alkane terpene and polycyclic aromatic hydrocarbon geochemistry of the mackenzie river and mackenzie shelf riverine contributions to beaufort sea coastal sediment abstract to study the largest source of river sediment to the arctic ocean we have collected suspended particulates from the mackenzie river in all seasons and sediments from the mackenzie shelf between the river mouth and the shelf edge these samples have been analyzed for alkanes triterpenes and polycyclic aromatic hydrocarbons pahs we found that naturally occurring hydrocarbons predominate in the river and on the shelf these hydrocarbons include biogenic alkanes and triterpenes with a higher plant peat origin diagenetic pahs from peat and plant detritus petrogenic alkanes triterpenes and pahs from oil seeps and or bitumens and combustion pahs that are likely relict in peat deposits because these components vary independently the season is found to strongly influence the concentration and composition of hydrocarbons in the mackenzie river while essentially the same pattern of alkanes diagenetic hopanes and alkyl pahs is observed in all river and most shelf sediment samples alkane and triterpene concentration variations are strongly linked to the relative amount of higher plant peat material polycyclic aromatic hydrocarbon molecular mass profiles also appear to be tied primarily to varying proportions of peat with an additional petrogenic component which is most likely associated with lithic material mobilized by the mackenzie river at freshet consistent with the general lack of alkyl pahs in peat the higher pahs found in the river are probably derived from forest and tundra fires a few anthropogenic pyrogenic compounds are manifest only at the shelf edge probably due to a weakening of the river influence we take this observation of pyrogenic pahs and the pronounced source differences between two sediment samples collected at the shelf edge as evidence of a transition from dominance by the mackenzie river to the geochemistry prevalent in arctic regions far removed from major rivers

changes in optical properties chemistry and micropore and mesopore characteristics of bituminous coal at the contact with dikes in the illinois basin abstract changes in high volatile bituminous coal pennsylvanian near contacts with two volcanic intrusions in illinois were investigated with respect to optical properties coal chemistry and coal pore structure vitrinite reflectance ro increases from 0 62 to 5 03 within a distance of 5 5 m from the larger dike and from 0 63 to 3 71 within 3 3 m from the small dike elemental chemistry of the coal shows distinct reductions in hydrogen and nitrogen content close to the intrusions no trend was observed for total sulfur content but decreases in sulfate content towards the dikes indicate thermochemical sulfate reduction tsr contact metamorphism has a dramatic effect on coal porosity and microporosity in particular around the large dike the micropore volume after a slight initial increase progressively decreases from 0 0417 cm3 g in coal situated 4 7 m from the intrusive contact to 0 0126 cm3 g at the contact strongly decreasing mesopore and micropore volumes in the altered zone together with frequent cleat and fracture filling by calcite indicate deteriorating conditions for both coalbed gas sorption and gas transmissibility

statistical analysis of the induced basel 2006 earthquake sequence introducing a probability based monitoring approach for enhanced geothermal systems summary geothermal energy is becoming an important clean energy source however the stimulation of a reservoir for an enhanced geothermal system egs is associated with seismic risk due to induced seismicity seismicity occurring due to the water injection at depth have to be well recorded and monitored to mitigate the seismic risk of a damaging event an appropriate alarm system needs to be in place for each individual experiment in recent experiments the so called traffic light alarm system based on public response local magnitude and peak ground velocity was used we aim to improve the pre defined alarm system by introducing a probability based approach we retrospectively model the ongoing seismicity in real time with multiple statistical forecast models and then translate the forecast to seismic hazard in terms of probabilities of exceeding a ground motion intensity level one class of models accounts for the water injection rate the main parameter that can be controlled by the operators during an experiment by translating the models into time varying probabilities of exceeding various intensity levels we provide tools which are well understood by the decision makers and can be used to determine thresholds non exceedance during a reservoir stimulation this however remains an entrepreneurial or political decision of the responsible project coordinators we introduce forecast models based on the data set of an egs experiment in the city of basel between 2006 december 2 and 8 approximately 11500 m 3 of water was injected into a 5km deep well at high pressures a six sensor borehole array was installed by the company geothermal explorers limited gel at depths between 300 and 2700 m around the well to monitor the induced seismicity the network recorded approximately 11200 events during the injection phase more than 3500 of which were located with the traffic light system actions where implemented after an ml 2 7 event the water injection was reduced and then stopped after another ml 2 5 event a few hours later an earthquake with ml 3 4 felt within the city occurred which led to bleed off of the well a risk study was later issued with the outcome that the experiment could not be resumed we analyse the statistical features of the sequence and show that the sequence is well modelled with the omori utsu law following the termination of water injection based on this model the sequence will last 31 29 14 years to reach the background level we introduce statistical models based on reasenberg and jones and epidemic type aftershock sequence etas models commonly used to model aftershock sequences we compare and test different model setups to simulate the sequences varying the number of fixed and free parameters for one class of the etas models we account for the flow rate at the injection borehole we test the models against the observed data with standard likelihood tests and find the etas model accounting for the on flow rate to perform best such a model may in future serve as a valuable tool for designing probabilistic alarm systems for egs experiments

fluid inclusion and vitrinite reflectance geothermometry compared to heat flow models of maximum paleotemperature next to dikes western onshore gippsland basin australia abstract nine basalt dikes ranging from 6 cm to 40 m thick intruding the upper jurassic lower cretaceous strzelecki group western onshore gippsland basin were used to study maximum temperatures t max reached next to dikes t max was estimated from fluid inclusion and vitrinite reflectance geothermometry and compared to temperatures calculated using heat flow models of contact metamorphism thermal history reconstruction suggests that at the time of dike intrusion the host rock was at a temperature of 100 135 c fracture bound fluid inclusions in the host rocks next to thin dikes t max systematically increases towards the dike margin to at least 500 c the estimated t max next to the thickest dike thickness d 40 m suggests an extended zone of elevated r v r to at least a distance from the dike contact x of 60 m or at x d 1 5 using a normalized distance ratio used for comparing measurements between dikes regardless of their thickness in contrast the pattern seen next to the thin dikes is a relatively narrow zone of elevated r v r heat flow modeling along with whole rock elemental and isotopic data suggests that the extended zone of elevated r v r is caused by a convection cell with local recharge of the hydrothermal fluids the narrow zone of elevated r v r found next to thin dikes is attributed to the rise of the less dense heated fluids at the dike contact causing a flow of cooler groundwater towards the dike and thereby limiting its heating effects the lack of extended heating effects suggests that next to thin dikes an incipient convection system may form in which the heated fluid starts to travel upward along the dike but cooling occurs before a complete convection cell can form close to the dike contact at x d r v r often decreases even though fluid inclusion evidence indicates that t max is still increasing further fluid inclusion evidence indicates that the evolution of water vapor or supercritical fluids in the rock pores corresponds to the zone where r v r begins to decrease the generation of the water vapor or supercritical fluids near the dike contact seems to change vitrinite evolution reactions these metamorphic conditions closer to the dike than x d 0 3 make vitrinite reflectance unreliable as a geothermometer the form of the r v r profile as it indicates t max can be interpreted using temperature profiles estimated from various heat flow models to infer whether the dike cooled by conduction incipient convection or a convection cell a contact aureole that consists of decreasing r v r or t max extending out to x d 2 and that has a t contact t magma t host 2 appears to be a signature of simple conductive cooling incipient convection is indicated by a r v r profile that decreases to background levels at x d r v r profile and consistently high r v r that may not decrease to background levels until beyond distances of x d 1 5

distribution and transport of hydrocarbons in surface sediments of the alaskan outer continental shelf abstract surface sediments from the outer continental shelf of alaska were analyzed for hydrocarbons as part of an environmental survey sponsored by noaa blm sediments were collected from the proposed oil lease areas of beaufort sea southeastern bering sea norton sound navarin basin gulf of alaska kodiak shelf and lower cook inlet data on normal and branched alkanes and di and triterpenoids from capillary gas chromatography gc and gas chromatography mass spectrometry gc ms indicate that the area displays little evidence of petroleum hydrocarbons i e seeps except at a few isolated stations beaufort sea sediments have the highest hydrocarbon budget whereas kodiak shelf sediments have the lowest the molecular markers of the hydrocarbons are of a mixed marine autochthonous and terrestrial allochthonous origin norton sound and cook inlet sediments contain the highest levels of terrigenous lipids and kodiak shelf the lowest the abundance of alkenes implies that relatively low oxidizing conditions exist in some of the depositional areas studied suggesting that extraneous petroleum hydrocarbons introduced into these sediments would be expected to have a relatively long residence time the distribution of polynuclear aromatic hydrocarbons pah is complex and shows a pyrolytic origin the data on perylene strongly favor the hypothesis that it is performed from terrigenous precursors and transported into the marine environment with no apparent in situ generation polynuclear aromatic hydrocarbons of diagenetic origin are probably dominant in gulf of alaska and kodiak shelf sediments two stations north of kalgin island in lower cook inlet and one in southeastern bering sea show typical weathered petroleum distribution of n alkanes and triterpenoids probable pathways of transport and fate of petroleum hydrocarbons in case of an oil spill are also briefly discussed

