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

satellite sar interferometry for the improved assessment of the state of activity of landslides a case study from the cordilleras of peru abstract in peru landslides have been causing damages and casualties annually due to the high mountain relief and distinct seasonal precipitation distribution satellite synthetic aperture radar sar interferometry represents one possibility for mapping surface deformation at fine spatial resolution over large areas in order to characterize aspects of terrain motion and potentially hazardous processes we present land surface motion maps derived from satellite sar interferometry insar for a part of the santa river basin between the cordilleras blanca and negra around the city of carhuaz in peru using both persistent scatterer interferometry psi and differential sar interferograms dinsar from alos 1 palsar 1 envisat asar alos 2 palsar 2 and sentinel 1 we mapped 42 landslides extending over 17 190 141 m2 within three classes of activity i e 0 2 cm a 2 10 cm a and 10 cm a a geomorphological inventory of landslides was prepared from optical satellite imagery and field experience and compared to the insar based slope instability inventory the two approaches provide slightly different information about landslide spatial and temporal activity patterns but altogether they can be combined for the assessment of the state of activity of landslides and possibly the development of hazard maps which are not systematically available in this region we conclude that alos palsar 1 and 2 and sentinel 1 data have a high potential to derive high quality surface deformation information of landslides in many mountainous regions worldwide due to their global and frequent acquisition strategies

yangtze river derived sediments in the southwestern south yellow sea provenance discrimination and seasonal transport mechanisms abstract the southwestern south yellow sea sys is influenced by tremendous sediment loads derived from the yellow river huanghe and the yangtze river changjiang however the influence of yangtze river sediments and their transport mechanism in this area remain unresolved in this study we present the grain size clay minerals and elemental compositions of surface sediments from the southwestern sys together with an analysis of field observation seawater salinity and suspended sediment data to investigate the provenance and transport mechanism of the sediments discrimination diagrams of clay minerals cr th vs sc al and rare earth elements rees indicate that the southwestern sys sediments are mainly derived from the old yellow river subaqueous delta and the yangtze river interestingly yangtze sediments enter the sys in ways that differ seasonally in summer yangtze sediments may be transported into the central sys by the dispersion of changjiang diluted water cdw and may also be transported northwestward by the subei coastal current scc to the area off the jiangsu coast in winter the yangtze derived sediments deposited off the jiangsu coast in summer are transported into the central and or even north sys under the combined effects of the scc yellow sea coastal current yscc and yellow sea warm current yswc throughout the transport processes there is an alternation between a source and sink of yangtze sediments off the jiangsu coast the coast serves as a sink of yangtze sediments in summer but as a source of sys sedimentation in winter the depositional and transport mechanisms of yangtze derived sediments are closely associated with seasonal variations in the circulation system of the sys

real time earthquake forecasting in italy abstract we have applied an earthquake clustering epidemic model to real time data at the italian earthquake data center operated by the istituto nazionale di geofisica e vulcanologia ingv for short term forecasting of moderate and large earthquakes in italy in this epidemic type model every earthquake is regarded at the same time as being triggered by previous events and triggering following earthquakes the model uses earthquake data only with no explicit use of tectonic geologic or geodetic information the forecasts are displayed as time dependent maps showing both the expected rate density of m l 4 0 earthquakes and the probability of ground shaking exceeding modified mercalli intensity vi pga 0 01 g in an area of 100 100 km 2 around the zone of maximum expected rate density in the following 24 h for testing purposes the overall probability of occurrence of an m l 4 5 earthquake in the same area of 100 100 km 2 is also estimated the whole procedure is tested in real time for internal use only at the ingv earthquake data center forecast verification procedures have been carried out in forward retrospective way on the 2006 2007 ingv data set making use of statistical tools as the relative operating characteristics roc diagrams these procedures show that the clustering epidemic model performs up to several hundred times better than a simple random forecasting hypothesis the seismic hazard modeling approach so developed after a suitable period of testing and refinement is expected to provide a useful contribution to real time earthquake hazard assessment even with a possible practical application for decision making and public information

evidence for transform faulting in the ionian sea the cephalonia island earthquake sequence of 1983 accurate locations of aftershocks of the january 17 1983 ms 7 0 main shock in the ionian islands have been determined as well as fault plane solutions for this main shock and its largest aftershock which are interpreted as a right lateral strike slip motion with a thrust component on a fault striking in about a ne sw direction

shallow earthquake inhibits unrest near chiles cerro negro volcanoes ecuador colombian border magma movement or reservoir pressurisation can drive swarms of low magnitude volcano tectonic earthquakes as well as occasional larger earthquakes m5 on local tectonic faults earthquakes m5 near volcanoes are challenging to interpret in terms of evolving volcanic hazard but are often associated with eruptions and in some cases enhance the ascent of magma we present geodetic observations from the first episode of unrest known to have occurred near chiles and cerro negro de mayasquer volcanoes on the ecuador colombian border a swarm of volcano tectonic seismicity in october 2014 culminated in a mw 5 6 earthquake south of the volcanoes satellite radar data spanning this earthquake detect displacements that are consistent with dextral oblique slip on a reverse fault at depths of 1 4 3 4 km within a ssw nne trending fault zone that last ruptured in 1886 gps station measurements capture 20 days of uplift before the earthquake probably originating from a pressure source 10 15 km south of volcan chiles at depths exceeding 13 km after the mw 5 6 earthquake uplift ceased and the rate of seismicity began to decrease potential mechanisms for this decline in activity include a decrease in the rate of movement of magma into the shallow crust possibly caused by the restriction of fluid pathways our observations demonstrate that an earthquake triggered during volcanic unrest can inhibit magmatic processes and have implications for the hazard interpretation of the interactions between earthquakes and volcanoes

the seismic cycle in southern california precursor or response the seismicity rate m 3 0 in southern california shows two cycles with periods of high activity 90 events year from 1945 1952 and 1969 1992 and lower activity 60 70 events year from 1952 1969 and 1992 present abrupt drops in the seismicity rate occur after the 1952 kern county m7 5 and the 1992 landers m7 3 earthquakes the sudden increase in 1969 does not coincide with any major event but approximates the time needed to reaccumulate the seismic moment released in the 1952 earthquake this temporal correlation with the preceding earthquake suggests that the seismic cycle lower seismicity after a major earthquake and higher seismicity before the next major earthquake should be interpreted as a response to the first earthquake rather than a precursor to the second southern california is now at a rate of seismicity as low as it experienced in the 1950s and 1960s

clay mineral record in lake baikal sediments the holocene and late glacial transition abstract we analyse the clay mineralogical composition of two 1 m long cores from elevated plateaus in the southern and northern basins of lake baikal our aim is to test the limits of classically used clay proxies for climate reconstructions mineralogical signature is determined by x ray diffraction on oriented aggregates from holocene and late glacial sediments mineralogical results are presented on a palaeomagnetic derived time scale sampling at a centimeter resolution allows for a sub millenial order reconstruction the evolution of clay derived climate proxies smectite illite peak intensity ratio s i is compared between the two locations with respect to other climate reconstructions for the lake baikal area and siberia during the late glacial punctual increases of s i are related to changes of particle source rather than any climate change at both sites the most intense chemical weathering conditions occured during the subboreal lagging the eurasian middle atlantic climate optimum s i follows a gradual but irregular increase through the holocene probably related to slow warming favourable to the development of the siberian soils the different sensitivity to hydrolysing conditions in northern and southern sites can be explained by a combination of local lithological and topographical parameters

