a common feeding system of the ne and s rifts as revealed by the bilateral 2002 2003 eruptive event at mt etna sicily italy mount etna volcano is often characterized by bilateral eruptive events involving both the south s and the north east ne rifts the last event occurred in 2002 2003 from october 27 to january 28 a detailed stratigraphically time controlled sampling of lavas and tephra of the southern eruptive fissure was performed in order to 1 track the petrological features of products during the eruption and 2 integrate the results with those previously obtained on the ne rift whole rock composition and textural observations were implemented by major and minor element analyses of plagioclases in lavas and tephra from both sides of the volcano fractionation models constrained by mass balance major and trace elements and rayleigh calculations suggest that magmas are linked by the same liquid line of descent by fractionating 9 11 of a mineral assemblage of cpx 52 69 plg 21 41 and ol 7 46 these new data allowed us to identify at least two feeding episodes through the southern fissure and infer that high k2o porphyritic magmas emitted on both the s and ne rifts derives by fractionation from the same parent magma however lavas and tephra from the southern flank were slightly more primitive textural and petrological study of plagioclase moreover indicates that chemical physical conditions in the deep feeding system were similar for magmas erupting from both rifts as suggested by the presence of dissolved rounded cores in both lavas magmas evolved differently on the s and the ne rifts only at shallow levels comparison with published seismotectonic data supports the idea that the main magma feeding the eruption on october 27 ascended along the same pathway at depth and was intercepted by the fracture system of the s and ne rifts at shallow depth between 6 and 3 km b s l

direct dating of sulfides by rbsr a critical test using the polaris mississippi valley type znpb deposit abstract the rb sr dating of sphalerites is a powerful method for directly determining the age of base metal deposits and testing models for large scale fluid flow however the uncertainty over the exact host phases for the trace amounts of rb and sr and the causes of variability in rb sr have caused concern over the reliability of the method here we show that the polaris mvt deposit with a geologically well constrained age of formation confirmed by paleomagnetic measurements and hosted in significantly older sedimentary rocks yields a consistent rb sr age of 366 15 ma providing the first unequivocal vindication of the reliability of the method

near real time mapping of peak ground acceleration and peak ground velocity following a strong earthquake during a disastrous earthquake the early assessment and timely reporting of the peak ground acceleration pga and peak ground velocity pgv maps will be crucial in an effective emergency response operation in this study we first derive an empirical relationship between m l and m w the pga and pgv attenuation relationships are deduced with data from the taiwan strong motion instrumentation program tsmip and the taiwan rapid earthquake information release system treirs site corrections of the attenuation relationships for shallow and large earthquakes in taiwan region are also obtained peak values of earthquake strong ground motion can be well determined in taiwan as soon as the earthquake location is determined and magnitudes are calculated by the treirs this peak ground motion value information can be immediately turned into the calculated pga and pgv maps that can be issued within two minutes of the earthquake origin time during any disastrous earthquake these maps are found to be very useful for immediate seismic damage assessment and dispatching of emergency response missions manuscript received 1 december 2000

shallow intrusive processes during 2002 2004 and current volcanic activity on mt etna 1 the understanding of shallow intrusive processes during 2002 2004 as well as the causes of the volcano tectonic seismicity has been improved at mt etna by comparing the inversion results from gps data with accurate 3d hypocentral locations our findings indicate that short periods of deflation about six months were followed by recharging phases after the end of both the 2001 and 2002 2003 flank eruptions during the last recharging phase june 2003 august 2004 modeling results and seismic observations suggest a composite mechanism of re injection of magma into the rift zones s and ne similar to that leading to the 2002 2003 flank eruption which could have triggered the summit eruption started on september 7 2004

time resolved seismic tomography detects magma intrusions at mount etna the continuous volcanic and seismic activity at mount etna makes this volcano an important laboratory for seismological and geophysical studies we used repeated three dimensional tomography to detect variations in elastic parameters during different volcanic cycles before and during the october 2002 january 2003 flank eruption well defined anomalous low p to s wave velocity ratio volumes were revealed absent during the pre eruptive period the anomalies trace the intrusion of volatile rich 4 weight percent basaltic magma most of which rose up only a few months before the onset of eruption the observed time changes of velocity anomalies suggest that four dimensional tomography provides a basis for more efficient volcano monitoring and short and midterm eruption forecasting of explosive activity

extreme 13ccarb enrichment in ca 2 0 ga magnesite stromatolite dolomite red beds association in a global context a case for the world wide signal enhanced by a local environment abstract the palaeoproterozoic positive excursion of 13 c carb is now considered as three positive shifts of 13 c carb separated by returns to 0 which all occurred between 2 40 and 2 06 ma this isotopic event is unique in terms of both duration 300 ma and 13 c enrichment up to 18 the mechanism responsible for one of the most significant carbon isotopic shifts in earth history remains highly debatable to date 13 c of 10 to 15 cannot be balanced by organic carbon burial forg as there is no geological evidence for an enhanced corg accumulation prior to or synchronous with the excursion instead termination of these excursions is followed by formation of a vast reservoir of 13 c depleted organic material 45 at shunga and by one of the earliest known oil generation episodes at 2 0 ga none of the three positive excursions of 13 c carb is followed by a negative isotopic shift significantly below 0 as has always been observed in younger isotopic events reflecting an overturn of a major marine carbon reservoirs this may indicate that forg was constant implying that the mechanism involved in the production of corg was different onset of intensive methane cycling resulting in c change is another possibility the majority of sampled 13 c carb rich localities represents shallow water stromatolitic dolostones red beds and evaporites formed in restricted intracratonic basins and may not reflect global 13 c carb values closely spaced drill core samples n 73 of stromatolitic dolostones from the 1980 27 ma tulomozerskaya formation in the onega palaeobasin russian karelia have been analysed for 13 c carb and 18 o carb in order to demonstrate that different processes were involved in the formation of 13 c carb rich carbonates the 800 m thick magnesite stromatolite dolomite red beds succession formed in a complex combination of environments on the karelian craton peritidal shallow marine low energy protected bights barred basins evaporative ephemeral ponds coastal sabkhas and playa lakes the carbonate rocks exhibit extreme 13 c enrichment with 13 c values ranging from 5 7 to 17 2 vs v pdb mean 9 9 2 3 and 18 o from 18 6 to 26 0 vs v smow mean 22 0 1 6 the tulomozerskaya isotopic excursion is characteristic of the global 2 4 2 06 ga positive shifts of carbonate 13 c 12 c although it reveals the greatest enrichment in 13 c known from this interval an external basin s is considered to have provided an enhanced corg burial and global seawater enrichment in 13 c the global background value for the isotopic shift at tulomozero time ca 2 0 ga is roughly estimated at around 5 an explosion of stromatolite forming microbial communities in shallow water basins evaporative and partly restricted environments high bioproductivity enhanced uptake of 12 c and pene contemporaneous recycling of organic material in cyanobacterial mats with the production and consequent loss of co2 and ch4 are believed to be additional local factors which may have enhanced 13 c from 5 up to 17 such factors should be taken into account when interpreting carbon isotopic data and attempting to discriminate between the local enrichment in 13 c and globally enhanced 13 c values we propose that many previously reported 13 c values from other localities where environmental interpretations are not available or have not been taken into account may not represent the global 13 c values

the deep structure of the north anatolian fault zone abstract multi scale full waveform inversion of complete continental and regional scale seismograms reveals the crustal and upper mantle signature of the north anatolian fault zone which shapes the neotectonics of turkey and the eastern mediterranean within the crust the fault zone is mostly bounded by several high velocity blocks suggesting that it developed along the edges of continental fragments with high rigidity below the crust the surface expression of the eastern and central parts of the north anatolian fault zone correlate with a pronounced low velocity band that extends laterally over 600 km around 100 km depth the low velocity band merges into the shallow anatolian asthenosphere thereby providing a link to the kirka afyon isparta volcanic field and the central anatolian volcanics we interpret the low velocity band beneath the north anatolian fault zone as the upper mantle expression of the tethyan sutures that formed 60 15 ma ago as a result of africa eurasian convergence the structurally weak suture facilitated the formation of the younger less than 10 ma crustal fault zone in this sense the north anatolian fault zone is not only a crustal feature but a narrow zone of weakness that extends into the upper mantle

the deformation offshore of mount etna as imaged by multichannel seismic reflection profiles abstract despite the clear evidence of active flank dynamics that is affecting the eastern side of mount etna the contribution of tectonic processes has not been yet understood so far the various models proposed to explain the observed flank deformation have been based on onshore structural data coming from the volcanic edifice the ionian offshore of mount etna has been only recently investigated using multichannel seismic profiles and offers the opportunity to image the structural features of the substrate of the unstable flank of the volcano this contribution aims at describing the deformation located offshore mount etna using multichannel seismic profiles recently acquired during three seismic surveys the onshore flank deformation of mount etna appears to be laterally confined by two tectonic guidelines trending roughly e w located to the north and south of the deforming flank the northern guideline in particular takes the surface expression of a sharp fault pernicana fault though often assumed that these boundary structures continue offshore as linear features connected to a frontal thrust ramp the occurrence of this simple offshore structural system has not been imaged in fact seismic data show a remarkable degree of structural complexity offshore mount etna the pernicana fault for instance is not continuing offshore as a sharp feature rather the deformation is expressed as ene wsw folds located very close to the coastline it is possible that these tectonic structures might have affected the offshore of mount etna before the pernicana fault system was developed less than 15 ka ago the southern guideline of the collapsing eastern flank of the volcano is poorly expressed onshore and does not show up offshore in fact seismic data indicate that the catania canyon a remarkable e w trending feature does not reflect a tectonic control seismic interpretation also shows the occurrence of a structural high located just offshore the edifice of mount etna whereas a complex deformation affects the boundary of this offshore bulge it shows only limited internal deformation part of the topography of the offshore bulge pre existed the constructional phase of mount etna being an extension of the hyblean plateau only in the northern part the bulge is a recent tectonic feature being composed by plio quaternary strata that were folded before and during the building of mount etna the offshore bulge is bounded by a thrust fault that can be related to the intrusion of the large scale magmatic body below mount etna

moment magnitude local magnitude calibration for earthquakes off canada s west coast local magnitude m l values of earthquakes off canada9s west coast are known to be underestimated by at least 0 5 magnitude units compared with other magnitude scales moment magnitude m w derived from moment tensor analysis provides the most robust estimate of the magnitude of earthquakes moment tensor analysis of regional seismic data in western canada is now possible due to the installation of more than 40 three component broadband stations in western canada the u s pacific northwest and southeast alaska moment tensor solutions are now possible down to m 4 0 more than 230 regional moment tensor solutions have been calculated off canada9s west coast at the geological survey of canada for 1995 2002 these solutions along with 14 previous solutions by oregon state university in 1994 1995 and 13 harvard solutions for 1984 1993 allow a systematic m w m l calibration for earthquakes in this region the study area extends from the queen charlotte islands region in the north to the area off the west coast of southern vancouver island at the northern end of the study area where there is little oceanic crust in the source receiver travel path m w is systematically larger than m l by 0 28 0 08 magnitude units at the southern end of the study area where there is a significant amount of ocean crust in the source receiver travel path m w is systematically larger than m l by 0 62 0 08 magnitude units calibration of m l with m w will allow the western canadian earthquake database to be used more effectively for tectonic studies and seismic hazard analysis

link between major flank slip and 2002 2003 eruption at mt etna italy 1 the 2002 2003 etna eruption is studied through earthquake distributions and surface fracturing in september 2002 earthquake induced surface rupture sinistral offset 0 48 m occurred along the e w striking pernicana fault pf on the ne flank in late october a flank eruption accompanied further 0 77 m surface rupturing reaching a total sinistral offset of 1 25 m the deformation then propagated for 18 km eastwards to the coastline sinistral offset 0 03 m and southwards along the nw se striking timpe dextral offset 0 04 m and later trecastagni faults dextral offset 0 035 m seismicity 4 km bsl on the e flank accompanied surface fracturing fault plane solutions indicate an overall ese wnw extension direction consistent with ese slip of the e flank also revealed by ground fractures a three stage model of flank slip is proposed inception september earthquake climax accelerated slip and eruption and propagation e and s migration of the deformation

