating both scattering and anelastic attenuation we find that the mean free path of seismic waves over this frequency band is 80 km for short lapse times and 400 km for long lapse times if we assume that scattering is entirely responsible for the observed attenuation we find that the minimum mean free path for short lapse times is about 75 km over all frequencies whereas for long lapse times the minimum mean free path decreases from 400 km at 0 75 hz to 90 km at 10 hz

qc qβ qi and qs attenuation parameters in the umbria marche italy region the attenuation of coda and s waves has been inferred for the umbria marche region central italy using seismic waveforms collected during the 1997 seismic crisis the selected dataset is composed of 343 small magnitude 1 4 ml 4 2 earthquakes recorded at a temporary array composed of 23 seismic stations the sato 1977 method based on the assumption of single isotropic scattering has been used to infer qc considering three different lapse times 20 30 and 40 s the coda normalization method aki 1980 has been used to infer q both qc and q show a clear frequency dependence with a different frequency dependent parameter the frequency dependence of qc is comparable with that previously found in the same area and around it using the method of wennerberg 1993 intrinsic and scattering attenuation have been separated intrinsic attenuation is found to be close to coda attenuation and dominates over scattering dissipation coda q increases with increasing lapse time but at a rate smaller than that observed in other areas of the earth coda and intrinsic attenuation in the umbria marche region are very high compared to other seismic active regions of the earth the retrieved high values of intrinsic attenuation may be explained in terms of the previously hypothesized fluid pressurized regime of the crust in the central apennines miller et al 2004

an independent assessment of the load unload response ratio lurr proposed method of earthquake prediction the load unload response ratio lurr method is a proposed technique to predict earthquakes that was first put forward by yin 1987 lurr is based on the idea that when an area enters the damage regime the rate of seismic activity during loading of the tidal cycle increases relative to the rate of seismic activity during unloading in the months to one year preceding a large earthquake since earth tides generally contribute the largest temporal variations in crustal stress it seems plausible that earth tides would trigger earthquakes in areas that are close to failure e g vidale et al 1998 however the vast majority of studies have shown that earth tides do not trigger earthquakes e g vidale et al 1998 heaton 1982 rydelek et al 1992 in this study we conduct an independent test of the lurr method since there would be important scientific and social implications if it were proven to be a robust method of earthquake prediction smith and sammis 2004 undertook a similar study and found no evidence that there was predictive significance to the lurr method we have repeated calculations of lurr for the northridge earthquake in california following both the parameters of x c yin personal communication and the somewhat different ones of smith and sammis 2004 though we have followed both sets of parameters closely we have been unable to reproduce either set of results our examinations have shown that the lurr method is very sensitive to certain parameters thus it seems likely that the discrepancies between our results and those of previous studies are due to unaccounted for differences in the calculation parameters a general agreement was made at the 2004 aces workshop in china between research groups studying lurr to work cooperatively to resolve the differences in methods and results and thus permit more definitive conclusions on the potential usefulness of the lurr method in earthquake prediction

earthquake trend around sumatra indicated by a new implementation of lurr method the current implementation of lurr load unload response ratio theory has shown promise in intermediate to short term earthquake forecasting through past practice but has also met difficulties at the same time in this paper a new implementation of lurr method is presented to address one of the problems the major change in the new implementation is that lurr values will result from a calculated maximum faulting orientation mfo instead of any focal mechanism selected by users after comparison with the world stress map the calculated mfo has been found to be in good agreement with the observation from the regional tectonic stress regime the mfo pattern in the indonesia region has a special feature which may be related to the unique subduction complexity the mfo pattern in the sumatra region in general is different from that in the java region after the 2004 m 9 0 sumatra andaman islands earthquake this phenomenon may be supported by the evidence of the recent observation that a section in the southern part of the sumatran arc is locked furthermore the mfo pattern before the 2004 main shock is different from that after the event retrospective examination of the indonesia region by means of this implementation can produce significant lurr anomaly not only prior to the 2004 main shock but also before the 2006 m 7 7 south java earthquake therefore future great earthquakes might favorably be forecasted if the lurr anomaly detected by mfo method could be considered a precursor

seismicity surveys with ocean bottom seismographs off western canada three arrays of ocean bottom seismographs have been deployed to study the seismicity at the northern end of the juan de fuca ridge system off western canada nearly 100 events were located with estimated accuracies generally better than 10 km all lying on or near the en echelon ridge transform fault plate boundaries as defined in this area by the magnetic anomalies the seafloor morphology and by other geophysical data the depths of 12 events were determined to lie between 2 and 6 km below the top of the crust the seismograms exhibit clear p and s wave arrivals along with phases that involve p to s and sometimes s to p conversion probably at the base of the sediments beneath the instruments the event magnitudes have been estimated from signal duration using four calibration events that were well recorded by a land station the magnitude estimates permit the determination of rough magnitude frequency of occurrence relations over the magnitude range of 1 to 3 that are in surprisingly good agreement with the recurrence relations for the area at larger magnitudes from 75 years of land station data the mean p wave velocity in the uppermost mantle from the earthquake datamore recorded by the sea floor arrays is 7 6 km s sup 1 and the mean v sub p v sub s ratio is 1 71 or a poisson s ratio of 0 24 less

estimates of q in central asia as a function of frequency and depth using the coda of locally recorded earthquakes digital recordings of microearthquake codas from shallow and intermediate depth earthquakes in the hindu kush region of afghanistan were used to determine the attenuation factors of the s wave coda qc and primary s waves q an anomalously rapid decay of the coda shortly after the s wave arrival observed also in a study of coda in central asia by rautian and khalturin 1978 seems to be due primarily to depth dependent variations in qc in particular we deduce the average qc in the crust and uppermost mantle 100 km depth is approximately four times lower than the deeper mantle 400 km depth over a wide frequency range 0 4 to 24 hz further while qc generally increases with frequency at any depth the degree of frequency dependence of qc depends on depth except at the highest frequency studied here 48 hz the magnitude of qc at a particular frequency increases with depth while its frequency dependence decreases for similar depths determinations of q and qc agree suggesting a common wave composition and attenuation mechanism for s waves and codas comparison of these determinations of qc in afghanistan with those in other parts of the world shows that the degree of frequency dependence of qc correlates with the expected regional heterogeneity such a correlation supports the prejudice that qc is primarily influenced by scattering and suggests that tectonic processes such as folding and faulting are instrumental in creating scattering environments

geochemistry and origin of tin polymetallic sulfide deposits hosted by the devonian black shale series near dachang guangxi china abstract two tin polymetallic sulfide deposits hosted by the devonian black shale series of the guangxi zhuang autonomous region occur in the dachang ore field the upper devonian frasnian epoch black shale series contains the giant tongkeng changpo deposit and the middle devonian givetian epoch reef limestone contains the giant longtoushan deposit intrusive rocks occur at lame and the western part of dachang ores occur as stratified bodies large veins stockworks and zones of veinlets ores are massive banded laminated and disseminated the ores contain more than 180 different minerals the most important of which are cassiterite sulfides and sulfosalts primary laminated sedimentary sulfide ores occur at tongkeng the mean ratio of sio 2 al 2 o 3 for shale marl is 3 5 but values averaging 56 and 67 respectively for ore and chert suggest a biogenic or hydrothermal source for silica ores and country rocks are rich in sb pb zn sn and cu granites are rich in sb w zn and sn dispersed elements such as te cd se and in are abundant in ores country rocks and granites implying contributions of sedimentary and intrusive activities to the ore formation mean y ho values for the black shale series 28 and granite 31 are similar to most shales and most volcanic rocks the y ho value for reef limestone is 47 comparable to sea water devonian black shale series are slightly lree enriched on chondrite normalized plots and show small negative eu anomalies mean eu 0 56 ce 0 9 and ce anom 0 07 values suggest a shallow water deposition near the redox boundary the 34 s values of sulfides from various deposits of dachang vary with the 34 s values for lame ranging from 2 to 2 and values for tongkeng changpo ranging from 4 9 to 2 6 the highly negative 34 s values 9 5 to 11 3 of huile and kengma sulfides suggest the important role of biogenic sulfur the mean 13 c value of organic matter of devonian black shale series is 24 6 the 30 si nbs 28 values of upper devonian black chert are 0 2 0 3 indicating a sedimentary origin the dachang black chert has been dated at 124 2 ma that of luofu section at 387 18 ma implying that the rb sr isotope of dachang chert was reset during yanshan movement these results suggest that the dachang tin polymetallic sulfide deposits exemplify strongly remobilized sedimentary mineralization

