observing earthquakes triggered in the near field by dynamic deformations we examine the hypothesis that dynamic deformations associated with seismic waves trigger earthquakes in many tectonic environments our analysis focuses on seismicity at close range within the aftershock zone complementing published studies of long range triggering our results suggest that dynamic triggering is not confined to remote distances or to geothermal and volcanic regions long unilaterally propagating ruptures may focus radiated dynamic deformations in the propagation direction therefore we expect seismicity triggered dynamically by a directive rupture to occur asymmetrically with a majority of triggered earthquakes in the direction of rupture propagation bilaterally propagating ruptures also may be directive and we propose simple criteria for assessing their directivity we compare the inferred rupture direction and observed seismicity rate change following 15 earthquakes m 5 7 to m 8 1 that occurred in california and idaho in the united states the gulf of aqaba syria guatemala china new guinea turkey japan mexico and antarctica nine of these mainshocks had clearly directive unilateral ruptures of these nine seven apparently induced an asymmetric increase in seismicity rate that correlates with the rupture direction the two exceptions include an earthquake preceded by a comparable magnitude event on a conjugate fault and another for which data limitations prohibited conclusive results similar but weaker correlations were found for the bilaterally rupturing earthquakes we studied although the static stress change also may trigger seismicity it and the seismicity it triggers are expected to be similarly asymmetric only if the final slip is skewed toward the rupture terminus for several of the directive earthquakes we suggest that the seismicity rate change correlates better with the dynamic stress field than the static stress change manuscript received 1 march 2002

shear and normal load perturbations on a two dimensional continuous fault 2 dynamic triggering 1 the influence of normal and shear stress static perturbations on a strike slip fault is addressed on the basis of a two dimensional continuous and quasi dynamic model friction along the fault plane is described using a rate and state friction law with depth variable properties normal and shear stress perturbations result in similar effects in terms of earthquake triggering iftm s is constant t ands being the amplitude of the shear and normal stress fluctuations respectively and m being a constant which can be interpreted as the static friction coefficient on the fault in a coulomb failure model therefore the coulomb stress changecff tm s is a useful tool to account simultaneously for normal and shear stress variations in our model we also show that when estimating the clock advance or clock delay of an earthquake the simple coulomb failure model is at first order in good agreement with our results during the first 90 of the earthquake cycle however it differs significantly during the last 10 due to the sharp velocity increase predicted by the rate and state friction law before rupture this suggests that as long as static variations of stress are concerned realistic fault models using rich laboratory based friction laws like rate and state friction laws may lead topredictions fairly close to the ones made using one of the simplest failure model i e the coulomb failure model this may explain why coulomb stress change computations although often based on drastic approximations have been able in many occasions to explain earthquake triggering sequences index terms 7209 seismology earthquake dynamics and mechanics 7215 seismology earthquake parameters 7260 seismology theory and modeling keywords earthquake triggering static triggering coulomb stress change rate and state friction laws clock advance delay

seismic fatigue failure may have triggered the 2014 mw7 9 rat islands earthquake seismic waves propagating from large earthquakes cause global transient stress changes capable of triggering other earthquakes at great distances the study of such remote and dynamic triggering phenomena provides a better understanding of the mechanisms that generate earthquakes i introduce an integrated seismicity model to stochastically evaluate the time intervals of consecutive earthquakes at global scales making it possible to detect a pair of earthquakes possibly related to each other i show a mw7 9 intermediate depth earthquake that occurred in the rat islands in 2014 is inferred to have been associated with a sequence of distant large mw 6 5 earthquakes originating from the kermadec islands the passage of seismic surface waves from the kermadec events that produced small stress changes varying within at most 10 pa at the hypocenter probably caused a reduction in the fault s strength by cyclic fatigue and eventually triggered its failure during their passage

impacts of hydrothermal dolomitization and thermochemical sulfate reduction on secondary porosity creation in deeply buried carbonates a case study from the lower saxony basin northwest germany the role of deep burial dissolution in the creation of porosity in carbonates has been discussed controversially in the recent past we present a case study from the upper permian zechstein 2 carbonate reservoirs of the lower saxony basin in northwest germany these reservoirs are locally characterized by high amounts of carbon dioxide co2 and variable amounts of hydrogen sulfide h2s which are derived from thermochemical sulfate reduction tsr and inorganic sources to study the contribution of these effects on porosity development we combine petrography stable isotope and rare earth and yttrium rey analyses of fracture cements with raman spectroscopy and 13c analyses of fluid inclusions it is shown that fluid migration along deep fault zones created and redistributed porosity fluid inclusion analyses of vein cements demonstrate that hydrothermal fluids transported inorganic co2 into the reservoir where it mixed with minor amounts of tsr derived organic co2 the likely source of inorganic co2 is the thermal decomposition of deeply buried devonian carbonates the rey distribution patterns support a hydrothermal origin of ascending iron and co2 rich fluids causing dolomitization of calcite and increasing porosity by 10 16 along fractures this porosity increase results from hydrothermal dolomitization and dissolution by acids generated from the reaction of fe2 with h2s to precipitate pyrite in contrast hydrothermal dolomite cements reduced early diagenetic porosity in dolomitic intervals by approximately 17 however the carbonate dissolution in the predominantly calcitic host rock results in a net increase in porosity and permeability in the vicinity of the fracture walls which has to be considered for modeling reservoir properties and fluid migration pathways