lead isotope compositions of late cretaceous and early tertiary igneous rocks and sulfide minerals in arizona implications for the sources of plutons and metals in porphyry copper deposits porphyry copper deposits in arizona are genetically associated with late cretaceous and early tertiary igneous complexes that consist of older intermediate volcanic rocks and younger intermediate to felsic intrusions the igneous complexes and their associated porphyry copper deposits were emplaced into an early proterozoic basement characterized by different rocks geologic histories and isotopic compositions lead isotope compositions of the proterozoic basement rocks define from northwest to southeast the mojave central arizona and southeastern arizona provinces porphyry copper deposits are present in each pb isotope province lead isotope compositions of late cretaceous and early tertiary plutons together with those of sulfide minerals in porphyry copper deposits and of proterozoic country rocks place important constraints on genesis of the magmatic suites and the porphyry copper deposits themselves the range of age corrected pb isotope compositions of plutons in 12 late cretaceous and early tertiary igneous complexes is 206 pb 204 pb 17 34 to 22 66 207 pb 204 pb 15 43 to 15 96 and 208 pb 204 pb 37 19 to 40 33 these pb isotope compositions and calculated model th u are similar to those of the proterozoic rocks in which the plutons were emplaced thereby indicating that pb in the younger rocks and ore deposits was inherited from the basement rocks and their sources no pb isotope differences distinguish late cretaceous and early tertiary igneous complexes that contain large economic porphyry copper deposits from less rich or smaller deposits that have not been considered economic for mining lead isotope compositions of late cretaceous and early tertiary plutons and sulfide minerals from 30 metallic mineral districts furthermore require that the southeastern arizona pb province be divided into two subprovinces the northern subprovince has generally lower 206 pb 204 pb and higher model th u and the southern subprovince has higher 206 pb 204 pb and lower model th u these pb isotope differences are inferred to result from differences in their respective post 1 7 ga magmatic histories throughout arizona pb isotope compositions of late cretaceous and early tertiary plutons and associated sulfide minerals are distinct from those of jurassic plutons and also middle tertiary igneous rocks and sulfide minerals these differences most likely reflect changes in tectonic setting and magmatic sources within late cretaceous and early tertiary igneous complexes that host economic porphyry copper deposits there is commonly a decrease in pb isotope composition from older to younger plutons this decrease in pb isotope values with time suggests an increasing involvement of crust with lower u pb than average crust in the source s of late cretaceous and early tertiary magmas lead isotope compositions of the youngest porphyries in the igneous complexes are similar to those in most sulfide minerals within the associated porphyry copper deposit this pb isotope similarity argues for a genetic link between them however not all pb in the sulfide minerals in porphyry copper deposits is magmatically derived some sulfide minerals particularly those that are late stage or distal to the main orebody or in proterozoic or paleozoic rocks have elevated pb isotope compositions displaced toward the gross average pb isotope composition of the local country rocks the more radiogenic isotopic compositions argue for a contribution of pb from those rocks at the site of ore deposition combining the pb isotope data with available geochemical isotopic and petrologic data suggests derivation of the young porphyry copper related plutons most of their pb and other metals from a hybridized lower continental crustal source because of the likely involvement of subduction related mantle derived basaltic magma in the hybridized lower crustal source an indiscernible mantle contribution is probable in the porphyry magmas clearly in addition pb was contributed from the local country rocks this is most evident in sulfide minerals in veins that are late stage hosted in proterozoic gneiss and or peripheral to the porphyry copper deposit

seismic amplitude tomography for crustal attenuation beneath china summary amplitude tomography reconstructs seismic attenuation directly from recorded wave amplitudes we have applied the tomography to amplitude data reported in the annual bulletin of chinese earthquakes and interpreted the regionally varying crustal attenuation in terms of tectonics the seismic amplitudes were originally recorded for determining the m l and m s magnitudes they generally correspond to the maximum amplitudes of the horizontal components of the short period s waves and intermediate period rayleigh waves both sets of measurements are sensitive to crustal structure the peak amplitudes from m l amplitudes spread spherically with significant dispersion and scattering m s amplitudes show cylindrical spreading with little dispersion average crustal q values for attenuation at 1 hz are 737 and 505 for m l and m s respectively with substantial regional variations frequency dependence in the attenuation is also indicated regions with the lowest attenuation high q values are beneath the south china block sichuan basin ordos platform the daxinganling and the korea craton these tend to be tectonically inactive regions which are generally dominated by intrusive and cratonic rocks in the upper crust regions with the highest attenuation low q values are beneath bohai basin yunnan eastern songpan ganzi terrain margins of the ordos platform and the qilian shan these are predominantly active basins grabens and fold belts the continental margin also highly attenuates both s and surface waves

geometry and kinematics of the fault systems controlling the unstable flank of etna volcano sicily abstract an updated tectonic framework of etna s unstable flank has been defined as a result of multidisciplinary analyses carried out by integrating geological and geophysical data the different typologies of datasets have been analyzed and correlated in order to constrain the geometry and kinematics of the fault systems controlling the unstable flank of etna volcano and to better understand their complex relationship with the offshore morphostructures of the continental margin in particular we have considered as the main structural elements the following four fault systems pernicana ragalna tremestieri trecastagni and timpe slip rates and kinematics have been estimated in both long and short terms respectively from geological and seismotectonic geodetic data data integration has allowed defining five kinematic domains in the sliding flank of etna 1 the ne block bordered by the pernicana fault and characterised by the highest deformation velocities ground velocity progressively diminishes toward south with a clockwise rotation of the vectors defining 2 the block embracing the central part of the timpe system 3 the giarre wedge 4 the medium east block bounded by the s tecla and trecastagni faults and 5 the se block bordered by the hidden belpasso ognina tectonic lineament the dynamics of these blocks takes place through discontinuous movements sudden short term accelerations related to the magma intrusion are superimposed to a fairly constant mid term ese sliding the proposed comprehensive model of the unstable flank provides the basic input parameters for applying analytical models to flank dynamics of etna volcano

genesis of the stratiform zhenzigou pb zn deposit in the north china craton rb sr and c o s pb isotope constraints abstract isotopes rb sr c o s and pb were investigated from the zhenzigou pb zn deposit in the qingchengzi mineral field qmf of the north china craton as an aid to determine the genesis of stratiform pb zn deposits in the liao ji rift a step dissolution rb sr age of 1798 8 ma with 206pb 204pb ratios of 17 7477 17 8527 were obtained from sphalerite sulfur isotopic ratios for pyrite 5 14 4 sphalerite 2 4 8 6 and galena 0 3 8 6 from zhenzigou have a narrower range than those from the host paleoproterozoic dashiqiao formation and granite in the area calcite and limestone from ore and wallrocks at the deposit have similar c and o isotope compositions with 13cpdb ranging from 6 0 to 2 3 and 18osmow from 9 8 to 13 7 which are similar to those of carbonatite and the mantle comprehensive analysis of the pb isotopic composition of the sulfide from the zhenzigou deposit and pb zn deposits in adjacent area show that the pb originated from the upper crust and mixed with pb from the mantle sulfur isotopes from zhenzigou deposit indicate that the mineralization has a volcanic eruption source the 13cpdb and 18osmow values indicate that the co2 originated from a mixed mantle marine carbonate and organic source combined with the study of regional metallogenic background this paper proposes that deposition of stratiform pb zn mineralization in the qmf began ca 2052 ma during development of the liaoji rift the mineralization extended to ca 1798 ma prior to deformation associated with the lvliang movement which dismembered the stratiform pb zn mineralization the veined mineralization in the region cross cuts the stratiform deposits and represents remobilized and redeposited deposits associated with the emplacement of triassic plutons such as the xinling and shuangdinggou granites

broken hill pb zn ag deposit a product of mantle metasomatism broken hill ore deposition occurred during the highest geothermal gradient coeval with an event of bimodal basic rhydacitic volcanism the depositional environment is interpreted as an ensialic rift on the basis of the sedimentary facies ferro and low k tholeiitic basalts and bimodal basic calc alkaline rhyolite rhyodacite volcanism the orebody is of unusual composition characterised by abundant carbonate fluorite and fluorapatite abundant lil k and rb rich premetamorphic alteration assemblages primordial s and pb isotopic values sr isotopes possibly indicating a heterogeneous source s se in the magmatic range and zoning suggestive of cooling of the ore fluid

long term stress strain analysis of volcano flank instability the eastern sector of etna from 1980 to 2012 1 we investigated the evolution of seismicity and deformation in the unstable eastern flank of etna volcano over a 30 year period from 1980 to 2012 a significant temporal correlation has been revealed between periods of flank acceleration and intensified seismic activity by comparing seismicity along the northern border pernicana fault system of the sliding flank and the deformation of the eastern flank two marked phases have been observed in 1984 1986 and in the years following 2002 these two phases are separated by an intermediate phase from 1987 to 2001 in which the flank sliding slowed down and the seismicity dropped drastically this common temporal evolution in the deformation rate and seismic release supports the hypothesis that the seismicity in the northern border can be viewed as a marker of the response to accommodate the stress exerted by the traction of the eastern flank sliding this interplay has also been corroborated by finite element method numerical computations that highlight a good correlation between the seismicity pattern and areas of positive stress changes induced by the sliding surface the two intense phases of flank acceleration are representative of two main different sources volcano flank instability stretching the eastern sector in the first 1984 1986 phase and magmatic intrusions pushing the eastern flank seaward since the 2002 2003 eruption establishing the relationship between flank acceleration and seismic activation therefore contributes to understanding etna s mechanical behavior and provides insights into the processes regulating the unstable flank response

elasto plastic modeling of volcano ground deformation abstract elasto plastic models for pressure sources in heterogeneous domain were constructed to describe assess and interpret observed deformation in volcanic regions we used the finite element method fem to simulate the deformation in a 3d domain partitioned to account for the volcano topography and the heterogeneous material properties distribution firstly we evaluated the extent of a heated zone surrounding the magmatic source calculating the temperature distribution by a thermo mechanical numerical model secondly we included around the pressurized magma source an elasto plastic zone whose dimension is related to the temperature distribution this elasto plastic model gave rise to deformation comparable with that obtained from elastic and viscoelastic models but requiring a geologically satisfactory pressure we successfully applied the method to review the ground deformation accompanying the 1993 1997 inflation period on mt etna the model considerably reduces the pressure of a magma chamber to a few tens of mpa to produce the observed surface deformation results suggest that the approach presented here can lead to more accurate interpretations and inferences in future modeling based assessments of volcano deformation

recent seismicity and tomographic modeling of the mount etna plumbing system the monitoring of seismic activity in eastern sicily southern italy has been recently improved in the framework of the poseidon project to investigate both tectonics and volcanic processes of mount etna this effort has produced a homogeneous and complete data set which we use to image the deep structure of the volcano and to define the space and time distribution of the recent seismicity encompassing the 1995 eruption diffuse eruptions between 1995 and 1997 a further magma intrusion started in 1997 and an increase of volcanic activity in july 1998 we inverted p wave arrival times from 307 selected local earthquakes to obtain a three dimensional velocity model of the volcano with a simultaneous inversion for hypocenters and velocity parameters the new tomographic images permit us to define the structure beneath the volcano from the surface down to 18 km depth the main structural feature revealed by our inversion is a high velocity body located beneath the central craters whose lateral extent increases from 6 km between 18 and 9 km depth to 12 km between 9 and 3 km depth near the surface the fast anomaly branches in two separate high vp regions which are located below the summit craters and the eastern flank valle del bove respectively the high velocity features are interpreted as high density cumulates of solidified magma that intruded the shallow crust we hypothesize that magma ascends the crust within the relatively small high velocity conduit below 9 km depth and is stored at depth shallower than 9 km within the broad high velocity region as also suggested by petrological data a sharp increase of seismicity in 1997 with earthquakes occurring at the border of the high velocity body suggests that mount etna sustained recent episodes of intrusions which possibly herald future eruptions no large low velocity anomaly interpretable as a melted magma chamber is imaged in the upper 18 km of the crust while a broad low velocity anomaly in the uppermost mantle revealed by regional seismic data possibly indicates the magma source region at depth earthquake occurrence from the deep source to the shallow intrusive area helps to trace the magma migration and the feeding of the volcanic system