the occurrence distribution and sources of polycycic aromatic hydrocarbons in the sediments of the georges river estuary australia concentrations of 13 polycylic aromatic hydrocarbons pah in sediment samples from the georges river estuary n s w have been determined by gas chromatography mass spectrometry gc ms the concentrations of individual pah were in the range of 0 1 5600 g kg m dry weight the average values of pah i i 1300 g kg l dry weight are well above those previously found in other industralized urban areas of australia the highest total pah concentrations in sediments are found in a section of the river which also has the highest concentrations of silt clay and organic matter indicating that the pah distribution may be controlled by sedimentation processes examination of the alkylated and non alkylated pah distributions in sediment extracts suggested that the main source of pah is from combustion products possibly associated with air particles with point source contributions of two ring pah from marinas and other boating activities at some sites

hydrocarbon geochemistry of the puget sound region iii polycyclic aromatic hydrocarbons in sediments abstract polycyclic aromatic hydrocarbon pah distributions and sources are characterized in 96 sediment samples from 24 210 pb dated cores collected at locations in the greater puget sound the highest pah concentrations are found within a few kilometers of several sources including industrial facilities in northern puget sound urban areas in central puget sound and river systems draining coal bearing strata regional patterns of combustion derived pah in surficial sediments indicate little atmospheric or waterborne exchange of pah between different regions of the sound significant subsurface maxima in combustion derived pah concentrations 210 pb dated at the 1950s occur only in sediment cores collected near urban centers perylene apparently derives from erosion of a terrestrial source with little or no evidence of in situ production at depth in sediment cores coal fragments are carriers of a characteristic suite of alkylated phenanthrene chrysene and picene derivatives concentrated near river mouths in central and southern puget sound

change in the probability for earthquakes in southern california due to the landers magnitude 7 3 earthquake the landers earthquake in june 1992 redistributed stress in southern california shutting off the production of small earthquakes in some regions while increasing the seismicity in neighboring regions up to the present this earthquake also changed the ratio of small to large events in favor of more small earthquakes within about 100 kilometers of the epicenter this implies that the probabilistic estimate for future earthquakes in southern california changed because of the landers earthquake the location of the strongest increase in probability for large earthquakes in southern california was the volume that subsequently produced the largest slip in the magnitude 7 1 hector mine earthquake of october 1999

tectonic implications and seismicity triggering during the 2008 baluchistan pakistan earthquake sequence abstract a damaging and widely felt moderate earthquake mw 6 4 hit the rural mountainous region of southwestern pakistan on october 28 2008 the main shock was followed by another earthquake of identical magnitude mw 6 4 on the next day the spatial distribution of aftershocks and focal mechanism revealed a nw se striking rupture with right lateral strike slip motion which is sympathetic to the nnw sse striking active mapped urghargai fault the occurrence of strike slip earthquakes suggests that along with the thrust faults strike slip faults too are present beneath the fold and thrust belt of sulaiman kirthar ranges and accommodates some of the relative motion of the indian and eurasian plates to assess the characteristics of this sequence the statistical parameters like aftershocks temporal decay b value of g r relationship partitioning of radiated seismic energy due to aftershocks and spatial fractal dimension d value have been examined the b value is estimated as 1 03 0 42 and suggests the tectonic genesis of the sequence and crustal heterogeneity within rock mass the low p value of 0 89 0 07 implies slow decay of aftershocks activity which is probably an evidence for low surface heat flow a value of spatial fractal dimension of 2 08 0 02 indicates random spatial distribution and that the source is a two dimensional plane filled up by fractures the static coseismic coulomb stress changes due to the foreshock mw 5 3 were found to increase stress by more than 0 04 bars at the hypocenter of the main shock thus promoting the failure the cumulative coseismic coulomb stress changes due to the foreshock and mainshocks suggest that most of the aftershocks occurred in the region of increased coulomb stress and to the se to the mainshock rupture

measuring the heterogeneity of the coseismic stress change following the 1999 mw7 6 chi chi earthquake seismicity quiescences are expected to occur in places where the stress has been decreased in particular following large main shocks however such quiescences can be delayed by hours to years and be preceded by an initial phase of earthquake triggering this can explain previous analyses arguing that seismicity shadows are rarely observed since they can only be seen after this triggering phase is over such is the case of the main rupture zone which experiences the strongest aftershock activity despite having been coseismically unloaded by up to tens of bars the 1999 m w 7 6 chi chi taiwan earthquake is characterized by the existence of several such delayed quiescences especially off the chelungpu fault on which the earthquake took place we here investigate whether these delays can be explained by a model of heterogeneous static stress transfer coupled with a rate and state friction law we model the distribution of coseismic small scale stress change by a gaussian law with mean tau bar and standard deviation the latter measures the level of local heterogeneity of the coseismic change in stress the model is shown to mimic the earthquake time series very well robust inversion of the tau bar and parameters can be achieved at various locations although on fault seismicity has not been observed for a sufficiently long time to provide more than lower bounds on those estimates for the chelungpu fault several quiescences have delays that can be well explained by local stress heterogeneity even at relatively large distances from the chi chi earthquake

effects of extreme heating on the elemental and isotopic compositions of an upper cretaceous coal abstract intrusion of igneous sills into coal seams in the maastrichtian vermejo formation of colorado new mexico rapidly and severely altered the organic matter content of the coal organic carbon concentrations drop from 65 in coal samples distant from sills to between 5 and 38 in coal samples close to a sill changes in organic matter c n ratios and 13 c values relative to distance from the sill indicate preferential losses of isotopically light forms of carbon from the coal the relatively high toc concentration elevated c n ratio and more negative 13 c value of coal closest to the sill suggest that rapid pyrolysis immobilized the thermal products as partially graphitized or mineral forms of carbon

alkane and pah depositional history sources and fluxes in sediments from the fraser river basin and strait of georgia canada hydrocarbon data for dated sediment cores from fraser basin lakes and the strait of georgia in canada reveal a pristine pre industrial background that remains unaltered in modern sediments far from human activities these pristine sediments contain polycyclic aromatic hydrocarbons pahs from combustion natural forest and prairie fires and alkanes and pahs from weathering of soils containing vascular plant remains and natural petroleum hydrocarbons and algal production at other locations examined however these natural loadings have been augmented over the past century by hydrocarbons from petroleum the combustion of liquid oil gasoline and solid coal wood fuels and from processing of wood either directly from disturbed land and slash burning or indirectly through pulp mill effluent although contamination is clearest where there are nearby human activities alkane profiles pah distributions and alkane unresolved complex mixtures suggest a widespread contamination from petroleum combustion products from human activities can also be identified although with less source specificity than with the petroleum products regional emissions from anthropogenic combustion processes appear to support modern pah increases within the fraser river basin and there is little evidence of inputs from global emissions principal components analysis using the new centred log ratio normalisation procedure to normalise data discriminates well between pahs entering lakes from runoff or the atmosphere and pah formed diagenetically within lake sediments as well as between combustion and petroleum pahs

hydrocarbons in washington coastal sediments the sources and distributions of polycyclic aromatic hydrocarbons pah and aliphatic hydrocarbons are characterized in seventeen sediments from a highly river influenced sedimentary environment off the southwestern coast of washington the major hydrocarbons are land derived introduced as preformed compounds and display long term stability in sediment cores a series of pah of anthropogenic origin and two naturally derived compounds retene and perylene dominate the pah composition in these sediments plantwax n alkanes are the major aliphatic hydrocarbon constituents aliphatic hydrocarbons of marine origin pristane and a series of four acyclic multibranched c25 polyolefins are also observed in many sediments the concentrations of these marine derived hydrocarbons decrease to negligible levels rapidly with sediment depth from the sea sediment interface suggesting degradation in general the major land derived hydrocarbons are concentrated in the midshelf silt deposit which extends northwestward along the continental shelf from the columbia river mouth a quantitatively more minor natural series of phenanthrene homologs also of terrestrial origin is preferentially advected further offshore and deposited in continental slope sediments these distributions are consistent with recognized particle associations for these compounds and sediment dispersal processes in this coastal environment sediment core records suggest the present pattern of dispersal has persisted for at least the past century and possibly since the late pleistocene

