near real time double difference event location using long term seismic archives with application to northern california we present a real time procedure that uses cross correlation and double difference methods to rapidly relocate new seismic events with high precision relative to past events with accurately known locations waveforms of new events are auto matically cross correlated with those archived for nearby past events to measure accu rate differential phase arrival times these data together with delay times computed from arrival time picks are subsequently inverted for the vector connecting the new event to its neighboring events using the double difference algorithm the new seis mic monitoring technique is applied to earthquakes recorded in northern california using near real time data feeds from the northern california seismic network ncsn and the northern california earthquake data center and a locally stored copy of the ncsn seismic archive new events are automatically relocated in near real time tens of seconds relative to a high resolution double difference earthquake catalog for northern california back testing using past events across northern california indi cates that the real time solutions are on average within 0 08 km laterally and 0 24 km vertically of the double difference catalog locations we show that the precision with which new events are located using this technique will improve with time helped by the continued increase in density of recorded earthquakes and growth of the digital seismic archives real time double difference location allows for monitoring spatio temporal changes in seismogenic properties of active faults with unprecedented res olution and therefore has considerable social and economic impact in the immediate evaluation and mitigation of seismic hazards

avulsions and the spatio temporal evolution of debris flow fans debris flows are water laden masses of sediment that move rapidly through channel networks and over alluvial fans where they can devastate people and property episodic shifts in the position of a debris flow channel termed avulsions are critical for debris flow fan evolution and for understanding flow hazards because avulsions distribute debris flow deposits through space and time however both the mechanisms of flow avulsion and their effects on the long term evolution of debris flow fans are poorly understood here we document and analyze the spatial and temporal patterns of debris flow activity obtained by repeat topographic analyses dendrogeomorphic and lichenometric reconstructions and cosmogenic radionuclide dating on 16 fans from japan usa switzerland france and kyrgyzstan where possible we analyze the observed spatio temporal patterns of debris flow activity in conjunction with high resolution topographic data to identify the main controls on avulsion we identify two main processes that control avulsions on debris flow fans operating over distinct time scales first during individual flows or flow surges deposition of sediment plugs locally blocks channels and forces subsequent flows to avulse into alternative flow paths plug deposition is a stochastic process but appears to depend in part on the sequence of flow volumes the geometry of the channel and the composition of the flows second over time scales of tens of events the average locus of debris flow deposition gradually shifts toward the topographically lower parts of a fan highlighting the importance of topographic compensation for fan evolution our documented debris flow avulsions often but not always follow a pattern of channel plugging backstepping of deposition toward the fan apex over one or more flows avulsion and establishment of a new active channel large flows can have contrasting impacts depending on whether or not they follow smaller flows that have deposited channel plugs these results suggest that avulsions and spatio temporal patterns of debris flow fan formation strongly depend on both the magnitude frequency distribution and the sequence of the flows feeding a fan while individual avulsions are generally abrupt and difficult to predict the presence of debris flow plugs and patterns of backstepping may be useful as indicators of impending avulsions over longer time scales the compensational tendency of flows to avulse into topographic depressions on the fan may also be used to identify sectors of the fan that are at risk of future inundation

spatio temporal reconstruction of lahars on the southern slopes of colima volcano mexico a dendrogeomorphic approach historical records of lahar occurrence and distribution are typically scarce in volcanic environments even more so if they occur outside of human settlements in the context of hazard assessment and process understanding documenting their temporal frequency and drivers of activity might be crucial on forested volcanoes lahars may significantly damage trees along their flow paths and sometimes even eliminate entire forest stands this study is based on growth disturbances in trees affected by lahars i to assess the potential of dendrogeomorphic techniques in lahar research and ii to analyze the temporal frequency and spatial patterns of lahars at montegrande and arena two of the most active of the ephemeral streams on the southern sector of colima volcano a total of 78 pinus leiophylla live trees were sampled along the ravines yielding evidence for 20 lahar events after the ad 1913 eruption adding seven events to the historic records although the number of lahars reconstructed with tree ring records can only be considered as a minimum frequency the method clearly improves the local lahar chronology despite the scarcity of meteorological records at the study sites the timing of reconstructed lahars points to heavy rainfalls after explosive activity as the main driver of events

long term stability of flow path structure in crystalline rocks distributed in an orogenic belt japan most evaluations of the contaminant retardation processes likely to be important in geological disposal e g for high level radioactive waste hlw consider only the present characteristics of fractures and associated mineral infills relatively little attention has been given to possible long term changes in these features and their influence on groundwater flow the work reported here seeks to provide analogous evidence that such changes are not likely to be important and hence to improve confidence in the presently adopted evaluation methodology and its long term applicability in the orogenic belt that is formed by the japanese islands there are wide areas of crystalline rock the rocks in each area have a distinctive age sequence which is partly reflected in the characteristics of the fracture systems and associated mineral fillings that occur these characteristics generally imply that groundwater and solutes can be conducted through fracture networks except in the cases of fault zones or crushed zones the structural and mineralogical features of these networks readily illustrate how certain contaminants might react and be retarded by the fracture fillings and open pore geometry due to chemical sorption and or physical retardation here we describe the fracture systems developed in crystalline rocks with different ages that are intruded into the japanese orogenic belt the aim is to build a model for the long term fracturing process and hence to evaluate fracture dstabilityt i n particular the comparisons are made between the fracture geometries and the frequencies observed in the 1 9 0 8 ma takidani granodiorite the youngest exposed pluton in the world the ca 67 ma toki granite and the ca 117 ma kurihashi granodiorite located in central to northwest japan the observations show that all these crystalline rocks have similar fracture frequencies with 1 to 2 fractures per meter in the massive part of rock bodies mineralogical studies and dating analyses of fracture fillings also suggest that fractures are relatively physically stable major new fractures tend not to be created in the massive part of rock bodies even when a pluton has been subjected to the regional stresses of plate movements with a duration of about 100 ma the results show the unique characteristics of the fracture forming process and the relatively stable geometries of fracture network systems in crystalline rocks distributed within the orogenic belt this analogue also enables us to provide a model to build confidence in a technical approach applicable for modeling of hydrogeology and geology over long time scales under the

deformation processes adjacent to active faults examples from eastern california 1 major seismogenic faults are embedded within narrow zones of inelastic off fault deformation ofd where both distributed displacement and modification of rock properties occur active distributed displacement may affect slip rate estimates seismic energy radiation and geodynamic models this study addresses the role of ofd in the displacement history and mechanical behavior of seismogenic faults by multisite study of deformed geologic features adjacent to 30 60 km long active strike slip faults of 10 km of dextral displacement in the mojave desert eastern california we find that distributed displacement accommodates 0 to 25 of the total displacement over zones of one to two kilometers width displacement occurs mostly within 100 200 m of faults and decreases nonlinearly away from the main fault we show evidence for distributed displacement through simple shear in the form of parallel secondary faults and progressive deformation of linear markers adjacent to the calico fault we also find evidence for shear via rotation and progressive fragmentation adjacent to the harper lake fault analysis of block dimensions show that blocks tend to decrease in size toward faults and that cumulative length of secondary faults is longer than the main fault by at least a factor of 10 based on crosscutting relationships and the relationship of ofd to geophysically imaged compliant zones around active faults we argue that distributed displacement is an active process and suggest that zones of diminished rigidity near faults may be at least in part driven by secondary faulting during the rupture propagation along the main fault