geology and geochemistry of the changlongshan skarn iron deposit anhui province china abstract the changlongshan skarn iron deposit is located in the northeastern part of the tongling fanchang fe cu district anhui province people s republic of china it is a specularite fe2o3 dominated iron deposit hosted in middle carboniferous to lower permian limestones with a drill indicated resource of 28 84 million tons of fe grading 35 9 58 6 both skarns and iron orebodies occur as tabular bodies along bedding parallel faults at some distance from the inferred granitic intrusions prograde skarn alteration consists mainly of andradite and hedenbergite whereas retrograde skarn is characterized by the development of actinolite chlorite and calcite the mineralogy of ores is dominated by specularite magnetite calcite and quartz primary fluid inclusions in garnet consist of aqueous liquid a vapour bubble and a halite crystal microthermometric measurements yield a homogenization temperature range for skarn alteration of 423 to 478 c with a salinity of 34 to 49 wt nacl equivalent fluid inclusions in calcite associated with mineralization generally consist of a vapour bubble and a liquid phase with a rare occurrence of three phase inclusions homogenization temperatures for two phase inclusions vary from 239 c to 303 c with a salinity of 13 to 22 wt nacl equivalent homogenization of three phase inclusions was observed between 264 and 287 c coupled with a salinity of 31 to 36 wt nacl equivalent stable isotope data indicate magmatic water was involved in the early stage of skarn formation 18 o h 2 o 3 7 to 7 6 dh2o 71 3 to 51 2 and a mixed magmatic meteoric water was responsible for the subsequent mineralization 18 o h 2 o 2 1 to 3 1 dh2o 40 1 to 28 1 geological and geochemical evidence obtained in this study supports a metasomatic replacement origin for the changlonshan iron deposit a conclusion contrary to previous syngenetic based interpretation

coda waves a review the analysis and interpretation of coda waves have received increasing attention since the early seventies in the past few years interest in this subject has spread worldwide and the study of high frequency seismic coda waves has become a very important seismological topic as a conclusion of the studies accomplished in this time coda waves are considered the result of scattering processes caused by heterogeneities acting on seismic waves p ands waves play a particularly important role in this interaction the process introduces an attenuation which added to the intrinsic absorption gives the observed apparent attenuation therefore coda waves constitute a thumbprint left by the heterogeneities on the seismograms coda waves offer decisive information about the mechanism of how scattering and attenuation take place this review describes coda waves in detail and summarizes the work done in this subject to 1986 the relation between coda waves and attenuation in the context of research on seismic scattering problems is stressed particular attention has been given to the application of coda waves to estimate source and medium parameters the state of the art of the temporal variations of coda wave shape and the possible use of these variations as an earthquake precursor also are presented care has been taken to introduce the statistical models used to deal with the heterogeneities responsible for scattering

sulfide mineralogy in the polymetallic cassiterite deposits of dachang p r china several important mineral deposits of sn zn cu pb and other metals associated with devonian sediments and yanshanian cretaceous granitic rocks are known in the dachang district guangxi early genetic hypotheses related the origin of the deposits entirely to the yanshanian granites recently it was suggested that in devonian times an earlier syngenetic metal concentration may have occurred later overprinted by the yanshanian metallogeny this contribution is aimed at placing constraints on the physicochemical conditions during the yanshanian ore formation remobilization by studying the sulfide chemistry arsenopyrite sphalerite stannite and fluid inclusion data on the two major deposits in the area i e the polymetallic cassiterite deposit of changpo and the zn cu skarn deposit of lamo sphalerite and arsenopyrite are quite abundant in both deposits stannite is minor but fairly widespread at changpo and quite rare at lamo they are accompanied by pyrite pyrrhotite galena chalcopyrite cassiterite fluorite and a large variety of other sulfides and sulfosalts the main compositional data for sphalerite and arsenopyrite are summarized as follows

nature age and tectonic setting of granitoid hosted orogenic gold deposits of the jiaodong peninsula eastern north china craton china the jiaodong gold province along the southeastern margin of the north china craton has combined production and resources of 900 tonnes of gold more than 95 of the gold in this province is hosted in mesozoic granitoids which intruded late archean metamorphic basement rocks episodically at ca 160 150 and 130 126 ma the deposits of the jiaodong peninsula form one of the largest provinces of granitoid hosted lode gold deposits in the world the jiaodong gold deposits occur as massive auriferous quartz veins hosted in subsidiary second or third order faults and as disseminated and stockwork style mineralization hosted in alteration zones along major regional scale faults mineralization took place during brittle reactivation d3 of pre existing d2 ductile shear zones wall rock alteration is dominated by k feldspar and sericite with also sulfide minerals and extensive silicification closest to the orebodies the alteration was accompanied by the introduction of volatiles fe mg k rb ag as au bi and sb enrichment of base metals in the gold lodes is generally low although locally significant gold deposition took place at temperatures of 250 to 350 c for most gold deposits and the ore fluids are co2 bearing and have calculated salinities of 6 13 wt nacl equiv deposits from the zhao ye xixia and muping rushan belts have similar if not identical structural controls alteration patterns ore mineral assemblages and stable isotope signatures lead isotope data indicate that the ore stage leads were buffered by their host rocks the granitoid hosted gold deposits in the zhao ye belt are most radiogenic the greenstone hosted deposits in the xixia belt is the least radiogenic and the granitoid hosted deposits in the muping rushan belt have intermediate compositions gold mineralization in the zhao ye xixia and muping rushan belts in the jiaodong gold province appears to be broadly contemporaneously at ca 130 120 ma as constrained by shrimp u pb zircon dating on host rocks and a post gold dike as well as by ar ar rb sr and k ar dating of hydrothermal alteration minerals and ores this early cretaceous age is about 100 million years younger than the peak of ultra high pressure metamorphism in the qinling dabie sulu orogen between the north china and yangtze cratons and about 500 km south of the gold province however it overlaps with the extension and exhumation stage of the collisional orogeny and the subduction of the pacific plate beneath the eurasian continental crust whereas the majority of the jiaodong gold deposits occur on the margin of the north china craton some also occur in the suture zone between the two cratons they are significantly landward relative to the subduction zone of the pacific plate compared with typical orogenic lode gold deposits globally lode gold deposits of ca 130 120 ma occurred on both sides of the tan lu fault zone available data favor a temporal link of gold mineralization with pacific plate subduction

lg coda q variation across eurasia and its relation to crustal evolution an extensive set of broadband and short period seismograms from regional seismic events has been used to derive a tomographic image of broad scale variations of lg coda q for most of eurasia the image indicates that lg coda q at a frequency of 1 hz varies between about 200 and 1000 lowest q values 800 are found in four regions the east european shield the siberian shield the indian shield and the southwestern and oldest portion of the altaid belt the pattern of lg coda q variation across eurasia suggests that crustal q in any region is directly proportional to the length of time that has elapsed since the most recent episode of large scale compressional tectonic activity or upper mantle heating that occurred there we interpret the low q as resulting largely from hydrothermal fluids generated by tectonic activity or heating that now reside in cracks and permeable portions of the eurasian crust crustal q increases with time after that activity as fluids are lost to the surface or absorbed by retrograde metamorphism

gold and silver metallogeny of the south china fold belt a consequence of multiple mineralizing events abstract the south china fold belt is part of the south china block that is interpreted to be the result of multiple tectonic and magmatic events that formed a collage of accreted proterozoic and phanerozoic terranes the jurassic to early cretaceous yanshanian period 180 90 ma a time of major tectono thermal events that affected much of eastern and southeastern china is of great metallogenic importance in the fold belt this period is linked to subduction of the pacific plate beneath the eurasian continent and is manifested by voluminous volcano plutonic activity of predominantly calc alkaline affinity the distribution of gold and silver deposits in the south china fold belt indicates the presence of two distinct metallogenic provinces a region of basement uplifts which are controlled by shear zones and form neoproterozoic inliers of metamorphosed iron rich rock types defines the first province in this province orogenic lodes and volcanic related epithermal deposits represent the more significant precious metal mineralization the second province is essentially confined to a belt of yanshanian felsic intermediate volcanic and subvolcanic rocks that extends along most of the southeastern china coast in an area known as the coastal volcanic belt deposits in the coastal volcanic belt are silver and or copper rich volcanic hosted and epithermal in character the precious metal metallogeny of the south china fold belt is interpreted to have developed in at least three stages one as a result of collision events during the caledonian orogeny ca 400 ma the second during the indosinian orogeny ca 200 ma and the third during or soon after the formation of the yanshanian magmatic belt yanshanian orogeny 180 90 ma the latter was responsible for a hydrothermal event that affected large sections of the belt and its proterozoic substrate this may have resulted in the redistribution and enrichment of precious metals from preexisting orogenic gold lodes in neoproterozoic basement rocks which are now exposed as windows in zones of tectonic uplift the yanshanian hydrothermal activity was particularly widespread in the coastal volcanic belt and resulted in the formation of both low and high sulfidation epithermal gold and silver and locally copper and other base metal mineralization it is suggested that the coastal volcanic belt has greater potential for world class epithermal and porphyry deposits than previously realised

site dependent coda q at mono craters california abstract the coda q of the early coda of shear waves was determined from a network of seismic stations deployed in the mono craters area during the summer of 1982 coda amplitudes determined from a moving window analysis were fit to single scattering theory with an l1 norm for center frequencies from 1 5 to 12 0 hz we find that station to station variations in coda q observed for frequencies between 6 and 12 hz are well correlated with near site geology coda q for stations on crystalline rocks is larger and more frequency dependent than for stations sited on bishop tuff adjacent to mono craters coda q from sites on bishop tuff away from mono craters is still lower and less frequency dependent these observations suggest that site effects dominate the early coda in the mono craters region and that the single scattering model is inappropriate the mechanisms generating these site effects are inferred to be 1 multiple scattering from resonant structures such as sedimentary basins volcanic edifices variable basement topography and surface topography and 2 near site attenuation