comment on influence of a basic intrusion on the vitrinite reflectance and chemistry of the springfield no 5 coal harrisburg illinois by stewart et al 2005 abstract in this communication we demonstrate that the intrusion temperature of about 600 c for the cottage grove dike provided by stewart et al stewart a k massey m padgett p l rimmer s m hower j c 2005 influence of a basic intrusion on the vitrinite reflectance and chemistry of the springfield no 5 coal harrisburg illinois international journal of coal geology 63 58 67 is questionable because their computation is based on an unrealistic heat flow model and the estimated contact temperature is derived from a geothermometer that is not calibrated for contact metamorphism in order to obtain an accurate and reliable intrusion temperature based on the contact temperature of the intrusion a reliable geothermometer in high temperature ranges should be used to calculate the peak temperature

seismicity at the border between central and southern apennines italy re evaluation of the early 1984 instrumental earthquake abstract we re evaluate the 1984 abruzzo lazio earthquake on the basis of original seismological data discussed in light of previous interpretations from other authors this sequence characterized by two distinct mainshocks ms 5 8 and ms 5 2 neis having low spatial and temporal separation developed at the border between central and southern apennines the sequence originated in a narrow area adjacent to the main nw se structures belonging to the apenninic chain crossed by fault segments with different orientation the spatio temporal evolution of the seismicity the focal mechanisms of some aftershocks never obtained before and waveform analysis suggest that the sequence developed in several stages the beginning of the two main stages was marked by two events ms 5 8 and ms 5 2 and the entire sequence was strongly controlled by the structural heterogeneity in the medium involved in the stress release process the ruptures nucleated on a ene wsw striking fault segment belonging to the nne striking ortona roccamonfina tectonic line and propagated towards ene the presence of the nw se structures belonging to the apennine chain and their geometry acted as a barrier to the spread of the aftershocks northeastward as a consequence a local concentration of static stress in the area enclosed between the northern edge of the rupture segment of the first mainshock and the nw striking structures triggered the ms 5 2 event on a w e pre existing fault segment in turn the static stress changes due to the second mainshock activated adjacent ne sw and nw se fault segments the nw striking structures belonging to the apennines acted as a structural barrier halting the propagation of the ruptures nucleating on a fault segment that belongs to the nne striking ortona roccamonfina tectonic line

perturbation of the izmit earthquake aftershock decaying activity following the 1999 mw 7 2 duzce turkey earthquake triggering and quiescence patterns of seismicity in western turkey following the occurrence of the 12 november 1999 m w 7 2 duzce earthquake are investigated the changes in seismicity rate are analyzed along the north anatolian fault segments that had ruptured 3 months earlier during the 17 august 1999 m w 7 4 izmit earthquake detection of triggering and quiescence is done by comparing the seismicity rate that would be expected if the duzce earthquake had not happened to the actual observed rate the expected rates are estimated by extrapolating the preexisting seismicity pattern using two complementary models a simple omori utsu s law and the etas model fault segments located to the east of the izmit epicenter show a mild case of quiescence following the duzce earthquake these segments had previously experienced an anomalous triggering episode in the 5 days preceding the duzce earthquake correlated with the occurrence of two strong m w 5 izmit aftershocks however it is not clear whether this observed quiescence is real or spurious as it coincides with a local reconfiguration of the seismological network a temporary increase of 0 1 to 0 15 in completeness magnitude would be enough to explain this apparent deactivation fault segments located to the west of the izmit epicenter exhibit triggering of seismicity following the duzce earthquake this observed triggering is mostly restricted to a cluster of events located in the geothermal area of yalova the increase of seismicity rate is delayed by 18 hours after the waves travelling from the duzce rupture had hit this zone our analysis suggests that this 15 day long reactivation can be explained by a short lived perturbation the local seismic activity then sustaining itself for the remaining 15 days we argue that this particular behavior is likely to correspond to a case of dynamic triggering by the end of year 1999 the yalova cluster shows a significant quiescence that lasted for several months this shutting down does not coincide with the occurrence of any local earthquake that would be large enough to stress shadow this area suggesting an aseismic cause to this pattern these results highlight the fact that 1 seismicity triggered by a major earthquake is not restricted to areas loaded by static stress and 2 that seismic activity associated with geothermal geological settings is highly sensitive to stress perturbations but also to aseismic processes that can both delay reactivation and cause this activity to suddenly decrease

hydrocarbon geochemistry of the puget sound region ii sedimentary diterpenoid steroid and triterpenoid hydrocarbons cyclic components of the aliphatic hydrocarbon mixtures extracted from puget sound sediment cores include a suite of c19 and c20 diterpenoid hydrocarbons of which fichtelite sandaracopimaradiene and isopimaradiene have been identified although apparently also derived from vascular plants these diterpenoid hydrocarbons have relative abundances distinctly different from the co existing plant wax n alkane suite five c27 c28 and c29 diasteranes and four c29 c30 and c31 17 h 21 h hopanes occur in relatively constant proportion as components of a highly weathered fossil hydrocarbon assemblage these chromatographically resolved cycloalkanes along with the strongly covarying unresolved complex mixture have been introduced to puget sound sediments from adjacent urban centres at increasing levels over the last 100 yr in the absence of any major oil spill naturally occurring triterpenoid hydrocarbons including hop 22 29 ene diploptene are also present a new group of c30 polyenes has been detected which contains compounds apparently structurally related to a co existing bicyclic c25 diene and to c20 and c25 acyclic multibranched hydrocarbons described in a previous paper barrick et al 1980

delayed seismicity rate changes controlled by static stress transfer on 15 june 2010 a m w5 7 earthquake occurred near ocotillo california in the yuha desert this event was the largest aftershock of the 4 april 2010 m w7 2 el mayor cucapah emc earthquake in this region the emc mainshock and subsequent ocotillo aftershock provide an opportunity to test the coulomb failure hypothesis cfs we explore the spatiotemporal correlation between seismicity rate changes and regions of positive and negative cfs change imparted by the ocotillo event based on simple cfs calculations we divide the yuha desert into three subregions one triggering zone and two stress shadow zones we find the nominal triggering zone displays immediate triggering one stress shadowed region experiences immediate quiescence and the other nominal stress shadow undergoes an immediate rate increase followed by a delayed shutdown we quantitatively model the spatiotemporal variation of earthquake rates by combining calculations of cfs change with the rate state earthquake rate formulation of dieterich 1994 assuming that each subregion contains a mixture of nucleation sources that experienced a cfs change of differing signs our modeling reproduces the observations including the observed delay in the stress shadow effect in the third region following the ocotillo aftershock the delayed shadow effect occurs because of intrinsic differences in the amplitude of the rate response to positive and negative stress changes and the time constants for return to background rates for the two populations we find that rate state models of time dependent earthquake rates are in good agreement with the observed rates and thus explain the complex spatiotemporal patterns of seismicity

anatomy of an intruded coal i effect of contact metamorphism on whole coal geochemistry springfield no 5 pennsylvanian coal illinois basin abstract if time and heating rate are important agents in coal maturation one might expect to see differences in chemical changes in response to maturation depending on the means of increased rank using a suite of samples obtained from an intruded pennsylvanian age coal in southern illinois we present whole coal chemical data comparing these data to extant geochemical data for coals that have undergone normal burial maturation we evaluated the hypothesis that if coal alteration occurs rapidly due to intrusion rather than gradually burial maturation then different relationships are seen in chemical composition proximate and ultimate analyses and vitrinite reflectance the pennsylvanian age asturian westphalian d springfield no 5 coal is mined at the big ridge mine near eldorado southern illinois this high volatile b bituminous coal was intruded by an ultramafic igneous intrusion during the early permian alteration occurs out to 1 2 dike thickness and includes an increase in random vitrinite reflectance rm from levels 0 7 to over 5 3 loss of liptinites and formation of devolatilization vacuoles and fine mosaic texture decreases in volatile matter vm and increases in fixed carbon fc appear to be less than would be expected for the level of reflectance seen within the alteration halo carbonate minerals have a major influence on proximate analyses but even following the removal of carbonates the decrease in vm is still less than would be seen in coals of similar vitrinite reflectance that were altered by normal burial maturation carbonate mineralization also contributes to variability in ultimate analysis values approaching the intrusion particularly for c and o after carbonate removal data for these coals do not appear to follow the normal burial coalification tracks when plotted on a van krevelen diagram and on a seyler chart these differences suggest that a slightly different maturation pathway may have been followed by these coals and by others that were altered rapidly by intrusion