quaternary normal and reverse faulting and the state of stress in the central andes of south peru field studies in the andes of southern peru show that in the high andes and pacific lowlands quaternary and recent faults are normal this extensional tectonics postdates compressional deformations of pliocene early quaternary age in the sub andes the observed deformations are compressional they affect early quaternary deposits some of the faults separate quaternary deposits from the bedrock and thus are clearly of tectonic origin and not landslide effects striations on the fault planes indicate n s trending extension in the high andes and pacific lowlands the total amount of crustal stretching is small probably of the order of 1 during the last 1 2 m y in the sub andes folds and faults affecting neogene and early quaternary deposits result from n s shortening nevertheless it is supposed that this n s shortening is of early quaternary age the present day compression probably strikes e w judging from focal mechanisms in the sub andes of central peru southern bolivia and northwest argentina data from structural analysis of faults and from earthquake focal mechanisms allow us to surmise the state of stress in the andes of southern peru the high andes and pacific lowlands subjected to n s trending extension are bounded by two zones of e w trending compression the sub andes to the east and the contact between the convergent nazca and south america plates to the west in our model the maximum horizontal compressive stress trajectory hmax is roughly parallel with the e w convergence between the two plates hmax corresponds to 1 in the sub andes and to 2 in the high andes the latter situation is caused by the elevated mass of the high andes where zz the vertical stress is inferred to be 1 thus the third principal stress axis being orthogonal to the other two axes it is oriented n s allowing extension to occur in that direction on the other hand in the sub andes zz is 3 and horizontal e w shortening occurs the state of stress in the andean continental crust above the 30 dipping slab appears to be different from that in the andes of central peru situated above the flat subducting segment in this region compressional deformantion affect a wider part of the cordillera

implications of fault constitutive properties for earthquake prediction the rate and state dependent constitutive formulation for fault slip characterizes an exceptional variety of materials over a wide range of sliding conditions this formulation provides a unified representation of diverse sliding phenomena including slip weakening over a characteristic sliding distance dc apparent fracture energy at a rupture front time dependent healing after rapid slip and various other transient and slip rate effects laboratory observations and theoretical models both indicate that earthquake nucleation is accompanied by long intervals of accelerating slip strains from the nucleation process on buried faults generally could not be detected if laboratory values of dc apply to faults in nature however scaling of dc is presently an open question and the possibility exists that measurable premonitory creep may precede some earthquakes earthquake activity is modeled as a sequence of earthquake nucleation events in this model earthquake clustering arises from sensitivity of nucleation times to the stress changes induced by prior earthquakes the model gives the characteristic omori aftershock decay law and assigns physical interpretation to aftershock parameters the seismicity formulation predicts large changes of earthquake probabilities result from stress changes two mechanisms for foreshocks are proposed that describe observed frequency of occurrence of foreshock mainshock pairs by time and magnitude with the first mechanism foreshocks represent a manifestation of earthquake clustering in which the stress change at the time of the foreshock increases the probability of earthquakes at all magnitudes including the eventual mainshock with the second model accelerating fault slip on the mainshock nucleation zone triggers foreshocks

late quaternary clay mineral record in central lake baikal academician ridge siberia abstract we investigated the mineralogical composition of two cores recovered on the academician ridge central lake baikal siberia sedimentological features show that the cores are unaffected by turbidity currents however hemipelagic deposition is not continuous but intermittently disturbed by syn or post sediment reworking e g bioturbation slumps faulting such modes of deposition are consistent with the complex uplift history of the ridge bulk mineralogy suggests that terrigenous sediment supplies are constant through glacial interglacial stages and diluted by diatom rich intervals related to warmer interglacial stages the core stratigraphy is based on the correlation of the diatom zonation and opal abundance with the marine oxygen isotope reference curve specmap the 8 m cores partly recover the last four interglacial glacial cycles i e since oxygen isotope stage 8 we test the use of clay minerals as a proxy for paleoclimatic reconstruction the clays are more weathered during the diatom rich intervals in agreement with warmer climate conditions however the mean clay composition does not change significantly through glacial interglacial stages this observation implies that in the academician ridge sediments a simple smectite illite ratio s i does not alone provide a reliable indicator of climatic variation it reflects the complex clay assemblages especially the smectite group delivered to central lake baikal smectites include primarily illite smectite mixed layers made of a mixture of montmorillonite and beidellite according to their behavior after cation saturation the illite smectite mixed layers are primarily transformed smectites with some neoformed smectites intermittently observed in addition al smectites occur in minor proportions we conclude that the s i ratio has a climatic significance only if it evolves in parallel with the weathering stage of the clays and is confirmed by a change in the composition of the smectites

factors governing abundance of hydrolyzable amino acids in the sediments from the n w european continental margin 47 50 n fifty six samples representing 6 sediment cores taken along the n w european continental margin from the shelf slope and abyssal plain of the goban spur and meriadzek terrace were quantitatively analysed for total hydrolyzable amino acids thaa and clay minerals in descending order the five most abundant amino acids making up more than 70 of the total were aspartic acid glycine serine alanine and glutamic acid clay mineral proportions were typical for the n e atlantic in order of descending abundance illite kaolinite chlorite smectite and mixed layers the meriadzek terrace area is characterised by fine grain suspension sedimentation with a low pelagic carbonate input and the lowest content of thaa in contrast the goban spur transect is characterised by much higher carbonate inputs and more vigorous hydrodynamics as judged from granulometry and the high abundance of minerals of shelf and continental origin and a generally higher thaa content the pelagic portion of thaa deposited at the sea floor is more readily mineralised during early diagenesis than the more refractory clay mineral associated continental portion along this margin the average mineralization of thaa down to 25 cm in the sediment is about 54 there is a significant affinity between chlorites and amino acids which we suggest may involve the formation of ionic bonds between the octahedral layers of the clay and the amino acids

ridge segmentation and the magnetic structure of the southwest indian ridge at 50 30 e 55 30 e and 66 20 e implications for magmatic processes at ultraslow spreading centers 1 the aim of this paper is to investigate the relationships between the segmentation and the magnetic structure of the ultraslow spreading southwest indian ridge contrary to faster spreading ridges magnetization usually decreases from high values along the neovolcanic axis to low values in the nontransform discontinuities there is a direct correlation between the deepening of the axial valley and the decrease of the magnetization from the neovolcanic axis toward the deepest parts of the axial discontinuities we suggest that less frequent eruptions as the distance from the segment center and the length of these discontinuities increase result in thinner extrusive lavas and thus control the along axis magnetization variations by thinning the magnetic source layer a unique segment centered at 50 28 e shows a marked low magnetization anomaly at its center similarly to the segments of the slow spreading mid atlantic ridge we suggest that in this segment both the mantle temperature and the magmatic activity are high enough for the lavas not to be highly fractionated a higher rate of melt production to the west of gallieni transform fault may have created some form of reservoir where mixing of melts occurs and where crystalline fractionation is low producing low magnetization lavas to the east magma chambers may be smaller with cooler mantle temperatures resulting in restricted mixing and significant fractionation which may lead to relatively high intensity magnetization lavas finally we propose that serpentinization of peridotites has no significant contribution to the variation of the magnetization along the axial valley off axis in thin crust areas upper mantle rocks may become progressively more altered as distance from the axis increases the strong faulting and alteration of a thin basaltic cap and underlying upper mantle rocks can produce the disappearance of the magnetic reversal pattern and the increase of the magnetization which is observed along the traces of the largest amagmatic discontinuities by contrast in thicker crust areas the upper mantle rocks are shielded from the alteration and the serpentinization process may be delayed resulting as on the mid atlantic ridge in slightly more positive magnetization values along the traces of axial discontinuities regardless of polarity