nucleation and triggering of earthquake slip effect of periodic stresses abstract results of stability analyses for spring and slider systems with state variable constitutive properties are applied to slip on embedded fault patches unstable slip may nucleate only if the slipping patch exceeds some minimum size subsequent to the onset of instability the earthquake slip may propagate well beyond the patch it is proposed that the seismicity of a volume of the earth s crust is determined by the distribution of initial conditions on the population of fault patches that nucleate earthquake slip and the loading history acting upon the volume patches with constitutive properties inferred from laboratory experiments are characterized by an interval of self driven accelerating slip prior to instability if initial stress exceeds a minimum threshold this delayed instability of the patches provides an explanation for the occurrence of aftershocks and foreshocks including decay of earthquake rates by time 1 a population of patches subjected to loading with a periodic component results in periodic variation of the rate of occurrence of instabilities the change of the rate of seismicity for a sinusoidal load is proportional to the amplitude of the periodic stress component and inversely proportional to both the normal stress acting on the fault patches and the constitutive parameter a 1 that controls the direct velocity dependence of fault slip values of a 1 representative of laboratory experiments indicate that in a homogeneous crust correlation of earthquake rates with earth tides should not be detectable at normal stresses in excess of about 8 mpa correlation of earthquakes with tides at higher normal stresses can be explained if there exist inhomogeneities that locally amplify the magnitude of the tidal stresses such amplification might occur near magma chambers or other soft inclusions in the crust and possibly near the ends of creeping fault segments if the creep or afterslip rates vary in response to tides observations of seismicity rate variations associated with seasonal fluctuations of reservoir levels appear to be consistent with the model

tectonics and metallogeny of mainland southeast asia a review and contribution abstract the southeast asia region is endowed with a diversity of mineral resources notably porphyry related skarn epithermal and sediment hosted orogenic gold deposits formation of these deposits was associated with a long and complex tectonic history of gondwana supercontinent break up arc magmatism backarc basin development together with arc continent and continent continent collisions that created the present day mainland se asia this paper summarizes historical and current se asian geological research and ore deposit studies here we present a new tectonic and metallogenic model for phanerozoic mainland se asia from this model we conclude that incipient arc backarc basin magmatism is the key to the formation of many important ore deposits in the truong son and loei fold belts the two major metallogenic belts in mainland se asia in addition triassic to cenozoic arc continent and continent continent collisions have led to the formation of many sediment hosted orogenic gold deposits in the sukhothai and the sibumasu terranes oblique cretaceous to recent subduction along the andaman sunda trench was responsible for gold and copper gold molybdenum porphyry and epithermal mineralization along the kawlin wutho mt popa arc in myanmar in the north and the sumatran volcanic arc in the south we anticipate that the present emphasis on exploring for shallower level epithermal deposits will increasingly lead to exploration for deeper level porphyry and porphyry related skarn systems in the coming decades

coda q for the state of washington abstract frequency dependent coda q values for subregions of the state of washington have been determined using a time domain coda decay method a total of 95 earthquakes digitally recorded on a regional seismograph network of over 100 short period stations were selected to obtain 206 on scale high signal to noise ratio traces for analysis grouping the data by structural regions of the state showed only small variations in coda q by region other than in a very localized area at mount st helens at mount st helens coda q was significantly lower than for all other areas an average of all of the data except that from the local mount st helens area results in a q relationship of q c 63 f 0 97 for the frequency band 2 to 16 hz there is little variation of this coda q relationship when using sources down to 50 km depth and thereby uniformly sampling the top 50 to 100 km of the crust and upper mantle

where is the north china south china block boundary in eastern china the qinling dabieshan belt results from the collision of the north china and south china blocks the eastern extension of the belt the sulu area consists of several stacked units from top to bottom these are 1 a weakly metamorphosed slate sandstone unit of neoproterozoic paleozoic age 2 a gneiss quartzite unit metamorphosed under high pressure p conditions 3 a marble amphibolite unit 4 an ultrahigh p unit that was very deeply subducted and then exhumed and 5 a migmatitic dome resulting from the melting of ultrahigh p rocks all these units underwent the same deformation which was characterized by a top to the northwest extensional ductile shearing during their exhumation granulite facies restites in the migmatite are not significantly different from granulitized eclogites derived from the ultrahigh p rocks the migmatite exhibits the same structural and petrologic evolution as that determined for the other units the resemblance of petrologic and structural features and the lack of ocean basin rock shows that the boundary between the north china block and south china block must be placed north of the sulu area

the xinqiao cu s fe au deposit in the tongling mineral district china synorogenic remobilization of a stratiform sulfide deposit abstract the cu s fe au deposit at xinqiao is located in the tongling mineral district anhui province people s republic of china it is a large scale polymetallic deposit with drilling indicated reserves of 0 5 million tonnes of cu averaging 0 71 75 5 million tonnes of s averaging 29 3 and 24 9 million tonnes of fe averaging 46 as well as 11 2 tonnes of au averaging at 4 7 g tonne plus 248 4 tonnes of ag averaging at 248 4 g tonne there are two major mineralization types in the xinqiao deposit one is the economically significant stratiform orebody hosted in the lower carboniferous gaolishan siltstone c1g and overlying middle carboniferous huanglong limestone c2h while the other is the less important skarn type mineralization restricted to the contact between the yanshanian diorite 110 168 ma and the lower permian qixia marble p1q the ore in the xinqiao deposit is dominated by massive pyrite with minor amount of chalcopyrite magnetite pyrrhotite galena sphalerite quartz and dolomite four stages of deformation have been recognized to affect the sedimentary rocks in the xinqiao area the first two d1 and d2 produced mainly ne sw and nne ssw trending open folds whereas d3 is characterized by normal faults striking nne ssw and d4 is dominated by post mineralization strike slip faults segmenting the orebody the structural information obtained by this study not only revealed the transgressive nature of the stratiform orebody but also identified a strong structural control on the formation of the deposit it is concluded that the xinqiao polymetallic deposit was formed through remobilization of a carboniferous sulfide source bed by hydrothermal solutions related to late yanshanian plutonism 110 ma during which d3 normal faulting played an important role in localization of the mineralization such a two stage ore forming model is consistent with the most recent genetic interpretations of the deposit

estimation of coda wave attenuation in the east anatolia fault zone turkey in this study the attenuation of coda waves qc f has been estimated for different lapse times and frequencies in the east anatolian fault zone eafz in turkey using a single back scattering model of s coda envelopes the data include 255 earthquakes recorded by ten stations the frequency dependent qc values are estimated at central frequencies of 1 5 3 6 8 12 and 18 hz using 20 30 40 s lapse time windows along this fault zone the frequency dependent qc obtained for all data and lapse time is qc 57 5f0 82 the entire study area is divided into six subregions according to the magnitude of the earthquakes and the location of the fault segments the estimated average frequency dependent relation for all lapse times are q text c left text i right 3 4 3f 0 9 3 for bingol karliova erzincan triple junction q text c left text ii right 56 3f 0 71 for bingol lake hazar segment q text c left text iii right 68 5f 0 75 for lake hazar sincik segment q text c left text iv right 72 5f 0 78 hazar sincik and celikhan golbasi faults q text c left text v right 59 7f 0 87 for kahramanmaras triple junction and q text c left text vi right 67 4f 0 94 for amanos range and karasu basin the lowest qc is determined between bingol and malatya the highest qc value is along amanos range in addition qc values are calculated for each regions at different lapse times the average qc value of the study region varies from 53 11 at 1 5 hz to 498 41 at 18 hz for 20 s lapse time window as its variation is from 116 11 at 1 5 hz to 749 75 at 18 hz of central frequency for 40 s lapse time window the increase of qc with lapse times changes from one subregion to another along the fault zone the rate of increment is significantly higher in bingol karliova erzincan triple junction than in the other subregions this rapid increase of low qc values in the junction reaches the general attenuation characteristics of the fault at 40 s lapse time finally the low q0 and high n values can be attributed to the energy loss as a result of the heterogeneity and activity along the fault zone the increase of qc with frequency lapse time may be related to heterogeneity decreases with depth the rapid increase of qc with depth in bingol karliova erzincan triple junction may be interpreted that the effect of the northern anatolian fault zone is effective in the upper crust is not so deep compared to eafz

revisiting the tidal activation of seismicity with a damage mechanics and friction point of view the load unload response ratio theory lurr puts forward the idea that the ratio of seismicity during times of increased tidal loading to times of decreased tidal loading takes on anomalously large values as the preparatory region of the earthquake approaches a critical state we repeated the calculations of lurr for several earthquakes in california for which results had been published using estimates of the parameters which could be determined from the published work we were unable to confirm any lurr ratio predictive significance we test an alternative method of evaluating the influence of tidal stresses on earthquakes based on damage mechanics as in rock mechanics experiments it may be that anomalous activation of seismicity prior to large earthquakes occurs only during those time intervals when the applied stress exceeds values previously attained we applied this approach to analyze the same data set used to test the lurr hypothesis and it also failed to reveal any significant precursory indications it may be that time dependent failure processes such as self driven nucleation occur on a time scale longer than the diurnal tide thus destroying the expected synchronization

coda q in the charlevoix quebec region lapse time dependence and spatial and temporal comparisons coda q is determined in the seismically active charlevoix region quebec using 34 earthquakes recorded on the six station charlevoix local telemetered network for comparison an average value of coda q for southeastern canada is determined from 32 events that occur over a much larger region at lapse times of 20 to 40 sec coda q at 1 hz q at charlevoix and for southeastern canada is 91 4 and 125 10 respectively at a 40 to 80 sec lapse time it is 200 3 and 305 15 respectively the lower q value at charlevoix in comparison with other parts of southeastern canada is in agreement with jin and aki s 1988 finding that q is lower in the vicinity of large earthquakes no statistically significant temporal change in coda q at charlevoix is observed over the 11 yr of data studied a variation of as little as 15 would be statistically apparent ongoing monitoring of coda q in the area is planned using the local network in order to investigate any temporal changes prior to future large earthquakes coda q is found to increase with lapse time lapse time is defined as time elapsed after the origin time this dependence could be due to any of the following nonzero source receiver distance nonisotropic scattering scattering from below the crust multiple scattering or increase of q with depth or with distance from both source and receiver