fluid rock reaction weakening of fault zones the presence of weak phyllosilicates may explain the low shear strengths of fault zones if they define well developed fabrics the growth of phyllosilicates is favored in meteoric water dominated granitic fault systems where mineral aqueous fluid equilibria predict that modal phyllosilicate will increase via feldspar replacement reactions in deeper more alkaline rock dominated regimes the reactions reverse and feldspars tend to replace phyllosilicates in mg rich mafic rocks however phyllosilicates chlorite biotite can replace stronger framework and chain silicates in both shallower approximately 10 km meteoric h sub 2 o dominated and in deeper alkaline rock dominated regimes where these phyllosilicates precipitate in active fault zones they contribute directly to reaction softening because low temperature deformation of phyllosilicates is not governed by frictional processes alone but can occur by pressure independent dislocation glide the strength of phyllosilicate rich fault rocks can be low at all depths low strain rate creep during interseismic periods can align phyllosilicate grains in foliated gouge and phyllonites where preferred orientations are strong and contiguity of phyllosilicates is large strengths of rocks within fault zones may approach minimum strengths defined by single phyllosilicate crystals fault zones containing localized high concentrations of phyllosilicates with strong preferred orientations in well defined folia can exhibit aseismic slip especially where mafic mg rich rocksmore occur along the fault like parts of the san andreas fault 104 refs 6 figs 1 tab less

continuous kurtosis based migration for seismic event detection and location with application to piton de la fournaise volcano la reunion abstract we present an automatic earthquake detection and location technique based on migration of continuous waveform data data are preprocessed using a kurtosis estimator in order to enhance the first arrival information then migrated onto a predefined search grid using precalculated p wave travel times and finally stacked local maxima in the resulting 4d space time grid indicate the locations and origin times of seismic events we applied our technique to earthquake swarms occurring on piton de la fournaise volcano la reunion france we located 5000 events from 12 different swarms that occurred between 2009 and 2011 our automated locations are consistent with those performed using manual picks and indicate that the seismicity concentrates around sea level multiplet analysis of the detected events and subsequent double difference relocation produce sharper images of the earthquake swarms our code waveloc is released in open source online material figures of seismicity distributions from waveloc synthetic test and stack amplitude values versus magnitudes

silica diagenesis ii general mechanisms abstract amorphous silica phases opal a precipitate in nature due to the formation of dense colloids in supersaturated alkaline aqueous solutions with low relative concentrations of other ions opal a dissolves and yields solutions of still relatively high silica content in pore waters containing abundant cations open framework polymers form which flocculate to yield opal ct opal ct becomes increasingly ordered primarily due to preferential growth of cristobalite relative to tridymite and crystal size increase opal ct dissolves to yield pore waters of low silica concentration which allows slow growth of quartz crystals from monomeric solution the quartz crystals then slowly increase in size and crystallinity carbonates appear to enhance opal ct formation possibly due to the activity of positively charged hydroxyl complexes hence polymerization in relatively pure systems is involved in opal a formation and polymerization in impure systems is involved in opal ct formation and slow growth from monomeric low silica concentration solutions is involved in precipitation of quartz in sedimentary realms

microfracturing paleostress and the growth of faults abstract we have analyzed the microfractures in samples taken near one thrust fault and five normal faults of known displacement to test the dependence of microfracture density and distribution on fault slip we have also recorded the orientation of microfractures as a function of distance from the associated fault surface in order to control as many parameters as possible shallow faults with similar lithologies were chosen they showed the same kind of deformation namely microfracturing without block rotation recrystallization extensive granulation or crystal plasticity the results of over 8000 microfracture measurements suggest that maximum microfracture density is independent of net slip we interpret this relationship as indicating that the preponderance of microfracturing occurs in proximity to the propagating fault tip the angular relationship between the shear plane and microfractures was commonly found to be between 5 and 20 significantly less than the 30 expected between the far field maximum principal stress and the shear surface this low angle between microfracture orientation and shear plane orientation is predicted for a local stress field associated with a propagating mode ii fault tip other possible explanations for the small angle for tensional microfractures and the shear surface are 1 the effective confining pressure was very low or 2 shear strength at failure was much larger than expected

monitoring velocity variations in the crust using earthquake doublets an application to the calaveras fault california we present a technique that greatly improves the precision in measuring temporal variations of crustal velocities using an earthquake doublet or pair of microearthquakes that have nearly identical waveforms and the same hypocenter and magnitude but occur on different dates we compute differences in arrival times between seismograms recorded at the same station in the freqency domain by cross correlation of short windows of signal a moving window analysis of the entire seismograms including the coda gives t the difference in arrival times versus running time along the seismogram the time resolution of the method is an order of magnitude better than the digitization interval the t technique is illustrated with a pair of microearthquakes m 1 7 and 2 0 that occurred before and after the coyote lake california earthquake m 5 9 of august 6 1979 and on the same segment of the calaveras fault that ruptured during the earthquake the coda wave arrivals for some stations are progressively delayed for the second earthquake in the doublet so that its seismogram appears as a stretched version of the earlier event we interpret this systematic variation in t along the coda as a change in the average s velocity in the upper crust in the time interval between the two doublets s wave velocities appear to have decreased by 0 2 in an oblong region 5 10 km in radius at the south end of the aftershock zone

the block structure and quaternary strike slip block rotation of central japan central japan is situated on the inflection point of the bow shaped japanese islands numerous nw se trending active faults arranged in parallel at intervals of 20 to 80 km are found in this area these active faults are more than 30 km long with shattered zones from 30 to 300 m wide several active faults constitute a given block boundary which serves as the dividing line for one of the four blocks that make up central japan the block boundaries require careful study since numerous historical earth quakes have occurred along these lines offset measurements of basement rocks created during the quaternary period due to left lateral faulting amount to 1 to 7 km gravity lineaments which link points of sudden change and saddles of bouguer anomalies are clearly found along the block boundaries the nw se trending active faults appearing on the ground surface are associated with motions of the block boundaries block rotational movement caused by left lateral faulting plays an important role in the crustal deformation of central japan rotational angles of the blocks calculated from the amount of displacement of basement rocks initiated during the quaternary period are estimated to be 3 to 7 in a clockwise manner

recent increase in debris flow activity in the tatras mountains results of a regional dendrogeomorphic reconstruction abstract debris flows are very frequent geomorphic agents that form relief of the high tatras mountains which are the highest mountain range in the carpathian arc the knowledge of their history is based on lichenometric dating historical orthophotos and incomplete archival records nevertheless complete chronologies of debris flows at an annual resolution for the high tatras mountains have not yet been reconstructed in this paper we present results of dendrogeomorphic research in the southern region of the mountains the great cold valley and small cold valley the research was undertaken to reconstruct regional year to year chronologies of debris flows which would present unique perspectives on the debris flow activity a total of 474 scars on the stems and branches of 414 pinus mugo were dated with a seasonal precision the best tool for distinguishing debris flow scars from snow avalanche scars in 12 debris flow tracks 22 debris flows over the last circa 30 years the valid chronological range in six event years were reconstructed a significant increase in debris flow activity verified using historical orthophotos has occurred since ad 2007 21 of 22 events occurred during the last decade two basic spatial patterns of debris flow activity were identified regional events with at least five debris flows in one or both valleys and local events with a maximum of two debris flows per year based on reports by several authors increase in extreme precipitation events during the last decade has been observed but debris flows have not occurred even during the most extreme precipitation events in the study area preparatory factors must play an important role at this stage a significant increase in summer and autumn temperatures at the turn of the 21st century has been reported in the high tatras mountains this could accelerate dis continuous permafrost thawing in the source zones increase the amount of material for the next transport and influence the increase in debris flow activity

dendrogeomorphic reconstruction of flash floods in the patagonian andes flash floods represent a significant natural hazard in small mountainous catchments of the patagonian andes and have repeatedly caused loss to life and infrastructure at the same time however documentary records of past events remain fairly scarce and highly fragmentary in most cases in this study we therefore reconstruct the spatiotemporal patterns of past flash flood activity along the los cipreses torrent neuquen argentina using dendrogeomorphic methods based on samples from austrocedrus chilensis pseudotsuga menziesii and nothofagus dombeyi we document 21 flash flood events covering the period a d 1890 2009 and reconstruct mean recurrence intervals of events at the level of individual trees being impacted which varies from 4 to 93 years results show that trees tend to be older younger in sectors of the torrent with gentler steeper slope gradients potential triggers of flash floods were analyzed using daily temperature and precipitation data from a nearby weather station weather conditions leading to flash floods are abundant precipitations during one to three consecutive days combined with temperatures above the rain snow threshold 2 c in the whole watershed