contemporary crustal deformation of northeast tibet from geodetic investigations and a comparison between the seismic and geodetic moment release rates abstract we processed the data recorded by 32 continuous gps stations from the crustal movement observation network of china and combined them with published gps observations in a common geodetic reference frame to better depict the ongoing crustal velocities and deformation field of northeast tibet the derived velocity field indicates that the deformation of northeast tibet is characterized mainly by crustal shortening coupled with the eastward extrusion of crustal material and clockwise block rotation we further used the gps velocity field to evaluate the strain rate tensors by the method of sandwell and wessel 2016 the strain rate field shows an obvious transition of the contraction rate from ne sw to nee sww and a decrease in the maximum shear strain rate from west to east was observed along the east kunlun fault and haiyuan fault indicating that the block rotation and lateral extrusion therein may be partitioned by ne sw oriented compression to some extent the inhomogeneity of the rotation strain rate implies that northeast tibet does not behave like a single rigid block but instead resembles a left lateral shear zone supporting the hypothesis that the northward transfer of motion along the east kunlun fault may play a significant role in the deformation style of this area the dilatation rate verified that most of northeast tibet experiences crustal thickening which coincides with the average uplift rate of 1 mm y revealed by gps velocities and channel steepness indices we also estimated the geodetic moment rates and compared them with the seismic moment rates estimated using the truncated gutenberg richter earthquake distribution the ratio of the seismic strain rate to the geodetic strain rate in the regions near the altyn tagh fault the qaidam basin adjoining the qilian mountains the haiyuan fault and the central part of the east kunlun fault are near unity indicating that the deformation in these areas is dominated by seismic release and may represent fully coupled seismogenic zones the occurrence of large earthquakes in the past estimated magnitudes m 6 coupled with a high geodetic deformation rate in these regions could indicate overdue m 6 earthquakes however other factors including the occurrence of creep and the long recurrence time of mw 8 0 earthquakes should be taken into consideration along the haiyuan fault by contrast in other regions including the southern and eastern parts of the haiyuan fault along the elashan fault and the northern qilian mountains the geodetic moment rate is higher than the seismic moment rate by a factor between 3 and 9 we propose that this phenomenon is related to the undersampling of long term earthquake rates within the seismic catalogue long term aseismic crustal deformation or a combination of these factors our study has implications for better comprehending the current seismotectonic pattern of northeast tibet

3d numerical deformation model of the intrusive event forerunning the 2001 etna eruption abstract 3d finite elements models were carried out in order to evaluate the ground deformation produced by the dike intrusion occurred at etna volcano in the 2001 the finite element method fem allows for considering the medium heterogeneity and the real topography of the volcano firstly we validated the method in a homogeneous elastic half space and compared the results with those obtained from analytical dislocation models we performed a convergence analysis to quantify the discretization errors which are sensitive to the size and quality of the mesh elements and can cause inaccurate numerical solutions secondly several numerical models were conducted to appreciate how the complex distribution of elastic medium parameters and the topography make the numerical results differ from the simple analytical solutions the numerical model which account for the real topography of etna volcano and medium heterogeneity well match the ground deformation observed at the gps stations between 11 and 16 july 2001 it appears that topography and heterogeneities provide more details about the ground deformation near the summit crater area that are missed when homogeneous half space models are used however only few discrepancies between the analytical and the numerical models are observed at the gps stations which coarsely sample the volcanic edifice far away from the summit craters

deformation history of the paleoproterozoic liaohe assemblage in the eastern block of the north china craton the paleoproterozoic liaohe assemblage and associated liaoji granitoids represent the youngest basement in the eastern block of the north china craton various structural elements and metamorphic reaction relations indicate that the liaohe assemblage has experienced three distinct deformational events d1 to d3 and four episodes of metamorphism m1 to m4 the earliest greenschist facies event m1 is recognized in undeformed or weakly deformed domains wrapped by the s1 schistosity suggesting that m1 occurred before d1 the d1 deformation produced small mostly meter scale isoclinal and recumbent folds f1 an associated penetrative axial planar schistosity s1 a mineral stretching lineation l1 and regional scale ductile shear zones concurrent with d1 was m2 metamorphism which occurred before d2 and produced low to medium pressure amphibolite facies assemblages regionally divergent motion senses reflected by the asymmetric f1 folds and other sense of shear indicators together with the radial distribution of the l1 lineation surrounding the liaoji granitoids imply that d1 represents an extensional event the d2 deformation produced open to tight f2 folds of varying scales s2 axial crenulation cleavages and ene ne striking thrust faults involving broadly nw se compression following d2 was m3 metamorphism that led to the formation of sillimanite and cordierite in low pressure type rocks and kyanite in medium pressure rocks the last deformational event d3 formed nw wnw trending folds f3 axial planar kink bands spaced cleavages s3 and strike slip and thrust faults which deflect the earlier d1 and d2 structures d3 occurred at a shallow crustal level and was associated with or followed by a greenschist facies retrograde metamorphic event m4 the liaohe assemblage and associated liaoji granitoids are considered to have formed in a paleoproterozoic rift the late spreading of which led to the occurrence of the early extensional deformation d1 and the m1 and m2 metamorphism and the final closing of which was associated with the d2 and d3 phases of deformation and m3 and m4 metamorphism

salt dome controlled sulfide precipitation of paleoproterozoic fe cu sulfide deposits eastern liaoning northeastern china the lower portion of the paleoproterozoic northern liaohe group liaoning northeast china comprises metavolcanics tuff dominated and metasediments mostly arkoses and dolostones that host stratiform strata bound fe cu sulfides and ca ba sulfates the ore bearing sequence consists of in ascending order pyroclastic rocks terrigenous clastics and carbonates all of which have been metamorphosed to greenschist amphibolite grade extensive albite rich breccias are present at the base of the succession and as pipes crosscutting a variety of lithologic units in the lieryu formation the geometry geochemistry and associated structures of these albite rich rocks suggest that they are metamorphosed salt domes the sulfide sulfate fe cu ores occur in a transitional zone between tuffs and dolomitic carbonates with those in the upper cycle being economically more important the sulfides were precipitated at two sites around venting centers as breccias lenses and veins and as stratiform pyrite chalcopyrite associated with anhydrite that is distal to the salt domes within each mining district the proximal ores are associated with brecciated albite and tourmaline rich rocks the sulfides in the proximal ores have delta 34 s values of 8 9 to 12 7 per mil whereas the distal ores have delta 34 s values of 2 6 to 8 8 per mil for the sulfides and 7 9 to 19 0 per mil for the anhydrite suggesting a sulfate dominated sulfur source with the pyrite delta 34 s variations arising mainly from decreasing temperatures away from the centers of the deposits the origin of the deposits is best described by a model in which sulfate carbonate rocks were deposited in peripheral sinks during salt diapirism the salt domes then acted as focuses for subsequent hydrothermal venting and were the centers of sulfide mineralization the sulfides precipitated during interaction of the reduced metal bearing hydrothermal fluids with the in situ sulfates that were the major source of the sulfur

rb sr sm nd and pb isotope systematics of pyrite implications for the age and genesis of lode gold deposits lode gold deposits commonly consist of pyrite and lesser amounts of lead and zinc sulfides accompanied by quartz and calcite their exact origin remains controversial mainly because of the scarcity of reliable geochronological data here we present direct rb sr dating of pyrite from a lode gold deposit and propose the method as a useful geochronological technique for gold mineralization for which age data are poor a positive correlation between present day 87 sr 86 sr and 87 rb 86 sr ratios of pyrite fes 2 subsamples from the linglong gold mine of china corresponds to an age of 122 123 ma which dates the age of gold mineralization the sr nd and pb isotopic compositions of pyrites and the associated rocks suggest that the hydrothermal fluids responsible for the pyrite and gold mineralization were probably derived from a mixed source i e degassing of mafic magmas and meteoric water that had leached the country rocks

numerical simulation of stress induced piezomagnetic fields at etna volcano summary 3 d magneto elastic models based on finite element method fem have been developed to compute piezomagnetic fields caused by magmatic overpressure sources we solved separately i the elastostatic equation for the stress field and ii the coupled poisson s equation for magnetic potential field the numerical computations were focused on a more realistic modelling of etna volcano where remarkable magnetic changes have been observed during eruptive events we evaluated the effects of topography and medium heterogeneities considering different multilayered crustal structures constrained by seismic tomography and geological evidences when topography and magneto elastic heterogeneities are included in the numerical models the piezomagnetic field changes show significant deviations from the homogeneous half space solution generally it was found that the analytical model overestimates the expected magnetic changes the numerical models of the piezomagnetic field showed significant differences in presence of strong magnetization contrasts and in proximity of steep cliffs that is at the volcano summit the fem approach presented here allows considering a picture of a fully 3 d model of etna volcano which could advance the reliability of model based assessments of magnetic observations

volcanomagnetic evidence of the magmatic intrusion on 13thmay 2008 etna eruption 1 during the onset of 2008 volcanic crisis at mt etna the near real time magnetic data provided a continuous updating of the volcano activity state on the northern flank on the morning of 13th may 2008 significant local magnetic field changes marked the resumption of the eruptive activity characterized by the opening of a fracture field on the northern flank and an eruptive fissure in the valle del bove in agreement with the northward propagation of seismic events magnetic signals at 5 stations in the summit area revealed a nearly nnw sse oriented magmatic intrusion which started at about 9 00 gmt propagated northward for about 2 km and stopped at 14 00 gmt before reaching the north east rift magnetic variations with amplitude ranging between 1 8 nt and 6 5 nt are consistent with those calculated from piezomagnetic models where stress induced changes in rock magnetization are produced by the magmatic intrusion

deformation of stratiform znpb barite deposits in the northern canadian cordillera abstract the major stratiform sediment hosted zn pb barite deposits of the northern canadian cordillera occur in the palaeozoic selwyn basin kechika trough they formed in euxinic fine grained clastic dominated extensional basins that developed within the carbonate platform of the passive margin of ancestral north america during the late jurassic to mid cretaceous these basins and the stratiform ore deposits were subjected to low greenschist facies regional metamorphism and fold and thrust deformation as they were incorporated into the western part of the rocky mountains mackenzie mountains foreland fold and thrust belt this paper summarises the results of detailed field and microscopic studies on four of these deposits the tom deposit the howards pass deposit the cirque deposit and the driftpile creek deposit the dominant mineralogy of these deposits is sphalerite galena pyrite and in some cases significant barite is present low greenschist grade metamorphism and deformation is characterised by cataclastic flow and brecciation in coarse grained massive pyritic sulphides and by folding recrystallisation and cleavage development in fine grained sulphides and barite relict primary depositional diagenetic structures are found within the orebodies deformation is characterised by strong pressure solution fabrics in barite in fine grained laminated pyrite layers and in mixed sulphide carbonate beds marked local transposition is found with significant remobilisation of galena barite and pyrite the deformation mechanics of these sulphide barite deposits are illustrated using schematic deformation mechanism maps

geochemical implications of rare earth element patterns in hydrothermal fluids from mid ocean ridges abstract rare earth element data are reported for vent fluids collected from eight deep sea hydrothermal areas including samples from sediment hosted and bare rock hydrothermal systems the morb normalized ree patterns from these diverse settings are remarkably similar to each other but distinctly different than seawater or basalt being lree enriched and possessing a strikingly positive eu anomaly the ree concentrations making up these patterns vary widely however both on a spatial and temporal basis when plotted against ionic radii these fluid trends are remarkably linear and show the same fractionation patterns exhibited by plagioclase during magma segregation this analysis suggests that the partitioning of the ree between fluid and rock during high temperature hydrothermal alteration of morb is dominated by crystochemical exchange during dissolution and recrystallization reactions at the exposed surfaces of plagioclase phenocrysts a comparison of ree ionic radii in eight coordination indicate that the partitioning of 3ree and 2eu are dominated by chemical substitution for ca 2 and sr 2 respectively these considerations predict that the total 3ree content of vent fluid varies in a systematic way during the transition from an rich morb plagioclase to ab rich hydrothermal plagioclase and that these parameters can be used as indicators of the average extent of alteration inside active hydrothermal systems

