applying the coulomb failure function with an optimally oriented plane to the 2008 mw 7 9 wenchuan earthquake triggering the coulomb failure function cff quantitatively describes static stress changes in secondary faults near the source fault of an earthquake cff can be employed to monitor how static stress transfers and then shed some light on the probability of successive events occurring around a source fault in this paper we focus on the cff and particularly on optimally oriented planes we present a unified model to determine an optimally oriented plane and its corresponding coulomb stress then apply the model to the 2003 mw 6 6 bam iran earthquake and the 2008 mw 7 9 wenchuan china earthquake thereby checking its effectiveness our results show that spatial correlation between positive coulomb stress changes and aftershocks are for the 2003 bam earthquake 47 06 when elastic coulomb stress changes are resolved on uniform planes and 87 53 when these are resolved on optimally oriented planes at depth for the 2008 wenchuan earthquake the correlations are 45 68 and 58 20 respectively it is recommended that account be taken of optimally oriented planes when drawing a coulomb stress map for analyzing earthquake triggering effects

observed evolution of linear and nonlinear effects at the dahan downhole array taiwan analysis of the september 21 1999 m 7 3 chi chi earthquake sequence in this paper the site characteristics of the dahan downhole array are studied by analyzing the september 21 1999 m 7 3 chi chi earthquake sequence including the main shock and some aftershocks the four level array 0 m 50 m 100 m and 200 m is located to the north of hualien city in eastern taiwan polarization analysis is used to check the orientation errors of the seismometers at different levels of depth if the surface instrument is chosen as reference the angle between the major polarization axes of the surface and any downhole records is the orientation error that must be corrected for the downhole accelerographs the orientation errors at depths of 50 m 100 m and 200 m are 32 120 and 84 after the corrections the coherency between the surface and downhole records is substantially improved spectral ratio analysis shows that the predominant frequency of the chi chi main shock shifts to a lower frequency we also simulate ground motions at different depths by using the haskell method with a linear velocity structure model the record at surface is chosen as the input motion compared with the observed data ground acceleration can be well reproduced for the aftershocks weak motion events of the september 21 1999 m 7 3 chi chi earthquake however for the chi chi main shock the synthetic waveform cannot match well with the observation neither in amplitude nor in phase this indicates that large ground shaking probably induced the nonlinear site effect at that time and the model used cannot support it

seismicity change revealed by etas pi and z value methods a case study of the 2013 nantou taiwan earthquake abstract on mar 27 2013 a ml6 2 earthquake occurred in the nantou area of central taiwan which caused one death and nearly 90 injured two months later another ml6 3 earthquake struck the same region on june 2 2013 the epicenter of which is close to the march ml6 2 earthquake seismicity is a sensitive indicator of stress rate and inelastic deformation process in crust therefore examination of temporal changes in seismicity is important to understand the preparatory processes of damaging inland earthquakes in this study we applied the epidemic type aftershock sequences model etas model to the earthquake data covering broader taiwan region which is maintained by the central weather bureau cwb of taiwan to investigate precursory temporal changes in seismicity for the ml6 2 nantou earthquake we regard the march ml6 2 and june ml6 3 earthquakes as an event sequence and especially focus on temporal changes in seismicity prior to the ml6 2 event application of more than one model to an earthquake catalog would be informative in elucidating the relationships between seismicity precursors and the preparatory processes of large earthquakes based on this motivation we further applied two different approaches the pattern informatics pi method and the zmap method which is a gridding technique based on the standard deviate z value test to the same earthquake data of cwb as a result we found that the epicenter of the 2013 ml6 2 nantou earthquake was surrounded by three main seismic quiescence regions prior to its occurrence the assumption that this is due to precursory slip stress drop on fault plane or its deeper extent of the ml6 2 nantou earthquake is supported by previous researches based on seismicity data geodedic data and numerical simulations using rate and state dependent friction laws

rupture process of the 2002 mw 7 9 denali earthquake alaska using a newly devised hybrid blind deconvolution method this paper investigates the kinematics of the rupture process of the main event of the mw 7 9 denali alaska earthquake of 3 november 2002 a newly devised hybrid blind deconvolution method is applied to deconvolve teleseismic broadband s wave displacement recordings of the earthquake so as to determine the apparent source time functions astfs at 10 stations located around the epicenter the derived azimuthal angle of slip strongly indicates that the event ruptured unilaterally in an east southeasterly direction as determined by the calculated astfs the total duration of the rupture process was about 74 sec based on the images of the static slip dis tribution three slip concentrated areas were located at depths of less than 10 km maximum slip was about 13 4 m centered at 170 km east of the hypocenter and the average slip on the observed rupture area reached 4 1 m one concentrated rupture velocity area located at 160 180 km east of the hypocenter coincided with a slip concentrated area of maximum slip amplitude strongly suggesting that seismic energy was released rapidly a region of the fault along the strike direction with high rupture velocity 80 120 km also had very low levels of slip indicating that this portion of the fault may well have been relatively weak maximum and minimum rupture velo cities were respectively 3 32 and 2 64 km sec while the average rupture velocity was about 2 95 km sec based on the average rupture velocity and the source duration it is suggested that the principal rupture length of the denali fault must have been greater than 210 km

testing the fossil record sampling proxies and scaling in the british triassic jurassic the quality of the fossil record varies immensely across taxa geographic regions environments and time intervals because much of this variation can be confounded when examining global patterns we present a detailed investigation of the british triassic and jurassic one of the most intensively studied pairs of systems in the world marine jurassic palaeodiversity is at least partly controlled by rock availability and accessibility the terrestrial record is patchier and effects of rock availability are overprinted by a stronger signal of sporadic preservation these results also fit a sea level driven common cause explanation as one would expect to see close correlation between rock availability and palaeodiversity in the marine realm but less so in the terrestrial formation counts and palaeodiversity do not correlate a surprising result given the number of earlier studies that have found close correlations however this study differs from most others in that formation counts and palaeodiversity metrics are derived from independent data sources and so within study redundancy is avoided the study confirms the complexity of rock fossil time series and the likelihood that the fossil record documents a complex mix of potential biological signal common cause signal and rock record and sampling bias it may be impossible to identify a useful simple sampling proxy for the fossil record that captures every bias and sampling error ironically when preservation is good sampling proxies representing rock availability such as outcrop area can be used to predict palaeodiversity but are ineffectual when the fossil record is patchy

origination and extinction through the phanerozoic a new approach abstract temporal patterns of origination and extinction are essential components of many paleontological studies but it has been difficult to obtain accurate rate estimates because the observed record of first and last appearances is distorted by the incompleteness of the fossil record here i analyze observed first and last appearances of marine animal and microfossil genera in a way that explicitly takes incompleteness and its variation into consideration this approach allows estimates of true rates of origination and extinction throughout the phanerozoic substantial support is provided for the proposition that most rate peaks in the raw data are real in the sense that they do not arise as a consequence of temporal variability in the overall quality of the fossil record even though the existence of rate anomalies is supported their timing is nevertheless open to question in many cases if one assumes that rates of origination and extinction are constant through a given stratigraphic interval then