surficial patterns of debris flow deposition on alluvial fans in death valley ca using airborne laser swath mapping data debris flows are a common event in mountainous environments they often possess the greatest potential for destruction of property and loss of lives in these regions delimiting the spatial extent of potential damage from debris flows relies on detailed studies of the location of depositional zones current research indicates debris flow fans have two distinct depositional zones however the two zones were derived from studies containing detailed analyses of only a few fans high resolution airborne laser swath mapping alsm data is used to calculate profile curvature and surface gradient on 19 debris flow fans on the eastern side of death valley the relationship between these parameters is assessed to 1 identify if debris flow fans are accurately represented by two depositional zones and 2 to assess how these terrain parameters relate to one another at the individual fan scale the results show at least three zones of deposition exist within the sampled fans these zones do not hold consistent when individual fan morphometry is analyzed in conjunction with localized fan surface gradients fans with consistently shallower gradients exhibit numerous depositional zones with more subtle changes in profile curvature steeper gradient fans exhibit significantly fewer zones with more pronounced local changes in profile curvature the surface complexity of debris flow fans is evident from these analyses and must be accounted for in any type of hazard studies related to these features

implications of mylonitic microstructures for the geotectonic evolution of the median tectonic line central japan the median tectonic line mtl the most prominent onshore fault in japan demarcates the cretaceous hiji quartz dioritic gneiss of the ryoke belt on the west from the high p t type sambagawa metamorphic rocks on the east in the takato area toward the mtl the hiji gneiss grades into strongly mylonitized rocks characterized by grain size reduction of quartz in the mylonitic rocks the development of fluxion banding sm is remarkably influenced by the existence of k feldspar forming a myrmekitic intergrowth brittle microstructures indicative of truly cataclastic deformation are observed only in mylonitic rocks close to the mtl early deep level ductile deformation apparently gave way to shallower brittle deformation at a later stage the attitude of stretching lineations lm and asymmetric microstructures observed in the mylonites suggest that sinistral strike slip shearing with a subordinate component of vertical slip took place during mylonitization in mid cretaceous time the mylonitic rocks and their protolith supposed to have constituted the eastern limb of the shear zone were probably eroded out and lost by upheaval of the sambagawa belt relative to the ryoke belt

groundwater mixing dynamics at a canadian shield mine temporal and spatial variations in geochemistry and isotopes in mine inflows at the con mine yellowknife are studied to access the impact of underground openings on deep groundwater flow in the canadian shield periodic sampling of inflow at 20 sites from 700 to 1615 m depth showed that salinities range from 1 4 to 290 g l with tritium detected at all depths three mixing end members are identified 1 ca na cl shield brine 2 glacial meltwater recharged at the margin of the retreating laurentide ice sheet at 10 ka and 3 modern meteoric water mixing fractions calculated for inflows on five mine levels illustrate the infiltration of modern water along specific fault planes tritium data for the modern component are corrected for mixing with brine and glacial waters and interpreted with an exponential piston flow model results indicate that the mean transit time from surface to 1300 m depth is about 23 years in the early period after drift construction in 1979 but decreases to about 17 years in the past decade the persistence of glacial meltwater in the subsurface to the present time and the rapid circulation of modern meteoric water since the start of mining activities underline the importance of gradient in addition to permeability as a control on deep groundwater flow in the canadian shield q 2000 elsevier science b v all rights reserved

tree ring based reconstruction of rockfalls at cofre de perote volcano mexico in this study dendrogeomorphic techniques are employed to analyse the temporal frequency and spatial distribution of rockfalls on a talus slope of la teta valley located on the nw slopes of cofre de perote volcano at 4000 m above sea level based on the interpretation of disturbance signals in growth rings of old growth pinus hartwegii lindl trees we identify 100 growth disturbances related with rockfall events dated between 1780 and 2011 with slightly more than half of these events being dated to the last 50 years the sectors most susceptible to rockfall correspond with the young rock lobes located at the foot of scarps roughly three in ten events has been triggered by regional m 6 earthquakes whereas half of the events activity coincides with periods characterized by severe prolonged summer rainfalls such as the ones occurred in 1995 1998 2005 and 2011

the 2008 may 29 earthquake doublet in sw iceland summary on 2008 may 29 an earthquake doublet shook the southwestern part of iceland the first main shock originated beneath mt ingolfsfjall located near the western margin of the south iceland seismic zone sisz approximately 40 km east of the capital reykjavik immediate aftershock activity was recorded by the sil seismic network operated by the icelandic meteorological office imo with both n s and e w structures illuminated over a broad area a continuous gps cgps network also operated by the imo recorded coseismic offsets with up to 200 mm of horizontal motion at the closest stations we estimate the coseismic surface deformation observed by campaign and continuous gps and satellite radar data insar we invert the geodetic data to find the optimal geometry location and slip on the main faults accounting for variation in the elastic parameters of the crust with depth our models indicate that most of the slip occurred on two n s structures spaced 5 km apart from a joint inversion of gps and insar data for variable slip models we find that most of the slip for the first ingolfsfjall event was concentrated at 2 4 km depth with a maximum of 1 9 m whereas the slip on the second kross fault was located deeper at 3 6 km depth with up to 1 4 m of motion the models give similar geodetic moments for the two main events equivalent to a moment magnitude of mw5 8 and mw5 9 for the first and second event respectively our estimated composite moment therefore equals a mw6 1 for the doublet smaller than the mw6 3 estimated from teleseismic data e g neic and harvard the geodetic data support rupture on two main faults and analysis of high rate 1 hz cgps data suggests that slip on the second fault initiated within 3 s of the first main shock static coulomb failure stress calculations indicate that the first event caused a stress increase in the area of the main asperity i e at the location of the largest slip patch on the second fault however we cannot rule out dynamic stress triggering due to the short time between the two main events the 2008 may 29 earthquake doublet appears to be a continuation of the earthquake sequence that started in 2000 june when two mw6 5 events struck the eastern and central part of the south iceland seismic zone in the span of 81 hr the 2000 june 2008 may sequence has released about half of the moment accumulated by plate motion since the previous earthquake sequence in 1896 1912 therefore continued earthquake activity with moderate size events rupturing n s faults in the sisz in the coming decades is likely

reconstruction of glacial lake outburst floods in northern tien shan implications for hazard assessment abstract glacier lake outburst floods glofs and related debris flows are among the most significant natural threats in the tien shan mountains of kyrgyzstan and have even caused the loss of life and damage to infrastructure in its capital bishkek an improved understanding of the occurrence of this process is essential so as to be able to design reliable disaster risk reduction strategies even more so in view of ongoing climate change and scenarios of future evolutions here we apply a dendrogeomorphic approach to reconstruct past debris flow activity on the aksay cone ala archa valley kyrgyz range where outbursting glacier lakes and intense rainfalls have triggered huge debris flows over the past decades a total of 96 picea abies l karst trees growing on the cone and along the main channel have been selected based on the evidence of past debris flow damage in their trunks these trees were then sampled using increment borers the dating of past events was based on the assessment of growth disturbances gd in the tree ring records and included the detection of injuries tangential rows of traumatic resin ducts reaction wood and abrupt growth changes in total 320 gd were identified in the tree ring samples in combination with aerial imagery and geomorphic recognition in the field reactions in trees and their position on the cone have allowed reconstruction of the main spatial patterns of past events on the aksay cone our findings suggest that at least 27 debris flows have occurred on the site between 1877 and 2015 and point to the occurrence of at least 17 events that were not documented prior to this study we also observe high process activity during the 1950s and 1960s with major events on the cone in 1950 1966 and 1968 coinciding with phases of slight glacier advance the spatial analyses of events also point to two different spatial patterns suggesting that quite dissimilar magnitudes probably occurred during glacier lake outburst floods and rainfall induced debris flow events the results presented here represent the longest annually resolved glof series in the region which in turn has key implications on risk assessment not just in the ala archa valley but also in the entire kyrgyz range northern tien shan