new data on the geodynamics of southern peru from computerized analysis of spot and sar ers 1 images abstract several geological structures are extracted from spot panchromatic and ers 1 radar images of the central andes arequipa area southern peru our new methodology of numerical image processing is an aid for identification of the structures this numerical approach helps to locate characterize and determine the amplitude of the vertical offset of structures the results show that the nw se trending major faults are principally normal with a small sinistral strike slip component the open ne sw faults are tension gashes extension in the studied area trends ne sw and the major nw se striking faults form an extensional en echelon pattern including an active volcanic zone these new kinematic results lead to a regional geodynamic model which takes into account oblique convergence between pacific and south america plates within the wadati benioff zone of the peru trench

thermal deformation and degassing remote sensing time series ce 2000 2017 at the 47 most active volcanoes in latin america implications for volcanic systems

global compilation of interferometric synthetic aperture radar earthquake source models 1 comparisons with seismic catalogs 1 while many earthquakes have now been studied using interferometric synthetic aperture radar insar data a full assessment of the quality and additional value of insar source parameters compared to seismological techniques is still lacking we compile a catalog of source models obtained using insar and estimate the corresponding centroid moment tensor cmt parameters we refer to this compilation as the icmt archive we compare source parameters from over 70 insar studies of 57 global earthquakes with those in the global cmt gcmt international seismological centre isc and engdahl hilst buland ehb seismic catalogs we find an overall good agreement between fault strike dip and rake values in the gcmt and icmt archives likewise the differences in seismic moment between these two archives are relatively small and we do not find support for previously suggested trends of insar leading to larger moments than seismic data however epicentral locations show substantial discrepancies which are larger for the gcmt median differences of 21 km than for the ehb and isc catalogs median differences of 10 km since insar data have a high spatial resolution and thus should map epicentral locations accurately this allows us to obtain a first independent estimate of epicentral location errors in the seismic catalogs earthquake depths from insar are systematically shallower than those in the ehb catalog with a median of differences of 5 km while this trend may be partly due to unmodeled crustal complexity it is also compatible with the observation that the rupture of crustal earthquakes tends to propagate upward in the seismogenic layer

lacustrine record of last millennia eruptions in northern chilean patagonia 45 47 s due to its tectonic setting the andean southern volcanism zone ssvz is characterized by frequent volcanic activity chilean patagonia lake sediments represent powerful archives of historical and

extension and dynamics of the andes inferred from the 2016 parina huarichancara earthquake the mw 6 1 2016 parina earthquake led to extension of the south peruvian andes along a normal fault with evidence of holocene slip we use interferometric synthetic aperture radar seismology and field mapping to determine a source model for this event and show that extension at parina is oriented ne sw which is parallel to the shortening direction in the adjacent sub andean lowlands in addition we use earthquake source models and gps data to demonstrate that shortening within the sub andes is parallel to topographic gradients both observations imply that forces resulting from spatial variations in gravitational potential energy are important in controlling the geometry of the deformation in the andes we calculate the horizontal forces per unit length acting between the andes and south america due to these potential energy contrasts to be 4 8 1012 n m along strike of the mountain range normal faulting at parina implies that the andes in south peru have reached the maximum elevation that can be supported by the forces transmitted across the adjacent foreland which requires that the foreland faults have an effective coefficient of friction urn x wiley jgrb media jgrb53009 jgrb53009 math 00010 2 additionally the onset of extension in parts of the central andes following orogen wide compression in the late miocene suggests that there has been a change in the force balance within the mountains we propose that shortening on weak detachment faults within the andean foreland since 5 9 ma reduced the shear tractions acting along the base of the upper crust in the eastern andes leading to extension in the highest parts of the range

earthquake source parameters along the hellenic subduction zone and numerical simulations of historical tsunamis in the eastern mediterranean abstract we studied source mechanism parameters and slip distributions of earthquakes with m w 5 0 occurred during 2000 2008 along the hellenic subduction zone by using teleseismic p and sh waveform inversion methods in addition the major and well known earthquake induced eastern mediterranean tsunamis e g 365 1222 1303 1481 1494 1822 and 1948 were numerically simulated and several hypothetical tsunami scenarios were proposed to demonstrate the characteristics of tsunami waves propagations and effects of coastal topography the analogy of current plate boundaries earthquake source mechanisms various earthquake moment tensor catalogues and several empirical self similarity equations valid for global or local scales were used to assume conceivable source parameters which constitute the initial and boundary conditions in simulations teleseismic inversion results showed that earthquakes along the hellenic subduction zone can be classified into three major categories 1 focal mechanisms of the earthquakes exhibiting e w extension within the overriding aegean plate 2 earthquakes related to the african aegean convergence and 3 focal mechanisms of earthquakes lying within the subducting african plate normal faulting mechanisms with left lateral strike slip components were observed at the eastern part of the hellenic subduction zone and we suggest that they were probably concerned with the overriding aegean plate however earthquakes involved in the convergence between the aegean and the eastern mediterranean lithospheres indicated thrust faulting mechanisms with strike slip components and they had shallow focal depths h

p and s deep velocity structure of the hellenic area obtained by robust nonlinear inversion of travel times we derived a new model for the p and s velocity structure of the lithosphere in the subduction area of the hellenic arc and the aegean sea from the inversion of travel times of local events the inversion technique applied is nonlinear since three dimensional ray tracing is incorporated at the same time an appropriate preconditioning of the final linearized system is used in order to reduce ray density effects on the results the p s coherency is controlled by an additional damping of the vp vs ratio the study focuses mainly on the structure of the hellenic subduction in the southern aegean region interesting features and details of the subducted slab can be recognized in the final tomographic images on the western part the shallower section of the slab is dipping at a very small angle 10 this changes to approximately 25 for the deeper part of the subduction resulting in a prominent kink at a depth of about 70 km which is in accordance with the general characteristics of the associated benioff zone the smaller eastern part of the slab is not resolved with the same detail but a clearly steeper subduction zone can be recognized moreover detailed information about the crustal thickness variations are inferred from the velocity structure and correlate very well with the existing results from refraction experiments finally the results confirm the recent suggestion concerning the existence of a low velocity crustal layer at shallow depths 10 15 km in the accretionary prism of the alpine belt

the 2001 skyros northern aegean greece earthquake sequence off fault aftershocks tectonic implications and seismicity triggering was identified as a possible site for the occurrence of a strong event by papadimitriou and sykes 2001 who applied an evolutionary stress model in the northern aegean area 4 the paper analyzes the details of the earthquakes in the skyros sequence aiming to contribute to the understanding of the seismotectonic properties in this area where the western termination of the north aegean strike slip faulting against the mainland of greece takes place the co seismic stress changes associated with the main shock are computed and the areas of static stress increases are correlated with the aftershock spatial distribution