the coulomb stress changes and seismicity rate due to the 1990 mw 7 3 rudbar earthquake we investigate correlation between the coulomb stress changes and the spatial distribution of the aftershocks of the 1990 m w 7 3 rudbar earthquake that occurred on and off the rudbar fault the coulomb stress changes indicate that the rudbar mainshock encouraged parts of the kelishom and kashachal strike slip faults located east of the main rupture as well as parts of the manjil thrust fault located south of the main rupture the central part of the manjil thrust which is sandwiched between two stress shadow zones experienced an increase in coulomb stress we observe that the events before and after the rudbar mainshock have different spatial distribution patterns we find that most of the aftershocks occurred in an area between the kabateh and zardgeli segments where the static coulomb stress is high while few aftershocks occurred in the stress shadow zone that extends to the northwest and southeast of the rudbar rupture the aftershocks that occurred in the stress shadow zones northwest of the baklor segment were related to the continuation of the background seismicity after the mainshock a burst of seismicity following the rudbar earthquake south of the zardgeli segment provides evidence for dynamic stress triggering for the aftershocks that affected these regions for the first 1 3 months after the mainshock we also compare the coulomb stress changes with the seismicity rate and find that the regions with high seismicity rate are in good agreement with the high stress such as the western end of the baklor and an area between the kabateh and zardgeli segments to validate the effects of the coulomb stress on the seismicity rate we resolved stress changes on the aftershock nodal planes and recognize that the aftershocks located between the kabateh and zardgeli segments and the surrounding areas were brought closer to failure

weakening of rock salt by water during long term creep the rheological properties of rock salt are of fundamental importance in predicting the long term evolution of salt based radioactive waste repositories and strategic storage caverns and in modelling the formation of salt diapirs and associated oil traps1 2 the short term high stress rheology of rock salt is well known from laboratory experiments however extrapolation to appropriately low stresses fails to predict the rapid flow seen in certain natural structures furthermore experiments have failed to reproduce the recrystallized microstructure of naturally deformed salt here we report experiments indicating that the above discrepancies can be explained by taking into account the influence of trace amounts of brine trace brine is always present in natural salt but sometimes escapes during experiments our tests on dry dilated salt show more or less conventional dislocation creep behaviour but brine bearing samples show marked weakening at low strain rates this is associated with dynamic recrystallization and a change of deformation mechanism to solution transfer creep because natural rock salt always contains some brine these results cast substantial doubt on the validity of presently accepted dislocation creep laws for predicting the long term rheological behaviour of salt in nature

temporal spatial rupture process of the 1999 chi chi earthquake from iris and geoscope long period waveform data using aftershocks as empirical green s functions a large earthquake m w 7 6 occurred near chi chi taiwan on 20 september 1999 utc and was followed by many moderate size aftershocks in the following days the two largest aftershocks with magnitudes m w 6 1 and 6 2 respectively were used as empirical green s functions egfs to retrieve the source time functions stfs and further image the temporal spatial rupture process of the mainshock for each station two types of stfs were retrieved one from p phases and another from s phases a total of 178 stf individuals were retrieved for source process analysis of the event from the stfs retrieved firstly similarities appeared on the stfs from most stations except that several stfs in special azimuths looked different or odd because of the focal mechanism difference between the mainshock and the egf aftershocks and secondly systematic shape variation with azimuth appeared the analysis of the stfs indicated that this event consisted of two subevents on the average the second event was about 7 sec later than the first one and the first event was about 15 larger than the second one in the moment release rate the total duration time of earthquake rupture process was about 26 sec from the image of the static slip distribution there were two slip concentrated areas on the fault plane and their centers were about 45 km away from each other the maximum slip of about 6 5 m appeared on the northern one the rupture area with the slip greater than 0 5 m was about 80 km long and 60 km wide the maximum stress drop was about 25 mpa 250 bar and the average stress drop on the entire fault was 9 2 mpa 92 bar from the snapshots of the temporal spatial variation of slip and slip rate the rupture initiated at the southern end and stopped at the northern end of the fault which suggested an overall unilateral rupture at a rupture velocity of about 2 5 km sec the depth of the initiation locus was about 20 km the rupture duration times on the subfaults were estimated a good correlation was noticed between the rupture duration time and slip amplitude of the subfaults the larger the slip amplitude the longer the rupture duration time of the subfault the maximum duration time for the subfaults was 16 sec which was about two thirds the total duration time of the earthquake rupture process in the beginning and near the end of the source process the rupture propagated like a self healing pulse of slip manuscript received 21 may 2001

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

ammonoid recovery after the permian triassic mass extinction a re exploration of morphological and phylogenetic diversity patterns the explosive ammonoid rediversification after the permian triassic mass extinction is now well understood in terms of taxonomic richness and biogeography using an updated dataset of early triassic ammonoids we compare morphological disparity and taxonomic richness patterns at the regional and global scales disparity evolved similarly at both scales suggesting a global influence of abiotic factors morphological diversification occurred early in the smithian and a marked contraction of the morphospace took place during the end smithian extinction we confirm that trends in disparity and richness were decoupled during the griesbachian and dienerian three macroevolutionary processes may be involved 1 a nonselective extinction at the permian triassic boundary 2 a dienerian constrained radiation with several homeomorphic genera 3 a potential deterministic extinction during the end smithian crisis we also demonstrate a superfamily imprint upon disparity for the spathian when most superfamilies occupied a restricted part of the morphospace sphaerocones were the most affected by the dienerian and end smithian extinction but explanations remain elusive on the one hand this may be linked to widespread harsh conditions at those times on the other hand as the sphaerocones occurred episodically during the early triassic this might be explained by a relaxing of ecological constraints or simply by convergent evolution supplementary materials the database including measurements of specimens illustrated in previously published plates and of unpublished specimens from utah south china and spiti as well as the number of genera present in each studied substage of the early triassic are available at www geolsoc org uk sup18571

estimation of the source time function based on blind deconvolution with gaussian mixtures it is demonstrated that the blind deconvolution method is fully capable of recovering the unknown green s function and of estimating the source time functions from observed seismic data of small earthquakes based on the assumption of the gaussian mixture model of the green s function the newly formulated algorithm is evaluated using synthetic seismic data along with those of the may 8 1996 mexico earthquake m c 4 6 since the estimated results closely match the theoretical input very well the method is then employed to analyze the source time functions of the july 7 1995 pu li taiwan earthquake m l 5 3 the stations triggered by this event were azimuthally well covered using the estimated source time functions information pertaining to the directivity effect is readily obtained and the actual fault plane of this event is identified thus clearly indicating that this method provides a most efficient way to estimate the source time function of a small earthquake

crystal size distribution csd in rocks and the kinetics and dynamics of crystallization crystal size distributions csds measured in metamorphic rocks yield quantitative information about crystal nucleation and growth rates growth times and the degree of overstepping t of reactions during metamorphism csds are described through use of a population density function n dn dl where n is the cumulative number of crystals per unit volume and l is a linear crystal size plots of ln n vs l for olivine pyroxene and magnetite in high temperature 1000 c basalt hornfelses from the isle of skye define linear arrays indicating continuous nucleation and growth of crystals during metamorphism using the slope and intercept of these linear plots in conjunction with growth rate estimates we infer minimum mineral growth times of less than 100 years at t 10 c and nucleation rates between 10 4 and 10 1 cm3 s garnet and magnetite in regionally metamorphosed pelitic schists from south central maine have csds which are bell shaped we interpret this form to be the result of two processes 1 initial continuous nucleation and growth of crystals and 2 later loss of small crystals due to annealing the large crystals in regional metamorphic rocks retain the original size frequency distribution and may be used to obtain quantitative information on the original conditions of crystal nucleation and growth the extent of annealing increases with increasing metamorphic grade and could be used to estimate the duration of annealing conditions if the value of a rate constant were known finally the different forms of crystal size distributions directly reflect differences in the thermal histories of regional vs contact metamorphosed rocks because contact metamorphism involves high temperatures for short durations resulting csds are linear and unaffected by annealing similar to those produced by crystallization from a melt because regional metamorphism involves prolonged cooling from high temperatures primary linear csds are later modified by annealing to bell shapes