coda q in southwestern british columbia canada abstract coda decay rates of 122 locally recorded earthquakes are used to infer frequency dependent coda q values at 21 short period stations in southwestern british columbia canada using the single scattering model coda q values q c are derived for a range of sampling volumes corresponding to maximum lapse times of 36 59 sec and maximum sampling depths of 70 110 km maps of q 0 q c inferred at 1 hz for different sampling volumes show a consistent trend of increasing q 0 to the northeast away from the subduction zone and into the coast belt batholith and decreasing q 0 toward the southeastern most stations near the vedder fault at the southern terminus of the coast belt q 0 increases gradually with sampling volume at all stations the dependence of q c on frequencies between 2 and 16 hz for different stations varies but on average ranges from 280 at 2 hz to 850 at 16 hz for sampling volumes that extend to depths of 90 km an average of all data for the same sampling volume size gives a relationship of q c 110 f 0 72 for frequencies in the 2 to 16 hz range which suggests significant differences in lithospheric coda attenuation properties in comparison with northwestern washington state where q c 63 f 0 97 changes in coda q correlate with the volume of brittle and fractured continental and subducting oceanic lithosphere sampled

multi methods combined analysis of future earthquake potential prior to an earthquake natural seismicity is correlated across multiple spatial and temporal scales many studies have indicated that an earthquake is hard to accurately predict by a single time dependent precursory method in this study we attempt to combine four earthquake prediction methods i e the pattern informatics pi load unload response ratio lurr state vector sv and accelerating moment release amr to estimate future earthquake potential the pi technique is founded on the premise that the change in the seismicity rate is a proxy for the change in the underlying stress we first use the pi method to quantify localized changes surrounding the epicenters of large earthquakes to objectively quantify the anomalous areas hot spots of the upcoming events next we delineate the seismic hazard regions by integrating with regional active fault zones and small earthquake activities then we further evaluate the earthquake potential in the seismic hazard regions using the lurr sv and amr methods retrospective tests of this new approach on the large earthquakes m 6 5 which have occurred in western china over the last 3 years show that the lurr and sv time series usually climb to an anomalously high peak months to years prior to occurrence of a large earthquake and the asymptote time t c predicted by the amr method correspond to the time of the actual events the results may suggest that the multi methods combined approach can be a useful tool to provide stronger constraints on forecasts of the time and location of future large events

attenuation of high frequency seismic waves in northeast india summary we studied attenuation of s and coda waves their frequency and lapse time dependencies in northeast india in the frequency range of 1 24 hz we adopted theories of both single and multiple scattering to bandpass filtered seismograms to fit coda envelopes to estimate q for coda waves qc and q for s waves qs at five central frequencies of 1 5 3 6 12 and 24 hz the selected data set consists of 182 seismograms recorded at ten seismic stations within epicentral distance of 22 300 km in the local magnitude range of 2 5 5 2 we found that with the increase in lapse time window from 40 to 60 s q0 qc at 1 hz increases from 213 to 278 while the frequency dependent coefficient n decreases from 0 89 to 0 79 both qc and qs increase with frequency the average value of qs obtained by using coda normalization method for ne india has the power law form of 96 8 21 5 f 1 03 0 04 in 1 24 hz we adopted energy flux model efm and diffusion model for the multiple scattered wave energy in three dimensions the results show that the contribution of multiple scattering dominates for longer lapse time close to or larger than mean free time of about 60 s the estimates of qc are overestimated at longer lapse time by neglecting the effects of multiple scattering some discrepancies have been observed between the theoretical predictions and the observations the difference could be due to the approximation of the uniform medium especially at large hypocentral distances increase in qc with lapse time can be explained as the result of the depth dependent attenuation properties and multiple scattering effect

simulation of the load unload response ratio and critical sensitivity in the lattice solid model the load unload response ratio lurr method is an intermediate term earthquake prediction approach that has shown considerable promise it involves calculating the ratio of a specified energy release measure during loading and unloading where loading and unloading periods are determined from the earth tide induced perturbations in the coulomb failure stress on optimally oriented faults in the lead up to large earthquakes high lurr values are frequently observed a few months or years prior to the event these signals may have a similar origin to the observed accelerating seismic moment release amr prior to many large earthquakes or may be due to critical sensitivity of the crust when a large earthquake is imminent as a first step towards studying the underlying physical mechanism for the lurr observations numerical studies are conducted using the particle based lattice solid model lsm to determine whether lurr observations can be reproduced the model is initialized as a heterogeneous 2 d block made up of random sized particles bonded by elastic brittle links the system is subjected to uniaxial compression from rigid driving plates on the upper and lower edges of the model experiments are conducted using both strain and stress control to load the plates a sinusoidal stress perturbation is added to the gradual compressional loading to simulate loading and unloading cycles and lurr is calculated the results reproduce signals similar to those observed in earthquake prediction practice with a high lurr value followed by a sudden drop prior to macroscopic failure of the sample the results suggest that lurr provides a good predictor for catastrophic failure in elastic brittle systems and motivate further research to study the underlying physical mechanisms and statistical properties of high lurr values the results provide encouragement for earthquake prediction research and the use of advanced simulation models to probe the physics of earthquakes

distinctive features of late palaeozoic massive sulphide deposits in south china abstract more than 20 sediment hosted massive sulphide deposits occur in late palaeozoic basins in south china these deposits are accompanied by a certain amount of volcanic rocks in the host sequence and are economically important for their cu pb zn au and ag reserves the deposits and their host strata were commonly intruded by mesozoic granitoids remobilisation of sedimentary ores and magmatic hydrothermal overprinting processes resulted in the coexistence of massive sulphides with vein skarn and porphyry type orebodies in the same region or within a single deposit the ore containing basins occur in different tectonic settings the lower yangtze basin occurs on a passive continental margin where the deposits are high in cu and au with minor pb and zn and recoverable ag co and mo the ores have a lower concentration of radiogenic lead and 34s values close to zero fluid inclusions are highly saline and na rich fluids and metals of the lower yangtze region are interpreted to have been derived essentially from deep sources including the precambrian basement by contrast basins of the nanling region formed in an intracontinental setting developed on a folded caledonian basement these deposits are higher in pb zn sn and w as well as cu with recoverable ag sb hg u bi tl and mo the ores are characterised by a higher concentration of radiogenic lead and a wide variation of 34s composition fluid inclusions have lower salinities and higher k na ratios fluids are considered to have been sourced substantially from seawater by convection metals for the nanling deposits were essentially derived from the caledonian basement by leaching the contrast in ore composition between these two regions appears to have been controlled by differences in basement composition of the ore forming basins

load unload response ratio and accelerating moment energy release critical region scaling and earthquake prediction the main idea of the load unload response ratio lurr is that when a system is stable its response to loading corresponds to its response to unloading whereas when the system is approaching an unstable state the response to loading and unloading becomes quite different high lurr values and observations of accelerating moment energy release amr aer prior to large earthquakes have led different research groups to suggest intermediate term earthquake prediction is possible and imply that the lurr and amr aer observations may have a similar physical origin to study this possibility we conducted a retrospective examination of several australian and chinese earthquakes with magnitudes ranging from 5 0 to 7 9 including australia s deadly newcastle earthquake and the devastating tangshan earthquake both lurr values and best fit power law time to failure functions were computed using data within a range of distances from the epicenter like the best fit power law fits in amr aer the lurr value was optimal using data within a certain epicentral distance implying a critical region for lurr furthermore lurr critical region size scales with mainshock magnitude and is similar to the amr aer critical region size these results suggest a common physical origin for both the amr aer and lurr observations further research may provide clues that yield an understanding of this mechanism and help lead to a solid foundation for intermediate term earthquake prediction

variation of seismic coda wave attenuation in the garhwal region northwestern himalaya seismic coda wave attenuation q text c 1 characteristics in the garhwal region northwestern himalaya is studied using 113 short period vertical component seismic observations from local events with hypocentral distance less than 250 km and magnitude range between 1 0 to 4 0 they are located mainly in the vicinity of the main boundary thrust mbt and the main central thrust mct which are well defined tectonic discontinuities in the himalayas coda wave attenuation q text c 1 is estimated using the single isotropic scattering method at central frequencies 1 5 3 5 7 9 12 16 20 24 and 28 hz using several starting lapse times and coda window lengths for the analysis results show that the q text c 1 values are frequency dependent in the considered frequency range and they fit the frequency power law q text c 1 left f right q 0 1 f n the q0 qc at 1 hz estimates vary from about 50 for a 10 s lapse time and 10 s window length to about 350 for a 60 s lapse time and 60 s window length combination the exponent of the frequency dependence law n ranges from 1 2 to 0 7 however it is greater than 0 8 in general which correlates well with the values obtained in other seismically and tectonically active and highly heterogeneous regions the attenuation in the garhwal region is found to be lower than the qc 1 values obtained for other seismically active regions of the world however it is comparable to other regions of india the spatial variation of coda attenuation indicates that the level of heterogeneity decreases with increasing depth the variation of coda attenuation has been estimated for different lapse time and window length combinations to observe the effect with depth and it indicates that the upper lithosphere is more active seismically as compared to the lower lithosphere and the heterogeneity decreases with increasing depth