response of seismicity to coulomb stress triggers and shadows of the 1999 mw 7 6 chi chi taiwan earthquake 1 the correlation between static coulomb stress increases and aftershocks has thus far provided the strongest evidence that stress changes promote seismicity a correlation that the chi chi earthquake well exhibits several studies have deepened the argument by resolving stress changes on aftershock focal mechanisms which removes the assumption that the aftershocks are optimally oriented for failure here one compares the percentage of planes on which failure is promoted after the main shock relative to the percentage beforehand for chi chi we find a 28 increase for thrust and an 18 increase for strike slip mechanisms commensurate with increases reported for other large main shocks however perhaps the chief criticism of static stress triggering is the difficulty in observing predicted seismicity rate decreases in the stress shadows or sites of coulomb stress decrease detection of sustained drops in seismicity rate demands a long catalog with a low magnitude of completeness and a high seismicity rate conditions that are met at chi chi we find four lobes with statistically significant seismicity rate declines of 40 90 for 50 months and they coincide with the stress shadows calculated for strike slip faults the dominant faulting mechanism the rate drops are evident in uniform cell calculations 100 month time series and by visual inspection of the m 3 seismicity an additional reason why detection of such declines has proven so rare emerges from this study there is a widespread increase in seismicity rate during the first 3 months after chi chi and perhaps many other main shocks that might be associated with a different mechanism

increased probability of large earthquakes near aftershock regions with relative quiescence it is shown that after a large earthquake of m6 class or over has taken place another event of similar size or larger is relatively more likely in the sense of rate per unit area to occur in the near field than in the far field in particular we show that the aftershock activity of the first event provides useful information for assessing the probability of a following large event in the neighborhood within a distance of a few degrees namely if the aftershock activity from the first event becomes relatively quiet compared to the normal decay the occurrence rate of larger events in the neighborhood is several times higher during the first decade after the main shock than would be the case for normal aftershock activity for measuring such phenomena precisely we need to model the normal aftershock activity in fact many aftershock sequences are more complex than the simple inverse power decay represented by the modified omori formula the epidemic type aftershock sequences etas model is a generalized version of the modified omori formula which fits well with various aftershock sequences including nonvolcanic type swarms using this model aftershock sequences are investigated for the 76 main shocks that occurred in and around japan during the last three quarters of a century the focus is placed on objective examination of whether or not in an aftershock sequence there exists a significant change point followed by relative quiescence that is a significant lowering of the seismicity from that predicted by the etas model relative quiescence can take place regardless of the seismicity level the extent of such quiescence if it exists is seen from the diagrams of cumulative numbers versus the transformed occurrence times based on the predicted occurrence rate by the estimated etas model it is thus demonstrated that relative quiescence can be a helpful factor in detecting anomalous aftershock activity this can then be used to forecast whether or not a large event is more likely to follow shortly within 6 years in the neighborhood within a distance of 3 of the initial event

the 1997 kagoshima japan earthquake doublet a quantitative analysis of aftershock rate changes we quantitatively map relative rate changes for the aftershock sequence following the second mainshock of the 1997 earthquake doublet m w 6 1 m w 6 0 in the kagoshima province japan using the spatial distribution of the modified omori law parameters for aftershocks that occurred during the 47 8 days between the two mainshocks we forecast the aftershock activity in the next 50 days and compare it to the actually observed rates the relative rate change map reveals four regions with statistically significant relative rate changes three negative and one positive our analysis suggests that the coseismic rate changes for off fault aftershocks could be explained by changes in static stress however to explain the activation and deactivation of on fault seismicity other mechanism such as unusual crustal properties and the presence of abundant crustal fluids are required

toggling of seismicity by the 1997 kagoshima earthquake couplet a demonstration of time dependent stress transfer 1 two m 6 well recorded strike slip earthquakes struck just 4 km and 48 days apart in kagoshima prefecture japan in 1997 providing an opportunity to study earthquake interaction aftershocks are abundant where the coulomb stress is calculated to have been increased by the first event and they abruptly stop where the stress is dropped by the second event this ability of the main shocks to toggle seismicity on and off argues that static stress changes play a major role in exciting aftershocks whereas the dynamic coulomb stresses which should only promote seismicity appear to play a secondary role if true the net stress changes from a sequence of earthquakes might be expected to govern the subsequent seismicity distribution however adding the stress changes from the two kagoshima events does not fully capture the ensuing seismicity such as its rate change temporal decay or migration away from the ends of the ruptures we therefore implement a stress transfer model that incorporates rate state friction in which seismicity is treated as a sequence of independent nucleation events that are dependent on the fault slip slip rate and elapsed time since the last event the model reproduces the temporal response of seismicity to successive stress changes including toggling decay and aftershock migration nevertheless the match of observed to predicted seismicity is quite imperfect due perhaps to inadequate knowledge of several model parameters however to demonstrate the potential of this approach we build a probabilistic forecast of larger earthquakes on the expected rate of small aftershocks taking advantage of the large statistical sample the small shocks afford not surprisingly such probabilities are highly time and location dependent during the first decade after the main shocks the seismicity rate and the chance of successive large shocks are about an order of magnitude higher than the background rate and are concentrated exclusively in the stress triggering zones

earthquakes casting stress shadows earthquakes may trigger or retard quakes on nearby faults but such relationships are difficult to verify observations showing that the landers earthquake in california shut down aftershocks from a preceding event validate such relationships

temperature effects on kerogen and on molecular and isotopic composition of organic matter in pierre shale near an igneous dike abstract a suite of siltstone samples from the upper cretaceous pierre shale from the contact zone of a 130 cm thick igneous dike near wolcott colorado u s a was taken from the contact to 170 cm from the dike to study the effects of temperature on the organic matter the sampled bedding interval was about 10 cm thick so variation in lithology and type of organic matter is minimal vitrinite reflectance values r 0 increase from 0 4 far from the dike to 3 3 near the dike contact geochemical measurements show systematic thermal effects analogous to those often observed for catagenesis and metagenesis in the depth range of 1 4 km within a sedimentary basin the h c ratio of kerogen and the hydrogen index rock eval decrease most rapidly in the 0 6 1 7 r 0 range in which the transformation ratio rock eval increases from 0 1 to 0 3 based on extraction of c 15 compounds the main increase of hydrocarbons and total extractable organic matter occurs between 0 6 and 1 0 reflectance the saturated aromatic hydrocarbon ratio increases almost twofold in this range of maturity however the pristane phytane ratio is essentially constant through the hydrocarbon generation zone but decreases slightly at high levels of thermal alteration r 0 1 2 the 13 c values for aromatic and saturated hydrocarbons are about 27 and 29 respectively and are constant to about 1 0 r 0 then both become heavier by about 2 at higher r 0 values

spatial variability of seismicity parameters in aftershock zones the spatial variability of the b value of the frequency magnitude relationship and the decay rate of aftershocks as described by the p value of the modified omori law is investigated by using dense spatial grids we map out the distribution of b and p values within the landers northridge morgan hill and kobe aftershock sequences considerable spatial variability is found with b values of independent subvolumes ranging from 0 6 to 1 4 and p values ranging from 0 6 to 1 8 these systematic and statistically highly significant differences argue that it is an oversimplification to assign one single p and b value to an aftershock sequence that extends up to 100 km the spatial distribution of these two parameters is compared with the slip distribution during the mainshock suggesting that the areas of largest slip release correlate with high b value regions we hypothesize that the frictional heat created during the event may influence the p value distribution within an aftershock zone while applied shear stress crack density and pore pressure govern the frequency magnitude distribution by investigating the frequency magnitude distribution separately for preseismic and postseismic periods for the morgan hill mainshock we find that only the volume in the vicinity of the highest slip release shows a significant increase in the b value which decays to premainshock values within a year surrounding areas of the aftershock zone show an approximately constant b value with time because the aftershock hazard after a mainshock depends strongly on both the b and p value we propose that aftershock hazard assessment can be improved by taking into account the spatial distribution of the parameters