determination of earthquake focal depths and source time functions in central asia using teleseismic p waveforms we developed a new method to determine earthquake source time functions and focal depths it uses theoretical green s function and a time domain deconvolution with positivity constraint to estimate the source time function from the teleseismic p waveforms the earthquake focal depth is also determined in the process by using the time separations of the direct p and depth phases we applied this method to 606 earthquakes between 1990 and 2005 in central asia the results show that the centroid moment tensor solutions which are routinely computed for earthquake larger than m5 0 globally using very long period body and surface waves systematically over estimated the source depths and durations especially for shallow events away from the subduction zone most of the 606 earthquakes occurred within the top 20 km of crust this shallow distribution of earthquakes suggests a high geotherm and a weak ductile lower crust in the region

high resolution dynamics of early jurassic marine extinctions the case of pliensbachian toarcian ammonites cephalopoda abstract the pliensbachian toarcian interval was marked by major environmental disturbances and by a second order mass extinction here we reappraise the taxonomic spatiotemporal and selective dynamics of extinctions over the whole interval by analysing a high resolution dataset of 772 ammonite species from nw tethyan and arctic domains on average 40 65 of ammonite species disappeared during each subchronozone but higher extinction pulses reaching 70 90 prevailed from the margaritatus to the dispansum chronozone the main extinctions corresponding to the gibbosus pliensbachian toarcian boundary semicelatum bifrons variabilis and dispansum events differed in their dynamics suggesting episodes of ecological stress related to climate change regression disturbance in the carbon cycle or anoxia the multi pulsed volcanic activity in the karoo ferrar province could well have triggered these ecological changes in addition ammonites experienced a morphological bottleneck during the gibbosus event 1 ma before the early toarcian diversity collapse typically drops in richness were related both to high extinctions and to declines in origination rates this feature could result from strengthened ecological stresses related to the temporal overlap of environmental disturbances after the early toarcian crisis the recovery of ammonites was rapid 2 ma and probably influenced by a coeval marine transgression supplementary material figures showing a comparison of extinction and origination patterns based on different datasets and variations of the morphospace occupation are available at http www geolsoc org uk sup18381

influence of static stress changes on earthquake locations in southern california earthquakes induce changes in static stress on neighbouring faults that may delay hasten or even trigger subsequent earthquakes1 10 the length of time over which such effects persist has a bearing on the potential contribution of stress analyses to earthquake hazard assessment but is presently unknown here we use an elastic half space model11 to estimate the static stress changes generated by damaging magnitude m 5 earthquakes in southern california over the past 26 years and to investigate the influence of these changes on subsequent earthquake activity we find that in the 1 5 year period following a m 5 earthquake any subsequent nearby m 5 earthquake almost always ruptures a fault that is loaded towards failure by the first earthquake after this period damaging earthquakes are equally likely to rupture loaded and relaxed faults our results suggest that there is a short period of time following a damaging earthquake in southern california in which simple coulomb failure stress models could be used to identify regions of increased seismic hazard

rupture process of the 2001 hyogo ken hokubu japan earthquake mw 5 2 and comparison between the aftershock activity and the static stress changes the 2001 hyogo ken hokubu earthquake m w 5 2 occurred in the northern part of hyogo prefecture in southwestern japan and some clusters of the following aftershock activity extended in a direction different from the mainshock strike direction first we investigate the rupture process of this event by inverting near source strong ground motion waveforms though it is an m 5 class event high quality waveforms were recorded by the high density strong ground motion networks to obtain accurate green s functions for the source inversion we calibrate the crustal structure models by forward modeling of the observed waveforms of small events the rupture process imaged from the inversion of the 0 4 2 0 hz waveforms is relatively simple a large slip area is located around the rupture nucleation point second we examine the effect of the static stress changes caused by the mainshock and the large aftershocks on the following seismicity we calculate the changes of coulomb failure function cff using the heterogeneous slip distribution on the fault plane of the mainshock estimated from the waveform inversion and taking into account the effects of the following large aftershocks in this way we obtain a complex spatiotemporal distribution of cff in the focal area most of the aftershocks separated from the mainshock fault occurred in the positive cff region this result suggests that these aftershocks were strongly affected by cff caused by the mainshock and the preceding large aftershocks

the pliensbachian and tithonian extinction events the claim by raup and sepkoski1 that an approximately 26 myr mass extinction periodicity can be recognized on a global scale at family level over the past 250 myr has excited much attention and provoked speculation about an ultimate extraterrestrial cause2 10 while the purported periodicity can be challenged on grounds of both the inaccuracy of the geological timescale11 and the method of extinction analysis12 there can be no doubting the reality of at least some of the 12 proposed extinction events such as those at or near the end of the permian triassic and cretaceous others are less widely acknowledged further analysis by raup and sepkoski13 confirms the importance of two of these events within the jurassic at the end of the pliensbachian and tithonian stages i demonstrate here that marine invertebrate mass extinctions at approximately these times occurred on a regional not a global scale they can be related to severe reductions in habitat area provoked either by regression of epicontinental sea or by widespread anoxia

recent large earthquakes near cape mendocino and in the gorda plate broadband source time functions fault orientations and rupture complexities the northward migration of the mendocino triple junction is associated with complex faulting within the gorda plate and in the convergent zone between the gorda and north american plates this region has experienced substantial recent large earthquake activity and quantification of these faulting processes is essential for understanding the evolution of the triple junction using an empirical green function deconvolution method for teleseismic and regional surface waves and body waves we obtain relative source time functions for the april 25 1992 cape mendocino thrust earthquake m w 7 2 its two large strike slip aftershocks on april 26 1992 m w 6 5 6 6 and two large strike slip events in the gorda plate that occurred july 13 1991 m w 6 8 and august 17 1991 m w 7 1 the removal of propagation effects using empirical green functions provides unusually detailed source rupture information and indicates that all the ruptures are less than 16 s in duration analyzing the directivity effects observed in the source time functions we resolve rupture directions and corresponding fault orientations for the four largest events and place some constraints on the smaller aftershock significant differences in the rupture duration and stress drop are observed between the cape mendocino mainshock and its two largest aftershocks the mainshock which ruptured westward on a shallow dipping plane either on or paralleling the interplate contact between the gorda and north american plates had a smooth 9 s long rupture with a 0 9 4 6 mpa static stress drop the two largest aftershocks occurred within the uppermost mantle of the gorda plate and have more complex ruptures with total durations of 14 15 s and static stress drops of less than 0 3 mpa perhaps reflecting a difference between mantle and crustal earthquakes in this region the aftershocks appear to have ruptured conjugate strike slip faults accounting for differences in their damage patterns the august 17 1991 gorda plate event ruptured a southwest striking fault while the july 13 1991 event ruptured a southeast striking fault with both events relieving north south compression within the deforming gorda plate the existence of multiple active faults in the region constitutes a significant earthquake hazard associated with the complex stress environment of the migrating triple junction