fine fracture structures in the geothermal region of hakone volcano revealed by well resolved earthquake hypocenters and focal mechanisms abstract we investigated precise hypocentral distribution and the mechanisms of small earthquakes in the geothermal region of hakone volcano central japan where swarm activity has been frequently observed earthquake swarms were remarkably prevalent in 2001 and 2006 and were accompanied by crustal deformation we first determined initial hypocenters using station corrections and one dimensional velocity structures as estimated by the joint hypocenter determination method then we applied the double difference method to relocate the initial hypocenters using the differential arrival time obtained by both manual picking and waveform cross correlation analysis subsequently we determined the focal mechanisms from the absolute p and sh wave amplitudes and p wave polarities from the relocated hypocenter distribution we found that most swarm earthquakes are distributed on thin plane like zones with width length of 100 m to 1 km we found that these plane like hypocentral distributions range from the e w to n s strikes and are consistent with one of the nodal planes of the focal mechanism it is likely that most swarm earthquakes occurred on pre existing fracture planes shaping the plane like hypocenter distributions previous studies suggested that a highly permeable fracture system has developed in the fault interaction area and these highly permeable fractures affect the occurrence of swarm earthquakes and surface geothermal activity since hakone volcano is located in the interaction area of the active tanna and hirayama faults it is suggested that the fracture planes revealed by the relocated hypocenter distribution have been developed by the activity of the two faults the fracture planes in the caldera might be channels for the hydrothermal water of hot springs in the caldera of hakone volcano which are rich in sodium chloride and considered to be composed of fluid heated by a deep seated magma the strike of the fracture plane on which the swarm earthquakes of the 2001 activity occurred is inconsistent with the orientation of open crack models estimated from geodetic data it is therefore possible that the hydrothermal fluid aseismically intruded the open cracks during the 2001 activity

3 d rotation of double couple earthquake sources summary we discuss 3 d rotations by which one double couple earthquake source can be rotated into another arbitrary double couple due to the symmetry of double couple sources there are four such rotations an algorithm is obtained in analytical form which is also available as a computer program solving the inverse problem of 3 d rotation of double couple earthquake sources i e for each pair of focal mechanisms or seismic moment tensor solutions the program finds all four rotations which rotate one mechanism into another this algorithm may be used in a wide variety of studies of stress field causing earthquakes investigations of the relationship between the focal mechanisms and the tectonic features of a seismogenic region etc the same inversion algorithm can be used to study the 3 d rotation of any symmetric second rank tensor such as the stress or strain tensor

dynamic seismic response of a stable intraplate region to a megathrust earthquake abstract the 2011 m9 0 tohoku oki megathrust earthquake produced strong ground motions with a peak ground acceleration of 1 52 cm s 2 in the korean peninsula inducing large dynamic stress changes in the crust sixty one triggered earthquakes with magnitudes of 0 5 2 5 including 17 unusual spatially clustered events were identified from continuous seismic record sections of dense seismic networks for 18 h following the megathrust earthquake the triggered earthquakes occurred in regions of high seismicity the earthquake occurrence frequency increased after the megathrust earthquake keeping the gutenberg richter b value invariant the seismic occurrence rates decreased with time following a modified omori law the focal mechanism solutions of triggered earthquakes are consistent with those observed before the megathrust earthquake an unusual earthquake swarm displays apparent migration with a speed of 28 6 4 4 m h the changes in pore fluid pressure induced by strong seismic waves may have caused the triggering of earthquakes the duration and strength of dynamic triggering may be highly dependent on the magnitude and distance of megathrust earthquake

some observations on the origins of large volumes of carbon dioxide accumulations in sedimentary basins large volumes of carbon dioxide i e up to 90 v v have been encountered in sedimentary basins from various geological settings but their origins remain enigmatic evidence from carbon and noble gas isotope analyses indicate a variety of interpretations for the origins of the co2 including mantle degassing metamorphic reactions or magmatic processes the formation of large accumulations of large volumes of co2 in sedimentary basins is discussed with specific reference to published data from the pannonian basin hungary the cooper eromanga basin australia and the south viking graben north sea these basins have occurrences of large volumes i e over 15 v v of isotopically heavy carbon dioxide thought to be of inorganic origin and although they differ somewhat in terms of sedimentary fill all have major structural features close to the gas accumulations the available geochemical data are currently neither sufficient to confirm the specific origin s of the co2 e g mantle derived carbonate metamorphism nor unscramble co2 mixed from two or more sources ongoing studies especially those involving noble gas analyses should provide fuller answers

improving local earthquake locations using the l1 norm and waveform cross correlation application to the whittier narrows california aftershock sequence experiments with different earthquake location methods applied to aftershocks of the october 1 1987 whittier narrows earthquake in california ml 5 9 suggest that local event locations can be greatly improved through the use of the l1 norm station corrections and waveform cross correlation the whittier narrows sequence is a compact cluster of over 500 events at 12 to 18 km depth located within the dense station coverage of the southern california seismic network scsn a telemetered network of several hundred short period seismographs scsn travel time picks and waveforms obtained through the southern california earthquake center are examined for 589 earthquakes between 1981 and 1994 in the vicinity of the mainshock using a smoothed version of the standard southern california velocity model and the existing travel time picks improved location accuracy is obtained through use of the l1 norm rather than the conventional least squares l2 norm approach presumably due to the more robust response of the former to outliers in the data a large additional improvement results from the use of station terms to account for three dimensional velocity structure outside of the event cluster to achieve greater location accuracy waveforms for these events are resampled and low pass filtered and the p and s wave cross correlation functions are computed at each station for every event pair for those events with similar waveforms differential times may be obtained from the cross correlation functions these times are then combined with the travel time picks to invert for an adjusted set of picks that are more consistent than the original picks and include seismograms that were originally unpicked locations obtained from the adjusted picks show a further improvement in accuracy location uncertainties are estimated using a bootstrap technique in which events are relocated many times for sets of picks in which the travel time residuals at the best fitting location are used to randomly perturb each pick improvements in location accuracy are indicated by the reduced scatter in the residuals smaller estimated location errors and the increased tendency of the locations to cluster along well defined fault planes median standard errors for the final inversion are 150 m in horizontal location and 230 m in vertical location although the relative locations within localized clusters of similar events are better constrained seismicity cross sections resolve the shallow dipping fault plane associated with the mainshock and a steeply dipping fault plane associated with a ml 5 3 aftershock these fault planes appear to cross and activity began on the secondary fault plane prior to the large aftershock