minimum magnitude of completeness in earthquake catalogs examples from alaska the western united states and japan we mapped the minimum magnitude of complete reporting m c for alaska the western united states and for the junec earthquake catalog of japan mc was estimated based on its departure from the linear frequency magnitude relation of the 250 closest earthquakes to grid nodes spaced 10 km apart in all catalogs studied mc was strongly heterogeneous in offshore areas the mc was typically one unit of magnitude higher than onshore on land also mc can vary by one order of magnitude over distance less than 50 km we recommend that seismicity studies that depend on complete sets of small earthquakes should be limited to areas with similar mc or the minimum magnitude for the analysis has to be raised to the highest com mon value of mc we believe that the data quality as reflected by the mc level should be used to define the spatial extent of seismicity studies where mc plays a role the method we use calculates the goodness of fit between a power law fit to the data and the observed frequency magnitude distribution as a function of a lower cutoff of the magnitude data mc is defined as the magnitude at which 90 of the data can be modeled by a power law fit mc in the 1990s is approximately 1 2 0 4 in most parts of california 1 8 0 4 in most of alaska aleutians and panhandle excluded and at a higher level in the junec catalog for japan various sources such as ex plosions and earthquake families beneath volcanoes can lead to distributions that cannot be fit well by power laws for the hokkaido region we demonstrate how neglecting the spatial variability of m c can lead to erroneous assumptions about deviations from self similarity of earthquake scaling

igneous activity and organic maturation in the midland valley of scotland abstract the general relationship of erich stach s research work to the effects of igneous activity on organic maturation is briefly considered the geological history of the midland valley of scotland is then reviewed as a graben which developed in devonian old red sandstone times and continued to do so as lithospheric tensional stretching was maintained throughout the carboniferous a significant factor in relation to the development of organic maturation was the widespread igneous activity that persisted throughout much of upper palaeozoic times calc alkaline volcanic rocks are a major feature within the molasse type deposits of the old red sandstone after a period of quiescence in later old red sandstone times the continuing tensional stretching initiated or rejuvenated major crustal fractures extensive volcanic sill and dyke activity exercised an important influence on the predominantly shallow water deltaic deposits of the carboniferous alkaline olivine basalts were erupted in the early carboniferous while volcanic activity in the later carboniferous was essentially phreatic two major intrusive episodes occurred the first of alkaline sills in early to mid carboniferous times which were closely related to volcanic plugs and eruptive centres the second in post westphalian times when tholeiitic sills and dykes with no known relationships with any extrusive rocks were injected the effects of this igneous activity on organic maturation can be considered under four headings 1 1 although the general development of maturation of carboniferous organic matter which includes many coal seams and oil shales was controlled to some degree by burial history the regional pattern of igneous activity was also influential thus there is a gradual increase of coalification from east to west in the midland valley which corresponds with an increasing thickness of volcanic pile in the central and westerly parts of the graben suggesting that there may have been a greater regional heat sink in the west during the carboniferous the level of coalification is nowhere particularly high except where affected by intrusions and regional reflectance gradients generally vary between r oil vitrinite 0 2 km to 0 4 km without displaying any consistent pattern 2 2 the post westphalian tholeiitic quartz dolerite midland valley sill which underlies most of the central and eastern parts of the graben has produced extensive reflectance thermal aureoles in the organic matter above and below the intrusion the olivine dolerite and teschenite sills of namurian early westphalian times many of similar thickness to the quartz dolerite intrusions fail to produce significant reflectance thermal aureoles this major difference in organic matter response to the intrusions can only be explained in terms of the initial rank level of the organic matter differences in degree of compaction of the sediments and particularly in the amount of water the sediments contained at the time of intrusion 3 3 maturation of organic matter closely associated with extensive surtseyan type volcanic activity in the eastern part of the graben displays no relationship to the regionally developed coalification in associated sediments although some vitrinite clasts in the pyroclastic deposits have had their reflectances raised to meta anthracitic rank reflectance levels of clasts in tuffs and agglomerates are generally not much raised above the regional reflectance level suggesting incorporation of organic matter in ash streams in which water was an important cooling and protective component 4 4 the close relationship of organic matter of all kinds with volcanic and intrusive igneous rocks has led to a marked increase of parent polycyclic aromatic hydrocarbons pah in the aromatic fractions of organic extracts the source of these hydrocarbons is the combustion and or pyrolysis of organic matter caused by the high temperatures of the igneous materials whether volcanic or intrusive these pah may be directly generated or absorbed from the surrounding environment

aftershocks halted by static stress shadows the role of permanent versus transient crustal stress changes in triggering earthquakes is debated analysis of the stress imparted by the joshua tree and nearby landers earthquakes in california in 1992 implies that a permanent drop in stress can halt aftershocks so such static stress changes should be incorporated into seismic hazard assessments

210pb derived sediment accumulation and mixing rates for the greater puget sound region abstract recent sediment accumulation rates of 46 1200 mg cm2 yr are calculated from excess 210pb activity profiles in 44 sediment cores from 27 sites in the greater puget sound region rates calculated for nine stations in the deeper waters of central puget sound average 480 mg cm2 yr and are greatest between seattle and tacoma near the southern end of this region the standard error of this mean is 113 mg cm 2 yr magnitudes and geographic trends of 210pb derived accumulation rates agree with limited data on sediment inputs and transport paths their accuracy is further supported by several independent approaches including comparison with particle fluxes collected in year long series of sediment trap deployments at two sites accumulation rates are calculated assuming no mixing beneath surface mixed layers of 2 22 cm sediment mixing coefficients in these surface layers average at least 43 cm2 yr four times greater than those reported in open washington coast sediments the difference is attributed to the greater benthic biomass in puget sound sediments particle residence times in surface mixed layers vary from 1 5 to 68 years and introduce corresponding uncertainties in ages of horizons beneath the mixed layers for most of this region these residence times will cause a 20 30 year time lag in achieving an equivalent response of surface sediment chemical concentrations to changes in concentrations in freshly depositing particles for constituents whose stability and phase associations resemble those of 210pb these time lags limit the ability of sediment chemistry monitoring programs to recognize recent changes in composition and fluxes of chemicals to sediments recent fluxes calculated from the product of surface sediment chemical concentration and accumulation rates will be inaccurate for chemicals if their input concentrations have changed in the last 20 30 years

a study of the effect of igneous intrusions on the structure of an australian high voltage bituminous coal abstract samples of heat affected coal taken near two igneous intrusions dykes in the victoria tunnel seam of the newcastle coalfield have been investigated by chemical analysis petrography fourier transform infrared spectroscopy and solid state 13 c nmr spectroscopy visual inspection of the seam near the intrusion showed four distinct zones these have been called in order of increasing distance from the dyke the massive cinder the banded cinder heat affected coal and apparently unaffected coal the samples show an increase in structural change as the distance from the dyke decreases with the samples taken from the massive cinder nearest the dyke being classified as semicokes ftir and 13 c nmr results together with the results of dipolar dephasing nmr experiments suggest that the predominant structural change in the heat affected zone is replacement of aromatic ethers and or phenols with hydrogen leading to an increase in proton aromaticity closer to the intrusion bond rupture leads to a marked loss of aliphatic groups while in the most affected region adjacent to the dyke aromatic crosslinking has also occurred to form coke like material