3 d rock salt fabrics in a shear zone suria anticline south pyrenees abstract the internal geometry of the evaporitic horizons serves as a good indicator of their large scale behaviour however the determination of the strain ellipsoid inside the deformed salt bodies can often be difficult moreover the relationship between the bulk strain ellipsoid and the grain shape ellipsoid is not straightforward and two parameters orientation and the dimension of the grain shape ellipsoid need evaluation the grain shape ellipsoid is not an indicator of the dimensions of the bulk strain ellipsoid the increase in shear strain led initially to a growth in grain volume followed by a reduction to a value near the original volume specifically due to the long axis change the orientation of the grain shape ellipsoid runs parallel to that of the strain ellipsoid after a certain amount of deformation these changes were accompanied by the growth of a new tectonically oriented grain population the rapid spatial changes in morphology contrast with the constant and strong 100 texture the intracrystalline deformation mechanism consistent with this texture is the 110 1 1 0 slip system nevertheless a mechanism such as fluid assisted grain boundary migration might have also taken place to account for the grain volume changes

slip distribution of the mw 5 9 1999 athens earthquake inverted from regional seismological data 1 we studied the kinematic rupture process of the moderate magnitude mw 5 9 1999 athens earthquake using broadband seismic recordings at regional distances the apparent source time functions astf obtained by retrieving the wave propagation and site effects from the seismic recordings using an empirical green s function method indicate a rather complex rupture with a source directivity primarily pointing towards athens to further characterize the faulting we inverted the astfs for the kinematic history of the rupture using a damped least square inversion scheme with inequality constraints the rupture extent is delimited by a 10 km along strike 20 km along dip zone the mean slip amplitude on the observed rupture area is equal to 25 cm the slip concentrates in two elongated zones with amplitudes reaching locally 60 cm the total rupture lasted between 5 and 6 s

source process of the 4 june 2000 southern sumatra indonesia earthquake source parameters of the 4 june 2000 southern sumatra indonesia earthquake m s 8 0 were estimated from teleseismic body waves recorded by long period seismograph stations of the global seismic network the analysis shows that the earthquake had a mechanism with a strike of 199 a dip of 82 and a rake of 5 and ruptured unilaterally from the northeast to the southwest nearly perpendicular to the java trench the focal mechanism of mainly left lateral strike slip with a small thrust component explains well the reason why no tidal waves were generated by this great earthquake the double couple component of this earthquake was 1 5 10 21 nm the compensated linear vector dipole component was 1 2 10 20 nm and the explosion component was 5 9 10 19 nm the analysis indicates that the source duration was about 16 sec the fault area is about 95 km in length and 60 km in width the average static slip is estimated to be about 11 m and the average static stress drop 90 mpa

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

multifractal and white noise evolutionary dynamics in jurassic cretaceous ammonoidea for more than a decade there has been interdisciplinary debate on whether fossil origination and extinction time series show evidence of self organized criticality soc or some other more complex hierarchical structure analyses of a new data set of jurassic and cretaceous ammonoid genera demonstrate that these taxonomic subgroups do not reproduce the patterns seen in larger data sets that pool disparate taxa rather originations and extinctions in these ammonoids show no evidence of soc limited evidence for a hierarchical multifractal pattern and at least within the suborder ammonitina evidence consistent with a white noise signal although a white noise pattern has been identified previously in an ammonoid family diversity time series the significance of such a result for ammonoid genus originations and extinctions is discussed here for the first time this white noise pattern indicates that processes acting on short time scales less than a few million years dominate the ammonitina origination and extinction records producing a nonhierarchical diversity dynamic because origination events in one interval do not appear to trigger originations in subsequent intervals ammonite evolutionary radiations were likely to be extremely rapid and driven by physical rather than biological opportunities for diversification

determinants of extinction in the fossil record the causes of mass extinctions and the nature of biological selectivity at extinction events are central questions in palaeobiology it has long been recognized however that the amount of sedimentary rock available for sampling may bias perceptions of biodiversity1 2 3 4 5 6 7 and estimates of taxonomic rates of evolution5 6 7 8 this problem has been particularly noted with respect to the principal mass extinctions5 6 7 8 9 10 11 12 here we use a new compilation of the amount of exposed marine sedimentary rock to predict how the observed fossil record of extinction would appear if the time series of true extinction rates were in fact smooth many features of the highly variable record of apparent extinction rates within marine animals can be predicted on the basis of temporal variation in the amount of exposed rock although this result is consistent with the possibility that a common geological cause determines both true extinction rates and the amount of exposed rock it also supports the hypothesis that much of the observed short term volatility in extinction rates is an artefact of variability in the stratigraphic record

reef expansion during the triassic spread of photosymbiosis balancing climatic cooling the paleoreefs database indicates that reef abundance increased profoundly during the triassic period from a pronounced low in the early triassic to a major peak in the norian this expansion is also evident when standardizing for sampling corresponding to the reef expansion is a relative increase of scleractinian corals as reef builders whereas the contribution of hypercalcifying sponges and microbes decreased during the triassic the numerical expansion of corals is paralleled by a proportional increase of morphological features that are suggestive of photosymbiosis such that the norian reef boom might be explained by the spread of photosymbiosis in corals the geographical expansion of reefs was far less pronounced especially concerning palaeolatitude late triassic reef growth was limited to more or less the same latitudinal range as modern reefs as oxygen isotope data and new modeling results indicate declining temperatures and co2 concentrations during the late triassic the lack of latitudinal expansion might be attributed to global cooling reef development during the triassic can thus be explained by the evolutionary spread of photosymbiosis balancing the effects of climatic cooling

extinction trajectories of benthic organisms across the triassic jurassic boundary abstract we analysed diversity and abundance patterns of benthic organisms across the triassic jurassic t j boundary based on the paleobiology database pbdb which compiles palaeontological collection data on a global scale while sepkoski s sepkoski j j jr 2002 a compendium of fossil marine animal genera bulletins of american paleontology 363 1 563 compendium on the stratigraphic ranges of marine animal genera suggests that the dominant macrobenthic groups of the late triassic experienced significant extinctions prior to the t j boundary a significant end triassic extinction peak is evident from pbdb s data this rhaetian extinction peak is found in both an analysis of the raw data of stratigraphic ranges and a sample standardized analysis of occurrence data 41 of all mesobenthic and macrobenthic genera crossing the norian rhaetian boundary became extinct within the rhaetian although this rate suffices to characterize the end triassic extinction as a true mass extinction against a middle triassic to middle jurassic background significantly reduced rhaetian origination rates add to the strong diversity depletion in the earliest jurassic as for other mass extinctions evidence for selective extinction is meagre when the analysis is limited to the boundary interval alone and when focused on taxonomic and ecological characteristics of individual genera when taxa are separated by environmental preferences however several determinants of extinction risk become evident suggesting that reef dwellers had a significantly higher extinction risk than level bottom dwellers taxa with an inshore preference were more strongly affected than offshore taxa taxa preferring carbonate substrates were more strongly hit than taxa preferring siliciclastic substrates and taxa preferentially inhabiting low latitudes had higher extinction rates than taxa more common at intermediate and high latitudes much of this selectivity is not independent and also seen in the intervals of background extinctions suggesting that the end triassic mass extinction represents an intensification of background extinctions but not a qualitatively different macroevolutionary regime one possible exception is related to preferences for depositional environments suggesting a selective rhaetian extinction in reefs and inshore settings