modelling of ground deformation and gravity fields using finite element method an application to etna volcano summary elastic finite element models are applied to investigate the effects of topography and medium heterogeneities on the surface deformation and the gravity field produced by volcanic pressure sources changes in the gravity field cannot be interpreted only in terms of gain of mass disregarding the ground deformation of the rocks surrounding the source contributions to gravity changes depend also on surface and subsurface mass redistribution driven by dilation of the volcanic source both ground deformation and gravity changes were firstly evaluated by solving a coupled axisymmetric problem to estimate the effects of topography and medium heterogeneities numerical results show significant discrepancies in the ground deformation and gravity field compared to those predicted by analytical solutions which disregard topography elastic heterogeneities and density subsurface structures with this in mind we reviewed the expected gravity changes accompanying the 1993 1997 inflation phase on mt etna by setting up a fully 3 d finite element model in which we used the real topography to include the geometry and seismic tomography to infer the crustal heterogeneities the inflation phase was clearly detected by different geodetic techniques edm gps sar and levelling data that showed a uniform expansion of the overall volcano edifice when the gravity data are integrated with ground deformation data and a coupled fem modelling was solved a mass intrusion could have occurred at depth to justify both ground deformation and gravity observations

origin of the inconsistent apparent re os ages of the jinchuan ni cu sulfide ore deposit china post segregation diffusion of os abstract apparent re os ages of some magmatic sulfide ore deposits are older than the zircon and baddeleyite u pb ages which are interpreted as the formation age of the host intrusions the jinchuan ni cu pge deposit of china the world s third largest is such a case we report apparent re os isochron ages of 1117 67 ma 1074 120 ma and 867 75 ma with initial 187os 188os ratios of 0 120 0 012 0 162 0 017 and 0 235 0 027 for disseminated ores sulfides from the disseminated ores and massive ores from jinchuan respectively using these data and re os ages from the literature we find that the oldest apparent re os age and lowest initial os isotope ratio are from disseminated ores which contain small amounts of sulfide minerals the highest initial os isotope ratios and youngest apparent re os ages consistent with the zircon and baddeleyite u pb ages are from massive ores containing 90 100 modal sulfide and net textured ores with about 25 modal sulfides yield apparent re os ages and initial os ratios intermediate between those of the disseminated and massive ores because os diffusion between sulfides is inhibited by the intervening silicates even at high temperatures re equilibration did not occur in the disseminated ore and the samples retained the os ratios of the contaminated magma leading to geologically meaningless ages that are older than the formation age of the rocks while os bearing sulfide minerals and magnetite show low closure temperatures of os diffusion and the sulfide minerals in the massive ore are closely connected with each other facilitating fast diffusion of os re equilibration of os was achieved during cooling of the ore from about 850 c after the segregation to about 400 c thus an age corresponding to the formation time and an elevated initial os ratio were yielded by the massive ore os isotopes in the net textured ore behave in the way intermediate between the disseminated and massive ores pb isotope data support the os results disseminated ores have heterogeneous pb isotope ratios whereas pb in the massive ores is more uniform consistent with pb isotopic equilibration in the massive ores but not in the disseminated ores

sensitivity of coulomb stress change to the parameters of the coulomb failure model a case study using the 2008 mw 7 9 wenchuan earthquake the coulomb stress change has been widely employed to interpret mainshock mainshock and mainshock aftershock triggering as well as interactions amongst earthquake faults and volcanoes this quantitative index is computed based on the coulomb failure criterion and is a function of fault parameters including the source and receiver fault geometries the friction coefficient on the receiver fault and skempton s coefficient of the host rock thus for the robust determination of the coulomb stress change the sensitivity of the coulomb stress change to these model parameters should be thoroughly assessed however notwithstanding numerous case studies almost no systematic investigation of the sensitivity of the coulomb stress change has been performed here we present an error estimator for the coulomb stress change and then quantitatively investigate the sensitivity of the coulomb stress change to the fault model parameters for the 2008 mw 7 9 wenchuan earthquake our results indicate that for this case the coulomb stress change is the most sensitive to the uncertainty in the dip angle of the receiver fault while the influences of the uncertainties in the slip model of the source fault the strike and rake angles of the receiver fault and the friction and skempton s coefficients cannot be neglected accordingly it is crucial to perform a realistic estimate of the uncertainty in the coulomb stress change by performing such calculation future coulomb stress analyses such as the stress triggering of earthquake sequence and the likelihoods of potential earthquakes could be based on more robust coulomb stress change maps

response of the san andreas fault to the 1983 coalinga nunez earthquakes an application of interaction based probabilities for parkfield 1 the parkfield cholame section of the san andreas fault site of an unfulfilled earthquake forecast in 1985 is the best monitored section of the world s most closely watched fault in 1983 the m 6 5 coalinga and m 6 0 nunez events struck 25 km northeast of parkfield seismicity rates climbed for 18 months along the creeping section of the san andreas north of parkfield and dropped for 6 years along the locked section to the south right lateral creep also slowed or reversed from parkfield south here we calculate that the coalinga sequence increased the shear and coulomb stress on the creeping section causing the rate of small shocks to rise until the added stress was shed by additional slip however the 1983 events decreased the shear and coulomb stress on the parkfield segment causing surface creep and seismicity rates to drop we use these observations to cast the likelihood of a parkfield earthquake into an interaction based probability which includes both the renewal of stress following the 1966 parkfield earthquake and the stress transfer from the 1983 coalinga events we calculate that the 1983 shocks dropped the 10 year probability of a m 6 parkfield earthquake by 22 from 54 22 to 42 23 and that the probability did not recover until about 1991 when seismicity and creep resumed our analysis may thus explain why the parkfield earthquake did not strike in the 1980s but not why it was absent in the 1990s we calculate a 58 17 probability of a m 6 parkfield earthquake during 2001 2011 index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 7260 seismology theory and modeling keywords coalinga earthquake parkfield stress change earthquake probability seismicity rate

ml measurements for northeastern united states earthquakes abstract local magnitudes m l are reported for 56 northeastern united states and canadian earthquakes using records from a pair of wood anderson torsion instruments which have operated at weston observatory since 1967 corrections to the richter m l formula are computed to take into account the difference in attenuation between southern california and the northeastern united states the corrected m l values for these events were compared to the previously reported magnitudes which had been calculated either from the nuttli 1973 m blg formula applied to 5 to 10 hz waves called m n or from a coda magnitude formula m c in general the m l determinations tend to underestimate the m n and m c values by about 0 4 magnitude units this confirms the fact that the m n scale is not appropriate when applied to high frequency waves as it is in the northeastern united states the reason for this appears to be in the relation of the period of the wave used in the magnitude determination to the corner period of the earthquake and earth response

single crystal 40ar 39ar dating of pyrite no fool s clock single crystals of dispersed trace pyrite from two igneous rocks were dated by using the 40 ar 39 ar laser probe method and the resulting ages were compared to step heating ages of associated amphibole and phlogopite the isochron ages for 0 1 0 3 mm cubes of pyrite agree well with the respective amphibole ages of these igneous samples preliminary step heating analyses of single pyrite crystals yield internal isochrons with indistinguishable although less precise ages both pyrite and amphibole are significantly older than associated phlogopite in one sample which has undergone postcrystallization alteration these results suggest that pyrite can give reliable and precise 40 ar 39 ar ages even in the presence of subsequent alteration given the ubiquity of pyrite in many geologic environments this technique has great promise for application to the dating of ores sediments and hydrocarbon migration all of which have been very difficult to date directly

an accurate and efficient method for including the effects of topography in three dimensional elastic models of ground deformation with applications to radar interferometry topography has a large effect on the results predicted by elastic surface deformation models in regions of significant relief in some cases topography may have more influence on the predicted deformation field than do model source parameters we have developed an approximate analytical technique for including topographic effects that retains most of the computational simplicity of elastic half space models while providing an accurate representation of topographic effects we use a series expansion of the elastic half space solution with a small slope approximation yielding a set of higher order corrections the integrated effect of these corrections is evaluated using fourier methods we investigate the effectiveness of our method by comparing predicted results for a tilted triaxial ellipsoid with those predicted by finite element models the resulting displacements and displacement gradients are in good agreement with finite element results both for relatively smooth topography synthetically generated and for the greater relief in the vicinity of mount etna volcano we then compare the results of our method with those predicted by traditional elastic half space models using different reference elevations and with a previously proposed method of estimating topographic effects our new method provides a significantly better fit to the finite element results than do the other methods our method is able to accurately portray both the number and the horizontal pattern of fringes in a synthetic interferogram when compared with finite element results in particular the method accurately represents the broadening of fringes that is observed in regions of high relief as well as reproducing the location of the fringe center and the topographically induced deviation of the fringes from a regular pattern elastic half space models typically show a fringe center that is displaced with respect to the finite element results indicating that parameter inversions based on such a model would provide incorrect estimates of the horizontal source position the lack of topographically generated fringe distortions in elastic half space results would also likely lead to inaccuracies in the predicted magnitude and orientation of proposed deformation sources our new technique over comes these limitations and should be useful when evaluating either traditional geodetic results or the greater areal coverage provided by interferometric observations

etna 2002 eruption imaged from continuous tilt and gps data 1 on the night of october 26 2002 intense explosive activity and lava effusion began suddenly on the southern flank of mt etna at an altitude of 2750 m during the 27 and 28 october a long field of eruptive fractures propagated radially along the north eastern flank of the volcano ground deformation changes recorded between 26 and 27 october from gps and tilt data collected at the permanent geodetic network of mt etna were modeled to infer the positions and dimensions of the two dikes the observed deformation pattern was consistent with a response of the edifice to a composite mechanism consisting of a vertical uprising dike in the upper southern flank and a lateral intrusion propagating along the north eastern sector the first dike which triggered the eruption crossed the volcano edifice in a few hours and was located in the same area as the 2001 eruption while the second lateral dike which crossed the ne flank was the primary cause of the recorded deformation pattern

the use of earthquake rate changes as a stress meter at kilauea volcano stress changes in the earth s crust are generally estimated from model calculations that use near surface deformation as an observational constraint but the widespread correlation of changes of earthquake activity with stress has led to suggestions that stress changes might be calculated from earthquake occurrence rates obtained from seismicity catalogues although this possibility has considerable appeal because seismicity data are routinely collected and have good spatial and temporal resolution the method has not yet proven successful owing to the non linearity of earthquake rate changes with respect to both stress and time here however we present two methods for inverting earthquake rate data to infer stress changes using a formulation for the stress and time dependence of earthquake rates application of these methods at kilauea volcano in hawaii yields good agreement with independent estimates indicating that earthquake rates can provide a practical remote sensing stress meter

how to cope with volcano flank dynamics a conceptual model behind possible scenarios for mt etna abstract volcano flank dynamics poses a serious hazard also involving the inhabited lower slopes mt etna is a well studied unstable volcano and a significant amount of data has been collected on the dynamics of its eastern and southern flanks we first propose a conceptual model to describe and explain flank dynamics at etna we identify the preconditions as due to the differential unbuttressing conditions at the volcano base and the triggering factors as shallow magmatic sources dikes reservoirs evidence and parameters and or observations for flank dynamics are listed summarizing the 1994 2010 period of activity based on this we then propose a set of scenarios possibly occurring in case of unrest of the unstable flanks of mt etna flank unrest is a variation in the steady state condition of the volcano flanks possibly accompanied by significant ground deformation seismicity and eruptions the scenarios may provide a general reference and recommendation in case of five types of multi hazard processes related either as a cause or effect to flank dynamics 1 edifice inflation 2 emplacement of dikes along the ne and or s rifts 3 seismicity along pernicana fault system 4 seismicity on the s sector 5 seismicity along timpe fault system each scenario is analyzed and recommendations are given the scenarios may or may not be related to each other in the sense that the probability of occurrence of one scenario may or may not be contingent or dependent upon the prior occurrence of another these scenarios provide a qualitative analysis of the multi hazard processes related to flank dynamics a more quantitative i e probabilistic characterization is under consideration