tin bearing skarns of south china geological setting and mineralogy tin in skarns forms a significant part of the total sn resource of south china and erosion of these primary deposits has produced rich alluvial concentrations creating the basis for a historically important tin mining industry the skarns are genetically related to s type transformation series granites of yanshanian age emplaced in carbonate sequences mainly of devonian and triassic age these occupy the hercynian indosinian structural depressions within the caledonian foldbelt constituting the nanling ranges of south china most of the sn skarns in this broadly defined province contain calcic mineral assemblages which include andradite grossular hedenbergite diopside actinolite tremolite idocrase wollastonite epidote chlorite and magnetite with or without various sulphides in certain cases sn is located in minerals such as cassiterite malayaite and nordenskioldine in many other deposits sn substitutes in the structure of calc silicates and oxides in particular in andradite titanite actinolite epidote axinite and rutile at gejiu in yunnan province andradite can carry up to 5 14 wt sno2 in this case it is believed that sn4 together with mg2 substitutes for fe3 in the octahedral sites a coupled substitution which can be represented by the equation sn4 mg2 2 fe3 the behavior of sn during skarn formation is governed by the p t x conditions of the skarn forming solutions eh and ph variations and changes in the chemical potentials of major and trace elements e g s2 play a crucial role in determining the prevailing equilibria during the high temperature and alkaline stage of prograde metasomatism an association of andradite diopside formed under oxidizing conditions when sn entered the lattice of andradite or in environments deficient in fe mg and al but rich in sn malayaite formed the association hedenbergite grossular was formed under reducing conditions and in this case sn was retained in the hydrothermal solutions becoming available for reactions at lower temperature the rare sn mineral nordenskioldine was formed at a late stage during prograde alteration where conditions were uncommonly b rich and depleted in f co2 and especially si sn was not deposited as cassiterite until the system evolved to retrograde low temperature and acid conditions during this stage cassiterite formed with magnetite actinolite and fluorite at the expense of tin bearing andradite e g shizhuyuan hunan province or precipitated from the ore forming solution together with chlorite and sulphides e g debao guangxi province or with quartz and sulphides e g dachang guangxi province cassiterite together with calcite even formed at the expense of nordenskioldine in place e g gejiu malayaite was also formed with quartz and calcite at this stage e g zhengjialong jiangxi province

regional variation of coda q in kopili fault zone of northeast india and its implications abstract kopili fault has been experiencing higher seismic and tectonic activity during the recent years these kind of active tectonics can be inspected by examining coda wave attenuation and its dependence with frequency exploiting single back scattering model we have endeavored to measure coda q and its associated parameters such as frequency dependent factor n and attenuation coefficient covering seven lapse time windows spanning from 30 to 90 s and central frequencies 1 5 3 5 6 9 and 12 hz the average estimated values of qc increase s with frequency and lapse time window from 114 at frequency 1 5 hz to 1563 at frequency 12 hz for 30 s window length and from 305 at frequency 1 5 hz to 2135 at frequency 12 hz for 90 s window length the values of q0 and n are also estimated for the entire kopili fault zone for this study region the q0 values vary from 62 to 348 and n varies from 0 57 to 1 51 within the frequency range 1 5 to 12 hz furthermore depth variation of attenuation of this region reveals that there is velocity anomaly at depth 210 220 km as there arises sharp changes in and n which are supported by available data reported by other researcher for this region finally we have tried to separate the intrinsic and scattering attenuation for this area it is observed that the entire region is dominated by mainly scattering attenuation but we can see an increase in intrinsic attenuation with depths in two stations namely tzr and bkd furthermore the obtained results are comparable with the available global data

sedimentary rock hosted au deposits of the dian qian gui area guizhou and yunnan provinces and guangxi district china abstract sedimentary rock hosted au deposits in the dian qian gui area in southwest china are hosted in paleozoic and early mesozoic sedimentary rocks along the southwest margin of the yangtze south china precambrian craton most deposits have characteristics similar to carlin type au deposits and are spatially associated on a regional scale with deposits of coal sb barite as tl and hg sedimentary rock hosted au deposits are disseminated stratabound and or structurally controlled the deposits have many similar characteristics particularly mineralogy geochemistry host rock and structural control most deposits are associated with structural domes stratabound breccia bodies unconformity surfaces or intense brittle ductile deformation zones such as the youjiang fault system typical characteristics include impure carbonate rock or calcareous and carbonaceous host rock that contains disseminated pyrite marcasite and arsenopyrite usually with m sized au commonly in as rich rims of pyrite and in disseminations late realgar orpiment stibnite and hg minerals are spatially associated with earlier forming sulfide minerals minor base metal sulfides such as galena sphalerite chalcopyrite and pb sb as sulphosalts also are present the rocks locally are silicified and altered to sericite clay illite rocks and or stream sediment geochemical signatures typically include elevated concentrations of as sb hg tl and ba a general lack of igneous rocks in the dian qian gui area implies non pluton related ore forming processes some deposits contain evidence that sources of the metal may have originated in carbonaceous parts of the sedimentary pile or other sedimentary or volcanic horizons this genetic process may be associated with formation and mobilization of petroleum and hg in the region and may also be related to as au and tl bearing coal horizons many deposits also contain textures and features indicative of strong structural control by tectonic domes or shear zones and also suggest syndeformational ore deposition possibly related to the youjiang fault system several sedimentary rock hosted au deposits in the dian qian gui area also are of the red earth type and au grades have been concentrated and enhanced during episodes of deep weathering

a new approach to earthquake prediction the load unload response ratio lurr theory the response to loading is different from that to unloading when the focal media is approaching instability the ratio of the response rate during loading to that during unloading called load unload response ratio y lurr could be a measure of the closeness degree to instability and is used in a new approach to earthquake prediction retrospective examination of some one hundred earthquake cases from m 4 to m 8 6 indicates that for more than 80 of the examined ones the value of y is much higher than 1 for a period before the main shock but the y value always fluctuates slightly about 1 during two decades for seven stable regions so that the parameter y could indicate a dangerous degree of an impending earthquake several earthquakes occurring on the chinese mainland in recent years as well as the northridge california u s a earthquake jan 17 1994 m w 6 7 have been predicted beforehand with this method

the northern cascadia subduction zone at vancouver island seismic structure and tectonic history the structure and tertiary tectonic history of the northern cascadia subduction zone have been delineated by a series of new multichannel seismic lines acquired across the continental shelf to the

the lower changjiang yangzi yangtze river metallogenic belt east central china intrusion and wall rock hosted cu fe au mo zn pb ag deposits abstract the lower valley of changjiang from wuhan of the hubei province in the west to zhenjiang of the jiangsu province in the east contains more than 200 polymetallic cu fe au mo zn pb ag deposits and is one of the most important metallogenic belts in china this metallogenic belt situated at the northern margin of the yangzi craton and bordered by the dabieshan ultrahigh pressure metamorphic belt to the north consists mainly of cambrian triassic marine clastic sedimentary rocks and carbonate and evaporite rocks which overlay a precambrian basement and are intruded by yanshanian 205 to 64 ma granitoid intrusions and subvolcanic complexes repeated tectonism from late proterozoic to triassic resulted in extensively developed networks of faults and folds involving the cambrian triassic sedimentary strata and the precambrian basement the yanshanian granitoid intrusions and subvolcanic complexes in the lower changjiang metallogenic belt are characterized by whole rock 18 o of 8 to 10 initial 87 sr 86 sr of 0 704 to 0 708 and ndt from 10 to 17 and have been interpreted to have originated from mixing between juvenile mantle and old crustal materials also the yanshanian granitoids exhibit eastward younging and increase in alkalinity i e from older calc alkaline in the west to younger subalkaline alkaline in the east which are related to oblique collision between the yangzi and sino korean cratons and tectonic evolution from early compressional to late extensional or rifting regimes most polymetallic deposits in the lower changjiang metallogenic belt are clustered in seven districts where the yanshanian magmatism is particularly extensive from west to east edong jiurui anqing guichi luzhong tongling ningwu and ningzhen mineralization is characterized by the occurrence of three distinct types of orebodies in individual deposits orebodies in yanshanian granitoid intrusions skarn orebodies at the contact zones between the yanshanian intrusions and late paleozoic early mesozoic sedimentary rocks and stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata the most important host sedimentary strata are the middle carboniferous huanglong formation lower permian and lower middle triassic carbonate and evaporite rocks the intrusion hosted and skarn orebodies exhibit well developed zonation in alteration assemblages metal contents and isotopic compositions within individual deposits and apparently formed from hydrothermal activities related to the yanshanian magmatism the stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata have long been suggested to have formed from sedimentary or volcano sedimentary exhalative processes in shallow marine environments however extensive research over the last 40 years failed to produce unequivocal evidence for syngenetic mineralization on the basis of geological relationships and isotope geochemical characteristics we propose a carbonate hosted replacement deposit model for the genesis of these stratabound massive sulfide orebodies and associated skarn orebodies this model suggests that epigenetic mineralization resulted from interactions between magmatic fluids evolved from the yanshanian intrusions with carbonate and evaporite wall rocks mineralization was an integral but distal part of the larger hydrothermal systems that formed the proximal skarn orebodies at the contact zones and the intrusion hosted orebodies the stratabound massive sulfide deposits of the lower changjiang metallogenic belt share many features with the well studied high temperature carbonate hosted replacement deposits of northern mexico and western united states particularly with respect to association with small shallow granitoid complexes structural and stratigraphic controls on mineralization alteration assemblages geometry of orebodies metal association metal zonation and isotopic systematics