the fossil record and spatial structuring of environments and biodiversity in the cenozoic of new zealand there is increasing evidence to suggest that drivers of bias in the fossil record have also affected actual biodiversity history so that controls of artefact and true pattern are confounded here we examine the role of spatial structuring of the environment as one component of this common cause hypothesis our results are based on sampling standardized analyses of the postmiddle eocene record of shelf molluscs from new zealand we find that spatial structuring of the environment directly influenced the quality of the fossil record contrary to our expectations however we find no evidence to suggest that spatial structuring of the environment was a strong or direct driver of taxic rates net diversity or spatial structuring in mollusc faunas at the scale of analysis stage to stage variation in sampling standardized diversity over the past 40 ma exhibits two superficially independent dynamics a changes in net diversity were associated primarily with changes in origination rate and b an unknown common cause related extinction rate to the quality of the fossil record and indirectly to spatial structuring of the environment we suggest that tectonic drivers manifest as second order sequence stratigraphic cycles are likely to have been a key element of this common cause our perceptions of biodiversity history are influenced strongly by secular biases in the quality of the fossil record e g raup 1976 peters foote 2001 many authors have argued against a literal reading of the record and various techniques to minimize the impacts of sampling biases have been developed e g connolly miller 2001 foote 2003 alroy 2010 in addition however a number of studies have proposed that the relationship between sampling biases and diversity dynamics may be complex these studies have suggested that there are latent common cause factors such as plate tectonics and sea level change which have affected simultaneously the quality of the fossil record and true macroevolutionary history e g newell 1952 sepkoski 1976 smith 2001 peters foote 2002 foote 2003 peters 2005 2006a wall et al 2009 demonstrating potential common causes separating their effects from simple preservation and sampling biases and interpreting them mechanistically are challenging problems that must be solved if palaeobiologists are to resolve true patterns and processes of macroevolutionary change through geological time the aim of the present paper is to examine the role of spatial structuring of the environment and of biodiversity in driving both macroevolutionary dynamics and biases in the fossil record fig 1 specifically we are interested in the extent to which partitioning of marine environments may have influenced biodiversity and the preservation of that diversity in part the study is founded on the expectation that the geographical range and evolution extinction dynamics of organisms occupying a particular habitat will be related to the area and fragmentation of that habitat e g rosenzweig 1995 maurer nott 1998 at the same time we anticipate that the quality of the marine fossil record will be influenced by for example the areal extent and distribution of depositional v non depositional or erosional environments factors that are also likely to affect habitat fragmentation and diversity to test the role of spatial structuring in the common cause hypothesis we use the exemplary well studied and relatively complete fossil record of post middle eocene level bottom shelf molluscs from new zealand e g crampton et al 2003 2006a this record is approximately from mcgowan a j smith a b eds comparing the geological and fossil records implications for biodiversity studies geological society london special publications 358 105 122 doi 10 1144 sp358 8 0305 8719 11 15 00 the geological society of london 2011 40 complete at the species level for the neogene as estimated using two very different approaches cooper et al 2006 crampton et al 2006a in this paper therefore we derive an index for spatial heterogeneity of the environment and adapt established indices of spatial differentiation in the new zealand cenozoic mollusc fauna we then compare time series of these measures to time series of sampling probability a proxy for the quality of the fossil record and sampling standardized estimates of overall species richness origination rate and extinction rate all analyses and computations reported here were undertaken using r r development core team 2010 materials and methods

a midcrustal ramp fault structure beneath the taiwan tectonic wedge illuminated by the 2013 nantou earthquake series 1 taiwan s active mountain belt is a spotlight for orogenic studies and was first used to test the critical taper wedge mechanics the concept of an orogenic wedge above a shallow detachment surface has been highly influential on current understanding of orogenic processes in taiwan however the recent ml 6 2 and ml 6 5 2013 nantou reverse faulting earthquakes in central taiwan have nucleated below the proposed detachment indicating that active mountain building is occurring below the orogenic wedge we estimate the coseismic slip distributions and fault geometry using the uniform stress drop slip inversions the earthquakes occur on essentially the same 30 dipping fault plane ramping up from 20km depth near a cluster of 1999 chi chi earthquake aftershocks to the shallow detachment and the chi chi fault plane the fault could be a deep extension of a mature shallow fault or a newly developed deep ramp fault that is not reflected in the surface geology

comparison of taxonomic diversity strontium isotope and sea level patterns sepkoski s compendium of 28 730 marine genera was analyzed with a view toward comparing taxonomic diversity strontium isotope stratigraphy and sea level changes the fossil record analyses discriminated between origination extinction and pass through genera and collectively delineated changes in number of genera with time at the largely stratigraphic stage level with notable exceptions of the cretaceous and tertiary taxonomic diversity generally paralleled both strontium isotope stratigraphy and sea level changes sampling bias was suggested in the tertiary where an increase in genera numbers toward the recent opposed the downward trends of both strontium isotope and sea level curves the removal of all recent genera from the sepkoski database confirmed the bias in producing complimentary downward trends in all curves regression analysis of taxonomic diversity with respect to sea level extent and time duration explained 82 of the variability of the remaining data sea level fluctuations are not always accompanied by significant changes in taxonomic diversity but strontium isotope analyses offers the potential of constraining the extent to which the magnitude of changes are associated with time duration

the first half of tetrapod evolution sampling proxies and fossil record quality abstract the first half of tetrapod evolution witnessed substantial diversification of the clade and several major turnovers and mass extinctions in the time since their origin more than 380 myr ago to the beginning of the middle jurassic 175 myr ago tetrapods apparently diversified fitfully reaching their highest level in the middle permian and showing major diversity declines in the late moscovian early permian wordian lower wuchiapingian end permian lower anisian lower ladinian late triassic lower norian to upper rhaetian end triassic and early jurassic upper sinemurian lower pliensbachian of these diversity drops only the end permian and end triassic correspond to recognised mass extinctions and the late moscovian and early norian drops to other previously identified environmental crises the remainder could be real extinction or turnover events or partially artefacts of biased sampling there are strong correlations between formation counts and tetrapod palaeodiversity suggesting a sampling component in the raw data but the covariation is not uniform through the whole time span being poor from devonian to middle permian and better from late permian to early jurassic there is limited evidence for covariation between the tetrapod palaeodiversity time series and other putative sampling metrics such as specimen completeness numbers of publications map areas gap bounded sedimentary units rock volumes formations and fossil collections modelling by multiple correlations shows that formation count is generally the best explanatory model either on its own or combined with other sampling time series however it is not clear that formation count is independent of the palaeodiversity time series because rises and falls in both signals could reflect variations in original diversity or in preservation or in sampling

a scale of greatness and causal classification of mass extinctions implications for mechanisms a quantitative scale for measuring greatness g of mass extinctions is proposed on the basis of rate of biodiversity diminution expressed as the product of the loss of biodiversity called magnitude m and the inverse of time in which that loss occurs designated as intensity i on this scale the catastrophic cretaceous tertiary k t extinction appears as the greatest since the ordovician and the only one with a probable extraterrestrial cause the end permian extinction was less great but with a large magnitude m and smaller intensity i only some of its individual episodes involved some semblance of catastrophe other extinctions during the phanerozoic with the possible exception of the end silurian diversity plunge were parts of a forced oscillatory phenomenon and seem caused by marine and land habitat destruction during continental assemblies that led to elimination of shelves and after the devonian rain forests and enlargement of deserts glaciations and orogenies that shortened and thickened the continental crust only exacerbated these effects during the mesozoic and cainozoic the evolution of life was linearly progressive interrupted catastrophically only at the k t boundary the end triassic extinction was more like the paleozoic extinctions in nature and probably also in its cause by contrast the current extinction resembles none of the earlier ones and may end up being the greatest of all

marine diversity through the phanerozoic problems and prospects the fossil record provides direct evidence of how diversity has changed over time but cannot be taken at face value diversity curves constructed from counting taxa in the rock record are seriously biased by unevenness of geographical and stratigraphical sampling effort inequality in the rock record available for sampling and inconsistent taxonomic practice sample standardization removes some bias but does not overcome more general incompleteness problems modelling that accounts for potential biases is a newer approach but needs accurate estimates of rock record and consistent taxonomic data uncertainty remains over whether the steep rise in diversity over the last 100 ma is real or reflects sampling bias the repeated rise and fall of marine diversity over time correlates closely with the areal extent of sedimentary deposits and independent estimates of the quality of the fossil record implying a common driving factor namely tectonically mediated sea level change however whether changes in diversity are primarily biological in origin or reflect sampling artefact remains contentious there is a distinct possibility that many of the apparent rises and falls in diversity over the phanerozoic including most of the mass extinctions arise either partially or entirely from rock record bias