elemental and major biochemical changes across an oxidation front in a relict turbidite an oxygen effect abstract the elemental and major biochemical compositions of the relict f turbidite sampled in two cores from the madeira abyssal plain were determined this fine grained distal sequence occurs at ca 9 m core depth and includes a surficial oxidized horizon defined by a distinct color change oxygen diffused downward through sediments above this interface and in ca 10 kyr destroyed 80 of the organic substances that below the front had survived degradation in the presence of porewater sulfate for ca 140 kyr these deposits provide an opportunity to establish the extent and selectivity of oxic sedimentary degradation under natural conditions without the usual complications of bioturbation and varying sources or sedimentation rates in both cores a sample from the upper oxidized layer was compared to two samples from the underlying unoxidized layers the unoxidized sequences of both turbidities contained 0 93 1 02 wt organic carbon oc and 0 10 0 11 wt total nitrogen tn approximately 20 of the initial oc and 40 of the initial tn remained in the oxidized horizons with a consequent decrease in atomic c n ratio from ca 11 to ca 5 all samples gave very low yields of lignin phenols and comparable oc normalized yields of total aldoses and amino acids and indicated predominantly marine organic matter om and nonselective oxic degradation of these biochemical classes compositions of individual aldoses and amino acids generally were also similar in surface and deep sediments except that the oxidized horizons yielded markedly elevated 3 5x percentages of nonprotein amino acids this study clearly demonstrates that prolonged exposure to oz can lead to organic matter alteration which is far more extensive than that obtained with sulfate alone in comparison to early diagenesis however alteration of the measured biochemicals was largely nonselective such oxidation reactions could control the distribution and composition of organic matter in slowly accumulating continental rise and deep ocean environments

modeling seismicity rate changes during the 1997 umbria marche sequence central italy through a rate and state dependent model 1 we model the spatial and temporal pattern of seismicity during a sequence of moderate magnitude normal faulting earthquakes which struck in 1997 the umbria marche sector of northern apennines italy by applying the dieterich 1994 rate and state dependent constitutive approach the goal is to investigate the rate of earthquake production caused by repeated coseismic stress changes computed through a 3 d elastic dislocation model in a homogeneous half space the reference seismicity rate is assumed time independent and it is estimated by smoothing the seismicity that occurred in the previous decade without declustering we propose an analytical relation for deriving the stressing rate directly from the reference seismicity rate this allows us to perform a tuning of the constitutive parameter a where a accounts for the direct effect of friction in the rate and state dependent model and is the effective normal stress into the dieterich model through a maximum likelihood method which yields for this seismic sequence a best fitting value equal to 0 04 mpa our computations show that although seven out of eight main shocks are located in areas of increased rate of earthquake production numerous aftershocks are located in seismicity shadows our simulations point out that the adopted value of a strongly affects the pattern of both seismicity shadow and areas of enhanced rate of earthquake production we conclude that solely accounting for static stress changes caused by the main shocks of this seismic sequence is not sufficient to forecast the complex spatial and temporal evolution of seismicity

postseismic relaxation driven by brittle creep a possible mechanism to reconcile geodetic measurements and the decay rate of aftershocks application to the chi chi earthquake taiwan we evaluate the effect of coseismic stress changes on the fault slip at midcrustal depth assuming a velocity strengthening brittle creep rheology we show that this model can help reconcile the time evolution of afterslip as measured from geodesy with aftershocks decay we propose an analytical expression for slip of the brittle creeping fault zone bcfz that applies to any dynamic or static stress perturbation including shear stress and normal stress changes the model predicts an initial logarithmic increase of slip with time postseismic slip rate decays over a characteristic time t r a that does not depend on the amplitude of the stress perturbation and it asymptotically joins the long term creep imposed by interseismic stress buildup given that the seismicity rate might be considered proportional to the sliding velocity of the bcfz the model predicts a decay rate of aftershocks that follows omori s law with a mathematical formalism identical to that of dieterich 1994 although based on a different mechanical rationale our model also differs from dieterich s model in that it requires that aftershock sequences and deep afterslip as constrained from geodetic measurements should follow the same temporal evolution we test this for the 1999 chi chi earthquake m w 7 6 and find that both sets of data are consistent with a model of afterslip due to the response of the bcfz the inferred relaxation time t r 8 5 years requires a value for a log v being the coefficient of friction in the range between 1 3 10 3 and 10 2

a detailed study of the active crustal deformation in the aegean and surrounding area abstract a detailed study of the active crustal deformation in the aegean sea and surrounding area is presented the estimation of the deformation velocities is not performed in broad seismic zones but in seismogenic sources of limited spatial extent where the seismic energy is practically released in order to describe the spatial variations of the components of the strain rate tensor the deformation analysis is based on previous work where the seismicity and the available focal mechanisms are used separately for estimating the rate and shape of the deformation respectively the calculations were performed for 63 seismogenic sources identified in the aegean sea and surrounding area which belong to eight belts with an almost uniform orientation of the stress field along the coasts of albania and northwestern greece up to leukada island the collision of the adria plate with eurasia results in a compressional velocity of about 4 mm yr in a direction n49 e almost normal to the coast line the dextral movement with almost 3 cm yr along the cephalonia transform fault with strike n45 e is expressed as an almost equal extension and compression in n s and e w direction respectively along the convex outer part of the hellenic arc a crustal shortening of 1 3 cm yr is observed in a mean direction n34 e the direction of this shortening is almost constant from the southern ionian islands zakynthos up to rodos while the shortening rate does not significantly change from the outer sources to the inner ones the aegean sea and surrounding area is characterised by an extensional deformation the direction of the maximum extension in the northern part of this area shows an anticlockwise rotation from east to west thus this extension has a nne direction in northwestern turkey n11 e a nnw direction in central and northern greece as well as along the southern aegean volcanic arc and its extension to southwestern turkey n12 w and a wnw direction in the westernmost part of this extensional area n72 w the mean value of the extensional velocities in this area is 5 mm yr the northern part of asia minor and of the aegean sea is characterised by the dextral strike slip movement of about 2 cm yr of the north anatolian fault and its continuation in the northern aegean where this movement gradually decreases to about 6 mm yr the vertical crustal upper 10 km of the crust thickening is about 2 mm yr along the convex side of the hellenic arc and the vertical crustal thinning is about 1 mm yr in the aegean sea these values were obtained from the component u 33 of the velocity tensor

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

mineralogical signatures of lake baikal sediments sources of sediment supplies through late quaternary abstract the mineralogical composition of late quaternary sediments was investigated in three piston cores recovered on elevated plateaus in lake baikal on continent ridge a northern extension of academician ridge in the north basin on the posolsky bank near the selenga delta and on the vydrino shoulder in the south basin the sediments are alternating biogenic diatom rich muds and terrigenous silty clays with sandy layers occurring in the southern vydrino core core stratigraphy is based on ams 14 c dates on pollen diatom zonation and magnetic record correlation the 6 10 m long cores cover the last 40 kyr in vydrino 60 kyr in posolsky and 185 kyr in continent ridge the bulk clay

the hellenic subduction zone a tomographic image and its geodynamic implications new tomographic images of the hellenic subduction zone demonstrate slab penetration in the aegean upper mantle to depths of at least 600 km beneath greece the lower part of the slab appears to be detached at a depth of about 200 km whereas it still seems to be unruptured beneath the southern aegean schematically we derive minimum time estimates for the duration of the hellenic subduction zone that range from 26 to 40 ma this is considerably longer than earlier estimates which vary between 5 and about 13 ma

clay clast aggregates in gouges new textural evidence for seismic faulting 1 spherical aggregates named clay clast aggregates ccas have been reported from recent investigations on retrieved clay bearing fault gouges from shallow depth seismogenic faults and rotary shear experiments conducted on clay bearing gouge at seismic slip rates the formation of ccas appears to be related to the shearing of a smectite rich granular material that expands and becomes fluidized we have conducted additional high velocity rotary shear experiments and low velocity double shear experiments we demonstrate that a critical temperature depending on dynamic pressure temperature conditions is needed for the formation of ccas this temperature corresponds to the phase transition of pore water from liquid to vapor or to critical which induced gouge pore fluid expansion and therefore a thermal pressurization of the fault a detailed examination by energy dispersive x ray spectrometry edx sem element mapping sem and transmission electron microscopy tem shows strong similar characteristics of experimental and natural ccas with a concentric well organized fabric of the cortex and reveals that their development may result from the combination of electrostatic and capillary forces in a critical reactive medium during the dynamic slip weakening accordingly the occurrence of ccas in natural clay rich fault gouges constitutes new unequivocal textural evidence for shallow depth thermal pressurization and consequently for past seismic faulting