coal metamorphism by igneous intrusion in the raton basin co and nm implications for generation of volatiles abstract the raton basin contains a series of tertiary mafic dikes and sills that have altered millions of tons of coal to natural coke and may have played a minor role in generating some of the large coalbed methane resources currently being exploited in this region four outcrops within the raton basin were selected to investigate local coal rank elevation and volatile generation due to intrusive activity coal and organic shale samples were collected on traverses across meter scale dikes and sills and were analyzed for vitrinite reflectance total organic carbon bulk carbon isotopic ratios and coke petrography reflectance patterns in the contact aureoles of the dikes display very consistent concave up patterns with reflectance values returning to background within one intrusion width from the contact bulk coal samples collected across dikes display an increase in 13c of approximately 1 approaching all contacts reflectance patterns within the contact aureoles of sills do not decrease significantly until one half of an intrusion width away from the contact but then drop steeply to background values by one intrusion width away bulk coal samples display complex isotopic patterns approaching sills with an initial increase in 13c followed by a steep decrease of approximately 1 5 approaching the top contacts the distinct isotopic and reflectance patterns for dikes and sills may indicate that the coal in the contact aureoles of the sills experienced a longer heating duration than the coal near the dike contacts this longer heating duration was due to the low thermal conductivity of coal which acts as a thermal insulator to the sills that intrude coal beds this style of intrusion is commonly observed throughout the central portions of the raton basin by contrast dikes intrude a variety of country rock types and are not insulated by coal heat may escape the contact zone through nearby sandstones or shales based on reflectance patterns hydrothermal convection played a role in heat transfer away from dikes data from both the dike and sill contacts suggest that time plays a role in controlling peak vitrinite reflectance values at least over the short heating durations tens of years expected for meter scale intrusions decreasing total organic carbon values approaching all contacts suggests the generation and escape of volatile species such as methane isotopic values within the contacts of dikes are consistent with the loss of 12c enriched methane the isotopic pattern observed at the contacts of sills may be due to accumulation of 12c rich pyrolytic carbon close to the contacts which is supported by petrographic observations even though multiple thin sheet intrusions are insignificant for conductive heating on a basin scale methane generation by sheet intrusions was volumetrically important in the raton basin because sills preferentially intrude coal beds in this region

methods for measuring seismicity rate changes a review and a study of how the m w 7 3 landers earthquake affected the aftershock sequence of the m w 6 1 joshua tree earthquake the development of fault interaction models has triggered the need for an accurate estimation of seismicity rate changes following the occurrence of an earthquake several statistical methods have been developed in the past to serve this purpose each relying on different assumptions e g stationarity gaussianity pertaining to the seismicity process

aberrations in the coalification patterns of the offshore coalfields of northumberland and durham united kingdom abstract the offshore extensions of the northumberland and durham westphalian coalfields are formed of continuous and linked sequences of sediments which lie in contrasting structural regimes respectively basin and block the coalfields have suffered different geothermal histories offshore northumberland basin sediments endured low heating rates and low maximum temperatures to give seams which even at the base of the succession hardly reached vitrinite reflectances of roil 0 60 apart from raised values due to igneous activity the offshore durham block succession was exposed to higher temperatures and heating rates due to the proximity of the lower devonian weardale granite underlying the block which was re activated during carboniferous times these geothermal conditions not only led to higher levels of reflectance and steeper maturation gradients offshore in the block succession than offshore in coals of the basin but also produced contrasting relationships between correlations of vitrinite oil reflectance and volatile matter yield of coals for the two structural zones and probably also for other property relationships as well reflectance profiles have been modified due to three circumstances first considerable variation locally in the raising of reflectance levels caused by igneous activity second lowering of vitrinite reflectance values due to arenaceous sediments being deposited immediately on top of vitrinite precursors within the coal forming organic matter and third possible interference from liptinite rich accumulations within coal seams or near to them in the succession which exuded aliphatic materials relatively early in coalification which were then absorbed by vitrinites or more likely deposition of the vitrinite precursors in a marine near marine and calcium rich environment so reducing reflectance values on coalification similar contrasting property relationships to those described here may have been produced by lower devonian granitoid bodies which have been identified on the north sea high if they also were re activated during the carboniferous

assessing elastic coulomb stress transfer models using seismicity rates in southern california and southwestern japan 1 we investigated whether observed changes in seismicity rate following the 1992 landers and 1995 kobe earthquakes correspond with predictions from coulomb stress transfer models to quantify the relationship between coulomb stress change and seismicity rate change we compared spatial changes in observed seismicity rates to the modeled changes in coulomb failure stress cfs for the two subject earthquakes we begin with the simplest and most common cfs model which assumes that regional stress orientations are uniform and the stress change is resolved on optimally oriented strike slip planes we then extended the cfs models to include the more geophysically realistic assumptions of spatially varying regional stress orientations and optimally oriented planes in three dimensions for all the tested cfs models we found that virtually everywhere seismicity rate changes could be resolved the rate increased regardless of whether the cfs theoretically promoted or inhibited failure and that we were not able to reliably resolve seismicity rate decreases an improvement in the correlation between the sign of the cfs and where rate increases occur when estimating the cfs on optimally oriented planes in three dimensions rather than two dimensions is a consequence of using optimally oriented planes and the ability to primarily observe rate increases the region of positive cfs increases by allowing more degrees of freedom so the correlation with positive rate change appears to increase the areas of highest seismicity rate following the main shock did not correlate with the sign or the magnitude of the cfs rather the areas most active after the main shock were also the most active before the main shock

a global search for stress shadows 1 debate continues regarding the relative proportion of earthquakes triggered by passing seismic waves versus static stress changes from a main shock static stress changes are expected to have long term effects on earthquake probabilities whereas dynamic stress changes due to the passing of seismic waves should not both mechanisms are expected to raise seismicity rates in some areas but only static stress change calculations predict rate decrease shadows thus identification of post main shock earthquake suppression is diagnostic of a static stress change process we note that in principle static stress change theory predicts suppression of particular earthquake mechanisms in a shadow zone rather than an overall rate reduction a stress shadow can therefore be characterized by a change in the average earthquake focal mechanism before and after a main shock that results from suppression of a given mechanism type we examined average mechanisms from 2 radii and 5 year periods before and after 119 ms 7 main shock earthquakes drawn from the harvard centroid moment tensor cmt catalog significant average mechanism changes caused by earthquake suppression were found in only two cases however by stacking the data we were able to resolve statistically significant suppression of particular post main shock focal mechanisms this indicates that while static stress shadows are subtle they are indeed present in the global catalog

coal petrographical characterization of the mecsek bituminous coal basin with special reference to the contact metamorphism of coal seams abstract the bituminous coals of the mecsek mountains were formed during the early lias and are of paralic origin the limnic complex of the layers consists of sandstone aleurite and coal and the upper layer contains marl of marine origin the 9 15 minable coal seams have a thickness of 1 2 14 0 m the mecsek coal field and the coal complex within it show a folded and fractured structure and with regard to their mechanical behaviour are strongly stressed 75 90 of the coal material is vitrinite and 1 14 is inertinite the quantity of liptinite is smaller than 9 the coal rank is that of gas coal and fat coal with a reflectivity of 0 85 1 5 respectively the coal rank differences and variations according to zones are the consequence of forces of various magnitude that occurred in the course of orogenic movements during the early cretaceous there was some under sea bed volcanic activity in this field the diabasic material of which appeared in the form of a bed vein along the coal seams and this has exerted a strong metamorphic influence on the coal it has resulted in thermo contact alteration i e in the appearance of natural coke and semicoke of various degrees of metamorphism this alteration badly affected the quality and technological characteristics especially the cokability of the coal

a comparison of seismicity characteristics and fault structure between stick slip experiments and nature fault zones contain structural complexity on all scales this complexity influences fault mechanics including the dynamics of large earthquakes as well as the spatial and temporal distribution of small seismic events incomplete earthquake records unknown stresses and unresolved fault structures within the crust complicate a quantitative assessment of the parameters that control factors affecting seismicity to better understand the relationship between fault structure and seismicity we examined dynamic faulting under controlled conditions in the laboratory by creating saw cut guided natural fractures in cylindrical granite samples the resulting rough surfaces were triaxially loaded to produce a sequence of stick slip events during these experiments we monitored stress strain and seismic activity after the experiments fault structures were imaged in thin sections and using computer tomography the laboratory fault zones showed many structural characteristics observed in upper crustal faults including zones of localized slip embedded in a layer of fault gouge laboratory faults also exhibited a several millimeter wide damage zone with decreasing micro crack density at larger distances from the fault axis in addition to the structural similarities we also observed many similarities between our observed distribution of acoustic emissions aes and natural seismicity the aes followed the gutenberg richter and omori utsu relationships commonly used to describe natural seismicity moreover we observed a connection between along strike fault heterogeneity and variations of the gutenberg richter b value as suggested by natural seismicity studies areas of low b value marked the nucleation points of large slip events and were located at large asperities within the fault zone that were revealed by post experimental tomography scans our results emphasize the importance of stick slip experiments for the study of fault mechanics the direct correlation of acoustic activity with fault zone structure is a unique characteristic of our laboratory studies that has been impossible to observe in nature