using remote sensing and a geographic information system to quantify rock exposure area in england and wales implications for paleodiversity studies rock outcrop area and number of sedimentary formations have been widely used as sampling proxies in paleodiversity studies and have often been found to correlate with apparent paleodiversity however rock exposure area is a better proxy for the amount of sedimentary rock available for study than the widely used measures of outcrop area i e map area or number of formations with the use of remote sensing and a geographic information system gis it is possible to quantify rock exposure area accurately on a regional scale rock exposure area does not correlate well with either outcrop area or number of sedimentary formations and the proportion of rock exposed in different areas can vary considerably with proximity to the coast bedrock age lithology land use and elevation therefore this suggests that the correlation of paleodiversity and rock volume estimates is best explained by a common cause hypothesis rather than a geologic sampling bias hypothesis gis methods offer an efficient and accurate method of quantifying regional sedimentary rock exposure and may provide a helpful approach to assessing rock record bias on patterns in the fossil record

crystal size distribution csd in rocks and the kinetics and dynamics of crystallization ii makaopuhi lava lake crystal size distribution csd theory has been applied to drill core samples from makaopuhi lava lake kilauea volcano hawaii plagioclase and fe ti oxide size distribution spectra were measured and population densities n were calculated and analyzed using a steady state crystal population balance equation n n0 exp l g slopes on ln n versus crystal size l plots determine the parameter g a product of average crystal growth rate g and average crystal growth time the intercept is j g where j is nucleation rate known temperature depth distributions for the lava lake provide an estimate of effective growth time allowing nucleation and growth rates to be determined that are independent of any kinetic model plagioclase growth rates decrease with increasing crystallinity 9 9 5 4 10 11 cm s as do plagioclase nucleation rates 33 9 1 6 10 3 cm3 s ilmenite growth and nucleation rates also decrease with increasing crystallinity 4 9 3 4 10 10 cm s and 15 2 2 10 3 cm3 s respectively magnetite growth and nucleation rates are also estimated from the one sample collected below the magnetite liquidus g 2 9 10 10 cm s j 7 6 10 2 cm3 s moments of the population density function were used to examine the change in crystallization rates with time preliminary results suggest that total crystal volume increases approximately linearly with time after 50 crystallization a more complete set of samples is needed for material with 50 crystals to define the entire crystallization history comparisons of calculated crystallization rates with experimental data suggests that crystallization in the lava lake occurred at very small values of undercooling this interpretation is consistent with proposed thermal models of magmatic cooling where heat loss is balanced by latent heat production to maintain equilibrium cooling

stratigraphic distribution of marine fossils in north america the stratigraphic distribution of fossils reflects a combination of physical and biological factors although many studies have addressed the distribution of fossils at a basin scale and within sedimentary sequences spanning 10 4 10 6 yr little is known about the distribution of fossils within longer duration sedimentary successions covering broad geographic regions here we combine a north american macrostratigraphic database with fossil occurrence data from the paleobiology database to quantify the stratigraphic distribution of fossils within hiatus bound marine sedimentary rock packages that have a mean duration of 10 7 yr we find that fossil collections and marine genera are when averaged over all phanerozoic sedimentary rock packages more abundant than expected in the top 40 of package durations and less common than expected in the bottom 25 generic first and last appearance datums fads and lads in north america are not randomly distributed among fossil collections instead lads are more common than expected in the top 20 of package durations whereas fads are more uniformly distributed this result is not consistent with an unconformity related sampling bias but is indicative of greater congruence in the temporal scales over which genus extinction and regression occur than genus initiation and transgression these results support the hypothesis that macroevolution particularly genus extinction and large scale patterns of sedimentation share a common set of forcing mechanisms that are related to the formation and destruction of shallow marine habitats

covariation in macrostratigraphic and macroevolutionary patterns in the marine record of north america students of earth history have long recog nized the correlation between the quantity of preserved sedimentary rock and the diversity of life recorded as fossils but paleontologists have yet to determine whether this pattern refl ects a causal relationship or a unidirec tional sampling bias in fossil data imposed by preserved rock quantity distinguishing between these two alternatives has been com plicated by the fact that many of the basic patterns of paleontologic and lithologic co variation have yet to be quantifi ed rigorously here we present the fi rst analyses of the co variation between the macrostratigraphic and macroevolutionary histories of north america based on geographically and tem porally explicit co occurrences of rocks and fossils the analyses use independent quan titative summaries of the stratigraphic and fossil records by integrating the paleobiology database paleodb and macrostrat a mac rostratigraphy database for north america which allows a more direct comparison of the stratigraphic and biological histories of the continent than has heretofore been possible within the macrostrat database the rock re cord is divided into discrete packages of sedi ment that are bound by hiatuses resolvable at the stage level using per interval per pack age rates of sediment package initiation and truncation and genus fi rst and last appear ances herein regional origination and extinc tion we fia substantially stronger positive correlation between sediments and biology for extinction like parameters than we do for origination like parameters four of the largest coincident pulses of regional extinc tion and sediment truncation occur during the widely recognized end ordovician late permian end triassic and end cretaceous mass extinction intervals a further compari son of the global ranges of north american genera to north american macrostratigra phy indicates that the regional and global extinction of genera are more likely to oc cur in the same stage than are global and regional originations together these results suggest that our general understanding of biodiversity dynamics from the fossil record may not be strongly biased by the preserva tion of sediments and leaves open the pos sibility that certain large perturbations to the earth system are responsible for major changes of state in both the sedimentary and biological systems

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

pattern of marine mass extinction near the permian triassic boundary in south china the meishan section across the permian triassic boundary in south china is the most thoroughly investigated in the world a statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251 4 million years ago coincident with a dramatic depletion of 13ccarbonate and an increase in microspherules

shear structures in anhydrite at the base of thrust sheets antalya southern turkey abstract minor scale structures in anhydrite layers and pods within one thrust contact of the antalya thrust system are described folds whose size range from some centimeters to several meters display a wide variety of attitudes their axes are curvilinear and vary from orthogonal to subparallel to the stretching lineation leading to sheath folds and eyed type sections shear bands are frequent in alternating white pure and brown clay rich anhydrite regularly spaced extensional shear bands form typical tilted block patterns in homogeneously foliated anhydrite they form isolated meter long extensional shear bands with brecciation along their central planes reverse fault type shear bands are associated with meter scale reclined folds with axes subperpendicular to the stretching lineation normal and reverse fault type shear bands are self exclusive and both indicate a sense of shear toward the south at the scale of thrust system a model of progressive deformation of the anhydrite layers is presented anhydrite layers which have undergone a strong unstable shearing deformation along a thrust have been boudinaged and now form elongate asymmetric pods in thinned layers normal extensional shear bands developed and recumbent fold axes are strongly reoriented toward the direction of the stretching lineation in the thickened layers reverse fault type shear bands developed particularly within the inverted limbs of asymmetric reclined folds whose axes are at a high angle to the stretching lineation

textural evolution of synthetic anhydrite halite mylonites the rheology and textural evolution of mylonites for both crustal and mantle rocks are generally poorly understood stress and strain partitioning between shear zones and wall rock foliation development flow mechanisms and constitutive relations are little known to address these problems we have begun an experimental study in which anhydrite and halite aggregates are deformed in simple shear homogeneous mixes at intervals of 10 vol of anhydrite and halite powders of 90 to 180 m grain size comprise the 1 mm thick zone between the 35 precut surfaces in 2 by 4 cm right circular cylinders of anhydrite all specimens are confined under 200 mpa pc and tested at 300 c t producing an aggregate of near zero porosity all specimens are shortened at an axial displacement rate of 5 l0 6 cm s to shear strains of about 2 0 most stress strain curves have a similar form they are characterized by an initial linear response that is followed by a work hardening region that leads to a plateau of constant stress whilst strain continues to accumulate this apparent steady state behavior is followed by a drop in stress to a second apparent steady state stress the strain at this stress drop and the magnitude of the drop increase with increasing anhydrite content the second lower steady state stress for all mixes approaches that of sheared pure halite optical examination of the fabrics shows that straining under the initial apparent steady state is accommodated by both mineral phases a foliation evolves as defined by mineral segregation and grain elongation of halite at 15 to 30 to the shear zone walls anhydrite grains rotate until their 001 010 slip system parallels the foliation the anhydrite also exhibits twin lamellae kinks and microfractures following the stress drop rheologic behavior is dominated by dynamic recovery in halite the recrystallized grain size increasing consistent with the lower stress level