the avtod aster volcanic thermal output database latin america archive abstract thermal spaceborne remote sensing has been used to study monitor and forecast volcanic activity for decades but these data have not been used systematically at high spatial resolution to study changes in volcano temperatures across an entire region spanning multiple decades to understand background thermal activity and its relation to unrest and eruption we have developed a first of a kind database that uses manual analysis to identify and collect data for volcanic thermal output with 90 m pixel spatial resolution for 330 potentially active volcanoes found in latin america between the years 2000 2017 this database is reliant on the advanced spaceborne thermal emission and reflection radiometer aster sensor due to its high spatial resolution data capability of detecting low level thermal features its accessibility and reliability compared to similar data types and the long time series available at multiple volcanoes a total of 88 latin american volcanoes were found to have some type of volcanic thermal feature detected by aster and here we document thermal features at 16 of these volcanoes detected from space for the first time we have recorded these thermal features including the temperature above background area above background and the timing and location of detection in the aster volcanic thermal output database avtod by comprehensively analyzing such a large dataset we are able to quantitatively analyze some of the issues with these data including 24 of all volcanoes in this study failing to meet the acquisition rates proposed by the current acquisition plan and 44 5 of all acquisitions being unusable due to interference from clouds we provide recommendations of how to update future acquisition plans that would focus on night time and cloud free acquisitions in order to confirm the validity of avtod it was tested against the existing moderate resolution imaging spectroradiometer modis based mirova database in some cases we found a high degree of correlation between the two datasets r2 0 87 in other cases however correlation was limited due to the difference in spatial resolution of these two data types by examining the maximum temperature detected by every volcano in the database we found 46 that never reach a temperature high enough to be detected by modis class thermal sensors the information in this database provides new insights about volcanic activity both on its own and in combination with other data types as well as a data driven approach to improve key features in future sensors

parallel thrust and normal faulting in peru and constraints on the state of stress abstract we present evidence for recent normal faulting in the cordillera blanca of peru along planes trending approximately n40 w parallel to the chain this type of faulting suggests that there is an important component of extension perpendicular to the chain and contrasts markedly with the underthrusting of the nazca plate on the west side of peru and with the folding and thrusting observed in the sub andes on the eastern flank of the chain these contrasting styles of deformation and associated stress fields can be explained by buoyancy forces due to the high mountains and crustal roots in so far as this explanation is correct the difference in elevation between zones of normal and thrust faulting can be used to place an upper bound of 500 bars on the average stress difference in the crust

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

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

some thoughts on the use of insar data to constrain models of surface deformation noise structure and data downsampling repeat pass interferometric synthetic aperture radar insar provides spatially dense maps of surface deformation with potentially tens of millions of data points here we estimate the actual covariance structure of noise in insar data we compare the results for several independent interferograms with a large ensemble of gps observations of tropospheric delay and discuss how the common approaches used during processing of insar data affects the inferred covariance structure motivated by computational concerns associated with numerical modeling of deformation sources we then combine the data covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling or averaging we illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum for the larger events our goal is to invert for the coseismic fault slip distribution for smaller events we infer the hypocenter location and moment we compare the results of inversions using several different resampling algorithms and we assess the importance of using the full noise covariance matrix

postseismic deformation following the 1999 chi chi earthquake taiwan implication for lower crust rheology on 1999 september 21 the mw 7 6 chi chi earthquake ruptured a segment of the chelungpu fault a frontal thrust fault of the western foothills of taiwan the stress perturbation induced by the rupture triggered a transient deformation across the island which was well recorded by a wide network of continuously operating gps stations the analysis of more than ten years of these data reveals a heterogeneous pattern of postseismic displacements with relaxation times varying by a factor of more than ten and large cumulative displacements at great distances in particular along the longitudinal valley in eastern taiwan where relaxation times are also longer we show that while afterslip is the dominant relaxation process in the epicentral area viscoelastic relaxation is needed to explain the pattern and time evolution of displacements at the larger scale we model the spatiotemporal behavior of the transient deformation as the result of afterslip on the decollement that extends downdip of the chelungpu thrust and viscoelastic flow in the lower crust and in the mid crust below the central range we construct a model of deformation driven by coseismic stress change where afterslip and viscoelastic flow are fully coupled the model is compatible with the shorter relaxation times observed in the near field which are due to continued fault slip and the longer characteristic relaxation times and the reversed polarity of vertical displacements observed east of the central range our preferred model shows a viscosity of 0 5 1 x 10 19 pa s at lower crustal depths and 5 x 10 17 pa s in the mid crust below the central range between 10 and 30 km depth the low viscosity zone at mid crustal depth below the central range coincides with a region of low seismicity where rapid advection of heat due to surface erosion coupled with underplating maintain high temperatures estimated to be between 300 c and 600 c from the modeling of thermo chronology and surface heat flow data

seismic hazard of volcanic activity abstract seismic activity is a common feature of volcanic eruptions the majority of volcanic earthquakes are small their magnitudes do not exceed 2 or 3 at the same time significant moderate size and large volcanic earthquakes may also occur the study of 28 significant m w 4 5 earthquakes associated with volcanic eruptions of 20th century allowed us to formulate the following results about seismic hazard of volcanic activity 1 during the 20th century only three large m w 7 0 earthquakes directly associated with volcanic eruptions in the world were recorded 2 the maximum magnitude m w was estimated to be 5 4 for earthquakes related to central eruptions 7 0 for caldera collapse 5 9 for central eruptions accompanied by flank and or fissure eruptions 7 1 for flank and or fissure eruptions without central eruptions and 5 9 for submarine eruptions for seismicity just before the eruption the maximum magnitude of earthquakes was estimated to be m w 7 1 for seismicity at the initial stage of eruption m w 7 0 for paroxysmal stage of eruption m w 5 6 and for final stage of eruption m w 6 1 3 it was shown that the recurrence time of eruptions of the same type of volcano associated with significant m w 4 5 earthquakes was more than 100 years for 86 of events studied

a computer interfaced sedigraph for modal size analysis of fine grained sediment a system has been developed allowing the direct storage on disc of size data from the x ray scanning settling tube sedigraph 5000et processing of the cumulative percentage data output to produce smooth frequency curves is described this allows rapid 15 min and precise m 0 1o discrimination of size modes peak heights median and silt and clay percentages of fine grained sediments an example of a mud turbidite is given showing systematic changes in bulk and modal properties not visible by eye lack of size segregation in the 1 m thickness of this turbidite shows that it may have been deposited from a highly concentrated flow rather than from a dilute waning turbidity current such flows may explain ungraded poorly graded muddy sediments also known as homogenites unifites or megaturbidites by other authors

changes in state of stress on the southern san andreas fault resulting from the california earthquake sequence of april to june 1992 the april to june 1992 landers earthquake sequence in southern california modified the state of stress along nearby segments of the san andreas fault causing a 50 kilometer segment of the fault to move significantly closer to failure where it passes through a compressional bend near san gorgonio pass the decrease in compressive normal stress may also have reduced fluid pressures along that fault segment as pressures are reequilibrated by diffusion that fault segment should move closer to failure with time that fault segment and another to the southeast probably have not ruptured in a great earthquake in about 300 years