relationship between peak ground acceleration peak ground velocity and macroseismic intensity in western chinarelationship between pga pgv and macroseismic intensity in western china

carbon isotopes and the rise of atmospheric oxygen new data for the isotopic composition of carbon in carbonate sediments deposited between 2 6 and 1 6 ga indicate that the value of 13c in these sediments underwent a very large positive excursion between 2 22 and 2 06 ga a reassessment of the earlier 13c data for carbonate sediments shows that this excursion was probably worldwide and that it was preceded and followed by several hundred million years during which the 13c of carbonate sediments differed little from that of modern carbonates the large 13c excursion between 2 22 and 2 06 ga was probably related to an abnormally high rate of organic carbon deposition which generated an abnormally high rate of o2 production we estimate that the total excess o2 produced during the excursion was between 12 and 22 times the present atmospheric o2 inventory the 13c data therefore suggest that the o2 content of the atmosphere increased very significantly between 2 22 and 2 06 ga this inference is supported strongly by several other lines of evidence

mesozoic metallogeny in east china and corresponding geodynamic settings an introduction to the special issue abstract the giant east china mesozoic metallogenic province hosts some of the world s largest resources of tungsten tin molybdenum antimony and bismuth ores of gold silver mercury lead zinc copper uranium and iron are also of major importance the province and its constituent metallogenic belts or regions south china middle lower yangtze river valley east qinling dabie interior of north china craton yan liao and north east china are the products of several pulses of igneous activity and mineralisation between 240 and 80 ma each successive stage has produced a distinctive suite of deposits that can be readily related to the geodynamic evolution of the region during the mesozoic this geodynamic evolution is linked to a complex series of tectonic events involving far field subduction plate collisions crustal thickening post collision collapse and rifting

coupling of eruptions and earthquakes at mt etna sicily italy a case study from the 1981 and 2001 events 1 changes in coulomb failure stress cfs induced by dike propagation during two flank eruptions on mt etna 1981 and 2001 are calculated for the most seismically active faults on the east slope of the volcano the right lateral timpe fault system oriented nnw sse and the left lateral pernicana fault oriented e w calculations performed using coulomb 2 5 software indicate that intrusion of a nnw dike on the nw side of the volcano 1981 eruption rises cfs on both the timpe and pernicana faults in contrast intrusion of a n s dike at high elevation on the south flank 2001 eruption rises cfs only on timpe fault system these results are compatible with the observed pattern of seismicity but emphasize an extremely heterogeneous state of stress on the east flank of the volcano

3 d finite element modelling of deformation and stress associated with faulting effect of inhomogeneous crustal structures summary modelling of deformation and stress caused by earthquake faulting or fault motion based on a homogeneous elastic half space model does not include crustal rigidity layering and lateral variations geological data and seismic surveys indicate that the crust is elastically inhomogeneous and that rigidity layering and heterogeneities are likely to affect the magnitude and pattern of deformation and stress we use the finite element method fem to investigate deformation and stress generated by strike slip tensile and thrust faulting considering rigidity layering in the crust for a fault with a dimension of 25 10 km and a slip value of 0 5 m cutting through the top 10 km of the crust the deformation and stress change associated with the three modes of faulting are calculated for an island arc crustal structure represented by three models of rigidity layering the results indicate i the maximum effect in horizontal displacements due to crustal layering for the investigated models is 19 7 mm and 28 8 mm for strike slip and tensile faulting respectively for thrust faulting the effect is up to 58 3 mm this remarkable effect is due to the offset of layers by thrust faulting which dynamically changes the crustal structure both horizontally and vertically ii the maximum effect in vertical deformation due to crustal rigidity layering for strike slip and tensile faulting is 5 mm in contrast the effect for thrusting is 30 3 mm iii the effect in the shear stress change at a depth of 7 5 km for the different styles of faulting ranges from 0 02 mpa to 0 10 mpa an additional modelling analysis of subduction thrusting at the japan trench with a detailed structural model based on seismic surveys further confirms the significant distortion caused by a homogeneous model that ignores crustal structural information overall the effect of crustal rigidity layering is at least 20 per cent for surface deformation and 15 per cent for stress changes at depth in light of the present accuracy of global positioning system gps observations 2 mm and the estimate of stress change required for earthquake hazard analysis ca 0 01 mpa the results from the numerical experiments indicate that crust inhomogeneity rigidity layering and lateral variations should be included in any quantitative models of faulting

contrasting triggering mechanisms of the 2001 and 2002 2003 eruptions of mount etna italy abstract mount etna produced two significant eruptions in 2001 and 2002 2003 which we have analysed using geological seismic and deformation data these eruptions showed some similarities such as the activating of two magmatic plumbing systems central lateral and eccentric but they differed in their triggering mechanisms while the 2001 eruption was largely the result of the emplacement of a n s eccentric dike independent from the central conduits consistent with e w regional extension the 2002 2003 eruption occurred in response to a major flank slip on the eastern and southeastern sides of the volcano this is demonstrated by the spatial and temporal distribution of seismicity and deformation preceding and accompanying the two eruptions during the months prior to the 2001 eruption most epicenters were concentrated on the southern flank at depths of 5 15 km below sea level during the 4 days before the eruption earthquake hypocenters migrated to shallower levels from 5 km bsl upward indicating the emplacement of the eccentric dike this is confirmed by the patterns of ground fracturing observed in the field and deformation documented by electronic distance measurements edm in contrast the months before the 2002 2003 eruption were characterised by shallower seismicity mainly concentrated along the active faults bordering the slipping flank sector flank slip accelerated in september 2002 and a second more vigorous acceleration of flank slip occurred on 26 27 october 2002 accompanying the opening of eruptive vents the very short 2 h seismic crisis preceding the onset of eruptive activity stands in neat contrast with the 4 days of intense seismicity before the 2001 eruption subsequently flank slip deformation extended all over the eastern and southeastern flanks of the volcano causing serious damage in this sector the events of 2001 2003 can be seen as a continuous chain of intimately interacting processes including regional tectonics magma accumulation and eruption and flank instability in this scenario the 2001 eruption led to increased flank instability that subsequently accelerated and culminated with the massive flank slip which in turn facilitated the 2002 2003 eruption this sequence of events points to a long term feedback mechanism between magmatism and flank instability at etna

fem based inversion for heterogeneous fault mechanisms application at etna volcano by dinsar data summary a procedure based on the finite element method fem for high resolution geodetic data inversion was developed to estimate non uniform slip distribution during the 2002 september 22 m3 7 earthquake rupture occurring only one month before the 2002 2003 eruption of etna volcano fem generated synthetic green s functions are combined with an inverse algorithm to simulate deformation of the earthquake for a 3 d problem domain that takes into account heterogeneity of material properties in the volcanic edifice the inversion of dinsar data shows complex kinematics of the northeastern flank of the etna volcano involving the pernicana fault system we detailed the coseismic shear rupture mechanism and highlighted a tensile mechanism never observed before related to a first attempt of magma intrusion which preceded the following october 26 eruption

temperature dependent viscoelastic modeling of ground deformation application to etna volcano during the 1993 1997 inflation period abstract we used the finite element method fem for modeling time dependent ground deformation due to volcanic pressure sources embedded in a viscoelastic medium especially in volcanic areas the presence of heterogeneous materials and high temperatures produce a lower effective viscosity of the earth s crust that calls for considering the thermal regime of crustal volume surrounding the magmatic sources we propose a thermo mechanical numerical model for evaluating the temperature dependency of the viscoelastic solution both temperature distributions and ground deformation are evaluated by solving an axi symmetric problem to estimate the effects of thermo viscoelastic response of the medium the thermo mechanical model permits to evidence that viscoelastic relaxation is responsible for significant time dependent variations in long term deformation these effects may be relevant for the interpretation and quantitative assessments of the pressure changes within magmatic sources with this in mind we reviewed the ground deformation observed on etna volcano during the 1993 1997 inflation period by setting up a fully 3d temperature dependent viscoelastic model since 1993 different geodetic measurements edm gps sar and leveling data identified an inflationary phase characterized by a uniform and continuous expansion of the overall volcano edifice that was not perturbed by eruptive activity the numerical model including significant viscoelastic material and reduced crustal rigidity around the magmatic source enables to produce deformation comparable with those obtained from elastic model requiring a significantly lower pressure for a purely elastic model with the same geometry and rigidity the pressure change necessary to describe the 1993 through 1997 inflation is around 320 mpa whereas for the viscoelastic model a pressure increase of about 200 mpa is required

structural deformation and mineralization in the early proterozoic liaojitite suite eastern liaoning province china abstract the liaojitite suite located in eastern liaoning province china formed in the eugeosyncline of an early proterozoic mobile zone structural deformation occurred during several orogenic episodes especially during the second deformation of the third episode the luliang orogeny 1900 2000 ma ago superposed dome shaped structures and their unevenly distributed groups formed during the luliang orogeny constitute the principal tectonic style in the mobile zone the tectonic style may be considered transitional in the evolution from an oval style in archean granite greenstone terrains to a linear style in phanerozoic terrains the superposed dome shaped structures contain the liaoji granite in the cores ringed successively by the boron bearing series and the outer turbidite series the simple appearances of the dome shaped structures mask their complicated multiply deformed nature which is revealed by tracing their formation and evolution from primary volcanic domes to granitic diapirs and finally to superposed dome shaped structures the evolution of the superposed dome shaped structures represents a change in crustal activity from simple shear to horizontal compression mineralization in the liaojitite suite was closely related to the three deformations of the luliang orogeny metallogenic elements were concentrated during the first deformation physical re emplacement of orebodies occurred during the second and third deformations

rb sr dating of sphalerite based on fluid inclusion host mineral isochrons a clarification of why it works nakai et al 1990 1993 brannon et al 1992 and christensen et al 1995a b recently published precise rb sr formation ages of sphalerites from various mississippi valleytype deposits this important advance in direct radiometric dating of ore deposition is based on a crush leach procedure in which the rb sr isotope composition of the fluid inclusion fraction termed leachate is analyzed separately from the residual host crystal termed residue isochron arrays were obtained by combining the fluid host mineral data pairs from several samples the resulting ages have yielded decisive chronological constraints on controversial genetic models as summarized for example by christensen et al 1995a where few alternative methods for dating are available although the method appears successful the above authors were unable to explain why the separation of sphalerite samples into fluid inclusion and residual solid fractions should yield an isochron age at all without an explanation the accuracy of the ages remains uncertain the aims of the present communication are to clarify the origin of the isochron patterns and to evaluate their age significance in the way they have been interpreted hitherto that is in the absence of independent geochronologic information our arguments are based first on analyses of synthetic fluid inclusions in quartz which we use as an experimental analogue of fluid inclusion bearing sphalerites in building on the analytical approach of shepherd and darbyshire 1981 for fluid inclusion dating pettke and diamond 1995a synthesized rbsr bearing aqueous fluid inclusions in quartz under high temperatures and pressures subsequent analysis of the separate fluid inclusion and quartz host fractions revealed rb sr patterns which are very similar to those found in natural sphalerite by nakai eta 1990 although recognizing that the analogy between the synthetic and natural samples is limited by important differences in crystal chemical behavior between sphalerite and quartz we are confident that the similarities between the isotopic results of these studies justify inferences being drawn regarding the dating of natural sphalerites second by manipulating the data published by nakai et a 1990 1993 brannon et a 1992 and christensen et a 1995a b we examine the nature of partitioning of rb and sr between sphalerite and hydrothermal parent fluid and thus arrive at conclusions on the validity of dating with fluid inclusion host sphalerite isotope arrays