stress and fluid driven failure during fracture array growth implications for coupled deformation and fluid flow in the crust brittle experimental deformation on dolomite rocks shows for the fi rst time the differ ence in growth of fracture networks by ordinary percolation and invasion percolation processes stress driven fracture growth in the absence of fl uid pressure is an ordinary percolation process characterized by distributed nucleation and growth of microfractures which coalesce with increasing strain to form a connected fracture network fluid pres sure driven fracture growth is more akin to an invasion percolation process characterized by preferential fracture growth occurring initially at the high fl uid pressure part of the rock with progressive deformation the network propagates rapidly through the sample and away from the high fl uid pressure reservoir x ray microtomography analysis suggests that the fracture network in three dimensions 3 d is probably a fully connected network at peak stress conditions whereas conventional 2 d analysis suggests that connectivity only occurs at shear failure the development of 3 d fracture connectivity prior to shear failure has important implications for fl uid fl ow and fl uid pressure changes immediately prior to rupture nucleation in active fault zones for fl uid migration in ore producing hydrothermal systems and for reservoir integrity in hydrocarbon systems

a sem cathodoluminescence study of quartz in mildly deformed granite from the region of the atotsugawa fault central japan abstract cathodoluminescence cl images of quartz in granite distributed around the atotsugawa fault in central japan were observed by scanning electron microscopy and compared to optical microscope observations of the same crystals narrow or wide dark bands or dots were commonly recognized in the cl images almost all dots or narrow bands correlate with isolated bubbles or semi planar bubble arrays along healed cracks respectively some wide bands correspond to cracks filled with other minerals chlorite calcite mica etc or can be distinguished as zones with an extinction differing from that of surrounding areas in quartz crushed zones composed of healed crack arrays other wide bands are healed cracks where quartz is precipitated in optical continuity the quartz cl images displayed overall textures composed of mineral filled cracks bubble arrays along healed cracks and crushed zones more clearly than normal optical images healed cracks containing quartz precipitated in optical continuity with the enclosing grains were distinctly revealed as dark bands in cl images the abundance of these minor deformation structures as revealed in cl images increases with proximity to the fault therefore cl textures of quartz are an important aid in examining brittle deformation textures and understanding the tectonic processes that produce them

japan sea opening history and mechanism a synthesis the respective tectonic effects of back arc spreading and continental collision in asia are considered either as two independent processes or as closely interrelated extrusion tectonics assumes that the opening of the south china sea and the left lateral motion along the red river fault are geometrically linked in a pull apart manner this model is not accepted by several workers because the structural link between the two processes is not clearly demonstrated in the case of the japan sea we can show without ambiguity that back arc opening was controlled by large intracontinental strike slip faults which can be easily understood as effects of the india asia collision far from the indenter the japan sea opened in the early miocene in a broad pull apart zone between two major dextral strike slip shear zones the first one extends from north sakhalin to central japan along 2000 km it has accommodated about 400 km of finite displacement deformation along it varies from dextral transpression in the north to dextral transtension in the south the second is between korea and sw japan and has accommodated a smaller displacement of about 200 km the extensional domain in between lies in the back arc region of japan distributed stretching of the arc crust resulted in the formation of most of the japan sea while localized oceanic spreading at the southern termination of the eastern transpressional shear zone shaped the japan basin the first oceanic crust was formed in a small triangle based on the eastern shear zone and spreading propagated westward inside the pull apart region timing of oceanic crust formation of formation of the dextral shear zones and of block rotation in between as well as the internal structure of the basins and the geometry of deformation along the master shear zones are used to reconstruct the opening history this evolution is discussed by comparison to other manifestations of the arc and back arc activity such as the history of sedimentation and volcanism the paper then suggests that the collision of india can have tectonic consequences as far north as japan and sakhalin and describes the geometrical relation of back arc opening there and diffuse extrusion

automatic seismic phase picking and consistent observation error assessment application to the italian seismicity summary accuracy of seismic phase observation and consistency of timing error assessment define the quality of seismic waves arrival times high quality and large data sets are prerequisites for seismic tomography to enhance the resolution of crustal and upper mantle structures in this paper we present the application of an automated picking system to some 600 000 seismograms of local earthquakes routinely recorded and archived by the italian national seismic network the system defines an observation weighting scheme calibrated with a hand picked data subset and mimics the picking by an expert seismologist the strength of this automatic picking is that once it is tuned for observation quality assessment consistency of arrival times is strongly improved and errors are independent of the amount of data to be picked the application to the italian local seismicity documents that it is possible to automatically compile a precise homogeneous and large data set of local earthquake pg and pn arrivals with related polarities we demonstrate that such a data set is suitable for high precision earthquake location focal mechanism determination and high resolution seismic tomography

brittle tectonothermal evolution in the forsmark area central fennoscandian shield recorded by paragenesis orientation and 40ar 39ar geochronology of fracture minerals in this paper we show how studies of fracture mineral paragenesis their orientation and ar 40 ar 39 geochronology can be applied in order to recognise the brittle tectonothermal evolution in an area samples were selected from nearly 18 km of drill cores from the upper i km of the fennoscandian shield obtained during the site investigation for a repository of spent nuclear fuel in forsmark central sweden four major events of fracturing and or reactivation of fractures associated with fracture mineralisation have been distinguished the first event was characterised by precipitation of epidote quartz and chlorite along preferably sub horizontal and gently dipping fractures or steep wnw ese to nw se fractures precipitation occurred between 1 8 and 1 1 ga possibly during the late stage of the svecokarelian orogeny close to 1 8 1 7 ga the second event is associated with precipitation of hematite stained adularia and albite prehnite laumontite calcite and chlorite preferably along steep ene wsw to nne ssw and nnw sse fractures precipitation occurred around 1107 7 to 1034 3 ma probably due to effects from the sveconorwegian orogeny this event was followed by a period with dissolution of fracture minerals and subsequent precipitation of mainly calcite quartz pyrite and asphaltite during the palaeozoic the formation fluid emanated from an overlying organic rich sedimentary cover precipitation occurred during reactivation of proterozoic fractures but formation of new fractures is also inferred possibly due to far field effects of the caledonian orogeny or elevated hydrostatic pressure due to its foreland basin the latest event is dominated by clay minerals chlorite and calcite along hydraulically conductive fractures these minerals are prominent along sub horizontal and gently dipping fractures but also occur in sets of steeply dipping fractures it is inferred that the hydraulically conductive fractures are proterozoic structures in which mineral precipitation has occurred during a long period however some of the near surface sub horizontal fractures may be quaternary in age c 2009 elsevier b v all rights reserved less

applying a three dimensional velocity model waveform cross correlation and cluster analysis to locate southern california seismicity from 1981 to 2005 we compute high precision earthquake locations using southern california pick and waveform data from 1981 to 2005 our latest results are significantly improved compared to our previous catalog by the following 1 we locate events with respect to a new crustal p and s velocity model using three dimensional ray tracing 2 we examine six more years of waveform data and compute cross correlation results for many more pairs than our last analysis and 3 we compute locations within similar event clusters using a new method that applies a robust fitting method to obtain the best locations satisfying all the differential time constraints from the waveform cross correlation these results build on the relocated catalogs of hauksson and shearer 2005 and shearer et al 2005 and provide additional insight regarding the fine scale fault structure in southern california and the relationship between the san andreas fault saf and nearby seismicity in particular we present results for two regions in which the seismicity near the southern saf seems to align on dipping faults