seismicity based earthquake forecasting techniques ten years of progress abstract earthquake fault systems interact over a broad spectrum of spatial and temporal scales and in recent years studies of the regional seismicity in a variety of regions have produced a number of new techniques for seismicity based earthquake forecasting while a wide variety of physical assumptions and statistical approaches are incorporated into the various methodologies they all endeavor to accurately replicate the statistics and properties of both the historic and instrumental seismic records as a result the last ten years have seen significant progress in the field of intermediate and short term seismicity based earthquake forecasting these include general agreement on the need for prospective testing and successful attempts to standardize both evaluation methods and the appropriate null hypotheses here we differentiate the predominant approaches into models based upon techniques for identifying particular physical processes and those that filter or smooth the seismicity comparison of the methods suggests that while smoothed seismicity models provide improved forecast capability over longer time periods higher probability gain over shorter time periods is achieved with methods that integrate statistical techniques with our knowledge of the physical process such as the epidemic type aftershock sequence etas model or those related to changes in the b value for example in general while both classes of seismicity based forecasts are limited by the relatively short time period available for the instrumental catalog significant advances have been made in our understanding of both the limitations and potential of seismicity based earthquake forecasting there is general agreement that both short term forecasting on the order of days to weeks and longer term forecasting over five to ten year periods is within reach this recent progress serves to illuminate both the critical nature of the different temporal scales intrinsic to the earthquake process and the importance of high quality seismic data for the accurate quantification of time dependent earthquake hazard

the reflection moho beneath the southern canadian cordillera the transition from the crust to the mantle beneath the canadian portion of the north american cordillera varies in depth geometry and tectonic age across the orogen these variations are rarely spatially related to the positions of morphologic or tectonic belts based on surface geology nor to nearly 25 km of structural relief identified in outcrop and on seismic reflection data the moho in this region is thus interpreted to be a long lived feature perhaps as old as proterozoic in the eastern part of the cordillera that probably has been active as a structural boundary during periods of crustal contraction and subsequent crustal stretching recognition of the moho and lower crust as a zone of localized tectonic activity provides a partial explanation for the problem of where regional detachments that underlie the foreland thrust and fold belt go as they project westward to deep structural levels beneath the interior of the orogen they likely project to the base of the crust where they flatten and

correlation of settler schist with darrington phyllite and shuksan greenschist and its tectonic implications coast and cascade mountains british columbia and washington amphibolite facies settler schist in the southeastern coast mountains of british columbia has long been correlated with chiwaukum schist of the cascade metamorphic core north cascade mountains no

coda q in different tectonic areas influence of processing parameters abstract published results of coda q show a large variation in values these variations are often claimed to be related to different tectonics whereas they might just be related to using different assumptions in the processing leading to different input parameters for the analysis in this study the effect of using different processing parameters is investigated and significant differences particularly at low frequencies are observed we find a new set of optimal parameters which we recommend using in future studies using a short lapse time of 30 s and optimal parameters data from both similar and very different tectonic regions are used to calculate coda q using the same program and the same parameters the regions considered are eastern anatolia the azores jan mayen northwestern and central argentina the shanxi rift system in china and southwestern norway we obtain the following relations eastern anatolia q 88 f 0 66 azores q 86 f 0 70 jan mayen q 90 f 0 72 northwestern and central argentina q 89 f 0 94 shanxi rift system q 99 f 0 89 and southwestern norway q 124 f 0 91 the results show that coda q is very similar for regions of similar tectonics and significantly different for regions with varying tectonics using alternative more common parameters gives different q but the regional differences remain so which parameters to use to get correct coda q values is still uncertain however coda q can clearly distinguish different tectonic areas provided identical processing parameters are used even if they are not optimal

numerical analysis of the relationship between time variant coda q and the variation in crustal stress summary coda q is a stochastic parameter reflecting the heterogeneities of medium that seismic waves travel through we confirmed that coda q would vary with the stress loaded to an elastic medium using numerical simulations of seismic wave propagation when the stress is loaded cracks in the crust could either close or newly open the closure and opening of the cracks are not random but depending on the magnitude and the direction of the stress and the crack aspect ratio the cracks in the medium after loading stress could be aligned in a specific orientation and elastic wave velocity field would become anisotropic due to the alignment of specific crack orientations elastic wave velocity is in general faster along the direction corresponding with the crack orientation while slower along the perpendicular direction in the numerical simulation the effect of anisotropy in elastic wave velocity field due to the selective closure and opening of the cracks is calculated using a 2 d finite difference method assuming elastic wave velocity to be a function of the magnitude of loaded stress the coda q calculated from seismic waves simulated for a model varies when the averaged normal stress changes our simulation indicated that the sensitivity of coda q 1 that is the reciprocal of the coda q would be 1 0 10 2 1 0mpa 1 against the magnitude of the confining pressure and 1 0 10 3 1 0 deg 1 against the direction of principal stress we would like to conclude that coda q a stochastic parameter reflecting heterogeneities of subsurface medium could become a quantitative state indicator of the stress field of the medium where seismic waves propagate through spatiotemporal variation of coda q reflects change in the stress field in the crust

tectonics and distribution of gold deposits in china an overview gold exploration in china has expanded rapidly during the last two decades since a modern approach to economic development has become a national priority china currently produces 180 tonnes t of gold annually which is still significantly less than south africa usa and australia however china is now recognized as possessing significant gold resources in a wide range of mineral deposit types present estimates of gold resources in china exceed 4 500 t which comprise 60 in gold only deposits more than 25 in base metal rich skarn porphyry and vein deposits and more than 10 in placer accumulations the major gold provinces in china formed during the main episodes of phanerozoic tectonism such tectonism involved interaction of china s three major precambrian cratons north china tarim and yangtze or south china when combined with cathaysia block with the angara or siberian kazakhstan kyrgyzstan and indian cratons resulting collisions included deformation of accreted oceanic sequences between the cratonic blocks the most important ore forming orogenies were 1 the late paleozoic variscan 405 270 ma which led to amalgamation of the angara north china and yangtze cratons 2 the indosinian 270 208 ma which led to the collision of north china and south china cratons 3 the yanshanian 208 90 ma which was largely influenced by the subduction of the izanagi pacific plates beneath eastern china and 4 the himalayan 90 ma indentation of the indian continent into eurasia no important precambrian gold systems are recognized in china mainly because of reworking of exposed precambrian rocks by these younger orogenies but there are a few caledonian 600 405 ma gold bearing systems in northern xinjiang most of china s orogenic epithermal and carlin like gold deposits are in the reworked margins of major cratonic blocks and in metasedimentary rock dominated fold belts adjacent to these margins accordingly the major gold provinces are present along the northern southeastern and southern margins of the north china craton along the southwestern and northwestern margins of the yangtze craton in the tianshan and altayshan orogenic belts in northern xinjiang and throughout the southeastern china fold belt gold placer deposits derived from these primary deposits are concentrated in the northernmost part of northeastern china and along the northwestern margin of the yangtze craton the major provinces with significant gold in porphyry related copper systems and base metal skarns are present in the yangtze river area along the northeastern and southeastern margin of the yangtze craton in the fold belt in southwestern china and scattered through northern china three quarters of the chinese gold only deposits occur within the north china craton margins half are located in the uplifted precambrian metamorphic rocks and most of the remainder are hosted in the phanerozoic granitoids that intruded the reworked precambrian terranes the abundance of granite hosted gold contrasts the north china craton with other precambrian cratons such as those in western australia central canada and zimbabwe where gold is mainly hosted in the archean greenstone belts this difference may be explained by the multiple episodes of phanerozoic tectonism along the north china craton margins resulting from the collision of the angara north china and south china cratons and from subduction of the izanagi pacific oceanic plates underneath the eastern china continent

tectonics of the qinling central china tectonostratigraphy geochronology and deformation history abstract the qinling orogen preserves a record of late mid proterozoic to cenozoic tectonism in central china high pressure metamorphism and ophiolite emplacement songshugou ophiolite assembled the yangtze craton including the lower qinling unit into rodinia during the 1 0 ga grenvillian orogeny the lower qinling unit then rifted from the yangtze craton at 0 7 ga subsequent intra oceanic arc formation at 470 490 ma was followed by accretion of the lower qinling unit first to the intra oceanic arc and then to the sino korea craton subduction then imprinted a 400 ma andean type magmatic arc onto all units north of the northern liuling unit oblique subduction created silurian devonian wnw trending sinistral transpressive wrench zones e g lo nan shang dan and late permian early triassic subduction reactivated them in dextral transpression lo nan shang xiang shang dan and subducted the northern edge of the yangtze craton exhumation of the cratonal edge formed the wudang metamorphic core complex during dominantly pure shear crustal extension at 230 235 ma post collisional south directed shortening continued through the early jurassic cretaceous reactivation of the qinling orogen started with nw se sinistral transtension coeval with large scale early cretaceous crustal extension and sinistral transtension in the northern dabie shan it presumably resulted from the combined effects of the siberia mongolia sino korean and lhasa west burma qiangtang indochina collisions and pacific subduction regional dextral wrenching was active within a ne sw extensional regime between 60 and 100 ma an early cretaceous andean type continental magmatic arc with widespread early cretaceous magmatism and back arc extension was overprinted by shortening related to the collision of yangtze indochina block with the west philippines block strike slip and normal faults associated with eocene half graben basins record paleogene nne ssw contraction and wnw ese extension the neogene is characterized by normal faults and nne trending sub horizontal extension pleistocene quaternary nw se extension and ne sw contraction comprises sinistral strike slip faults and is part of the nw se extension imposed across eastern asia by the india asia collision