40ar39ar dating of the quartz samples from two mineral deposits in western yunnan sw china by crushing in vacuum abstract the primary aim of this study is to investigate the possibility of dating fluid inclusions of quartz samples using the 40 ar 39 ar method by crushing in vacuo the samples are from the lushui tin tungsten deposit and the shangmanggang gold deposit in western yunnan sw china coexisting muscovite s 90ms and quartz s 90qw in a piece of tungsten ore from the former deposit were selected and the isochron age of s 90qw by crushing 38 6 1 9 ma shows excellent coincidence with that of s 90ms by stepped heating 38 6 0 8 ma the isochron age and plateau age by crushing of the quartz smg 8qz from the latter deposit indicate that the gold mineralization occurred at 144 ma these ages are respectively agreeable with the evaluated ages from the geologic facts in addition since the potassium concentration calculated from 39 ar released by crushing in the quartz sample smg 8qz was as high as 0 24 electron probe analysis was applied to investigate the occurrence of potassium and the results reveal that the majority of potassium scattered in the microcrystal quartz grains

la icp ms u pb zircon ages of the liaohe group in the eastern block of the north china craton constraints on the evolution of the jiao liao ji belt abstract as a major lithostratigraphic unit of the palaeoproterozoic jiao liao ji belt in the eastern block of the north china craton the liaohe group consists of an assemblage that is transitional from a lower arkose and volcanic rich sequence langzishan li eryu and gaojiayu formations through a middle carbonate rich sequence dashiqiao formation to an upper argillaceous sequence gaixian formation tectonically associated with the liaohe group are large volumes of granitoid rocks named the liaoji granite whose emplacement age has been dated at about 2 1 2 2 ga regionally the liaohe group and the associated liaoji granite extend along a nee trending belt that is flanked by 2 45 2 55 ga basement gneisses u pb zircon data and cathodoluminescence cl imaging are used to constrain the maximum depositional and metamorphic ages of the liaohe group which are critical in understanding the tectonic setting and history of the jiao liao ji belt cathodoluminescence images reveal that most detrital zircon grains from the liaohe group are characterized by concentric oscillatory zoning with comparatively low luminescence and high th u ratios suggesting magmatic origin but minor zircon grains have structureless overgrowth or recrystallization rims that are characterized by low th u ratio indicating metamorphic origin results of this study show that the detrital zircon grains of the langzishan formation the lowest sequence of the liaohe group have concordant u pb ages ranging from 2 05 to 2 24 ga suggesting that the liaohe group was deposited at some time after 2 05 ga although most overgrowth or recrystallization rims are too narrow to be analyzed some rims yield concordant or upper intercept ages around 1 93 ga interpreted as the peak metamorphic age of the liaohe group detrital zircon grains from the dashiqiao formation in the middle sequence of the liaohe group have concordant u pb ages ranging from 2 25 to 2 53 ga some of which are similar to those of the basement gneisses in the area this study indicates that the liaohe group was deposited after the emplacement of the liaoji granite and the latter may be a major component of the provenance for the langzishan formation in contrast the protoliths of the middle sequence of the liaohe group were most probably derived from the basement gneisses these new zircon ages for the liaohe group and recent data for the liaoji granite combined with lithological structural and metamorphic considerations support a rifting model for the evolution of the jiao liao ji belt

shrimp u pb zircon geochronology of palaeoproterozoic metasedimentary rocks in the north china craton evidence for a major late palaeoproterozoic tectonothermal event abstract although metasedimentary successions are widely distributed across the north china craton those of palaeoproterozoic age are restricted to three orogenic belts namely the trans north china orogen the khondalite belt and the jiao liao ji belt prior to this work some of those successions were considered to be archaean in age the palaeoproterozoic metasedimentary rocks contain detrital igneous zircon grains with ages ranging from 3 0 to 2 1 ga with the majority recording an age between 2 3 and 2 0 ga this latter group define a series of magmatic events that occurred between formation of the archaean basement and deposition of the metasedimentary rock protoliths the metasedimentary rocks occur as two associations older volcano sedimentary units that formed between 2 37 and 2 0 ma and younger sedimentary units that formed mainly between 2 0 and 1 88 ga all these rock associations were then subjected to metamorphism during the late palaeoproterozoic 1 88 and 1 85 ga tectonothermal event named the luliang movement in early chinese literature which was a continent continent collision that led to the amalgamation of the north china craton

shrimp u pb zircon geochronology of the liaoji granitoids constraints on the evolution of the paleoproterozoic jiao liao ji belt in the eastern block of the north china craton abstract the paleoproterozoic jiao liao ji belt lies at the eastern margin of the eastern block of the north china craton and is composed mainly of the liaohe group and the liaoji granitoids the liaoji granitoids are divisible into pre tectonic magnetite and hornblende biotite monzogranitic gneisses and post tectonic or anorogenic porphyritic monzogranites and alkaline syenites shrimp u pb zircon geochronology combined with cathodoluminescence cl imaging has enabled for resolution of magmatic and metamorphic events that can be directed towards understanding the history of the paleoproterozoic jiao liao ji belt shrimp u pb zircon analyses reveal that the pre tectonic magnetite monzogranitic gneisses were emplaced in the period 2176 2166 ma and metamorphosed at 1914 ma and the pre tectonic hornblende biotite monzogranitic gneisses were emplaced at 2150 2143 ma these data demonstrate that the pre tectonic monzogranitic gneisses of the liaoji granitoids were not younger than the deposition of the liaohe group as previously considered since the latter contains a large amount of 2100 2000 ma detrital zircons in contrast the pre tectonic monzogranitic gneisses of the liaoji granitoids or similar aged granitoids may have been an important component of the provenance for the liaohe group shrimp u pb zircon analyses also reveal that the post tectonic porphyritic monzogranites and granites in the jiao liao ji belt were emplaced at 1875 10 and 1856 31 ma respectively simultaneously with the emplacement of the alkaline syenites that was dated at 1857 20 and 1843 23 ma similar post tecotnic or anorogenic granites are not only limited to the jiao liao ji belt but are also found in the north and south korea suggesting that the 1 85 ga post tectonic or anorogenic granitic magmatic event may have occurred in both the korean peninsula and the eastern block of the north china craton the shrimp zircon ages of this study combined with lithological structural metamorphic and geochemical data is consistent with a rift closure model which suggests that the archean complexes on the northern and southern sides of the jiao liao ji belt were originally situated on a single continental block that underwent paleoproterozoic rifting associated with the formation of the liaohe group and liaoji granitoids and closed upon itself at 1 9 ga

toward a realistic deformation model of the 2008 magmatic intrusion at etna from combined dinsar and gps observations abstract the combination of i dinsar data capable of observing deformation pattern at a spatial resolution unachievable with other sparse geodetic measurements ii continuous gps data able to provide temporal constraints on source evolution and iii numerical modeling procedures appropriate to consider a non uniform opening distribution of a source embedded in a 3d heterogeneous medium allowed us to infer a complex and realistic deformation model of the magmatic intrusion that occurred in the northern flank of etna on 13 may 2008 numerical modeling of ground deformation data defines a near vertical dyke intruded for 2 5 km starting from a depth of 1400 m asl right below the summit craters and reaching shallow crust level in the northern flank from the estimated opening distribution of the propagating magma filled crack which reached a maximum value of about 2 m a volumetric expansion of crustal rocks of about 5 3 106 m3 was obtained also we clarified the temporal evolution of the northward magmatic intrusion which lasted just over 5 h with an initial magma propagation velocity of about 1 2 km h and decreased to about 0 24 km h as the driving pressure lowered due to the effusive activity started at southern vents

volcanomagnetic changes accompanying the onset of the 2002 2003 eruption of mt etna italy abstract remarkable changes in the local magnetic field were associated with the onset of the 2002 2003 flank eruption at mt etna after differential magnetic field measurements were filtered from the external noise by using adaptive filters we recognized two stages in the total intensity changes which are closely related to different volcanic events a rapid variations of about 4 5 nt associated with october 26 seismic swarm recorded beneath the summit craters b step like variations of 9 10 nt coincident with october 27 eruptive fissures opening up in the north flank these observations are generally consistent with those calculated from simple magnetic models of these volcanic processes in which the magnetic changes are generated by stress redistribution due to magmatic intrusions at different depth the magnetic data not only allow the timing of the intrusive event to be described in greater detail but also together with other volcanological and geophysical evidences permit some constraints to be set on the characteristics of propagation of a shallow dike firstly at around midnight on 26 october magma was rapidly injected to a depth of 3 4 km just below the summit craters secondly after 1 00 on 27 october continued intrusion magma occurred upward and culminated a few hundred meters below the free surface fractured along a n e direction thirdly at about 2 28 magma gave rise to an explosive fissural vent at the northern base of the ne crater near 3000 m a s l finally at about 5 00 the first eruptive fissure became active along the eastern border of the ne rift at 2500 m a s l the rate of growth of the magnetic anomalies moreover leads to the interpretation that the magmatic intrusion travelled northward from base of the ne crater to the ne rift at approximately 14 m min

magma faults and gravitational loading at mount etna the 2002 2003 eruptive period 1 mount etna is characterized by a complex structural setting that influences its evolution in order to understand how the interaction between dike forming intrusions and faulting influences the kinematics of the volcanic edifice we developed a numerical model it takes account of the topography the medium heterogeneities the gravitational loading and the most active crustal discontinuities a parameterization of the apparent coefficient of friction as a function of the depth has been considered in the range from 0 01 to 0 5 the density values used young s modulus and poisson s ratio range from about 1700 to 3200 kg m3 8 5 to 140 gpa and 0 15 to 0 35 respectively the model was applied to the 2002 2003 etna eruption the resulting deformation pattern was in agreement with the data provided by the continuous gps stations and the seismological knowledge obtaining displacements up to 1 m some discrepancies between the recorded ground deformation field and the modeled displacements allowed us to make some hypotheses on the volcano tectonic e g for the pernicana fault or regional tectonic origin acireale s alfio fault system of the crustal discontinuities moreover our results suggested that the pernicana fault is characterized by a very low apparent coefficient of friction less than 0 1 furthermore we evaluated the contribution of the gravitational loading and found that it implies a variation of about 10 of the overall deformation pattern our results clearly showed that the weight of the volcanic edifice acts in opposition to the magmatic intrusions conversely we found that the presence of medium heterogeneities may favor the eastern flank movements toward the se and the spreading of the summit area playing a fundamental role in ascending magma finally we investigated the shallow sliding model and found that dike forming intrusions produce negligible displacements less than 1 mm along the subhorizontal detachment surface therefore the gravitational loading during dike forming intrusions is not able to trigger sliding processes along this plane

fluid inclusion rb sr isochrons for dating mineral deposits the precise dating of mineral deposits has important implications for understanding the lifetime of ore forming systems and their temporal relationship to various geological events not all deposits provide material suitable for conventional radiometric dating or data which are amenable to unequivocal interpretation nor is it easy to verify that such samples have remained isotopically closed since their formation fluid inclusions provide an alternative closed system approach by analysing the isotopic composition of rband sr in inclusions within quartz from the carrock fell tungsten vein deposits cumbria we demonstrate here the feasibility of obtaining rb sr fluid inclusion isochrons the age for the mineralization 392 5 myr is in good agreement with the mean k ar age 387 6 myr for the vein micas and confirms the significance of fluid inclusions as precise rb sr geochronometers