evolution of the lower saxony basin abstract the lower saxony basin is a 300 km long and 65 km wide late jurassic and early cretaceous trough which parallels the northern margin of the rhenish massif this basin became inverted during the senonian and paleocene the lower saxony basin is the most important oil province of germany past production amounts to 200 10 6 t of oil 1 5 10 9 bbl the lower saxony basin is superimposed on the late carboniferous variscan foredeep basin and the frontal structures of the variscan fold belt during the permian to middle jurassic the area formed part of the northwest european basin differential subsidence of the lower saxony basin was initiated during the late jurassic and persisted till albian time this involved reactivation of permo carboniferous fracture systems by divergent wrenching a major aptian deep seated laccolith is evident in the western part of the lower saxony basin during the senonian and paleocene sinistral convergent wrenching induced uplift of the basin floor and folding of its sedimentary fill the margins of the inverted lower saxony basin are thrust over the adjacent stable platform areas the differential subsidence of the lower saxony basin can be related to a period of major crustal extension in the north sea rift basin inversion coincides with important orogenic events in the alpine system and is thought to have been induced by intra plate compressional stresses

hydrothermal mixing carbonate dissolution and sulfide precipitation in mississippi valley type deposits a large number of mississippi valley type mvt deposits are located within dissolution zones in carbonate host rocks some genetic models propose the existence of cavities generated by an earlier event such as a shallow karstification that were subsequently filled with hydrothermal minerals alternative models propose carbonate dissolution caused by the simultaneous precipitation of sulfides these models fail to explain either the deep geological setting of the cavities or the observational features which suggest that the dissolution of carbonates and the precipitation of minerals filling the cavities are not strictly coeval we present a genetic model inspired by the textural characteristics of mvt deposits that accounts for both the dissolution of carbonate and precipitation of sulfides and later carbonates in variable volumes the model is based on the mixing of two hydrothermal fluids with a different chemistry depending on the proportion of the end members the mixture dissolves and precipitates carbonates even though the two mixing solutions are both independently saturated in carbonates we perform reactive transport simulations of mixing of a regional groundwater and brine ascending through a fracture both saturated in calcite but with different overall chemistries ca and carbonate concentrations ph etc as a result of the intrinsic effects of chemical mixing a carbonate dissolution zone which is enhanced by acid brines appears above the fracture and another zone of calcite precipitation builds up between the cavity and the surrounding rock sulfide forms near the fracture and occupies a volume smaller than the cavity a decline of the fluid flux in the fracture would cause the precipitation of calcite within the previously formed cavities therefore dissolution of carbonate host rock sulfide precipitation within the forming cavity and later filling by carbonates may be part of the same overall process of mixing of fluids in the carbonate host rock

late ordovician mass extinction in the selwyn basin northwestern canada geochemical sedimentological and paleontological evidence we present a detailed study of the trace element and stable isotope geochemistry sedimentology and fossil distributions in two avalanche lake av4b av1 ordovician silurian boundary sections in the selwyn basin trilobites and conodonts indicate a profound extinction at the end of the ordovician which is constrained stratigraphically within a 3 in magnitude is recorded in the extinction interval iridium abundances 0 051 ppb in the extinction interval are low and fail to provide evidence for an impact the highest ir abundance is found to be associated with reduced sedimentation in a condensed horizon cerium anomalies indicate a s

fluid induced swarm earthquake sequence revealed by precisely determined hypocenters and focal mechanisms in the 2009 activity at hakone volcano japan 1 a swarm earthquake sequence is often assumed to be triggered by fluid flow within a brittle fault damage zone which is assumed to be highly permeable however there is little seismological evidence of the relation between the fluid flow within the fault damage zone and the occurrence of swarm earthquakes here we precisely determine the hypocenters and focal mechanisms of swarm earthquakes that occurred in the caldera of hakone volcano central japan using data from a dense seismic network we demonstrate that the swarm earthquakes are concentrated on four thin plane like zones each of which has a thickness of approximately 100 m one of the nodal planes of the focal mechanisms agrees with the planar hypocenter distribution the swarm earthquakes that occurred during the initial stage of the activity exhibited a migration of hypocenters that appears to be represented by the diffusion equation based on the spatiotemporal distribution of the earthquakes the hydraulic diffusivity is estimated to be approximately 0 5 1 0 m2 s the observations imply that swarm earthquakes were triggered by the diffusion of highly pressured fluid within the fault damage zone a burst like occurrence of the swarm earthquakes is also observed in the later stage these swarm earthquakes are thought to have been triggered primarily by local stress changes caused by the preceding activity the complicated spatiotemporal pattern is thought to have been caused by the effect of the fluid flow within the high permeability damage zones as well as the stress perturbations generated by the swarm earthquakes themselves

tracing element sources of hydrothermal mineral deposits ree and y distribution and sr nd pb isotopes in fluorite from mvt deposits in the pennine orefield england fluorite from mississippi valley type mvt deposits in the south pennine orefield england displays significantly different distributions of rare earths and yttrium rey compared to fluorite from similar mvt deposits in the north pennine orefield samples from the south pennine orefield display negative ce and positive gd and y anomalies but lack any eu anomaly indicating that the rey were mobilized from relatively pure marine sedimentary carbonates in marked contrast fluorite from the north pennine orefield lacks any ce and gd anomalies but shows a pronounced positive eu anomaly suggesting that the rey were provided by different source rock s that the mineralizing hydrothermal fluid had experienced higher temperatures prior to fluorite precipitation and that it was derived from deeper crustal levels in the north compared to the south the isotopic composition of sr in blue john fluorite from the south pennine orefield suggests that sr was mobilized from lower carboniferous tournaisian limestones whereas pb isotopes suggest that in contrast to rey and sr pb was derived from aluminosilicate rocks neither nd nor sr or pb isotopes can be used to radiometrically date the formation of blue john fluorite all isotope systems studied indicate that the limestone host rock of this fluorite mineralization did not contribute to the trace element budget of the hydrothermal fluid our results show that different solutes in a natural water hydrothermal fluid groundwater etc may be derived from different sources and that the study of a small set of elements or isotope ratios may not provide full insight into the genesis or history of a mineralization or a hydrothermal fluid our data provide evidence for the uncoupling of sr nd and pb during fluid rock interaction and fluid migration and show that the use of plots such as 87sr 86sr vs end to learn about mixing relationships as is commonly done in igneous geochemistry is unreliable when applied to natural waters and their precipitates