grain boundary microcracking of granitic rocks from the northeastern region of the atotsugawa fault central japan sem backscattered electron images abstract backscattered electron bse images from granitic rocks gathered in and around the northeastern region of the atotsugawa fault in central japan were examined by scanning electron microscopy bse images reveal that grain boundary microcracking strongly depends upon the mineralogy of the two adjacent grains at grain boundaries there are six possible different mineral pairings of the three main constituent minerals quartz plagioclase and k feldspar found in granitic rocks each grain boundary can be separated into one of two types a partially to entirely open grain boundary or a closed grain boundary grain boundaries can be classified by their decreasing sense of openness 1 quartz feldspars plagioclase and k feldspars 2 quartz quartz 3 piagioclase plagioclase 4 k feldspar plagioclase and 5 k feldspar k feldspar boundaries microcracks in grain boundaries are commonly found in a wide zone offset of the shattered zone of the fault the number and types of partially to entirely open grain boundaries increase with proximity to the fault following the above sequence the number and types can be used to detail the special zoning of rock masses around a fault

faults and their associated host rock deformation part i structure of small faults in a quartz syenite body southern israel we analyze pervasive and discontinuous deformation associated with small faults in a quartz syenite body in southern israel the analysis includes detailed mapping measurement of in situ mechanical rock properties and microstructural study of the faults the mapped faults have 1 100 m long horizontal traces consisting of linked curved segments the segmented nature of the faults is also apparent at the 1 10 mm scale the observed deformation features are breccia as well as intra and inter granular fractures these features are accompanied by reduction of the young modulus and uniaxial strength of the host rock the deformation features are zoned from a central fault core through a damage zone to the protolith at distances of 0 05 0 06 the fault length shear strains up to 300 were calculated from measured marker lines displacements and distortion in proximity to the faults we argue here that the fault related deformation during fault propagation is manifested by highly localized deformation in a process zone having a width of 0 001 0 005 of the fault length fault related deformation due to subsequent slip along the existing faults is analyzed in part ii the observed self similarity of the discontinuities over five length orders of magnitude and the outstanding lack of tensile microcracks suggest fault initiation and growth as primary shear fractures q 2003 elsevier science ltd all rights reserved

an automatic seismic event processing for detection and location the p m c c method we present a new method for automatic detection and location of seismic events recorded on a network it is based on a progressive study of the interstation correlation functions which leads to a consistent set of time delays when a seismic phase is present three different examples are processed on networks of different sizes

processing automatic seismic event detections an iterative sorting algorithm improving earthquake hypocentres using interevent cross correlation processing automatic seismic event detections an iterative sorting algorithm improving earthquake hypocentres using inter event cross correlation

automatic seismic event detection using migration and stacking a performance and parameter study in hengill southwest iceland we investigate the performance of a seismic event detection algorithm using migration and stacking of seismic traces the focus lies on determining optimal data dependent detection parameters for a

particle size and energetics of gouge from earthquake rupture zones surprisingly considering the forces that we see at the surface not all the energy involved in an earthquake is transformed into ground motion much of it is consumed by frictional heating and rock pulverization an analysis of pulverized rock or gouge collected from the san andreas fault in california and from a rupture zone at 2 km depth in a south african gold mine contradicts the commonly held view that gouge surface energy is a negligible component of earthquake energy balance the analysis reveals unexpected diminutive particles in gouge samples indicating that pulverization not frictional heating is the major consumer of earthquake energy at depth this might explain the heat flow anomaly seen in the san andreas fault system and perhaps some other long standing puzzles in earthquake energetics grain size reduction and gouge formation are found to be ubiquitous in brittle faults at all scales1 2 3 4 and most slip along mature faults is observed to have been localized within gouge zones5 6 this fine grain gouge is thought to control earthquake instability3 6 7 8 and thus understanding its properties is central to an understanding of the earthquake process7 9 here we show that gouge from the san andreas fault california with 160 km slip and the rupture zone of a recent earthquake in a south african mine with only 0 4 m slip display similar characteristics in that ultrafine grains approach the nanometre scale gouge surface areas approach 80 m2 g 1 and grain size distribution is non fractal these observations challenge the common perception that gouge texture is fractal10 11 and that gouge surface energy is a negligible contributor to the earthquake energy budget3 9 12 we propose that the observed fine grain gouge is not related to quasi static cumulative slip but is instead formed by dynamic rock pulverization during the propagation of a single earthquake

strike slip fault terminations at seismogenic depths the structure and kinematics of the glacier lakes fault sierra nevada united states 1 structural complexity is common at the terminations of earthquake surface ruptures similar deformation may therefore be expected at the end zones of earthquake ruptures at depth the 8 2 km long glacier lakes fault glf in the sierra nevada is a left lateral strike slip fault with a maximum observed displacement of 125 m within the fault pseudotachylytes crosscut cataclasites showing that displacement on the glf was accommodated at least partly by seismic slip the western termination of the glf is defined by a gradual decrease in the displacement on the main fault accompanied by a 1 4 km wide zone of secondary faulting in the dilational quadrant of the glf the secondary faults splay counterclockwise from the main fault trace forming average angles of 39 with the main fault slip vectors defined by slickenlines plunge more steeply west for these splay faults than for the glf static stress transfer modeling shows that the orientations of the splays and the plunge of displacement on those splays are consistent with displacement on the main fault the glf termination structure shows that structural complexity is present at the terminations of faults at seismogenic depths and therefore ruptures that propagate beyond fault terminations or through step overs between two faults will likely interact with complex secondary fault structures models of dynamic rupture propagation must account for the effect of preexisting structures on the elastic properties of the host rock additionally aftershock distributions and focal mechanisms may be controlled by the geometry and kinematics of structures present at fault terminations

microfracture analysis of fault growth and wear processes punchbowl fault san andreas system california abstract fabric and timing relations of mode i microfractures are used to test current hypotheses for the origin of damage along large displacement faults by the processes of fault growth and wear oriented samples 0 075 m to 1 km from the punchbowl fault surface i e ultracataclasite layer document an increase in development of preferred orientation and increase in density of microfractures towards the ultracataclasite layer defining a zone of fault related microfracture damage about 100 m thick a distinct microfracture set that is perpendicular to the slip direction of the fault is present throughout the damage zone this implies that the average orientation of the maximum principal compressive stress within the damage zone was nearly normal to the fault surface two additional microfracture sets are present one oriented at low angles to the fault within meters of the ultracataclasite layer and another low angle set that occurs in the outermost damage zone the preferred orientations and timing relations are most consistent with local damage accumulation from stress cycling associated with slip on a geometrically irregular relatively weak fault surface low angle microfractures nearest the ultracataclasite layer also may record wear associated with the passage of earthquake ruptures and those in the outermost damage zone may be consistent with andersonian fault formation and subsequent fault weakening

microscopic features of quartz and clay particles from fault gouges and infilled fractures in granite discriminating between active and inactive faulting abstract to assist in identifying faults that have a significant potential for displacement at or near the ground surface we carried out in depth investigations on fault gouges and a fracture infilled with clay clay vein in the kojaku granite on the tsuruga peninsula central japan we sampled several fault gouges at different stages of evolutions and clay rich infilling of a fracture with no evidence of offset based on our field observations gouge in an active fault is characterized by 1 stacked layers of different colors made up of comminuted fragments and clays and 2 injection of the fragments and clays from the gouge into the surrounding rocks indicating an accumulation of seismic induced shearing our thin section observations and x ray diffraction analyses show that all our samples are similar in the degree of fragmentation and mineral composition and because of this our study became focused mainly on microscopic features using laser diffraction particle size analysis scanning electron microscopy sem and transmission electron microscopy tem we identified the mineralogical and textural characteristics of the samples in order to improve our ability to discriminate between active and inactive faulting particle size distribution analysis showed that the gouge in the active fault contains the greatest abundance of finer particles due to multiple slip events which contrasts with the clay rich infilling of a fracture sem examination of the quartz particles showed that the gouge in the active fault contains more particles that have retained sharp and smooth crystal surfaces formed by fracturing than do either the gouges in minor faults that show no evidence of recent shear or the clay rich infilling of a fracture in contrast tem observations of very fine clay minerals approximately