intermediate depth seismicity in the aegean defined by teleseismic data the most reliably located intermediate depth earthquakes in the aegean area selected from the international seismological centre catalogue deepen towards the internal part of the hellenic arc and reach a maximum depth of 150 km during the last 20 years most have occurred at the eastern and western ends of the arc and very little activity is found in the middle area north of crete the seismic zone defines a contorted slab of lithosphere in the western part a very shallow dipping seismic zone extends 200 km northeast from the trench and then steepens abruptly at depths of about 50 80 km eventually reaching dips of 45 the 100 km and 150 km isodepth contours are not parallel to the hellenic trench in the western part the geometry of the slab is more consistent with a south southwestward translation of the aegean arc with respect to the african plate than with a rotation around a pole located close to the aegean region

nd and pb isotope signatures of the clay size fraction of labrador sea sediments during the holocene implications for the inception of the modern deep circulation pattern holocene on the basis of sediment supply variations for the last 12 kyr three sources have contributed to the sediment mixture the north american shield the pan african and variscan crusts and the mid atlantic ridge clay isotope signatures indicate two mixtures of sediment sources the first mixture 12 2 6 5 ka is composed of material derived from the north american shield and from a young crustal source from 6 5 ka onward the mixture is characterized by a young crustal component and by a volcanic component characteristic of the midatlantic ridge since the significant decrease in proximal deglacial supplies the evolution of the relative contributions of the sediment sources suggests major changes in the relative contributions of the deep water masses carried by the western boundary undercurrent over the past 8 4 kyr the progressive intensification of the western boundary undercurrent was initially associated mainly with the transport of the northeast atlantic deep water mass until 6 5 ka and with the denmark strait overflow water thereafter the establishment of the modern circulation at 3 ka suggests a reduced influence of the denmark strait overflow water synchronous with the full appearance of the labrador seawater mass our isotopic data set emphasizes several changes in the relative contribution of the two major components of north atlantic deep water throughout the holocene index terms 4267 oceanography general paleoceanography 4558 oceanography physical sediment transport 1040 geochemistry isotopic composition chemistry 9325 information related to geographic region atlantic ocean 9604 information related to geologic time cenozoic keywords clay size fraction sedimentary mixings deep circulation nd and pb isotopes north atlantic labrador sea

deformation and seismicity near sabancaya volcano southern peru from 2002 to 2015 we use interferometric synthetic aperture radar insar and local seismic data to investigate the cause of earthquake sequences near sabancaya volcano in southern peru from 2002 to 2014 with a particular focus on events leading up to the august 2014 phreatic eruption insar observed deformation associated with earthquake swarms in late 2002 february 2013 and july 2013 is modeled by fault slip with no need for magmatic sources to explain the deformation the majority of the seismicity is an expression of the regional tectonic system which is characterized by e w trending normal faults but a link to the magmatic system is possible the mw 5 9 earthquake on 17 july 2013 occurred on a previously unmapped normal fault that continued to deform in the months following the earthquake an increase in long period and hybrid seismicity and changes in fumarolic emissions in 2013 2014 culminating in the august 2014 eruption indicates the involvement of both tectonic and magmatic systems

an insar based survey of volcanic deformation in the central andes we extend an earlier interferometric synthetic aperture radar insar survey covering about 900 remote volcanos of the central andes 14 27 s between the years 1992 and 2002 our survey reveals broad 10s of km roughly axisymmetric deformation at 4 volcanic centers two stratovolcanoes are inflating uturuncu bolivia and hualca hualca peru another source of inflation on the border between chile and argentina is not obviously associated with a volcanic edifice here called lazufre and a caldera cerro blanco also called robledo in northwest argentina is subsiding we explore the range of source depths and volumes allowed by our observations using spherical ellipsoidal and crack like source geometries we further examine the effects of local topography upon the deformation field and invert for a spherical point source in both elastic half space and layered space crustal models we use a global search algorithm with gradient search methods used to further constrain best fitting models inferred source depths are model dependent with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure source depths relative to sea level are 8 18 km at hualca hualca 12 25 km for uturuncu 5 13 km for lazufre and 5 10 km at cerro blanco deformation at all four volcanoes seems to be time dependent and only uturuncu and cerro blanco were deforming during the entire time period of observation inflation at hualca hualca stopped in 1997 perhaps related to a large eruption of nearby sabancaya volcano in may 1997 although there is no obvious relation between the rate of deformation and the eruptions of sabancaya we do not observe any deformation associated with eruptions of lascar chile at 16 other volcanoes that had recent small eruptions or fumarolic activity or associated with a short lived thermal anomaly at chiliques volcano we posit a hydrothermal system at cerro blanco to explain the rate of subsidence there for the last decade we calculate the ratio of the volume of magma intruded to extruded is between 1 10 and that the combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate

the origin of volcano tectonic earthquake swarms volcano tectonic vt seismicity is commonly recorded prior to and during eruptions vt seismicity may reflect stresses induced by dike propagation as indicated by propagating hypocenters and fault plane solutions fps reflecting regional stresses or stresses induced by dike inflation indicated by randomly distributed hypocenters and fps with pressure axes rotated 90 to regional maximum compression although numerical models of dike induced stresses indicate that both regimes should occur during dike emplacement this has not yet been observed according to published seismic data instead 90 rotated fps are observed in some cases while propagating hypocenters mark dike formation in other cases we suggest that differences in the seismic expression of upper crustal magma migration may result from differences in the regional tectonic setting and in the nature of magma wall rock interactions ultimately it may be possible to use information contained in vt seismicity to forecast changes in a volcano s behavior by establishing the characteristic stress field response for a given volcano or through a deeper understanding of the complex relationships between vt seismicity local crustal stresses and the physical mechanisms of magma migration

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

unravelling fluvial deposition and pedogenesis in ephemeral stream deposits in the vicinity of the prehistoric rock shelter of ifri n ammar ne morocco during the last 100 ka abstract our study focuses on the ephemeral stream deposits of wadi selloum to identify phases of morphodynamic stability pedogenesis and activity flooding in the direct vicinity of the rock shelter of ifri n ammar ne morocco as one of the oldest settlement sites of anatomically modern humans amh in north africa ifri n ammar documents periodical occupations since 170 ka since the discontinuous settlement record may reflect climate forcing with subsequent landscape changes we aim at reconstructing the palaeoenvironmental variability recorded in the ephemeral stream deposits in addition to the use of micromorphological sedimentological geochemical and mineralogical methods the geochronological framework of ephemeral stream deposits was established by the application of different luminescence dating techniques the deposition ages between 102 8 ka and 1 3 0 2 ka span different morphodynamically stable and active phases periods of enhanced aggradation occurred around 100 ka 75 ka 55 ka after the lgm and during the holocene whilst sedimentation ended after 1 3 ka the wadi selloum might be characterised by enhanced flooding during humid phases pedogenesis may be used as environmental indicator for more humid climate conditions during mis 3 palaeo calcisol the early holocene calcisol and the late holocene fluvisol this study thus provides first insights into the palaeoenvironmental changes around the rock shelter of ifri n ammar during the last glacial interglacial cycle