effect of igneous intrusion on the organic geochemistry of a siltstone and an oil shale horizon in the midland valley of scotland abstract the effect of rapid thermal stress on the organic geochemistry of a siltstone intruded by a quartz dolerite dyke and an oil shale intruded by an alkali dolerite sill has been studied using optical petrography rock eval pyrolysis gas chromatrography and gas chromatography mass spectrometry maturity dependent ratios derived from both the aliphatic and aromatic hydrocarbon fractions corroborate the observation of raymond and murchison 1988b that the alkali dolerite sills which were intruded soon after sedimentation had a lesser effect than the later quartz dolerite intrusions the maturity parameters based on the alkylnaphthalene and alkylphenanthrene isomer ratios are more suitable for studying maturity variations in heat affected samples than those based on the commonly used aliphatic biological markers these aromatic compounds survive to higher ranks and the isomer ratios continue changing

seismicity analysis through point process modeling a review the occurrence times of earthquakes can be considered to be a point process and suitable modeling of the conditional intensity function of a point process is useful for the investigation of various statistical features of seismic activity this manuscript summarizes likelihood based methods of analysis of point processes and reviews useful models for particular analyses of seismicity most of the analyses can be implemented by the computer programs published by the author and collaborators

thermal alteration of cretaceous black shale by diabase intrusions in the eastern atlantic ii effects on bitumen and kerogen abstract the thermal effects of three one major and two minor miocene diabase intrusions on cretaceous black shales from dsdp site 41 368 have been analyzed a concentration gradient was observed especially for the hydrocarbons decreasing towards the major intrusion and between the three sills the thermally altered samples in the proximity of and between the sills contained elemental sulfur and an excess of thermally derived pristane over phytane whereas the unaltered sediments contained no elemental sulfur and more phytane than pristane a maximum yield of the extractable hydrocarbons was observed at a depth of 7 m below the major sill two classes of molecular markers were present in this bitumen suite the first was sesqui di and triterpenoids and steranes which could be correlated with both terrigenous and autochthonous sources they were geologically mature and showed no significant changes due to the thermal stress the second class was found in the altered samples which contained only polynuclear aromatic hydrocarbons with low alkyl substitution and sulfur and oxygen heterocyclic aromatic compounds these compounds were derived from pyrolytic reactions during the thermal event kerogen was isolated from all of these samples but only traces of humic substances were present the h c n c 13 c 34 s and d all exhibit the expected effects of thermal stress the kerogen becomes more aromatized and richer in 13c 34s and d in the proximity of and between the sills maturation trends were also measured by the vitrinite reflectance and electron spin resonance where the thermal stress could be correlated with an elevated country rock temperature and an increased degree of aromaticity the effects of in situ thermal stress on the organic rich shales resulted in the generation and expulsion of petroliferous material from the vicinity of the sills

forecasting the evolution of seismicity in southern california animations built on earthquake stress transfer 1 we develop a forecast model to reproduce the distribution of main shocks aftershocks and surrounding seismicity observed during 1986 2003 in a 300 310 km area centered on the 1992 m 7 3 landers earthquake to parse the catalog into frames with equal numbers of aftershocks we animate seismicity in log time increments that lengthen after each main shock this reveals aftershock zone migration expansion and densification we implement a rate state algorithm that incorporates the static stress transferred by each m 6 shock and then evolves coulomb stress changes amplify the background seismicity so small stress changes produce large changes in seismicity rate in areas of high background seismicity similarly seismicity rate declines in the stress shadows are evident only in areas with previously high seismicity rates thus a key constituent of the model is the background seismicity rate which we smooth from 1981 to 1986 seismicity the mean correlation coefficient between observed and predicted m 1 4 shocks the minimum magnitude of completeness is 0 52 for 1986 2003 and 0 63 for 1992 2003 a control standard aftershock model yields 0 54 and 0 52 for the same periods four m 6 0 shocks struck during the test period three are located at sites where the expected seismicity rate falls above the 92 percentile and one is located above the 75 percentile the model thus reproduces much but certainly not all of the observed spatial and temporal seismicity from which we infer that the decaying effect of stress transferred by successive main shocks influences seismicity for decades finally we offer a m 5 earthquake forecast for 2005 2015 assigning probabilities to 324 10 10 km cells

effects of igneous intrusions on coalbed methane potential gunnedah basin australia abstract the gunnedah basin nsw australia contains more than 500 gt of coal and has been the subject of recent coalbed methane exploration large areas of the basin contain igneous intrusions and large areas of coal have been heat affected as a consequence a detailed study has been undertaken of coal seams intersected in a cored coalbed methane exploration drillhole in which two sill form igneous intrusions are present comparisons are made between coals that are unaltered and coals that have been heat affected using petrographic and chemical data coal seam gas desorption data and gas chemical analysis data results demonstrate that the two igneous intrusions have had a very positive effect on coalbed methane development the gas content in a number of heat affected coal seams within thermal aureoles above and below the sills is substantially higher than in adjacent unaffected coal seams in addition the intrusions have had little effect on gas quality the coals in the heat affected zone were found to contain gas with approximately 95 methane the coals in the thermal aureoles were found under the microscope to contain characteristic micropores and slits which collectively may serve to enhance gas adsorption capacity permeability and gas desorption gas contents below each of the sills is substantially higher than above the sill confirming earlier results that the sills appear to have acted as a reservoir seal during and for some time after intrusion the background coal rank in acm yannergee ddh 1 is in the high volatile bituminous range the igneous intrusions have resulted in an increase in rank such that large areas of coal have moved into the optimal thermogenic gas generation window this rank increase has affected a major part of the coal bearing sequence

azaarenes in puget sound sediments the first quantitative measurements of azaarenes in marine sediments are reported for puget sound in northwestern washington state u s a two to four ring azaarenes in concentrations as low as 50 ppb relative to organic carbon are measured in 210pb dated sediments using glass capillary gas chromatography combined with nitrogen selective detection azaarene distributions are geographically and temporally variable azaarene distributions in upper sediment layers suggest that total azaarene concentrations are related to proximity to urban areas and may be anthropogenically derived subsurface maxima between 6 and 17 cm in several cores resemble similar maxima in pah and organo sulfur compounds trace quantities of azaarenes present in sediments deposited prior to urbanization of the puget sound region suggest low level natural azaarene sources one core containing particulate coal produced a concentrated and complex azaarene mixture suggesting either introduction of mined coal or erosion of regional coal deposits analyses of possible azaarene sources indicate that although azaarene compositions vary between sources coal azaarenes can be distinguished from petroleum azaarenes by their ratios of 2 ring to 3 ring azaarenes and may identify predominant azaarene inputs in environmental samples gross differences in azaarene composition exist between european and american air particulates and sediments suggesting differences in azaarene sources

earthquake doublet in kagoshima japan rupture of asperities in a stress shadow two shallow moderate m 6 earthquakes occurred in the northwestern part of kagoshima prefecture kyushu southern japan i discuss the effect of the stress change due to the first earthquake 26 march 1997 on the occurrence of the second earthquake 13 may 1997 the rupture characteristics of the two earthquakes are inferred in two steps to form the basis of the discussion i first invert strong ground motion data to construct kinematic source models and then estimate the distribution of static stress drop from the derived dislocation distributions the rupture process of the march event is simple and well described with rupture of a single asperity patch of high stress drop on the other hand multiple asperities on conjugate faults ruptured during the may event the maximum value of static stress drop for both earthquakes is about 4 mpa and seems lower than those of other japanese intraplate earthquakes the hypocenter and the largest asperity of the may earthquake are located in a stress shadow caused by the march earthquake thus the rupture history of the may earthquake is difficult to explain with a static stress change model other mechanisms such as fluid migration and dynamic stresses were also investigated but failed to explain the triggering i propose the coupled effect of static change in shear stress and normal stress under the rate and state dependent friction law as a possible mechanism