lead isotopic compositions of diverse igneous rocks and ore deposits from southwestern new mexico and their implications for early proterozoic crustal evolution in the western united states u pb zircon measurements from some of the basement rocks in southwestern new mexico have ages that range from 1 650 to 1 450 m y the largest ore deposits occur near silver city in the southwest part of the region studied they are associated with laramide alkali to calc alkaline plutons and their lead isotopic compositions are the least radiogenic in the region this lead exhibits lower crustal upper mantle characteristics and for the major producing porphyry copper deposits the 206 pb 204 pb ratios are less than 18 0 lead from more silicic mid tertiary volcanic rocks and associated ore deposits has somewhat higher 208 pb 204 pb ratios that reflect a greater crustal involvement in their origin in a regional trend to the northeast ore lead becomes more radiogenic and at hansonburg 200 km from silver city lead in the mississippi type deposits is clearly derived from upper crustal sources on the 207 pb 204 pb 206 pb 204 pb plot data from all of the rocks and ores that we have analyzed form an array that lies below the average orogene curve of doe and zartman 1979 a common source is implied for the lead the isotopic composition of which was similar to that found in 1 750 m y old stratiform deposits as far apart as pecos new mexico and jerome arizona such a composition indicates that over a large region of the southwestern united states continental crust developed between 1 750 and 1 450 m y ago possibly in an island arc environment basement rocks that are 1 750 m y old extend northward through colorado to utah galena data obtained in previous studies show that the fraction of older sialic lead in those rocks increases toward the archean craton in wyoming the crust apparently developed southward from wyoming in stages at 2 400 m y ago or before 2 100 m y ago and 1 750 m y ago with incorporation of older sialic material in each stage as far south as milford utah

surface wave array tomography in se tibet from ambient seismic noise and two station analysis ii crustal and upper mantle structure summary we determine the 3 d shear wave speed variations in the crust and upper mantle in the southeastern borderland of the tibetan plateau sw china with data from 25 temporary broad band stations and one permanent station interstation rayleigh wave phase velocity dispersion curves were obtained at periods from 10 to 50 s from empirical green s function egf derived from ambient noise interferometry and from 20 to 150 s from traditional two station ts analysis here we use these measurements to construct phase velocity maps from 10 to 150 s using the average interstation dispersion from the egf and ts methods between 20 and 50 s and estimate from them with the neighbourhood algorithm the 3 d wave speed variations and their uncertainty the crust structure parametrized in three layers can be well resolved with a horizontal resolution about of 100 km or less because of the possible effect of mechanically weak layers on regional deformation of particular interest is the existence and geometry of low shear velocity layers lvls in some regions prominent lvls occur in the middle crust in others they may appear in the lower crust in some cases the lateral transition of shear wave speed coincides with major fault zones the spatial variation in strength and depth of crustal lvls suggests that the 3 d geometry of weak layers is complex and that unhindered crustal flow over large regions may not occur consideration of such complexity may be the key to a better understanding of relative block motion and patterns of seismicity

insight into mt etna italy kinematics during the 2002 2003 eruption as inferred from seismic stress and strain tensors 1 seismic activity linked to the 2002 03 mt etna eruption was investigated by analyzing the md 2 3 earthquakes the results of 3d relocation were used to compute fault plane solutions and a selected dataset was inverted to determine stress and strain tensors the analysis revealed a complex kinematic response of the eastern flank dominated by fast stress propagation and reorientation we hypothesize that a vertical dike intruded the southern flank generating an extensional regime that triggered a radial intrusion in the northeast sector of the volcano the combined effects gave rise to a rotation of the stress tensor that controlled the activation of the pernicana fault system the volcanic and tectonic interactions produced a second reorientation of the stress tensor causing a structural response in the southeast lower flank the overall result of the deformation processes observed during the eruption was an e w extension on the eastern flank of the volcano

intrusive mechanism of the 2002 ne rift eruption at mt etna italy inferred through continuous microgravity data and volcanological evidences 1 in october 2002 a new eruption began at etna lava flows were issued from two different fissure systems on the ne and s flanks of the volcano a continuous microgravity sequence acquired at a station on the n slope 2800 m a s l shows a marked decrease about 400 gal in less than one hour about 4 hours before lava was first emitted from the eruptive fissures along the ne rift this anomaly reversed soon afterward at a high rate the strong gravity decrease is interpreted as the opening by external forces of a shallow fracture system 1 km w of the gravity station magma from the central conduit entered the new fracture system passively and propagated through it towards lower portions of the ne rift both the arrangement of the new fracture system and the eruptive dynamics are in keeping with the inferred intrusive mechanism

crustal thickening and lateral extrusion during the indo asian collision a 3d viscous flow model abstract the 2000 km crustal shortening from the indo asian collision in the past 40 70 million years has been accommodated mainly by crustal thickening in the himalayan tibetan plateau and lateral extrusion of blocks of asian continents however the spatiotemporal evolution of crustal thickening and lateral extrusion hence the far field impact of the indo asian collision on asian tectonics remains controversial here we present a 3d viscous flow model that simulates the partitioning of crustal material between thickening and lateral extrusion during the indo asian collision the model assumes conservation of crustal mass and is constrained by the history of the indo asian plate convergence and by the present day topography of the himalayan tibetan plateau the results show that much of the early collision was absorbed by crustal thickening within the himalayan tibetan plateau however lateral extrusion of crustal material has gradually become dominant in the past 10 20 myr indicating increasing influence of the indo asian collision on asian tectonics

suppression of large earthquakes by stress shadows a comparison of coulomb and rate and state failure stress shadows generated by california s two most recent great earthquakes 1857 fort tejon and 1906 san francisco substantially modified 19th and 20th century earthquake history in the los angeles basin and in the san francisco bay area simple coulomb failure calculations which assume that earthquakes can be modeled as static dislocations in an elastic half space have done quite well at approximating how long the stress shadows or relaxing effects should last and at predicting where subsequent large earthquakes will not occur there has however been at least one apparent exception to the predictions of such simple models the 1911 m 6 0 earthquake near morgan hill california occurred at a relaxed site on the calaveras fault we examine how the more complex rate and state friction formalism based on laboratory experiments might have allowed the 1911 earthquake rate and state time to failure calculations are consistent with the occurrence of the 1911 event just 5 years after 1906 if the calaveras fault was already close to failure before the effects of 1906 we also examine the likelihood that the entire 78 years of relative quiet only four m 6 earthquakes in the bay area after 1906 is consistent with rate and state assumptions given that the previous 7 decades produced 18 m 6 earthquakes combinations of rate and state variables can be found that are consistent with this pattern of large bay area earthquakes assuming that the rate of earthquakes in the 7 decades before 1906 would have continued had 1906 not occurred these results demonstrate that rate and state offers a consistent explanation for the 78 year quiescence and the 1911 anomaly although they do not rule out several alternate explanations

imaging composite dike propagation etna 2002 case 1 late on the night of 26 october 2002 a dike intrusion started suddenly at mount etna producing intense explosive activity and lava effusion on the southern flank five to six hours afterward a long field of eruptive fractures propagated radially along the northeastern flank of the volcano producing marked variations at the permanent tilt network the dike propagation velocity was inferred by the associated seismicity we modeled the temporal evolution of the continuously recorded tilt data both during the vertical dike propagation on the high south flank on 26 october and during the radial propagation along the northeast flank between 27 and 28 october the reproduction of the recorded tilt signal allowed us to describe the geometry and characteristics of the two dikes in greater detail than the previous static inversion we deduced that the eruption was characterized by an unusual composite mechanism clearly showing a transition from a nearly pure opening mode displacement to a mechanism characterized by an equally strong normal dip slip component and a smaller left lateral strike slip component in this study we demonstrate the interaction between the final segment of the dike and a preexisting structure that was reactivated in response to the intrusion we show that tilt and its modeling represent a powerful tool to verify and constrain dike intrusions in detail

the sr and nd isotopic variations of the chinese loess plateau during the past 7 ma implications for the east asian winter monsoon and source areas of loess abstract 143 nd 144 nd and 87 sr 86 sr ratios of the acid insoluble residues of the red clay and overlying loess paleosols from the lingtai profile of the loess plateau china were investigated the results show that variations of the 87 sr 86 sr ratios of the lingtai profile can be divided into two stages from 7 ma b p to 2 5 ma b p the acid insoluble residues in the red clay rc formation are characterized by higher 87 sr 86 sr ratios with an average of 0 7230 from 2 5 ma b p to the present the acid insoluble residues in the wuchen loess wl4 ws1 lishi loess l15 s1 malan loess l1 and holocene loess s0 have relatively lower 87 sr 86 sr ratios and display an overall descending trend from 0 7223 at 2 5 ma b p to 0 7182 at the present among three possible interpretations for the variations of 87 sr 86 sr ratios of acid insoluble residues of the loess provenance change chemical weathering change or grain size distribution change only grain size distribution change provides a satisfactory interpretation this implies that the east asian winter monsoon strength was weak and relatively stable from 7 ma b p to 2 5 ma b p but became continuously enhanced from 2 5 ma b p to the present all the red clay and the overlying loess paleosols in the lingtai profile have generally identical e nd 0 implying that the source regions of these eolian deposits of the chinese loess plateau may be relatively stable and has not changed since 7 ma b p

the role of the pernicana fault system in the spreading of mt etna italy during the 2002 2003 eruption flank instability and collapse are observed at many volcanoes among these mt etna is characterized by the spreading of its eastern and southern flanks the eastern spreading area is bordered to the north by the e w trending pernicana fault system pfs during the 2002 2003 etna eruption ground fracturing along the pfs migrated eastward from the ne rift to as far as the 18 km distant coastline the deformation consisted of dextral en echelon segments with sinistral and normal kinematics both of these components of displacement were one order of magnitude larger 1 m in the western previously known portion of the pfs with respect to the newly surveyed 9 km long eastern section 0 1 m this eastern section is located along a pre existing but previously unknown fault where displaced man made structures give overall slip rates 1 1 9 cm year only slightly lower than those calculated for the western portion 1 4 2 3 cm year after an initial rapid motion during the first days of the 2002 2003 eruption movement of the western portion of the pfs decreased dramatically while parts of the eastern portion continued to move these data suggest a model of spreading of the eastern flank of etna along the pfs characterized by eruptions along the ne rift instantaneous short lived meter scale displacements along the western pfs and more long lived centimeter scale displacements along the eastern pfs the surface deformation then migrated southwards reactivating one after the other the nnw sse trending timpe and trecastagni faults with displacements of 0 1 and 0 04 m respectively these structures along with the pfs mark the boundaries of two adjacent blocks moving at different times and rates the new extent of the pfs and previous activity over its full length indicate that the sliding eastern flank extends well below the ionian sea the clustering of seismic activity above 4 km b s l during the eruption suggests a deep decollement for the moving mass the collected data thus suggests a significant movement volume 1 100 km3 of the eastern flank of etna both on shore and off shore

tectonic control on the eruptive dynamics at mt etna volcano sicily during the 2001 and 2002 2003 eruptions abstract the eruptive events of the july august 2001 and october 2002 january 2003 at mt etna provide new insights for reconstructing the complex geometry of the feeding system and their relationship to regional tectonics the 2001 eruption took place mainly on the upper southern sector of the volcano the eruption was preceded by a large earthquake swarm for a few days before its onset and accompanied by ground deformation and fracturing the development of surface cracking along with the seismic pattern has allowed us to recognize three distinct eruptive systems the sw ne nnw sse and n s systems which have been simultaneously active such eruptive systems are only the upper portions of a complex feeding system that was fed at the same time by two distinct magmas the sw ne and nnw sse systems connected with the se crater conduit were fed by magma coming from depth whereas the n s system served instead as an ascending pathway for an amphibole bearing magma residing in a shallow reservoir the eruptive activity started again on october 2002 on the ne rift zone where about 20 eruptive vents were aligned between 2500 and 1900 m a s l and on the southern flank from the central crater to the montagnola the onset of eruptive activity was accompanied by a seismic swarm as in the 2001 eruptive event two independent feeding systems formed characterized by distinct magmas the sw ne system controlled the feeding of the northeast rift and was accommodated by left lateral displacement along the wnw ese trending pernicana fault the n s system fed the eruptions on the southern flank moreover the associated crustal deformation triggered seismic reactivation of tectonic structures in the eastern flank of the volcano and offshore these two last eruptions indicate that at mt etna the ascent of magma as well as the accommodation of deformation is strongly dominated by local extensional structures that are connected to a regional tectonic regime

structural constraints on the spatial distribution of aftershocks 1 calculations of static stress changes due to large earthquakes have shown that the spatial distribution of aftershocks is predictable to first order with aftershocks primarily occurring in areas experiencing positive stress changes delineation of these areas relies on resolving the stress perturbation onto planes with known orientations common practice is to use poorly constrained regional stress information to compute optimally oriented failure planes assuming that they exist everywhere here we show that this assumption is not supported by observation but rather that aftershock failure planes are controlled by geological structure we argue that useful aftershock hazard estimates are better made by replacing information on regional stress with statistical measures of structural orientations