development of a new approach to earthquake prediction load unload response ratio lurr theory the seismogenic process is nonlinear and irreversible so that the response to loading is different from unloading this difference reflects the damage of a loaded material based on this insight a new parameter load unload response ratio lurr was proposed to measure quantitatively the proximity to rock failure and earthquake more than ten years ago in the present paper we review the fundamental concept of lurr the validation of lurr with experimental and numerical simulation the retrospective examination of lurr with new cases in different tectonic settings california usa and kanto region japan the statistics of earthquake prediction in terms of lurr theory and the random distribution of lurr under poisson s model finally we discuss lurr as a parameter to judge the closeness degree to soc state of the system and the measurement of tidal triggering earthquake the load unload response ratio lurr theory was first proposed in 1984 yin 1987 subsequently a series of advances were made yin and dyin 1991 yin 1993 yin et al 1994a b 1995 maruyama 1995 in this paper the new results after 1995 are summarized yin et al 1996 wang et al 1998a zhuang and yin 1999

lithospheric structure in the southern canadian cordillera from a network of seismic refraction lines lithospheric velocity structure and its relationship to regional tectonics and development of the southern canadian cordillera are derived from a synthesis of interpretations from nine in line seismic refraction wide angle reflection profiles and broadside data recorded during the lithoprobe southern cordillera refraction experiment score and other refraction experiments across southern british columbia and one profile in northwestern washington consistency of the score two dimensional models at their intersection positions is achieved through application of a simultaneous inversion of all relevant traveltime data the cross sectional and map presentations demonstrate the strong degree of three dimensional heterogeneity within the crust and upper mantle a first order characteristic is the continuous increase in crustal velocities westward from the foreland belt to the insular belt the variations do not correlate with the morphogeological belts they do correspond with large scale geological and or

coda q in the northern cascadia subduction zone using seismograms recorded at 66 canadian seismic stations coda q was estimated from earthquakes in southwestern british columbia and northern washington state employing the single backscattering approximation a total of 580 earthquakes with magnitudes ranging from 1 2 to 6 4 depths from 0 to 67 km and epicentral distances of 5 110 km were selected to obtain 3022 high signal to noise ratio traces for analysis an average of all the data yields a relationship for coda q of q c 72 f 0 91 there is little variation of this coda q relationship when using either crustal or in slab sources which represent uniform sampling of the crust and upper mantle crustal earthquakes result in a relationship of q c 73 f 0 89 and for in slab events q c can be expressed as q c 69 f 0 94 in general q q c at 1 hz increases from the west coast of vancouver island to the east southeast within the coast belt stations on west central vancouver island closest to the landward projection of the nootka fault zone and the location of the only two known large crustal earthquakes 1918 m 7 and 1946 m 7 3 on vancouver island have the lowest q values in our study area suggesting a contrast in q between the north and south of the island online material figure showing principal tectonic units and station locations and tables of average q and alpha values with estimated uncertainties

intrinsic and scattering attenuation of the mt fuji region japan summary mount fuji is the focus of intense study because of its potential hazard signaled by seismic geologic and historical activity based on extensive seismic data recorded in the vicinity of mt fuji coda quality factor q 1c using a single scattering model hypothesis and intrinsic and scattering quality factor q 1i and q 1s using the multiple lapse time window mltw method were measured to focus the study on the magmatic structure below mt fuji the data were separated into two groups a near fuji region of rays traversing an area with radius 5 km around the summit r 20 km this classification shows the largest discrepancy of q 1c at a range of sampling volumes corresponding to overlapped sampling depth of about 80 km further the spatial division shows significant difference of q 1i and q 1s at hypocentral distance of 80 km the large difference of q 1s in bandwidths 2 4 and 4 8 hz indicates lithospheric heterogeneity beneath mt fuji with a characteristic heterogeneity scale length of about 1 km the results have a small error range due to the large data sample showing that all q 1 values in the near fuji area are greater than those of the far fuji area and q 1i for both the near and far fuji areas is higher than q 1s at high frequencies the q 1i and q 1s values for far fuji are in the range of values for typical non volcanic areas the q 1i values of the near fuji area are lower than those of other volcanic areas considered where as values of q 1s are not the low q 1i for the volcanic region of near fuji suggests that the magmatic activity indicated by percent partial melt in the vicinity of mt fuji is not as active as hot spot volcanoes such as kilauea hawaii

coda q estimates in the hong kong region abstract complementing a series of recent seismic hazard studies for hong kong we have estimated the q factor using 25 local earthquakes within 200 km of hong kong digitally recorded from january 1998 to july 2000 by eight short period stations of the hong kong observatory seismic monitoring network by analyzing the coda wave at frequencies 2 20 hz we obtained a q f relation of q 256 f 0 7 the values of q 0 q at 1 hz determined for three distance ranges r are 224 for r 50 km 342 for 50 r r 200 km the results are consistent with the spatial variations of the q factor in the wider region of south china the results fill an important gap in knowledge about the q factor and associated crustal attenuation conditions in the pearl river delta region including hong kong and provide useful insight into the influence of epicentral distance range in coda q measurements allowing better understanding of the degree of complexity in the crustal structure of the region

spatial and temporal correlation between coda q and seismicity in china a map of coda q at 1 hz q was constructed for china by analyzing more than 1000 seismograms from 80 seismic stations distributed throughout china the resultant contour map of q shows a strong correlation with the epicenters of historic great earthquakes in china the high q regions are devoid of the epicenters and the low q regions are full of them a remarkably linear relation was found between the logarithm of coda q and the maximum earthquake within the area sampled by coda waves radius of about 150 km from each station when we consider earthquakes which occurred from 1700 to present roughly speaking if q is 1000 m max is about 4 and if q is 100 m max is about 8 this relation will be very useful for siting critical facilities such as nuclear power plants and waste disposal sites we also found evidence in support of the migration of low q region coincident with the well known migration of high seismicity region over the distance of several hundred kilometers during the period of several hundred years if the migration is due to a diffusion process the diffusion constant is of the order of 100 km2 yr which agrees very well with those associated with the aftershock migration fluid injection and vp vs anomaly comparison of coda q with q1 estimated from the intensity data shows that they agree very well for q1 150 supporting the validity of the s to s single backscattering model for coda waves for q1 150 however coda q becomes constant independent of q1 this behavior is qualitatively consistent with numerical experiments of frankel and clayton and suggests that coda q may be measuring the intrinsic q of about 150 for these regions where q1 150 this limiting coda q value may depend on regions because coda q lower than 100 has been observed in some active regions in this study and also coda q as low as 30 to 40 has been reported in california mexico and italy

the northern limit of the subducted juan de fuca plate system analysis of data recorded at an array of three component broadband seismograph stations deployed on northern vancouver island and the adjacent british columbia mainland at the northern end of the cascadia subduction zone provides the first constraints on the s wave velocity structure of this region and permits us to define the northern limit of the subducted juan de fuca plate system during a 2 year period more than 80 teleseisms were recorded at our five stations the method of receiver function analysis was used to constrain the s velocity structure to upper mantle depths beneath the northern three stations a relatively simple continental crust is interpreted with a well defined moho near 37 39 km depth an upper crustal s velocity discontinuity at these stations is interpreted as the top of the high velocity rocks of the wrangellia terrane in contrast more complicated structure dominated by pronounced low velocity zones dipping to the ne are interpreted beneath our southern two stations the shallower low velocity zone is 6 8 km thick has an s velocity contrast of 0 6 1 1 km s and lies within the continental crust this feature is similar to a pronounced low velocity layer the e zone imaged beneath southern vancouver island the deeper low velocity zone is interpreted as the subducted oceanic crust we interpret the pronounced change in s velocity structure that we observe as the northern limit of the subducted oceanic plate beneath vancouver island this change coincides with significant changes in topography heat flow gravity and geochemistry