estimation of debris flood magnitudes based on dendrogeomorphic data and semi empirical relationships abstract magnitude estimations of hydrogeomorphic processes contain crucial information for hazard assessments and for the understanding of longer term landscape evolution in this study we reconstruct magnitudes of debris floods for a torrential catchment in tyrol by combining dendrogeomorphic time series of events with semi empirical equations used to predict event volumes reconstructed debris flood magnitudes cover eight decades a d 1930 2008 and vary from 2900 to 45 900 m 3 we illustrate that magnitude estimates derived from tree ring data and semi empirical equations represent a valuable contribution to the documentation and understanding of hydrogeomorphic processes and that they can complement fragmentary time series in small watersheds for periods covering decades up to centuries limitations of the approach are mainly inherent to the age and spatial distribution of sampled trees and may thus influence reconstructed event magnitudes as one goes back in time

quantitative description and analysis of earthquake induced deformation zones along strike slip and dip slip faults 1 deformation zones are belts of high strains that can occur at the ground surface centered or asymmetrical relative to the trace of an earthquake fault and can range in width from a meter or two up to hundreds of meters in order to minimize damage to engineering structures within deformation zones one needs to be able to determine the characteristics of the deformation zones we develop an elastic plastic model of fault slip propagation to explain formation of deformation zones and estimate certain parameters to characterize deformation zones our theory suggests the ratio of widths of deformation zones in hanging wall and footwall of dipping faults should be controlled by fault dip angle and the kind of fault the relations are different for strike slip and dip slip faults also the total width of the deformation zone normalized with fault slip during the earthquake should be determined by the dip angle the exponent of the yield condition and the kind of fault the theoretical parameters measured for deformation zones along the strike slip duzce bolu fault at kaynasli turkey and two deformation zones along the chi chi thrust fault taiwan agree well with parameters determined from geophysical and geological sources the theoretical model also indicates that the winnetka strain belts related to the 1994 northridge earthquake could have formed above a previously unknown blind fault at winnetka the analysis suggests that the winnetka fault is a normal dip slip fault dipping 54 s with a fault tip depth of 360 m

origin and mechanical significance of foliated cataclastic rocks in the cores of crustal scale faults examples from the median tectonic line japan 1 the median tectonic line mtl is japan s largest onshore fault and has been active since the mid cretaceous foliated cataclastic fault rocks are exceptionally well exposed in the fault core at anko nagano prefecture following an early phase of mylonitization and exhumation during left lateral shearing brittle fracture and cataclasis occurred leading to the development of centimeter to submillimeter spaced fault zone parallel fracture systems these fracture systems established an initial architectural hierarchy that influenced the subsequent development of foliated cataclasites and gouge initially fracture systems coalesced to form interconnected zones of fine grained ultracataclasite fluid influx at the onset of grain scale brittle deformation led to precipitation of fibrous chlorite within the ultracataclasites ultimately leading to the development of an interconnected network of foliated phyllosilicate rich cataclasites and gouges in the core of the mtl the brittle reduction of grain size and ingress of a chemically active fluid phase simultaneously promoted reaction softening and diffusive mass transfer in the foliated ultracataclasites leading to rate dependent frictional viscous flow at sub byerlee friction values associated weakening is indicated by the preferential localization of deformation within the ultracataclasites a protracted sequence of carbonate mineralization and cementation events is also recognized during the fault rock evolution and suggests episodic periods of fluid overpressuring a crustal scale fault zone model is proposed suggesting that the foliated cataclasites gouges are weak in the long term and represent shallower crustal equivalents of phyllonitic fault rocks exposed in more deeply exhumed fault zones including other parts of the mtl

joint relative location of earthquakes without a pre defined velocity model an example from a peculiar seismic cluster on katla volcano s south flank iceland relative location methods are commonly used to precisely locate earthquake clusters consisting of similar waveforms repeating waveforms are often recorded at volcanoes where however the crust s

dendrogeomorphic reconstruction of lahar activity and triggers shiveluch volcano kamchatka peninsula russia lahars are highly concentrated water saturated volcanic hyperconcentrated flows or debris flows containing pyroclastic material and are a characteristic mass movement process on volcanic slopes on kamchatka peninsula russian federation lahars are widespread and may affect remote settlements historical records of past lahar occurrences are generally sparse and mostly limited to events which damaged infrastructure on the slopes or at the foot of volcanoes in this study we present a tree ring based reconstruction of spatiotemporal patterns of past lahar activity at shiveluch volcano using increment cores and cross sections from 126 larix cajanderi trees we document 34 events covering the period ad 1729 2012 analyses of the seasonality of damage in trees reveal that 95 of all lahars occurred between october and may and thus point to the predominant role of the sudden melt of the snow cover by volcanic material these observations suggest that most lahars were likely syn eruptive and that lahar activity is largely restricted to periods of volcanic activity by contrast rainfall events do not seem to play a significant role in lahar triggering

snow avalanche activity after fire and logging disturbances northern gaspe peninsula quebec canada in mountainous areas ecological disturbances causing forest fragmentation may influence the pattern and regime of snow avalanches in the northern gaspe peninsula quebec at two sites located on treed slopes of a south north oriented valley tree removal by fire and logging operations was the precursor factor for avalanche activity years of high magnitude snow avalanches were identified based on tree ring techniques these avalanches were different from those identified by dube et al 2004 for three undisturbed scree slope sites in the same area the lack of synchronicity in avalanche occurrences between disturbed and undisturbed sites suggests a strong influence of local factors e g disturbance local topography slope aspect vegetation the first avalanche years were recorded in 1941 and 1988 after a fire in 1938 and logging operations in 1986 1987 respectively both of these years had above average snowfalls this indicates that climate total annual snowfall was also a contributing facto

recent debris flow processes and resultant form and facies of the dolomite alluvial fan owens valley california abstract a multiphase debris flow triggered by an afternoon thunderstorm was deposited 22 august 1984 on the dolomite alluvial fan of owens valley california two tracts 10 300 cm thick accumulated during this event together covering 68 000 m2 26 of the fan with 50 000 m3 of sediment both tracts consist of numerous paired boulder rich levees 100 300 cm high on the proximal fan and multiple attached lobes 20 100 cm thick on the distal fan each levee lobe pathway was built by an individual surge with flow path switching caused by clogging of the frontal bouldery snout of the ensuing surge the levees consist of clast supported to matrix supported muddy pebbly cobbly boulder gravel displaying a well developed radially aligned a axis clast fabric the lobes mostly consist of matrix supported muddy pebbly cobble gravel the clast supported lobe margins are enriched in cobbles displaying a strongly preferred slope parallel a axis fabric along the sides that changes to a slope perpendicular fabric at the snout the distal ends of most of the clast rich lobes are overlain and offlapped by clast poor debris flow lobes of granular mud 10 30 cm thick the central zones of the levees and most lobes were surficially washed by recessional stage water flows that moved winnowed granules sand and mud off the fan the radial change from levees in the proximal fan to lobes distally is morphologically expressed as two intersecting slope segments the upper one sloping 9 12 and the lower one 3 5 this direct relationship between the constituent forms and slope values also is characteristic of pre 1984 deposits suggesting that the 1984 event is typical of the primary processes constructing the dolomite fan the pronounced radial change from levees to lobes and its manifestation as a slope inflection was caused by the selective loss on the upper fan of most of the boulders from the passing debris flow surges boulders were sorted from the surges because of their greater buoyancy which caused them to be preferentially concentrated in the part of the flow that subsequently was sheared off as levees this selective boulder removal depleted the flow of the clasts that provided lateral support facilitating flow expansion and the onset of lobe development thus the resultant facies assemblage is a function of the specific sediment grain size suite available in the catchment colluvium and the transport characteristics of this mix when transformed into a debris flow by the rapid addition of heavy rainfall during infrequent thunderstorms