ambient noise rayleigh wave tomography in western sichuan and eastern tibet abstract we perform rayleigh wave tomography in western sichuan and eastern tibet by applying the ambient noise method to broadband data recorded at 49 stations from the sichuan digital seismic network cross correlations of vertical component ambient noise data are computed in one hour segments and stacked over 7 months from june to december 2007 then rayleigh wave group dispersion curves from 6 to 48 s were measured using the multiple filter analysis method group velocity maps at periods from 8 to 44 s were inverted the resulting group velocity maps generally show good correlations with tectonic features the sichuan basin is clearly resolved with lower group velocities at the short periods 8 to 20 s due to thick sedimentary layers and a prominent low velocity zone exhibits in the middle crust beneath the eastern margin of the tibetan plateau the longmen shan thrust belt marks not only the rapid lateral velocity variation between the topographically high tibetan plateau and low elevation sichuan basin but also the transition from the thick crust beneath the tibetan plateau to the normal continental crust beneath the sichuan basin

onto what planes should coulomb stress perturbations be resolved 1 coulomb stress maps are produced by computing the tensorial stress perturbation due to an earthquake rupture and resolving this tensor onto planes of a particular orientation it is often assumed that aftershock fault planes are optimally oriented in other words the regional stress and coseismic stress change are used to compute the orientation of planes most likely to fail and the coseismic stress is resolved onto these orientations this practice assumes that faults capable of sustaining aftershocks exist at all orientations an assumption contradicted by the observation that aftershock focal mechanisms have strong preferred orientations consistent with mapped structural trends here we systematically investigate the best planes onto which stress should be resolved for the landers hector mine loma prieta and northridge earthquakes by quantitatively comparing observed aftershock distributions with stress maps based on optimally oriented planes two and three dimensional main shock orientation and regional structural trend we find that the best model differs between different tectonic regions but that in all cases models that incorporate the regional stress field tend to produce stress maps that best fit the observed aftershock distributions although not all such models do so equally well our results suggest that when the regional stress field is poorly defined or in structurally complex areas the best model may be to fix the strike of the planes upon which the stress is to be resolved to that of the main shock but allow the dip and rake to vary

lead isotope signatures of epithermal and porphyry type ore deposits from the romanian carpathian mountains lead isotope analyses have been performed on the two major miocene mining districts of romania baia mare and apuseni mountains these two districts have different non overlapping 206pb 204pb isotopic signatures ranging from 18 752 to 18 876 and 18 497 to 18 740 in the baia mare district epithermal deposits are overall homogeneous in their lead isotopic compositions and have values similar to the average of the calc alkaline volcanic rocks these results suggest a magmatic signature for the pb and possibly other metals in the hydrothermal fluids however magmas in this district show isotopic evidence of crustal assimilation in the southern apuseni mountains the lead isotope compositions of sulfide minerals in porphyry copper deposits are clustered confirming that pb and probably other metals were derived principally from associated porphyry stocks on the other hand lead isotope data on sulfides in epithermal ore deposits are much more scattered indicating a notable contribution of pb from local country rocks in the apuseni mountains fertile volcanics are few and appear to come from a more primitive mantle derived source most of the analysed volcanic rocks seem barren differences in lead isotopic compositions between the baia mare district and the apuseni mountains are due to a different basement and probably to variations in crustal assimilation superimposed on variations in the mantle source composition in the apuseni mountains pb may be partly inherited from the previous mesozoic magmatic hydrothermal stage from a geodynamic point of view it seems that the nature and the source of volcanic rocks and their position related to the collision area of the carpathian arc are not the only factors controlling the fertility of a volcanic district

empirical mw ml mb and ms conversions in western china local magnitude m l body wave magnitude m b and surface wave magnitude m s which are saturated at certain values and may lead to an incorrect energy estimation of a large earthquake are largely used in quantifying the size of an earthquake in western china based on the catalog from the china earthquake data center cedc and moment magnitude m w provided by the global centroid moment tensor global cmt project we test the general orthogonal regression gor and the ordinary least squares ols methods in m w m l m s and m b conversions for earthquakes in three different tectonic structures of western china for m l and m b linear trends vary according to tectonic structures which implies different body wave attenuations in the three structures for m s the results are similar whether using the gor or the ols method but slopes of regression lines are not close to 1 which indicates routine misestimates of m s in western china the gor slopes are uniformly larger than the ols slopes in all magnitude conversions standard deviations are between 0 06 and 0 13 for the gor method but are between 0 12 and 0 25 for the ols thus the gor is found to be superior to the ols method and its use is recommended conversions of different magnitudes to m w not only imply different patterns of seismic wave attenuations but will also benefit immediate assessment of seismic damage after occurrence of a destructive earthquake in the future online material earthquake catalog and tables showing differences between magnitude estimates for m w m l m b and m s

static stress changes induced by the magmatic intrusions during the 2002 2003 etna eruption 1 the shallow intrusive processes that occurred during 2002 2003 etna eruption as well as the complex interaction between the magma intrusive events and the tectonic response of the volcano s eastern flank are investigated with numerical deformation modeling and the estimation of changes in the static coulomb stress ground deformation and volcanologic evidence clearly indicate a composite mechanism of intrusion on both the southern and northeastern flanks of the volcano geodetic data inversions have been based on a homogeneous elastic half space model although geological data and seismic tomography indicate that mt etna is elastically inhomogeneous and that rigidity layering and heterogeneities are likely to affect the magnitude and pattern of the deformation field to account for topographic effects as well as a complicated distribution of material properties we use the finite element method fem to provide a more realistic model the presence of medium heterogeneity strongly affects the amplitudes of the static stress changes seismicity matches well the areas of positive increase in the static stress caused by the intrusive events along the southern and northeastern flanks the changes in the state of stress generated by the southern dike produce an extensional stress field that favors magma propagation along the north east rift the highest seismic releases were associated with the activation of two fault systems the timpe fault system and the pernicana fault the static stress changes resolved onto these faults indicate that the magma intrusions on the southern and northeastern flanks encouraged these seismogenic structures to slip

stress transferred by the 1995 mw 6 9 kobe japan shock effect on aftershocks and future earthquake probabilities the kobe earthquake struck at the edge of the densely populated osaka kyoto corridor in southwest japan we investigate how the earthquake transferred stress to nearby faults altering their proximity to failure and thus changing earthquake probabilities we find that relative to the pre kobe seismicity kobe aftershocks were concentrated in regions of calculated coulomb stress increase and less common in regions of stress decrease we quantify this relationship by forming the spatial correlation between the seismicity rate change and the coulomb stress change the correlation is significant for stress changes greater than 0 2 1 0 bars 0 02 0 1 mpa and the nonlinear dependence of seismicity rate change on stress change is compatible with a state and rate dependent formulation for earthquake occurrence we extend this analysis to future mainshocks by resolving the stress changes on major faults within 100 km of kobe and calculating the change in probability caused by these stress changes transient effects of the stress changes are incorporated by the state dependent constitutive relation which amplifies the permanent stress changes during the aftershock period earthquake probability framed in this manner is highly time dependent much more so than is assumed in current practice because the probabilities depend on several poorly known parameters of the major faults we estimate uncertainties of the probabilities by monte carlo simulation this enables us to include uncertainties on the elapsed time since the last earthquake the repeat time and its variability and the period of aftershock decay we estimate that a calculated 3 bar 0 3 mpa stress increase on the eastern section of the arima takatsuki tectonic line attl near kyoto causes fivefold increase in the 30 year probability of a subsequent large earthquake near kyoto a 2 bar 0 2 mpa stress decrease on the western section of the attl results in a reduction in probability by a factor of 140 to 2000 the probability of a mw 6 9 earthquake within 50 km of osaka during 1997 2007 is estimated to have risen from 5 6 before the kobe earthquake to 7 11 afterward during 1997 2027 it is estimated to have risen from 14 16 before kobe to 16 22

modeling of alos and cosmo skymed satellite data at mt etna implications on relation between seismic activation of the pernicana fault system and volcanic unrest abstract we investigate the displacement induced by the 2 3 april 2010 seismic swarm the largest event being of ml 4 3 magnitude by means of dinsar data acquired over the volcano by the cosmo skymed and alos radar systems satellite observations combined with leveling data allowed us to perform a high resolution modeling inversion capable of fully capturing the deformation pattern and identifying the mechanism responsible for the pfs seismic activation the inversion results well explain high gradients in the radar line of sight displacements observed along the fault rupture the slip distribution model indicates that the fault was characterized by a prevailing left lateral and normal dip slip motion with no fault dilation and hence excludes that the april 2010 seismic swarm is a response to accommodate the stress change induced by magma intrusions but it is due to the tectonic loading possibly associated with sliding of the eastern flank of the volcano edifice these results provide a completely different scenario from that derived for the 22 september 2002 m3 7 earthquake along the pfs where the co seismic shear rupture was accompanied by a tensile mechanism associated with a first attempt of magma intrusion that preceded the lateral eruption occurred here a month later these two opposite cases provide hints into the behavior of the pfs between quiescence and unrest periods at etna and pose different implications for eruptive activity prediction and volcano hazard assessment the dense pattern of ground deformation provided by integration of data from short revisiting time satellite missions together with refined modeling for fault slip distribution can be exploited at different volcanic sites where the activity is controlled by volcano tectonic interaction processes for a timely evaluation of the impending hazards

stable isotope studies and processes of carbonate formation in hungarian alkali basalts and lamprophyres evolution of magmatic fluids and magma sediment interactions processes of carbonate formation have been related to c and o isotopic compositions in the mesozoic alkali basalt mecsek mts and lamprophyre transdanubian range suites of hungary in the studied magrnatic rocks carbonates are present as ocelli amygdales xenoliths veins and groundmass carbonate c and o isotope studies of these types of carbonate have yielded information on the origin of the carbonates and indicated the following processes of formation that determined the 13c and 18o values of the carbonates 1 crystallization of magmatic carbonate textural characteristics and 13c values suggest formation of magmatic carbonate in alkali basalt and lamprophyre dikes whereas the 18o compositions of these carbonates indicate low temperature oxygen isotope exchange with magmatic fluids 2 assimilation of sedimentary carbonate by silicate magmas even completely recrystallized amygdales and ocelli of basalts and lamprophyres have preserved their sedimentary 13c values in contrast variations in the extent of mobilization and isotope exchange with magmatic fluids are reflected in differences in the ranges of the 18o values of amygdales ocelli and veins and can be attributed to different amounts of fluids involved in the magmatic events 3 low temperature alteration of magmatic rocks caused only 18o enrichment in the carbonate amygdales of basalts and the groundmass carbonates of lamprophyres indicating that no externally derived co2 was present in the alteration fluids 4 degassing of magma and magmatic fluid correlations between 13c and 18o data magma crystallization depths and amygdale sizes in the alkali basalts suggest that co2 degassing has been responsible for the negative 13c and positive 18o shifts observed a similar trend was found in the lamprophyres but the extent of the 18o shift indicates that in these rocks h2o degassing also played an important role

buoyancy controlled eruption of magmas at mt etna buoyancy controls the ability of magma to rise its ascent rate and the style of the eruptions geophysical geological and petrological data have been integrated to evaluate the buoyancy of magmas at mt etna the density difference between host rocks and magmas is mainly related to the amount of h2o dissolved in the magma and to the bubble liquid separation processes in the depth interval 22 2 km b s l highly hydrated h2o 3 basaltic magmas or mixtures of bubbles liquid have positive buoyancy and rise rapidly conversely bubble depleted liquids with an intermediate h2o content 1 5 having neutral buoyancy will spread out and form magmatic reservoirs at different depths until cooling crystallization further modify composition and density these different processes account for the magma compositions location of magmatic reservoirs as determined by geophysical methods and the complex eruptive cycles slow effusions fire fountains and plinian eruptions that have been observed in the history of the volcano