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

testing the stress shadow hypothesis 1 a fundamental question in earthquake physics is whether aftershocks are predominantly triggered by static stress changes permanent stress changes associated with fault displacement or dynamic stresses temporary stress changes associated with earthquake shaking both classes of models provide plausible explanations for earthquake triggering of aftershocks but only the static stress model predicts stress shadows or regions in which activity is decreased by a nearby earthquake to test for whether a main shock has produced a stress shadow we calculate time ratios defined as the ratio of the time between the main shock and the first earthquake to follow it and the time between the last earthquake to precede the main shock and the first earthquake to follow it a single value of the time ratio is calculated for each 10 10 km bin within 1 5 fault lengths of the main shock epicenter large values of the time ratio indicate a long wait for the first earthquake to follow the main shock and thus a potential stress shadow whereas small values indicate the presence of aftershocks simulations indicate that the time ratio test should have sufficient sensitivity to detect stress shadows if they are produced in accordance with the rate and state friction model we evaluate the 1989 mw 7 0 loma prieta 1992 mw 7 3 landers 1994 mw 6 7 northridge and 1999 mw 7 1 hector mine main shocks for each main shock there is a pronounced concentration of small time ratios indicating the presence of aftershocks but the number of large time ratios is less than at other times in the catalog this suggests that stress shadows are not present by comparing our results to simulations we estimate that we can be at least 98 confident that the loma prieta and landers main shocks did not produce stress shadows and 91 and 84 confident that stress shadows were not generated by the hector mine and northridge main shocks respectively we also investigate the long hypothesized existence of a stress shadow following the 1906 san francisco bay area earthquake we find that while bay area catalog seismicity rates are lower in the first half of the twentieth century than in the last half of the nineteenth this seismicity contrast is also true outside of the bay area in regions not expected to contain a stress shadow this suggests that the rate change is due to a more system wide effect such as errors in the historical catalog or the decay of aftershocks of the larger 1857 fort tejon earthquake

the cottage grove fault system illinois basin late paleozoic transpression along a precambrian crustal boundary the cottage grove fault system in southern illinois has long been interpreted as an intracratonic dextral strike slip fault system we investigated its structural geometry and kinematics in detail using 1 outcrop data 2 extensive exposures in underground coal mines 3 abundant borehole data and 4 a network of industry seismic reflection profiles including data reprocessed by us structural contour mapping delineates distinct monoclines broad anticlines and synclines that express paleozoic age deformation associated with strike slip along the fault system as shown on seismic reflection profiles prominent near vertical faults that cut the entire paleozoic section and basement cover contact branch upward into outward splaying high angle reverse faults the master fault sinuous along strike is characterized along its length by an elongate anticline 3 km wide that parallels the southern side of the master fault these features signify that the overall kinematic regime was transpressional due to the absence of suitable piercing points the amount of slip cannot be measured but is constrained at less than 300 m near the ground surface the cottage grove fault system apparently follows a precambrian terrane boundary as suggested by magnetic intensity data the distribution of ultramafic igneous intrusions and patterns of earthquake activity the fault system was primarily active during the alleghanian orogeny of late pennsylvanian and early permian time when ultramafic igneous magma intruded along en echelon tensional fractures

seismicity rate changes along the central california coast due to stress changes from the 2003 m 6 5 san simeon and 2004 m 6 0 parkfield earthquakes abstract we investigated the relationship between seismicity rate changes and modeled coulomb static stress changes from the 2003 m 6 5 san simeon and the 2004 m 6 0 parkfield earthquakes in central california coulomb stress modeling indicates that the san simeon mainshock loaded parts of the rinconada hosgri and san andreas strike slip faults along with the reverse faults of the southern los osos domain all of these loaded faults except for the san andreas experienced a seismicity rate increase at the time of the san simeon mainshock the parkfield earthquake occurred 9 months later on the loaded portion of the san andreas fault the parkfield earthquake unloaded the hosgri fault and the reverse faults of the southern los osos domain which both experienced seismicity rate decreases at the time of the parkfield event although the decreases may be related to the decay of san simeon triggered seismicity coulomb stress unloading from the parkfield earthquake appears to have altered the aftershock decay rate of the southern cluster of san simeon aftershocks which is deficient compared to the expected number of aftershocks from the omori decay parameters based on the pre parkfield aftershocks dynamic stress changes cannot explain the deficiency of aftershocks providing evidence that static stress changes affect earthquake occurrence however a burst of seismicity following the parkfield earthquake at ragged point where the static stress was decreased provides evidence for dynamic stress triggering it therefore appears that both coulomb static stress changes and dynamic stress changes affect the seismicity rate

a constitutive law for rate of earthquake production and its application to earthquake clustering seismicity is modeled as a sequence of earthquake nucleation events in which the distribution of initial conditions over the population of nucleation sources and stress ing history control the timing of earthquakes the model is implemented using solutions for nucleation of unstable fault slip on faults with experimentally derived rate and state dependent fault properties this yields a general state variable constitutive formulation for rate of earthquake production resulting from an applied stressing history to illustrate and test the model some characteristics of seismicity following a stress step have been explored it is proposed that various features of earthquake clustering arise from sensi tivity of nucleation times to the stress changes induced by prior earthquakes the model gives the characteristic omori aftershock decay law and interprets aftershock parameters in terms of stress change and stressing rate earthquake data appear to support a model prediction that aftershock duration defined as the time for rates to return to the back ground seismicity rate is proportional to mainshock recurrence time observed spatial and temporal clustering of earthquake pairs arises as a consequence of the spatial depen dence of stress changes of the first event of the pair and stress sensitive time dependent nucleation applications of the constitutive formulation are not restricted to the simple stress step models investigated here it may be applied to stressing histories of arbitrary complexity the apparent success at modeling clustering phenomena suggests the possibil ity of using the formulation to estimate short to intermediate term earthquake probabil ities following occurrence of other earthquakes and for inversion of temporal variations of earthquake rates for changes in driving stress

analysis of shallow and deep earthquake doublets in the fiji tonga kermadec region for the fiji tonga kermadec area and for the period from january 1977 to july 2003 the harvard cmt catalogue lists 1022 shallow 410 intermediate and 633 deep earthquakes of moment magnitude from 4 9 to 8 0 the magnitude threshold above which the catalogue is complete is 5 3 5 4 and the number of earthquakes of magnitude above this value is 691 for shallow 329 for intermediate and 476 for deep events respectively the proportion of earthquakes associated with doublets and multiplets against the total number of earthquakes is approximately the same in both data sets and therefore all earthquake pairs were considered regardless of their magnitude we investigated all the pairs of earthquakes that occurred at a centroid distance of less than 40 60 or 90 km from each other and within a time interval of 200 300 or 450 days depending on their magnitude we found 208 pairs of shallow 31 of intermediate and 92 of deep events to ascertain whether these earthquakes in pairs are not connected by chance the possibility of their occurrence in an uncorrelated poissonian catalogue was considered it was assumed that in such a catalogue the inter event time is exponentially distributed the earthquake magnitude follows the gutenberg richter relation and the distribution of centroid distances between the events in pairs is controlled by its non parametric kernel estimate the probability of the appearance of the observed proportion of doublets of shallow earthquakes in the poissonian catalogue was found to be very low the low probability of occurrence in a semi random catalogue created by randomising centroid locations in the actual data set also indicates major importance of the distance criterion used for a doublet specification in general shallow earthquakes tend to form pairs at shorter distances and within shorter time intervals than deep earthquakes both the distance and the time intervals do not depend on the magnitude of involved events the largest number of pairs of deep earthquakes is observed at a depth of about 600 km and the proportion of deep events associated with doublets against the number of all events increases with depth from comparison of the focal mechanism of earthquakes in pairs measured by the 3 d rotation angle it follows that deep earthquakes forming pairs have a more diverse focal mechanism than shallow events the rotation angle for three quarters of shallow pairs and only for about one third of deep pairs is reasonably small the azimuth between two events forming a doublet is in about 60 65 of cases close to the strike of one of nodal planes of the first or the second event

reliability of coulomb stress changes inferred from correlated uncertainties of finite fault source models 1 static stress transfer is one physical mechanism to explain triggered seismicity coseismic stress change calculations strongly depend on the parameterization of the causative finite fault source model these models are uncertain due to uncertainties in input data model assumptions and modeling procedures however fault model uncertainties have usually been ignored in stress triggering studies and have not been propagated to assess the reliability of coulomb failure stress change cfs calculations we show how these uncertainties can be used to provide confidence intervals for co seismic cfs values we demonstrate this for the mw 5 9 june 2000 kleifarvatn earthquake in southwest iceland and systematically map these uncertainties a set of 2500 candidate source models from the full posterior fault parameter distribution was used to compute 2500 cfs maps we assess the reliability of the cfs values from the coefficient of variation cv and deem cfs values to be reliable where they are at least twice as large as the standard deviation cv 0 5 unreliable cfs values are found near the causative fault and between lobes of positive and negative stress change where a small change in fault strike causes cfs values to change sign the most reliable cfs values are found away from the source fault in the middle of positive and negative cfs lobes a likely general pattern using the reliability criterion our results support the static stress triggering hypothesis nevertheless our analysis also suggests that results from previous stress triggering studies not considering source model uncertainties may have lead to a biased interpretation of the importance of static stress triggering