deconvolution of teleseismic body waves for enhancing structure beneath a seismometer array abstract we discuss three stacking deconvolution techniques for enhancing signal of earth structure contained in the seismograms of teleseismic body waves recorded by a seismometer array the goal of the deconvolution is to remove from the seismograms the complications due to the source for three component data the removal of the source can be efficiently achieved by deconvolving one component from another as in the receiver function analysis in the case of an array if the structure beneath individual stations varies the source wavelet can be estimated and removed from the seismograms by stacking this allows structural analysis in the situations when only single component seismometers are used or when a particular component can provide additional independent information here we compare the efficacy of conventional time domain stacking cepstral averaging and autocorrelation stacking the latter is a new approach developed here for cepstral averaging we present conditions that stabilize the convergence examples are presented using synthetics and real data from a broadband seismic array experiment conducted in the cascadia subduction zone oregon in 1993 to 1994 data from subduction zones are particularly well suited because of the spatially rapidly varying structure we find that all three methods work well for low frequencies which are not sensitive to the time alignment of the seismic traces the latter two methods do not require precisely aligned seismograms and their advantage becomes evident at higher frequencies where the appropriate time alignment is harder to achieve at high frequencies time domain stacking is likely to fail

the cretaceous tertiary biotic transition mass extinctions are recognized through the study of fossil groups across event horizons and from analyses of long term trends in taxonomic richness and diversity both approaches have inherent flaws and data that once seemed reliable can be readily superseded by the discovery of new fossils and or the application of new analytical techniques herein the current state of the cretaceous tertiary k t biostratigraphical record is reviewed for most major fossil clades including calcareous nannoplankton dinoflagellates diatoms radiolaria foraminifera ostracodes scleractinian corals bryozoans brachio pods molluscs echinoderms fish amphibians reptiles and terrestrial plants macrofossils and palynomorphs these reviews take account of possible biasing factors in the fossil record in order to extract the most comprehensive picture of the k t biotic crisis available results suggest that many faunal and floral groups ostracodes bryozoa ammonite cephalopods bivalves archosaurs were in decline throughout the latest maastrichtian while others diatoms radiolaria benthic foraminifera brachiopods gastropods fish amphibians lepidosaurs terrestrial plants passed through the k t event horizon with only minor taxonomic richness and or diversity changes a few microfossil groups calcareous nannoplankton dinoflagellates planktonic foraminifera did experience a turnover of varying magnitudes in the latest maastrichtian earliest danian however many of these turnovers along with changes in ecological dominance patterns among benthic foraminifera began in the latest maastrichtian improved taxonomic estimates of the overall pattern and magnitude of the k t extinction event must await the development of more reliable systematic and phylogenetic data for all upper cretaceous clades

ecological disruption precedes mass extinction mass extinctions are dramatic features of the fossil record in which extinction risk is substantially elevated above background levels although extinction risk varies markedly over geologic time as well as geographically it was particularly elevated and global in extent during the so called big five events the late ordovician late devonian end permian end triassic and end cretaceous 1 these events were originally recognized by variations in extinction rate in marine animal families and their importance remains in analyses at the genus level and that account for variable preservation over geologic time 2 3 increasing attention has concentrated on understanding the ecological effects of mass extinction and other lesser but still significant extinction episodes 4 10 in pnas sheets et al 11 document the ecological changes in marine planktonic communities not only during but preceding the late ordovician 447 444 ma mass extinction

rupture properties of the giant sumatra earthquake imaged by empirical green s function analysis empirical green s function egf analysis has remained little used to image the rupture properties of the giant 26 december 2004 sumatra earthquake the 2 november 2002 foreshock m w 7 2 close to the mainshock epicenter gives us the opportunity to use its waveforms to empirically simulate the rayleigh wave propagation of the sumatra earthquake we first show that the exceptional size of the sumatra earthquake does not prevent use of the egf technique four aftershocks m w 5 9 6 1 distributed along the sumatra andaman trench are shown to have consistent rayleigh waves for periods between 100 and 200 sec at a lower frequency we present two large earthquakes of the mexican subduction zone m w 7 2 7 3 close to the selected egf magnitude for which long period green s functions 100 2000 sec remain very similar even if event epicenters are separated by about 650 km this justifies the possibility of using the 2002 foreshock as an egf for the whole rupture process of the sumatra earthquake and shows more generally the very broad range of application of egf technique then a specific analysis reveals that seismic moment magnitude is close to 9 1 seismic moment equal to 5 6 10 22 n m moment release analysis along the sumatra andaman trench shows two main slip episodes one next to the northern extremity of sumatra 20 m slip and the other one along the nicobar islands 10 m slip with a global extent of 1150 1200 km rupture velocity varies between values around 2 5 km sec in the first half of the rupture and values closer to 2 km sec in the second half total duration imaged by rayleigh waves is 580 sec 20 sec and no activity of the fault is found in the time scale between 600 and 2000 sec in the hypothesis of even longer timescale slip this phenomenon would be of the order of 10 20 of the global moment and likely restricted to the andaman islands

coulomb stress triggering of earthquakes along the atalanti fault central greece two april 1894 m6 events and stress change patterns abstract two m6 events occurred 15 20 km apart in central greece on april 20 and april 27 1894 we identify the april 27 1894 rupture 2nd in the sequence with the atalanti segment of the atalanti fault zone because of unequivocal surface rupturing evidence reported by skouphos skouphos t 1894 die swei grossen erdbeben in lokris am 8 20 und 15 27 april 1894 zeitschrift ges erdkunde zu berlin vol 24 pp 409 474 coulomb stress transfer analysis and macroseismic evidence suggest that the april 20 1894 event 1st in the sequence may be associated with the martinon segment of the same fault zone our stress modelling suggests that this segment may have ruptured in an m 6 4 event producing a 15 km long rupture which transferred 1 14 bar in the epicentral area of the april 27th 1894 event thus triggering the second m 6 6 earthquake along the atalanti segment and producing a 19 km long rupture we also examined three alternative fault sources for the first event however all these produce smaller stress stresses for triggering the second event the proposed slip model for the second earthquake is capable of producing coastal subsidence of the order of centimetres to decimetres which fits the geological data the 1894 earthquake sequence was followed by a difference in the timing of subsequent m 5 events in each of the relaxed areas stress shadows a negative change in coulomb failure stress 0 6 bar which terminated between 22 37 years north and 80 years south

mylonitic deformation of evaporites in decollements examples from the southern alps france abstract the ductile deformation of triassic evaporites is described in two decollements from the southern alps of france the arc de nice and arc de digne nappes we show that deformation is not chaotic as is commonly considered on the contrary it is commonly well organized and is consistent with progressive shearing typical shear structures include mylonitic foliation stretching lineations folds of various shapes and orientations a type folds and sheath folds asymmetrical pressure shadows composed of gypsum fibres shear bands and boudinage at two sites lineation directions and analysis of shear criteria allow the kinematics of nappe emplacement to be determined computer modelling of pressure shadows allows deformation mechanisms and strain measurements to be determined the results of the analysis can be placed in the context of the regional framework of the two decollements 1 deformation at the nice site corresponds to dextral wrenching on a lateral ramp of the decollement along the western limit of the arc de nice nappe deformation in the ductile fault zone is close to simple shear 2 deformation in the second site is associated with a ramp which affects the decollement in front of the arc de digne nappe the deformation corresponds to shearing towards the southwest including a pure shear component this result can be explained by taking into account the effects of the ramp geometry upon the deformation in the decollement this shows that deformation analysis of evaporites in decollements can be used to understand the mechanisms and kinematics of nappe emplacement