dynamic response of frequent tremors at aso volcano to teleseismic waves from the 1999 chi chi taiwan earthquake abstract teleseismic waves from the 1999 chi chi taiwan earthquake dynamically triggered isolated tremor and micro earthquakes at aso volcano japan which is at a distance of 1400 km immediately after the arrival of the p waves short period tremor spt began to occur more frequently for about 2000 s and during and after the arrival of surface waves 2 micro earthquakes were observed around the crater observations of frequent spt are an indication of triggered isolated tremor which consists of both spt and long period tremor lpt components for the cases of arrivals of seismic waves from other large teleseisms from march 1995 to june 2002 triggering of isolated tremor was observed during 1998 1999 during this period increased thermal supply to the crater was observed while the background activity was relatively low and the volcanic system beneath the crater was more responsive to external stress perturbations

a magma hydrothermal system beneath hakone volcano central japan revealed by highly resolved velocity structures high resolution images of subsurface structures are necessary to understand the transport processes of crustal fluids from deep magma sources and their relationship to earthquake swarms in active volcanic regions based on a seismic tomography approach we have developed a new model for the magma hydrothermal system beneath hakone volcano central japan where shallow earthquake swarms and crustal deformation associated with inflation of an open crack source are often observed by applying travel time data for local earthquakes to a tomographic inversion we obtained highly resolved seismic velocity structures that show a region of low p wave velocity vp low s wave velocity vs and high vp vs ratios at depths of 10 20 km beneath the volcano corresponding to the location of the open crack source we suggest that the high vp vs ratios represent a deep magma chamber with a high concentration of melt and or fluids deep low frequency earthquakes located just beneath this high vp vs zone may indicate that magmatic fluids are supplied from below above the high vp vs zone a region of low vp low vs and low vp vs ratios exists at depths of 3 10 km suggesting the presence of crack filled water or co2 supplied from the inferred deep magma chamber many earthquake swarms occur in this low vp vs zone indicating that crustal fluids play an important role in generating the swarms similar relationships between magma reservoirs overlying hydrothermal systems and swarm activity have been reported from other volcanic areas and thus may be a ubiquitous feature beneath active volcanoes

earthquake triggering by static and dynamic stress changes 1 in this study we aim to understand the effect of static and dynamic stress changes in promoting earthquake failures on secondary faults toward this goal we solve the equation of motion of a spring slider dynamic system including inertia and using rate and state dependent constitutive laws we separately investigate the dynamic response of this fault analog system to a sudden stress change represented either as a stress step or as a stress pulse which are used to model permanent static and transient dynamic stress perturbations the induced earthquake failure does not occur immediately at the application of the coseismic stress change but it is delayed in time we define this time interval as the triggering delay for a given stress perturbation we analyze the dependence of triggering delays on different system conditions and constitutive parameters our results clearly show that the effects of static and dynamic stress changes are quite different while a static stress change is able to advance as well as to delay an induced instability depending on its sign a dynamic stress pulse is only able to promote a nearly instantaneous failure provided its amplitude is positive and large enough with respect to the direct effect of friction in other words dynamic stress changes can only cause nearly instantaneous failures without any relevant triggering delay these results should be considered in interpreting the seismicity rate changes caused by large earthquakes at least as long as seismic events are interpreted as sliding instabilities obeying rate and state dependent friction laws

remotely triggered seismic activity in hakone volcano during and after the passage of surface waves from the 2011 m9 0 tohoku oki earthquake abstract immediately after the march 11 2011 m9 0 tohoku oki earthquake seismic activity increased remarkably beneath hakone volcano central japan at an epicentral distance of 450 km the heightened seismicity was initiated during the passage of the large amplitude surface waves from the main shock and continued over the subsequent 2 months we obtained hypocenters and focal mechanisms of the seismic sequence with the aim of clarifying the physical mechanism responsible for the remotely triggered seismicity we used data from a dense seismic network containing 56 online permanent and offline temporary stations in and around the hakone volcano we found that the earthquakes that occurred during the passage of the surface waves are located at the lower depth limit of ordinary seismicity in the caldera these earthquakes have larger magnitudes than both the ordinary seismicity prior to the tohoku oki earthquake and the seismicity triggered after the passage of the surface waves the focal mechanism that we determined is a strike slip fault type with the p axis in the nw se direction which is consistent with the focal mechanisms of earthquakes that occurred after the passage of the surface waves and the tectonic stress field in the region we also tried to detect missing events that occurred immediately after the passage of the surface waves by using a waveform correlation technique the detected events are distributed near the hypocenters of the earthquakes that occurred during the passage of the surface waves the origin times of the first four events after the arrival of surface waves are consistent with the phases of the decrease in normal stress generated by the surface waves the results suggest that the changes in dynamic stress due to the surface waves from the 2011 tohoku oki earthquake contributed significantly to the initiation of the sequence of triggered seismic activity assuming that normal stress changes on the faults did play an important role in the triggering of earthquakes we propose that fluid flow induced by the oscillation of permeability on the faults is the main mechanism for the initiation of post tohoku oki earthquakes beneath the hakone volcano