opening mode of the japan sea inferred from the palaeomagnetism of the japan arc the western edge of the pacific plate is marked by a chain of back arc basins stretching from the aleutians through japan and the philippines to new zealand most of the basins lie behind volcanic island arcs far from continents and are the result of extension of the oceanic lithosphere1 but the japan sea is bounded on one side by continental crust the sikhote alin and korean peninsula of the asian continent and on the other by an active arc with continental fragments it can thus be said to be associated more with continental rifting1 4 than with oceanic processes we report here palaeomagnetic data from the japan arc which indicate that since the early miocene north east japan has rotated counter clockwise through 47 around a vertical axis while south west japan has rotated clockwise through 56 refs 5 8 we attribute this differential rotation which took place concurrently between 21 and 11 myr ago to the back arc opening of the japan sea8 with a double door mode that is there are two fan shaped spreading basins facing each other such a fan shaped opening is probably peculiar to the geological phenomenon of rifting of a continental fragment from thick continental lithosphere

evaluation of growth disturbances of picea abies l karst to disturbances caused by landslide movements abstract dendrogeomorphic methods are frequently used in landslide analyses although methods of landslide dating based on tree rings are well developed they still indicated many questions the aim of this study was to evaluate the frequently used theoretical scheme based on the event response relationship seventy four individuals of norway spruce picea abies l karst exhibiting visible external disturbance were sampled on the girova landslide the largest historical flow like landslide in the czech republic this landslide reactivated in may 2010 and post landslide tree growth responses were studied in detail these growth responses were compared with the intensity and occurrence of visible external tree disturbance tilted stems damaged root systems and decapitation twenty nine trees 39 2 died within one to four years following the 2010 landslide movement the trees that died following the landslide movement were significantly younger and displayed significantly greater stem tilting than the live trees abrupt growth suppression was a more frequent response among the dead trees whereas growth release dominated among the live trees only two trees 2 7 created no reaction wood in response to the landslide movement forty four percent of the trees started to produce reaction wood structure after a delay which generally spanned one year some eccentric growth was evident in the tree rings of the landslide year and was significant in the first years following the landslide movement missing rings were observed only on the upper sides of the stems and no false tree rings were observed the results confirm the general validity of event response relationship nevertheless this study points out the limitations and uncertainties of this generally accepted working scheme

textural evidence for recent co seismic circulation of fluids in the nojima fault zone awaji island japan abstract the hirabayashi borehole awaji island japan was drilled by the geological survey of japan gsj 1 year after the hyogo ken nanbu kobe earthquake 1995 mjma 7 2 this has enabled scientists to study the complete sequence of deformation across the active nojima fault from undeformed granodiorite to the fault core in the fault core different types of gouge and fractures have been observed and can be interpreted in terms of a complex history of faulting and fluid circulation above the fault core and within the hanging wall compacted cataclasites and gouge are cut by fractures which show high apparent porosity and are filled by 5 50 m euhedral and zoned siderite and ankerite crystals these carbonate filled fractures have been observed within a 5 5 m wide zone above the fault but are especially abundant in the vicinity 1 m of the fault the log normal crystal size distributions of the siderite and ankerite suggest that they originated by decaying rate nucleation accompanied by surface controlled growth in a fluid saturated with respect to these carbonates these carbonate filled fractures are interpreted as the result of co seismic hydraulic fracturing and upward circulation of fluids in the hanging wall of the fault with the fast nucleation of carbonates attributed to a sudden fluid or co2 partial pressure drop due to fracturing the fractures cut almost all visible structures at a thin section scale although in some places the original idiomorphic shape of carbonates is modified by a pressure solution mechanism or the carbonate filled fractures are cut and brecciated by very thin gouge zones these features are attributed to low and high strain rate mechanisms respectively the composition of the present day groundwater is at near equilibrium or slightly oversaturated with respect to the siderite calcite dolomite and rhodochrosite taken together this suggests that these fractures formed very late in the evolution of the fault zone and may be induced by co seismic hydraulic fracturing and circulation of a fluid with a similar composition to the present day groundwater they are therefore potentially related to recent earthquake activity

kinematic analysis of sinistral cataclastic shear zones along the northern margin of the mino belt central japan abstract in this paper cataclastic shear zones along the northern margin of the mino belt central japan are described and the significance of the shearing in the tectonic evolution of sw japan is examined the mino belt in sw japan is composed of accretionary complexes of jurassic to early cretaceous age field investigation revealed that remarkable cataclastic shear zones trending east to northeast run along the northern margin of the mino belt closely spaced cleavage is developed in these shear zones lineation on the cleavage plunges at shallow to moderate angles deformation structures e g composite planar fabric and asymmetric structure of clasts in the sheared rocks clearly indicate a sinistral sense of shear the shearing ceased by latest cretaceous time because the sheared rocks are overlain by unsheared upper cretaceous volcanic rocks the sinistral shearing may be closely related to cretaceous sinistral movement along the eastern margin of asia sinistral shearing along the northern margin of the mino belt can be considered as a key for re examining the tectonic development of sw japan

architectural evolution of the nojima fault and identification of the activated slip layer by kobe earthquake 1 evolutionary history of nojima fault zone is clarified by comprehensive examinations of petrological geophysical and geochemical characterizations on a fault zone in deep drilled core penetrating the nojima fault on the basis of the results we reconstruct a whole depth profile of the architecture of the nojima fault and identify the primal slip layer activated by 1995 kobe earthquake the deepest part 8 to 12 km depth of the fault zone is composed of thin slip layers of pseudotachylite 5 to 10 mm thick each 10 cm in total middle depth 4 to 8 km depth of the fault zone is composed of fault core 6 to 10 m thick surrounded by thick 100 m thick damage zone characterized by zeolite precipitation the shallow part of the fault zone 1 to 4 km depth is composed of distributed narrow shear zones which are characterized by combination of thin 0 5 cm thick each 10 cm in total ultracataclasite layers at the core of shear zones surrounded by thicker 1 to 3 m thick damage zones associated with carbonate precipitation an extremely thin ultracataclasite layer 7 mm thick activated by the 1995 kobe earthquake is clearly identified from numerous past slip layers overprinting one of the shear zones as evidenced by conspicuous geological and geophysical anomalies the nojima fault zone was 10 to 100 times thicker at middle depth than that of shallower and deeper depths the thickening would be explained as a combination of physical and chemical effects as follows 1 thickening of fault core at middle depth would be attributed to normal stress dependence on thickness of the shear zone and 2 an extreme thickening of damage zone in middle depth of the crust would result from the weakening of the fault zone due to super hydrostatic fluid pressure at middle depths the high fluid pressure would result from faster sealing with low temperature carbonate at the shallower fault zone

coalescence microseismic mapping earthquakes are commonly located by linearized inversion of discrete arrival time picks made from signals recorded at a network of seismic stations if mis picks are made these will contribute to the location therefore causing potential bias for data recorded by a dense seismic array direct imaging methods can be applied instead we describe the coalescence microseismic mapping method which is a bridge between the two approaches and will operate with seismic data recorded continuously on a sparse array by continuously mapping scalar signals derived from the envelope of seismic arrivals we derive robust estimates of the spatio temporal coordinates of the origins of seismic events noisy data are migrated away from the correct origin so do not contribute to errors in location the method is rooted in a bayesian formulation of event location traveltime inversion allows imaging of source locations and has the capacity to handle errors in modelled traveltimes it has the advantage of working with any 3 d velocity model which therefore may include anisotropy it also automatically incorporates both p and s wave data a multiresolution grid search leads to an efficient implementation with a search over a larger domain including joint inversion for location and velocity structure possible where warranted by the data quality we discuss the theory and implementation of this method and illustrate it with real data from microseismic events in iceland caused by melt intrusion in the crust