the shaping of salt diapirs abstract six parameters shape the geometry of passive diapirs associated with stiff overburden rates of salt supply s dissolution d sediment accumulation a erosion er extension e and shortening sh these parameters change in space and time and hence influence the geometry of the structure as it forms a complex six parameter plot representing the evolution history of a salt diapir can be simplified into three separate graphs this study recommends adding to plots of s against a a second of rate of salt supply s this time with extension rate e and a third of rate of sediment accumulation a plotted against extension rate e integrating these three plots on a single diagram results in a complete description of the evolution history of a diapir when it is applied to three dimensional data however if applied to a profile the plot shows only the two dimensional evolution history of the diapir lateral forces extension or compression have a significant role in moulding the geometry of a salt diapir by influencing the space which it occupies by incorporating extension in the moulding plots of salt diapirs this study introduces the rate of sediment accumulation multiplied by extension e a as a significant factor in moulding salt diapirs by using this rate against the rate of salt supply this study redefines the conventionally accepted interpretation of upward narrowing upward widening and columnar diapirs upward narrowing diapirs form when the rate of salt supply is less than the rate of sediment accumulation multiplied by extension upward widening diapirs form when the salt supply is greater than the rate of sediment accumulation multiplied by extension columnar diapirs form when the rate of salt supply is equal to the rate of sediment accumulation multiplied by extension this new relationship explains the absence of columnar and upward widening diapirs in passive margins where thin skinned extension dominates and emphasizes the significance of lateral movement extension and shortening in moulding the geometry of salt diapirs

rupture directivity effect and stress heterogeneity of the 2013 nantou blind thrust earthquakes taiwan abstract we investigated broadband evidence of the rupture directivity effect and estimated stress drop for the 2013 nantou blind thrust earthquakes the 0327 and 0602 crustal events from three individual analyses using empirical green s functions deconvolution source time function analysis source spectral ratio analysis and broadband waveform modeling of a strong motion generation area although these two adjacent events have similar focal mechanisms the 0327 event shows only up dip directivity to the west with an estimated stress drop of 9 0 mpa and the 0602 event displays significant rupture directivity to the southwest with an estimated stress drop of 14 2 mpa the obvious variance in the rupture behavior and stress drop of these two nearby events which might be related to immature blind faulting suggests that this region requires additional study of the stress heterogeneity to better assess the seismic hazard

coulomb stress changes and seismicity in central taiwan due to the nantou blind thrust earthquakes in 2013 abstract due to the two earthquakes 27 march 2013 event m l 6 2 namely 0327 event and 2 june 2013 event m l 6 5 namely 0602 event occurring at the nantou area of the central taiwan we investigate the relationship between the coulomb stress changes and the seismicity in the paper we first employed the refined homomorphic deconvolution method to invert the kinematic source processes of these two earthquakes from the teleseismic data recorded by incorporated research institutions for seismology iris and then calculated the coulomb stress changes of these two events the total durations of the rupture process for the 0327 and 0602 events were 12 s and 15 s respectively the epicenter of the 0602 event and the epicenters of the aftershocks m l 3 of the 0327 event were concentrated in a region with positive coulomb stresses caused by the 0327 event this indicates that the derived source process was available and coincided with physical properties in a manner that strongly suggests that the 0602 event was triggered by the 0327 event according to the coulomb stress changes caused by the 0602 event at a depth of 4 km and its vertical cross section most of the aftershocks m l 3 of the 0602 event were located in a region with positive coulomb stress changes greater than 0 1 bar in addition almost all the epicenters of the earthquakes m l 3 in central taiwan between july 15 2013 and january 27 2015 were located in a region with positive coulomb stress changes at a depth of 6 km contributed by the 0327 and 0602 events these findings indicate that if the background stress in the central taiwan is intense high the coulomb stress changes contributed by the two events may affect the seismicity of central taiwan in this period of time and that a region with extreme positive coulomb stress changes may be the place in which potential earthquakes will occur in the future moreover the proposed inversion method can derive the proper source model efficiently without any statistical assumptions

completeness of the known graptoloid palaeontological record using a high resolution chronology of graptoloid first and last appearances we apply mathematical models that allow the simultaneous inference of the probability distribution of species durations and the effective sampling rate relating those durations to the observed stratigraphic ranges this approach allows the completeness of the documented palaeontological record of graptoloids to be assessed we estimate that c 75 of species in the geographical regions that contribute to the stratigraphic data have been sampled and that of those species known from more than a single stratigraphic horizon c 85 of their original durations on average are represented by their global composite stratigraphic ranges as expected in light of their biostratigraphic importance graptoloids have one of the most completely documented records among groups of fossil organisms we expect that application of the methods used herein will show comparably complete records for other biostratigraphically relevant groups supplementary material the r code and data are available at https doi org 10 6084 m9 figshare c 4547174

phanerozoic trends in skeletal mineralogy driven by mass extinctions changes in ocean chemistry that favoured the precipitation of aragonite or calcite are thought to have influenced the skeletal mineralogy of marine calcifyers an investigation of the original skeletal mineralogy of large numbers of marine taxa suggests that the selective recovery of marine organisms from mass extinctions has a much greater influence on the overall percentage of aragonitic organisms than the mg ca ratio of the oceans marine calcifying organisms that produce sediments and build reefs generally have skeletons and shells that are composed of either aragonite or calcite long term changes in the estimated mg ca ratios of sea water tend to correspond to changes in the prevailing mineralogy of these creatures1 2 high mg ca ratios are expected to favour the spread of aragonitic organisms whereas calcitic taxa are thought to benefit from low mg ca ratios3 4 5 6 here we test these patterns throughout the phanerozoic eon and assess the relative impacts of changing ocean chemistry and mass extinctions on the evolutionary success of calcifying organisms we find that mass extinctions are more important in regulating long term patterns of skeletal mineralogy than the mg ca ratios of the global oceans furthermore selective recovery from mass extinctions is usually more important than selective extinction in driving the phanerozoic pattern of skeletal mineralogy but even in the recovery phase there is no clear connection between changes in the dominance of aragonite or calcite and the mg ca ratio of the oceans thus providing further evidence for the complexity of biotic recoveries7

a rupture model for the 1999 chi chi earthquake from inversion of teleseismic data using the hybrid homomorphic deconvolution method this study investigates the kinematics of the rupture process of the ml 7 3 chi chi taiwan earthquake on september 21 1999 by applying the proposed hybrid homomorphic deconvolution method to deconvolve teleseismic broadband p wave displacement recordings of the earthquake this study derives the apparent source time functions astfs at ten stations located around the epicenter to further characterize the fault the kinematic history of the rupture was inverted from astfs using a genetic algorithm coupled with nonlinear iterative technique the calculated asfts reveal that the total rupture event lasted for approximately 27 s static slip distribution images indicate that most slip occurred at shallower portions of the fault plane especially 20 55 km north of the epicenter the maximum slip reached 20 m at 45 km north of the epicenter and the average slip throughout the observed rupture area was approximately 2 m large asperities on the fault appeared at 25 35 km and 40 50 km north of the hypocenter and coincided with relatively high rupture velocity this suggests that the earthquake s energy may have been released quickly the rupture velocity decreased upon encountering an asperity and increased again after passing the asperity this implies that the rupture required more time to overcome the resistances of the asperities the maximum rupture velocity was 3 8 km s while the average rupture velocity was approximately 2 2 km s the rise time distribution suggests that larger slip amplitudes generally correspond to shorter rise times on the subfaults