crystal chemical controls on rare earth element concentrations in fossil biogenic apatites and implications for paleoenvironmental reconstructions abstract fossil biogenic apatites display rare earth element ree patterns which have been proposed to reflect environmental and biological controls on past seawater composition these patterns can be separated in two groups 1 patterns that are similar to those of open ocean and epicontinental waters and 2 patterns that exhibit a strong enrichment in intermediate ree bell shaped patterns because ree trapping in biogenic apatites occurs mostly post mortem it is essential to understand the crystal chemical inorganic factors that can influence the fractionation of ree between apatite and water a model is proposed by which partition coefficients of ree between apatite and water for a substitution mechanism can be extrapolated from mineral melt partition data to seawater or sedimentary basin conditions these are compared with available experimental partition coefficients for ree adsorption mechanism and used to discuss ree patterns in fossil biogenic apatites calculations of ree patterns for apatites at equilibrium with water show that the bell shaped patterns in fossil apatites can be explained by fractionation with seawater or continental fluids at low temperature under crystal chemical control involving a substitution mechanism and in the context of extensive or late diagenesis in that case the equilibrium composition of the fluid cannot be unequivocally determined from observed ree concentrations in fossil apatites this type of sample is inappropriate to discuss the past environmental or biological controls on ree concentrations in the ocean other sample compositions suggest little to moderate alteration of the original oceanic to freshwater pattern through the adsorption mechanism in the context of weak or early diagenesis and may be used with caution for that purpose

dynamic stresses coulomb failure and remote triggering dynamic stresses associated with crustal surface waves with 15 30 sec periods and peak amplitudes 5 km the latter is consistent with the observation that extensional or transtensional tectonic regimes are more susceptible to remote triggering by rayleigh wave dynamic stresses than compressional or transpressional regimes locally elevated pore pressures may have a role in the observed prevalence of dynamic triggering in extensional regimes and geothermal volcanic systems

origins of co2 in permian carbonate reservoir rocks zechstein ca2 of the nw german basin lower saxony permian carbonate reservoir rocks stassfurt carbonate of the co2 province lower saxony basin nw germany are locally characterised by high amounts of co2 leading to serious problems on exploration in order to receive information on the major co2 sources and co2 migration and accumulation processes mineralogical geochemical and stable isotope analyses c 13 o 18 were carried out on authigenic precipitations within the stassfurt carbonate rocks ca2 these rocks contain early diagenetic e g formed in soft sediment carbonate minerals calcite dolomite and anhydrite in concretions and small cracks in addition large up to 2 cm wide carbonate cemented fractures formed in solid ca2 rocks semi quantitative estimates of the diagenetic mineral content showed variations between the investigated rock cores nine out of 12 ca2 rock cores are derived from wells situated in the area of modem ch4 rich reservoirs and have distinct fracture systems developed in contrast the other three rock cores are from wells characterised by co4 rich reservoirs and lack fractures of similar thickness the assumed relationship between tectonically induced fractures and the gas content of the ca2 reservoir rocks implies co2 degassing of the ca2 rocks at approximately 102 degrees c to similar to 150 degrees c assumed delta 18o pore water variation from 0 parts per thousand to 4 parts per thousand smow ree distribution indicates at least three types of fracture and crack filling carbonates two carbonate generations formed from evolving diagenetic pore waters whereas one type reflects carbonate formation under hydrothermal influence the ages of these cementations derived from rb sr and u pb isotope analyses indicate their fort nation during late stage of or after the inversion of the lower saxony basin in late cretaceous times the stable carbon isotope composition of the authigenic carbonate minerals reflects at least two carbon source endmembers available during diagenesis whereas many early formed carbonates are related to the permian c 13 rich carbon source those carbonates which precipitated or recrystallised during early to late stage diagenesis and or were induced by local tectonic events incorporated c 12 enriched co from organic degradation processes the stable oxygen isotope values of authigenic carbonates probably still reflect low temperatures of mineral formation from permian sea water as it is assumed for non recrystallised carbonates or late stage high temperature up to similar to 150 degrees c precipitation ftoin sea water derived pore waters which may have been locally influenced by o 18 enriched fluids however most of the carbonate samples investigated are recrystallised crystal enlargement of concretionary and fracture carbonate is observed and hence these carbonates are at least partly re equilibrated original o 18 content reduced with surrounding pore waters at elevated temperature similar to the authigenic carbonate at least two sources may explain the concentration carbon isotope relationship of modem co present in the ca 2 reservoir rocks an organic derived co2 endmember source delta c 13 near 20 parts per thousand is present in relatively low concentrations whereas large co concentrations derived from an endmember source with all isotope value near 0 parts per thousand although the latter source is unknown such heavy co sources are most likely attributed to carbonate decomposition processes c 2005 elsevier b v all rights reserved

stable carbon isotopic ratios of ch4 co2 bearing fluid inclusions in fracture fill mineralization from the lower saxony basin germany a tool for tracing gas sources and maturity abstract the stable carbon isotopic ratios 13 c of methane ch 4 and carbon dioxide co 2 of gas rich fluid inclusions hosted in fracture fill mineralization from the southern part of the lower saxony basin germany have been measured online using a crushing device interfaced to an isotopic ratio mass spectrometer irms the data reveal that ch 4 trapped in inclusions seems to be derived from different source rocks with different organic matter types the 13 c values of ch 4 in inclusions in quartz hosted by carboniferous rocks range between 25 and 19 suggesting high maturity coals as the source of methane methane in fluid inclusions in minerals hosted by mesozoic strata has more negative carbon isotope ratios 45 to 31 and appears to represent primary cracking products from type ii kerogens i e marine shales there is a positive correlation between increasing homogenization temperatures of aqueous fluid inclusions and less negative 13 c ch 4 values of in co genetic gas inclusions probably indicating different mtaturity of the potential source rocks at the time the fluids were released the co 2 isotopic composition of ch 4 co 2 bearing inclusions shows slight negative or even positive 13 c values indicating an inorganic source e g water rock interaction and dissolution of detrital marine calcite for co 2 in inclusions we conclude that the 13 c isotopic ratios of ch 4 co 2 bearing fluid inclusions can be used to trace migration pathways sources of gases and alteration processes furthermore the 13 c values of methane can be used to estimate the maturity of the rocks from which it was sourced results presented here are further supported by organic geochemical analysis of surface bitumens which coexist with the gas inclusion rich fracture fill mineralization and confirm the isotopic interpretations with respect to fluid source type and maturity