characteristics and genesis of gangdese porphyry copper deposits in the southern tibetan plateau preliminary geochemical and geochronological results porphyry type cu mo au deposits have been discovered along the gangdese magmatic arc in the southern tibetan plateau extensive field investigations and systematic studies of geochemistry s pb isotopic tracing together with re os and 40ar 39ar isotopic dating indicate that the mineralisation of the copper belt is genetically related to emplacement of late orogenic granitic porphyries during the post collisional crustal relaxation period of the late himalayan epoch these porphyries are petrochemically k enriched and belong to shoshonitic to high k calc alkaline series they display enrichment of large ion lithophile elements lile rb k u th sr pb and depletion of high field strength elements hfse nb ta ti and the heavy rare earth elements hree and y without eu anomalies these characteristics demonstrate that subduction played a dominant role in their petrogenesis and residual garnet was left in the magma sources pb isotope data show a linear correlation in the plumbotectonic framework diagram ranging from orogenic pb in the eastern segment of the copper belt to mantle pb in the western segment these constitute a mixing line of the indian oceanic morb with indian oceanic sediments and suggest that the porphyry magmas were dominantly derived from partial melting of subducted oceanic crusts mixed with a minor quantity of sediments and mantle wedge components the gangdese porphyry copper polymetallic belt has alteration characteristics and zonation typical of porphyry type copper deposits which include potassic alteration k feldspathisation and biotitisation silicification sericitisation and propylitisation mineralisation mainly occurs in strongly altered granitic cataclasite at the exo contact with veinlet disseminated textures the porphyries themselves are weakly mineralised with disseminated pyrite and chalcopyrite the copper deposits contain simple ore mineral associations consisting of chalcopyrite pyrite bornite molybdenite sphalerite and oxidised minerals of malachite covellite and molybdite during supergene oxidation primary ores underwent secondary enrichment to form economic orebodies with cu grade ranging from 1 to 5 ore sulphides of the copper belt display s and pb isotopic compositions identical to the ore bearing porphyries their 34s values vary between 3 8 and 2 4 and are typical of mantle sulphur the 206pb 204pb 207pb 204pb and 208pb 204pb ratios vary in the ranges 18 106 to 18 752 15 501 to 15 638 and 37 394 to 39 058 respectively and yielded radiogenetic lead enriched signatures twelve molybdenite samples from the copper belt yielded isochron ages of 14 76 0 22 ma and 13 99 0 16 ma for the nanmu and chongjiang deposits and model ages of 13 5 to 13 6 ma for the lakang e deposit meanwhile 40ar 39ar isotopic dating of two biotite phenocrysts from the chongjiang and lakang e deposits give plateau ages of 13 5 1 0 ma and 13 42 0 10 ma respectively during the geodynamic evolution of the gangdese collision orogenic belt intrusion of the ore bearing porphyries took place just before the rapid uplift and e w extension of the southern plateau and the ore forming process may have occurred simultaneously with the uplift and extension 14 0 1 ma

regionalization of crustal coda q in the continental united states a contour map of crustal q sub 0 values for the entire united states is presented based on a scattering model to explain the coda waves of local and near regional earthquakes these coda q sub 0 values are in good agreement with q of lg waves data are obtained from over 250 local earthquakes with most magnitudes between 3 0 and 5 0 recorded by 25 wwssn and 27 lrsm stations throughout the continental united states these two sets of data provide a range of frequencies from 0 5 to 3 5 hz a frequency dependence of q is observed in the range of frequencies considered a power law dependence of the form q q sub 0 f f sub 0 sup eta is assumed the value of frequency dependence eta is found to be maximum in the tectonically active western united states and least in the stable regions of the central and south central united states the lowest q sub 0 values are obtained in the western united states with values ranging from 140 to 200 in the coastal plains average crustal q sub 0 values for the basin and range province vary from 200 to 300 increasing gradually to 400 in the colorado plateau region q sub 0 valuesmore in the columbia plateau vary from 200 to 400 q sub 0 values increase very rapidly along the central and southern rocky mountains from 400 to 800 east of the rocky mountains q sub 0 values increase gradually in the interior plains to a maximum value of around 1300 in the mississippi embayment region farther east q sub 0 values decrease gradually to an almost constant value of 1000 along the appalachian mountains coastal regions of eastern and northeastern united states have a crustal q sub 0 value between 900 to 700 regions of north central and gulf coastal plains show low q sub 0 values ranging from 600 to 400 and less the source factor b f sub p a measure of the intensity of scattering was obtained for several different regions of the continental united states regions of high q sub 0 values exhibit low intensity of scattering less

mapping of coda wave attenuation and its frequency dependency over eastern indian shield the study area comprises two tectonic blocks namely the chotanagpur microplate and the singhbhum microplate waveform data of 112 local earthquakes of magnitude mw 2 5 were considered for the present analysis coda q qc for each event at eight different central frequencies 1 14 hz and four different coda windows was estimated using back projection algorithm the average q0 qc at 1 hz and exponent values were regionalized by projecting each value in selected square grid of dimension 0 1 0 1 back projection algorithm was used for inversion of qc and the final values were computed after ten iterations when the residual error was reduced to acceptable level inversion was stabilized by a nine point spatial smoothening gaussian filter to compute the qc values for each frequency and subsequently combined values of q0 and were also computed the final power law equation of the coda wave attenuation for the concerned region was found to be qc 336 38 16 50 f 0 83 0 036 q0 varies from 180 to 255 270 to 360 297 to 386 and 340 to 420 and vary from 0 9 to 1 02 0 79 to 0 89 0 79 to 0 88 and 0 79 to 0 86 for 30 35 40 and 45 s coda windows increase in q0 and decrease in values with increase of coda window length shows the depth dependency of seismic wave attenuation at 1 hz frequency the central part surrounding the receiver lying at the junction of the chotanagpur and the singhbhum tectonic provinces documents lower q0 and higher values and presumably caused by more heterogeneities present in the area the higher concentration of lower magnitude earthquakes in this area support this observation the mapping values of attenuation can be utilized for hazard assessment of the area

one dimensional reactive transport models of alteration in the tongchang porphyry copper deposit dexing district jiangxi province china in the tongchang porphyry copper deposit the main hydrothermal alteration is most intense in and near the contact zone and gradually attenuates inward and outward showing a symmetrical zoning with respect to the contact zone detailed field investigations of wall rock alteration and ore controlling fractures combined with laboratory studies of lithology mineral composition and fluid inclusions have led to an assessment of initial and boundary conditions and physical parameters such as species concentration mineral volume fraction temperature porosity reactive surface area and flow velocity required for dynamic modeling of this system we have developed a new program to model the coupled process of fluid flow involving advection and diffusion and chemical reactions incorporating mineral dissolution precipitation and have numerically simulated the spatial and temporal evolution of the systems for a duration of 100 000 yr in the simulations transient temperature fields are calculated for the main temperature range of ore formation from 200 degrees to 350 degrees c simulated mineral assemblages are generally in agreement with those observed in the real system the important conclusions drawn from the combined researches of geology and geochemistry as well as dynamics of coupled fluid transport and reactions are as follows fluid flow and reactions were mainly controlled by the fractures striking around north south and dipping to the west in the exocontact zone schistosity cleavages were also important fluid pathways in addition to the fractures the formation of closely spaced fractures in the contact zone and especially in the exocontact zone by tectonic activity after potassium metasomatism and the reactive flow from the contact zone inward and outward were the principal reasons for the occurrence of the contact zone symmetrical alteration zone in the porphyry body both the dissolution and precipitation of minerals were important the rate of dissolution or precipitation of minerals gradually decreased in time the nearer it was to the contact zone spatially the earlier the dissolution or precipitation of minerals was finished in the exocontact metamorphic wall rock the main processes were the transport and precipitation of sio sub 2 sub aq the rate of silification gradually decreased in time and space in the alteration of porphyry body na super was evidently removed from the alteration zone and ca super 2 removed from the intense alteration zone to weak alteration zone and the fluid was weakly acidic ph asymp 4 in the metamorphic wall rock sio sub 2 sub aq was mainly brought in from fluid the evolution of sio sub 2 sub aq cl super ca super 2 and co 3 super 2 was intimately correlated with alteration mineralization intensity

variation of coda wave attenuation in the alborz region and central iran summary more than 340 earthquakes recorded by the institute of geophysics university of tehran igut short period stations from 1996 to 2004 were analysed to estimate the s coda attenuation in the alborz region the northern part of the alpine himalayan orogen in western asia and in central iran which is the foreland of this orogen the coda quality factor qc was estimated using the single backscattering model in frequency bands of 1 25 hz in this research lateral and depth variation of qc in the alborz region and central iran are studied it is observed that in the alborz region there is absence of significant lateral variation in qc the average frequency relation for this region is qc 79 2f1 07 0 08 two anomalous high attenuation areas in central iran are recognized around the stations las and raz the average frequency relation for central iran excluding the values of these two stations is qc 94 2f0 97 0 12 to investigate the attenuation variation with depth qc value was calculated for 14 lapse times 25 30 35 90s for two data sets having epicentral distance range r 100 km data set 1 and 100 r 200 km data set 2 in each area it is observed that qc increases with depth however the rate of increase of qc with depth is not uniform in our study area beneath central iran the rate of increase of qc is greater at depths less than 100 km compared to that at larger depths indicating the existence of a high attenuation anomalous structure under the lithosphere of central iran in addition below 180 km the qc value does not vary much with depth under both study areas indicating the presence of a transparent mantle under them

review receiver function studies in the southern canadian cordillera receiver function analysis has proven to be a powerful yet inexpensive tool for estimating the s wave velocity structure of the crust and upper mantle beneath three component seismograph stations in the southern canadian cordillera receiver function studies using a portable broadband seismograph array across southwestern british columbia provided site specific estimates for the location of the subducting juan de fuca plate the oceanic crust was imaged at 47 53 km beneath central vancouver island and 60 65 km beneath the strait of georgia further these studies revealed a prominent low velocity zone vs 1 0 km s that coincides with the e reflectors imaged 5 10 km above the subducting plate on lithoprobe reflection lines the e low velocity zone was shown to extend into the upper mantle beneath the strait of georgia and the british columbia mainland to depths of 50 60 km combining the receiver function and refraction models revealed a high poisson s ratio 0 27 0 38 for this feature the contin