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

afterslip and aftershocks in the rate and state friction law istituto nazionale di geofisica e vulcanologia italy ingv centre national de la recherche scientifique cnrs exxonmobil upstream research company

the eruptive chronology of the ampato sabancaya volcanic complex southern peru abstract we have reconstructed the eruptive chronology of the ampato sabancaya volcanic complex southern peru on the basis of extensive fieldwork and a large dataset of geochronological 40 k 40 ar 14 c and 3 he and geochemical major and trace element data this volcanic complex is composed of two successive edifices that have experienced discontinuous volcanic activity from middle pleistocene to holocene times the ampato compound volcano consists of a basal edifice constructed over at least two cone building stages dated at 450 400 ka and 230 200 ka after a period of quiescence the ampato upper edifice was constructed firstly during an effusive stage 80 70 ka and then by the formation of three successive peaks the northern southern 40 20 ka and central cones 20 10 ka the southern peak which is the biggest experienced large explosive phases resulting in deposits such as the corinta plinian fallout during the holocene eruptive activity migrated to the ne and constructed the mostly effusive sabancaya edifice this cone comprised many andesitic and dacitic blocky lava flows and a young terminal cone mostly composed of pyroclastic material most samples from the ampato sabancaya define a broad high k magmatic trend composed of andesites and dacites with a mineral assemblage of plagioclase amphibole biotite ortho and clino pyroxene and fe ti oxides a secondary trend also exists corresponding to rare dacitic explosive eruptions i e corinta fallout and flow deposits both magmatic trends are derived by fractional crystallisation involving an amphibole rich cumulate with variable amounts of upper crustal assimilation a marked change in the overall eruptive rate has been identified between ampato 0 1 km 3 ka and sabancaya 0 6 1 7 km 3 ka this abrupt change demonstrates that eruptive rates have not been homogeneous throughout the volcano s history based on tephrochronologic studies the late holocene sabancaya activity is characterised by strong vulcanian events although its erupted volume remained low and only produced a local impact through ash fallout we have identified at least 6 eruptions during the last 4 5 ka including the historical ad 1750 1784 and 1987 1998 events on the basis of this recurrent low to moderate explosive activity sabancaya must be considered active and a potentially threatening volcano

role of magma mixing in the petrogenesis of tephra erupted during the 1990 98 explosive activity of nevado sabancaya southern peru the nevado sabancaya in southern peru has exhibited a persistent eruptive activity over eight years following a violent eruption in may june 1990 the explosive activity consisted of alternated vulcanian and phreatomagmatic events followed by declining phreatic activity since late 1997 the mean production rate of magma has remained low 106 107 m3 per year

the geometry of the wadati benioff zone and lithospheric kinematics in the hellenic arc abstract accurate locations of 961 shallow and intermediate depth earthquakes which occurred between 1956 and 1995 in the hellenic arc 34 39 n 19 28 e are used to define the plate boundaries in this area reliable fault plane solutions for 77 shallow and intermediate depth earthquakes are also used in order to define the interaction between the different plates in the arc an ocean continent type of interaction occurs on a curved surface which is defined by the shallow branch 20 100 km of the wadati benioff zone the intersection of this zone with the earth s surface is a curve which follows the convex outer side of the sedimentary arc western peloponnese west of cythera south coast of crete east coast of rhodes and dips at low angle 30 to the aegean sea coupling between the subducted oceanic crust and the overriding of the aegean lithospheric plate takes place on this surface the deep branch 100 180 km of the wadati benioff zone is dipping freely without coupling at a high angle 45 beneath the south aegean trough and the volcanic arc the high shallow seismicity h 20 km which is observed in the southwestern convex outer side of the arc ionian sea is attributed to the fast southwestward motion of the aegean plate location of strong deep earthquakes h 100 km in the fore arc area of the southwestern part of the hellenic arc west of cythera indicates that oceanic crust is destroyed in this part of the hellenic trench due to roll back of the descending lithospheric slab

palaeogeographical and palaeoenvironmental reconstruction of the medjerda delta tunisia during the holocene abstract the progradation of the medjerda delta has been the subject of many studies since the 19th century the scale and the rapidity of this phenomenon interested researchers in various fields early on such as geomorphology geology palaeogeography history archaeology or geoarchaeology indeed the delta prograded by around 10 km over 3 millennia at the time of its foundation supposedly at the end of the 12th century bc the phoenician city of utica was located on a promontory bathed by the sea but the sediments carried by the medjerda progressively sealed the bay leaving the tip of the utica promontory now 10 km inland this area is therefore an exception to the general pattern along the tunisian coast since as over the same period everywhere else there is a regression of the coastline owing to a sea level rise of several decimeters based on multi proxy analyses of two coring transects this paper aims to reconstruct the palaeoenvironments and the palaeogeography of the medjerda delta s progradation since the mid holocene some aspects of which are described in ancient sources the results highlight in particular an episode of high intensity flooding around the 4th century ad which is consistent with episodes of high floods and an increase in sedimentation rates recorded in the watershed at the end of the roman period the gradual abandonment of the city of utica can certainly be related to the activity of the medjerda river but our results show that it is because of an increase of fluvial sediment contribution in connection with an erosive crisis in the headwaters and not because of the change of course of the river which had occurred long before

on the increase of background seismicity rate during the 1997 1998 umbria marche central italy sequence apparent variation or fluid driven triggering abstract we investigate the temporal evolution of background seismicity rate in the umbria marche sector of the northern apennines that was struck by the 1997 1998 colfiorito seismic sequence specifically we apply the epidemic type aftershock sequences etas model to separate the background seismicity rate from the coseismic triggered rate of earthquake production analyzed data are extracted from the catalogo della sismicita italiana csi1 1 catalog of italian seismicity 1981 2002 which contains for the study area 12 163 events with m l 1 5 the capability of the etas model to match the observed seismicity rate is tested by analyzing the model residuals and by applying two nonparametric statistical tests the runs and the kolmogorov smirnov tests to verify the fit of residuals to poisson hypothesis we first apply the etas model to the seismicity that occurred in the study area during the whole period covered by the csi1 1 catalog our results show that the etas model does not explain the temporal evolution of seismicity in a time interval defined by change points identified from time evolution of residuals and encompassing the colfiorito seismic sequence we therefore restrict our analysis to this period and analyze only those events belonging to the 1997 1998 seismic sequence we again obtain the inadequacy of a stationary etas model with constant background rate to reproduce the temporal pattern of observed seismicity we verify that the failure of the etas model to fit the observed data is caused by the increase of the background seismicity rate associated with the repeated colfiorito mainshocks we interpret the inferred increase of background rate as a consequence of the perturbation to the coseismic stress field caused by fluid flow and or pore pressure relaxation in particular we show that the transient perturbation caused by poroelastic relaxation can explain the temporal increase of background rate that therefore represents a fluid signal in the seismicity pattern

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

earthquake classification location and error analysis in a volcanic environment implications for the magmatic system of the 1989 1990 eruptions at redoubt volcano alaska abstract determination of the precise locations of seismic events associated with the 1989 1990 eruptions of redoubt volcano posed a number of problems including poorly known crustal velocities a sparse station distribution and an abundance of events with emergent phase onsets in addition the high relief of the volcano could not be incorporated into the hypoellipse earthquake location algorithm this algorithm was modified to allow hypocenters to be located above the elevation of the seismic stations the velocity model was calibrated on the basis of a posteruptive seismic survey in which four chemical explosions were recorded by eight stations of the permanent network supplemented with 20 temporary seismographs deployed on and around the volcanic edifice the model consists of a stack of homogeneous horizontal layers setting the top of the model at the summit allows events to be located anywhere within the volcanic edifice detailed analysis of hypocentral errors shows that the long period lp events constituting the vigorous 23 hour swarm that preceded the initial eruption on december 14 could have originated from a point 1 4 km below the crater floor a similar analysis of lp events in the swarm preceding the major eruption on january 2 shows they also could have originated from a point the location of which is shifted 0 8 km northwest and 0 7 km deeper than the source of the initial swarm we suggest this shift in lp activity reflects a northward jump in the pathway for magmatic gases caused by the sealing of the initial pathway by magma extrusion during the last half of december volcano tectonic vt earthquakes did not occur until after the initial 23 hour long swarm they began slowly just below the lp source and their rate of occurrence increased after the eruption of 01 52 ast on december 15 when they shifted to depths of 6 to 10 km after january 2 the vt activity migrated gradually northward this migration suggests northward propagating withdrawal of magma from a plexus of dikes and or sills located in the 6 to 10 km depth range precise relocations of selected events prior to january 2 clearly resolve a narrow steeply dipping pencil shaped concentration of activity in the depth range of 1 7 km which illuminates the conduit along which magma was transported to the surface a third event type named hybrid which blends the characteristics of both vt and lp events originates just below the lp source and may reflect brittle failure along a zone intersecting a fluid filled crack the distribution of hybrid events is elongated 0 2 0 4 km in an east west direction this distribution may offer constraints on the orientation and size of the fluid filled crack inferred to be the source of the lp events