petrological and geochemical constraints on porosity difference between lower triassic sour and sweet gas carbonate reservoirs in the sichuan basin abstract petrographic features carbon and oxygen isotopes and trace elements were determined and fluid inclusions were analyzed on late diagenetic cements and vug fillings from the lower triassic carbonates to account for much higher porosities in the sour dolomite reservoirs than in the sweet limestones in northeastern sichuan basin in the ne side to the kaijiang liangping trough dolostone reservoirs have porosities mainly from 6 to 12 up to 28 and contain 9 20 h 2 s the dolomite includes pre bitumen re crystallized silt sized crystals without occurrence of fluid inclusions and late burial dolomite the late burial dolomite has been measured to have fluid inclusions homogenization temperatures hts from 72 to 128 c part of the dolomites with hts up to 121 c show corroded edges or replacement by tsr calcites tsr calcites show 13 c values from 2 3 to 18 9 feo from null to 810 g g and so 3 from 50 to 18 700 g g vug filling tsr calcites have much lower feo and so 3 than the replacement calcites of anhydrite suggesting that dissolved fe 2 released from the dissolution of dolomite and anhydrite as a result of tsr may have reacted with tsr h 2 s and precipitated as pyrite the dissolution may have released 13 c rich co 2 resulting in the present day co 2 having 13 c values significantly heavier than those of the tsr calcites as light as 18 9 the dolomite and anhydrite dissolution during late stage of tsr may have enlarged or redistributed porosity in the ne side dolostones in contrast oolitic limestone reservoirs in the sw side contain significantly lower sulfates and thus no significant late diagenetic dissolution and tsr the porosity difference in the two sides resulted from original physical property due to early dolomitization and subsequent improvement from anhydrite and dolomite dissolution as a result of tsr

propagation of an earthquake triggering front from the 2011 tohoku oki earthquake 1 increases in seismicity have been widely observed at varying distances from the source area following large earthquakes the increased number of earthquakes are usually called aftershocks if the area is within a rupture length of the mainshock and called remotely triggered events if they are well beyond that distance these earthquakes can be explained as being induced by static and or dynamic stress changes due to the mainshock however clear observations of dynamic triggering have been inadequate to differentiate between the two mechanisms this study shows that early post seismic events triggered by the 2011 mw 9 0 tohoku oki earthquake systematically propagated over japan in a southwestern direction associated with the strong seismic waves from the source the propagation front was consistent with the arrivals of large amplitude surface waves traveling at 3 1 to 3 3 km s and extending to a distance of 1 350 km there were no observations of triggered earthquakes in the northern direction dynamic stress changes toward the north were comparable to or smaller than those necessary for triggering in the southwestern direction static stress changes were one to two orders smaller than dynamic stress changes at remote distance indicating that static stress was not the main mechanism of the triggering furthermore the dynamic stress strain changes play an important role for remote triggering if the value is more than 500 kpa in stress or 10 6 in strain

migration of early aftershocks following the 2004 parkfield earthquake a significant number of the early aftershocks following large shallow earthquakes are missing in existing earthquake catalogues an analysis of the waveforms of 3 647 relocated earthquakes along the parkfield section of the san andreas fault reveals 11 times more aftershocks within three days of the 2004 parkfield earthquake than listed in a standard catalogue large shallow earthquakes are immediately followed by numerous aftershocks a significant portion of these events is missing in existing earthquake catalogues mainly because seismicity after the mainshock can be masked by overlapping arrivals of waves from the mainshock and aftershocks1 2 3 4 however recovery of the missing early aftershocks is important for understanding the physical mechanisms of earthquake triggering2 3 4 and for tracking postseismic deformation around the rupture zone associated with the mainshock5 6 7 here we use the waveforms of 3 647 relocated earthquakes8 along the parkfield section of the san andreas fault as templates9 10 to detect missing aftershocks within three days of the 2004 magnitude 6 0 parkfield earthquake we identify 11 times more aftershocks than listed in the standard catalogue of the northern california seismic network we find that the newly detected aftershocks migrate in both along strike and down dip directions with logarithmic time since the mainshock consistent with numerical simulations of the expansion of aftershocks caused by propagating afterslip11 12 the cumulative number of early aftershocks increases linearly with postseismic deformation in the first two days supporting the view that aftershocks are driven primarily by afterslip13 14

transient triggering of near and distant earthquakes we demonstrate qualitatively that frictional instability theory provides a context for understanding how earthquakes may be triggered by transient loads associated with seismic waves from near and distance earthquakes we assume that earthquake triggering is a stick slip process and test two hypotheses about the effect of transients on the timing of instabilities using a simple spring slider model and a rate and state dependent friction constitutive law a critical triggering threshold is implicit in such a model formulation our first hypothesis is that transient loads lead to clock advances i e transients hasten the time of earthquakes that would have happened eventually due to constant background loading alone modeling results demonstrate that transient loads do lead to clock advances and that the triggered instabilities may occur after the transient has ceased i e triggering may be delayed these simple clock advance models predict complex relationships between the triggering delay the clock advance and the transient characteristics the triggering delay and the degree of clock advance both depend nonlinearly on when in the earthquake cycle the transient load is applied this implies that the stress required to bring about failure does not depend linearly on loading time even when the fault is loaded at a constant rate the timing of instability also depends nonlinearly on the transient loading rate faster rates more rapidly hastening instability this implies that higher frequency and or longer duration seismic waves should increase the amount of clock advance these modeling results and simple calculations suggest that near tens of kilometers small moderate earthquakes and remote thousands of kilometers earthquakes with magnitudes 2 to 3 units larger may be equally effective at triggering seismicity our second hypothesis is that some triggered seismicity represents earthquakes that would not have happened without the transient load i e accumulated strain energy would have been relieved via other mechanisms we test this using two new seismicity models that 1 are inherently unstable but slide at steady state conditions under the background load and 2 are conditionally stable such that instability occurs only for sufficiently large perturbations for the new seismicity models very small amplitude transients trigger instability relative to the clock advance models the unstable steady state models predict that the triggering delay depends inversely and nonlinearly on the transient amplitude as in the clock advance models we were unable to generate delayed triggering with conditionally stable models for both new seismicity models the potential for triggering is independent of when the transient load is applied or equivalently of the prestress unlike in the clock advance models in these models a critical triggering threshold appears to be inversely proportional to frequency further advancement of our understanding will require more sophisticated quantitative models and observations that distinguish between our qualitative yet distinctly different model predictions

increasing background seismicity and dynamic triggering behaviors with nearby mining activities around fangshan pluton in beijing china dynamic triggering in western fangshan pluton beijing china has been repeatedly identified but previous studies are limited by sparse seismic station coverage here we systematically analyze continuous waveforms recorded by both permanent stations and a temporary seismic network 40 days before and after the 11 march 2011 mw 9 1 tohoku oki and the 14 april 2012 mw 8 6 indian ocean earthquakes we first build a template database using a short term average to long term average method next we apply the matched filter technique that cross correlates the template waveforms with continuous data to detect additional seismic events overall we detect 1956 and 950 seismic events around the tohoku oki and indian ocean main shocks respectively most detected events are shallow 5 km and clustered at beiling syncline in western fangshan pluton which is adjacent to a running coalmine seven and 10 events are detected during the large amplitude surface waves of the two main shocks respectively but no similar burst is detected following their major foreshock and aftershocks multiple statistical tests indicate that the short term bursts after the two main shocks are dynamically triggered we suggest that mining related activities may perturb the subsurface stress conditions and hence make the region more susceptible for dynamic triggering than other places

methane dominated thermochemical sulphate reduction in the triassic feixianguan formation east sichuan basin china towards prediction of fatal h2s concentrations abstract new sour pools have recently found in the lower triassic feixianguan fm carbonate reservoirs in the east sichuan basin in china with h 2 s up to 17 4 by volume a recent blowout from a well drilled into this formation killed hundreds of people as a result of the percentage concentrations of h 2 s in order to assess the origin of fatal h 2 s as well as the cause of petroleum alteration h 2 s concentrations and the isotopes 34 s and 13 c have been collected and measured in gas samples from reservoirs anhydrite pyrite and elemental sulphur 34 s values have been measured for comparison the high concentrations of h 2 s gas are found to occur at depths 3000 m temperature now at 100 c in evaporated platform facies oolitic dolomite or limestone that contains anhydrite nodule occurrence within the reservoirs where h 2 s concentrations are greater than 10 its 34 s values lie between 12 0 and 13 2 cdt this is within the range of anhydrite 34 s values found within the feixianguan fm 11 0 to 21 7 average 15 5 3 5 cdt thus h 2 s must have been generated by thermochemical sulphate reduction tsr locally within the reservoirs burial history analysis and fluid inclusion data reveal that the temperature at which tsr occurred was greater than about 130 140 c suggesting that the present depth temperature minimum is an artifact of post tsr uplift both methane and ethane were actively involved in tsr since the petroleum became almost totally dry no alkanes except methane and methane 13 c values become significantly heavier as tsr proceeded methane 13 c difference thus reflects the extent of tsr while it is tempting to use a present day depth control 3000 m to predict the distribution of h 2 s in the feixianguan fm this is an invalid approach since tsr occurred when the formation was buried some 1000 2000 m deeper than it is at present the likelihood of differential uplift across the basin means that it is important to develop a basinal understanding of the thermal history of the feixianguan fm so that it is possible to determine which parts of the basin have been hotter than 130 140 c

three dimensional velocity structures of mount fuji and the south fossa magna central japan 1 we present the three dimensional structures of the p wave velocity vp s wave velocity vs as well as the p wave to s wave velocity ratio vp vs beneath mount fuji and the south fossa magna japan using arrival time data collected from 2002 to 2005 by a dense seismograph array the high resolution data set and improved methodology reveal not only several velocity features that are consistent with previous studies but also important new details that clarify the velocity structures associated with volcanic processes beneath mount fuji and the collision tectonics of the south fossa magna one such particular feature is a low vp low vs and low vp vs anomaly at depths of 7 17 km beneath mount fuji that corresponds with the locations of deep low frequency dlf earthquakes the coincidence of the velocity anomaly and the dlf locations suggests that supercritical volatile fluid such as h2o and co2 may be abundant in the low vp vs region and may play an important role in generating dlf earthquakes this anomaly overlies a deeper low vp low vs and high vp vs anomaly at depths of 15 25 km that may represent a zone of basaltic partial melt a low vp low vs and low vp vs anomaly is seen at depths of 6 14 km beneath mount hakone isovelocity surfaces vp 6 0 km s and vs 3 5 km s corresponding to the upper limit of hypocenter distribution below mount fuji may define the upper surface of the philippine sea plate whose existence in a seismic gap beneath mount fuji has been controversial

remotely triggered seismicity in the yellowstone national park region by the 2002 mw 7 9 denali fault earthquake alaska coincident with the arrival of low frequency large amplitude surface waves of the mw 7 9 denali fault earthquake dfe an abrupt increase in seismicity was observed in the yellowstone national park region despite the large epicentral distance of 3100 km within the first 24 hr following the dfe mainshock we located more than 250 earthquakes which occurred throughout the entire yellowstone na tional park region the elevated seismicity rate continued for about 30 days and followed a modified omori law decay with a p value of 1 02 0 07 for a declus tered earthquake catalog the seismicity following the 2002 dfe uniquely stands out with a significance of 30r the increase in seismicity occurred over all magnitude bands in general we observed that seismicity following the dfe outlined the spatial pattern of past seismicity routinely observed in the yellowstone national parkregion however we found significant differences in triggered seismicity inside and outside the caldera earthquakes inside the yellowstone caldera occurred preferentially as clusters close to major hydrothermal systems were of larger magnitude and seis micity decayed more rapidly this suggests that either different trigger mechanisms were operating inside and outside the caldera or that the crust responded differently to the same trigger mechanism depending on its different mechanicalstate compared with other sites that experienced remote earthquake triggering following the 2002 dfe yellowstone showed the most vigorous earthquake activity we attribute this to strong directivity effects of the dfe which caused relatively large peak dynamic stresses 0 16 0 22 mpa in yellowstone and to the volcanic nature of yellowstone