time dependent earthquake occurrence rates along the hellenic arc seismicity rate changes in the hellenic subduction zone southern aegean sea were studied by applying the dieterich 1994 rate state dependent friction model combined with static coulomb stress changes cff the coseismic slip of the strongest earthquakes with moment magnitude m w 6 0 was considered to contribute to the stress field evolution along with the continuous tectonic loading stress changes were calculated just after each strong event and their influence was examined in connection with the smaller magnitude earthquake occurrence rates qualitative and quantitative comparison between the observed seismicity rates smoothed by the means of a probability density function and the expected ones as they were forecasted by the rate state model were investigated for the interseismic periods study periods between subsequent strong earthquakes the calculations aim to identify areas of expected increased seismicity rates as candidates to accommodate enhanced seismic activity results strongly depend on the determination smoothing of the unperturbed reference seismicity rates and data adequacy seismicity rate results were filtered by certain criteria and constraints in an attempt to overcome model uncertainties epicentral errors rupture models parameter values and to provide reliable results for specific areas of major interest that is in areas with increased positive coulomb stress changes values the modeling approach resulted in satisfactory correlation between observed and synthetic seismicity rates and in particular the two strong m w 6 earthquakes that occurred in 2013 are located in areas of increased expected seismicity rates

holocene evolution of deep circulation in the northern north atlantic traced by sm nd and pb isotopes and bulk sediment mineralogy 1 bulk mineralogy sm nd and pb elemental and isotopic compositions of the clay size fraction of holocene sediments were analyzed in three deep north atlantic cores to trace the particle provenance the aims of the present paper are to identify the origin of the particles driven by deep currents and to reconstruct deep circulation changes over the holocene in the north atlantic the three cores are retrieved in fracture zones two of them are located in the island basin along the gyre of north atlantic deep water and the third core is located off the present deep circulation gyre in the labrador sea whereas sedimentary supplies in the labrador sea were constantly derived from proximal sources the geochemical mixing trends in the iceland basin samples indicate pronounced changes in the relative contribution of continental margin inputs over the past 6 kyr supplies from western european margin that sharply increased at 6 kyr were progressively diluted by a larger contribution of scandinavian margins over the last 3 kyr changes in composition of the particles imply significant reorganization of paleocirculation of the deep north atlantic components in the eastern basins mainly reorganizations for both iceland scotland overflow water and norwegian sea overflow water moreover the unusual pb isotopic composition of the oldest sediments from the southern iceland basin indicates that distal supplies from greenland margin were driven into the iceland basin supporting a deep connection between labrador sea and iceland basin through the charlie gibbs fracture zone prior the holocene transition period

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

volcanic hotspots of the central and southern andes as seen from space by aster and modvolc between the years 2000 and 2010

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

amino acids and hexosamines in the hess rise core during the past 220 000 years abstract core sediment samples collected from the hess rise north pacific were analyzed for 20 common amino acids aa and two hexosamines ha to understand the relation between glacial interglacial variations and deposition preservation of sedimentary organic matter om the sediments are predominantly carbonaceous carbonates 35 80 aa based parameters aspartic acid glycine ratio and serine threonine relative mole content suggest that calcareous plankton was the major source of om in these sediments this inference is supported by the similarity in distribution patterns of aa and ha contents with that of organic carbon low values of aa ha and glucosamine galactosamine ratios average 4 4 and 1 1 respectively imply that much of the planktonic om was replaced by microbial om the relative molar concentration of two nonprotein aa alanine and aminobutyric acid varied with age of sediments i e they were less abundant in recent sediments and more abundant in the oldest sediments this trend is an indicator of extremely slow but continuous enzymatic degradation of proteinaceous om within the sediments so far bulk om has been believed to be one of the best proxies for estimation of primary productivity however it may be an underestimate even for the late quaternary sediments comparison of aa and ha content variations with specmap stack revealed their enhanced deposition and preservation during glacial periods relative to interglacial periods this in turn affected not only the planktonic production in surface waters but also the benthic community including bacteria on the seafloor

stress and aftershock constrained joint inversions for coseismic and postseismic slip applied to the 2004 m6 0 parkfield earthquake 1 both aftershocks and geodetically measured postseismic displacements are important markers of the stress relaxation process following large earthquakes postseismic displacements can be related to creep like relaxation in the vicinity of the coseismic rupture by means of inversion methods however the results of slip inversions are typically non unique and subject to large uncertainties therefore we explore the possibility to improve inversions by mechanical constraints in particular we take into account the physical understanding that postseismic deformation is stress driven and occurs in the coseismically stressed zone we do joint inversions for coseismic and postseismic slip in a bayesian framework in the case of the 2004 m6 0 parkfield earthquake we perform a number of inversions with different constraints and calculate their statistical significance according to information criteria the best result is preferably related to a physically reasonable model constrained by the stress condition namely postseismic creep is driven by coseismic stress and the condition that coseismic slip and large aftershocks are disjunct this model explains 97 of the coseismic displacements and 91 of the postseismic displacements during day 1 5 following the parkfield event respectively it indicates that the major postseismic deformation can be generally explained by a stress relaxation process for the parkfield case this result also indicates that the data to constrain the coseismic slip model could be enriched postseismically for the 2004 parkfield event we additionally observe asymmetric relaxation process at the two sides of the fault which can be explained by material contrast ratio across the fault of 1 15 in seismic velocity

the 14 february 2008 earthquake m6 7 sequence offshore south peloponnese greece source models of the three strongest events abstract we investigate the rupture process of the strongest events of the 14 february 2008 sequence which ruptured 30 km of the western hellenic trench three were the strongest events of the sequence the first one m 6 7 occurred on 14 february 2008 at a depth of 30 km on a low angle 10 thrust fault followed within 2 h by an m 6 1 aftershock at a depth of 33 km also on a low angle thrust fault and the third one on 20 feb 2008 of m 6 0 which is characterized as a strike slip event at shallower depth 10 km we used the m 6 1 aftershock as empirical green s function egf to invert for the slip distribution of the strongest m 6 7 event of the sequence we were able to identify the low angle plane strike 288 dip 10 and rake 73 as the fault plane the slip model is dominated by two distinct slip patches which extend towards sse from the hypocenter thus implying rupture directivity toward the island of crete a result which is further supported by our teleseismic waveform inversion results maximum slip is estimated at 270 cm while average slip on the ruptured area area of subfaults of non zero slip was 70 cm most of the slip 95 of total is confined in an area of 34 22 km 2 we attribute the occurrence of the shallow strike slip event just above the interplate thrusting at depth to slip partitioning due to the deflection of slip vectors from the expected plate convergence vector

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control