dynamic stresses coulomb failure and remote triggering corrected abstract dynamic stresses associated with crustal surface waves with 15 30 s periods and peak amplitudes

kinematics of crystal growth in syntectonic fibrous veins abstract detailed observations of a set of fibrous antitaxial calcite veins in a slate reveal that some of the calcite fibres do not connect material markers on both sides of the vein and can therefore not have tracked the full opening trajectory during vein growth this calls for a better understanding of the mechanisms of fibre formation and reliable criteria to test the tracking hypothesis based on surface roughness characteristics of the vein wall we develop a simple model for shape growth of crystals in a crack seal environment which can account for both tracking and non tracking behaviours and propose a set of tracking criteria for antitaxial veins finally we discuss ways by which the model can be tested against natural examples

origin of late dolomite cement by co2 saturated deep basin brines evidence from the ozark region central united states studies of fluid inclusions in regionally extensive late dolomite cement ldc throughout the ozark region show that co2 effervescence was widespread during dolomite precipitation on the basis of quantitative analyses of inclusion fluids reaction path modeling shows that ldc with trace amounts of sulfides can be deposited by effervescence of a co2 saturated basin brine as it migrates to shallower levels and lower confining pressures this precipitation mechanism best explains occurrences of ldc in the ozark region and may account for ldc found in sedimentary basins worldwide

regional epigenetic dolomitization in the bonneterre dolomite cambrian southeastern missouri a dolomite bed averaging 6 m in thickness forms the base of a limestone and shale facies of the bonneterre dolomite cambrian southeastern missouri the dolomite immediately overlies the lamotte sandstone and covers an area of more than 16 600 km 2 it is proposed that this basal dolomite formed as a result of interaction with warm basin derived water circulating through the underlying lamotte sandstone and that the dolomitization event coincided with the emplacement of mississippi valley type sulfide ores in the nearby viburnum trend this hypothesis is supported by 1 petrographic evidence that suggests an origin at temperatures 50 c 2 cathodoluminescent microstratigraphy of dolomite cements which is correlative with that in gangue dolomite cements in the nearby orebodies and 3 stable oxygen and carbon isotope values that are consistent with a basinal origin of the dolomitizing water the basal dolomite bed may represent one of the most extensive epigenetic dolomites yet documented this implies that a basinal water can alter rocks over a wide area at a considerable distance from its source

remotely triggered seismicity in yunnan southwestern china following the 2004 mw9 3 sumatra earthquake 1 following the 2004 mw9 3 sumatra earthquake seismicity rate increased sharply over a wide area of up to 2700 km away in yunnan province southwestern china raised seismicity lasts for 14 days during this period more than 800 earthquakes with magnitude between 1 5 and 5 1 occurred this is perhaps the most impressive example of remotely triggered seismicity yet observed major events were clustered at several sites that exhibit complex fault geometries such as step overs and junctures we use statistic approaches including the statistics to examine the statistical significance of the seismic rate increases associated with the sumatra main shock and conclude that there is a reasonable probability that the raised seismicity was remotely triggered by the sumatra earthquake both rapid onset of dynamic triggering the very first event is a m4 6 earthquake occurred during the passage of the rayleigh wave from the sumatra earthquake and delayed response activated a few hours to a few days after the sumatra earthquake are well established the triggered activities show more earthquake swarm like characteristics as indicated by the epidemic type aftershock sequence modeling results large percentage of random components and less magnitude dependence in omori law type self triggering multiple sources of evidence including intensive hydrothermal activities and low velocity and high vp vs zones in the lower to middle crust suggests that magma mantle generated fluids have a role in the region high fluid pressure in branched fault zones weakened the faults making them sensitive to external disturbances and leading to fluid driven seismicity

widespread seismicity excitation throughout central japan following the 2011 m 9 0 tohoku earthquake and its interpretation by coulomb stress transfer 1 we report on a broad and unprecedented increase in seismicity rate following the m 9 0 tohoku mainshock for m 2 earthquakes over inland japan parts of the japan sea and izu islands at distances of up to 425 km from the locus of high 15 m seismic slip on the megathrust such an increase was not seen for the 2004 m 9 1 sumatra or 2010 m 8 8 chile earthquakes but they lacked the seismic networks necessary to detect such small events here we explore the possibility that the rate changes are the product of static coulomb stress transfer to small faults we use the nodal planes of m 3 5 earthquakes as proxies for such small active faults and find that of fifteen regions averaging 80 by 80 km in size 11 show a positive association between calculated stress changes and the observed seismicity rate change 3 show a negative correlation and for one the changes are too small to assess this work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there which is likely quite common

aftershock triggering by complete coulomb stress changes 1 we examine the correlation between seismicity rate change following the 1992 m7 3 landers california earthquake and characteristics of the complete coulomb failure stress cfs changes cfs t that this earthquake generated at close distances the time varying dynamic portion of the stress change depends on how the rupture develops temporally and spatially and arises from radiated seismic waves and from permanent coseismic fault displacement the permanent static portion cfs depends only on the final coseismic displacement cfs diminishes much more rapidly with distance than the transient dynamic stress changes a common interpretation of the strong correlation between cfs and aftershocks is that load changes can advance or delay failure stress changes may also promote failure by physically altering properties of the fault or its environs because it is transient cfs t can alter the failure rate only by the latter means we calculate both cfs and the maximum positive value of cfs t peak cfs t using a reflectivity program input parameters are constrained by modeling landers displacement seismograms we quantify the correlation between maps of seismicity rate changes and maps of modeled cfs and peak cfs t and find agreement for both models however rupture directivity which does not affect cfs creates larger peak cfs t values northwest of the main shock this asymmetry is also observed in seismicity rate changes but not in cfs this result implies that dynamic stress changes are as effective as static stress changes in triggering aftershocks and may trigger earthquakes long after the waves have passed

remotely triggered earthquakes in south central tibet following the 2004 mw 9 1 sumatra and 2005 mw 8 6 nias earthquakes