on the incidence of debris flows from the early little ice age to a future greenhouse climate a case study from the swiss alps 1 tree ring based reconstructions of 123 debris flow events in a case study area of the swiss alps since ad 1570 show enhanced activity during the wet periods 1864 1895 following the last lia glacier advance and in the early decades of the 20th century in contrast comparably low activity can be observed since 1995 with only one event recorded from the reconstructions and based on rcm simulations there are indications that debris flow frequencies might continue to decrease in a future climate as precipitation events are projected to occur less frequently in summer but become more common in spring or fall

mass movements and tree rings a guide to dendrogeomorphic field sampling and dating abstract trees affected by mass movements record the evidence of geomorphic disturbance in the growth ring series and thereby provide a precise geochronological tool for the reconstruction of past activity of mass movement the identification of past activity of processes was typically based on the presence of growth anomalies in affected trees and focused on the presence of scars tilted or buried trunks as well as on apex decapitation for the analyses and interpretation of disturbances in tree ring records in contrast clear guidelines have not been established with largely differing or no thresholds used to distinguish signal from noise at the same time processes with a large spatial footprint e g snow avalanches landslides or floods will likely leave growth anomalies in a large number of trees whereas a falling rock would only cause scars in one or a few trees along its trajectory based on the above considerations we examine issues relating to the interpretation and dendrogeomorphic dating of mass movements particular attention is drawn to sampling in terms of sample distribution across a study site the actual selection of trees as well as to sample size i e number of trees sampled based on case studies from snow avalanche debris flow and landslide sites we demonstrate that thresholds can indeed improve dating quality and at the same time minimize noise in time series we also conclude that different thresholds need to be used for different processes and different periods of the reconstruction especially for the early stages of the reconstruction when the number of potentially responding trees will be much smaller this paper seeks to set standards for dendrogeomorphic fieldwork analysis and interpretation for different processes of mass movements

spatial distribution and characteristics of fracture zones near a long lived active fault a field based study for understanding changes in underground environment caused by long term fault activities abstract fracture zone development has a substantial impact on long term changes in the underground environment because fracture zones are potential major groundwater flowpaths as well as a locus for mechanical disturbance by fracturing to understand fracture zone development we surveyed the spatial distribution and characteristics of fracture zones in areas around the atotsugawa fault a long lived active fault in central japan within 500 m of the atotsugawa fault trace the number of exposed fracture zones increases sharply and most fracture zones greater than 2 m width are concentrated the width of the clay rich fault gouge in the majority of fracture zones is less than 1 m fracture zones greater than 2 m width along the atotsugawa fault are composed mainly of a zone with numerous fractures and breccia and are considered to act as a major conduit controlling regional groundwater flow based on rock features and deformation fabrics at meso and microscopic scales once fracture zones had formed epigenetic deformation was concentrated in the older fracture zones fracture zones formed by fracturing along hydrothermal veins or fracturing and weathering that accompanied displacement along joints schistosities or lithological boundaries are sparsely but widely distributed in the study area though most of their width are less than 2 m the existence of unfavorable hydraulic characteristics needs to be studied by engineered methods for the purpose of site selection and design of underground facilities

exploring debris flow history and process dynamics using an integrative approach on a dolomitic cone in western austria the evolution of a debris flow cone depends on a multitude of factors in the hydrogeomorphic system investigations of debris flow history and cone dynamics in highly active catchments therefore require an integrative approach with a temporal and spatial resolution appropriate for the goals of the study we present the use of an orthophoto time series to augment standard dendrogeomorphic techniques to describe the spatio temporal dynamics of debris flows on a highly active cone in the western austrian alps analysis of seven orthophotos since 1951 revealed a migration of active deposition areas with a resulting severe loss of forest cover 80 and a mean tree loss per year of 10 4 range 1 3 16 6 trees per year analysis of 193 pinus mugo ssp uncinata trees allowed the identification of 161 growth disturbances corresponding to 16 debris flows since 1839 and an average decadal frequency of 0 9 events as a result of the severe loss of forest cover we speculate that 20 of the more recent events were actually captured in the tree ring record giving a decadal return interval of 7 5 events for a period of 60 years based on three annual field observations it is evident that this catchment the barenrufe produces very frequent 1 yr small in the order of a few 10 to 100 m3 debris flows with minor material relocation the specific challenges of tree ring analysis in this tree species and in highly active environments are explicitly addressed in the discussion and underline the necessity of employing complementary methods of analysis in an integrative manner copyright 2012 john wiley sons ltd

dendrogeomorphic dating of rockfalls on low latitude high elevation slopes rodadero iztaccihuatl volcano mexico dynamics and rates of rockfalls have been repeatedly studied in mountain environments with archival records as well as lichenometric radiocarbon or dendrogeomorphic approaches in this study we test the potential of conifers growing at a low latitude high elevation site as a dendrogeomorphic tool to reconstruct to calendar dates associated rockfall activity analysis is based on tree ring records of mexican mountain pine pinus hartwegii lindl growing at timberline 4000 m above sea level a s l and at the runout fringe of a north northeast nne facing slope of the dormant iztaccihuatl volcano mexico which is subject to frequent rockfalls the potential and limitations of tree ring data are demonstrated based on 67 rockfall impacts dated in the increment ring series of 24 trees since ad 1836 while findings of this paper are site specific the study clearly shows the potential of dendrogeomorphic approaches in extra alpine low latitude environments and for the understanding of rockfall processes in space and time copyright 2011 john wiley sons ltd

thickness of the seismic slip zone this article reviews geologic and other evidence constraining the thickness of the principal slip zone psz that accommodates the bulk of coseismic shear displacement during an individual rupture event surface deformation from rupturing may occupy swaths tens of meters or more in width but trenches across active faults generally reveal that incremental slip is accommodated by a psz that is tens of centimeters or less in thickness geomorphic evidence coupled with the observations from trenching suggest a psz may stay well localized for distances of several kilometers through many rupture episodes mine exposures and exhumed fault zones demonstrate that pszs separating different lithologies within the fault core although contained within damage zones of variably fractured rock ranging up to hundreds of meters in thickness often comprise just a few centimeters of gouge ultracataclasite that have accommodated large finite displacements 1 km microstructural studies demonstrate incremental slip localized still further down to 1 10 mm as do other fault rock assemblages slickensides and slickenfibers fault veins of pseudotachylyte friction melt intravein septa in hydrothermal fault infills the accumulated evidence indicates that localization of coseismic shearing to less than 10 cm on planar faults is widespread throughout the crustal seismogenic zone with extreme localization to less than 1 cm not uncommon however some distributed coseismic shear may also develop especially at rupture irregularities coseismic reduction of shear resistance from friction melting t 1000 c or from transient thermal pressurization of aqueous fluids t 100 c requires slip during moderate to large earthquakes u 1 m to be restricted to narrow zones respectively a few centimeters or tens of centimeters in thickness given the evidence for slip localization the apparent scarcity of pseudotachylyte suggests either that seismic friction melting is a rare phenomenon or that pseudotachylyte is only rarely preserved in recognizable form within mature hydrated fault zones

a regional reconstruction of debris flow activity in the northern calcareous alps austria dendrogeomorphic dating of historical debris flow events is a highly valuable tool for improving historical records in the field of natural hazard management previous dendrogeomorphic investigations generally have focused on case studies of single torrents however regional investigations may offer a more accurate reconstruction of regional patterns of activity and therefore may have an advantage over individual cases the aim of the study is to provide a regional reconstruction of debris flow events for a site in the northern calcareous alps of western austria gamperdonatal vorarlberg and to document spatial and temporal morphological changes in individual and neighboring torrents analysis of 442 trees 268 pinus mugo ssp uncinata 164 picea abies and 10 abies alba allowed identification of 579 growth disturbances corresponding to 63 debris flow events since a d 1839 the majority of growth disturbances were in the form of growth suppression or release 76 owing to the nature of both the deposited material and the process characteristics regional patterns of event frequency indicated a paucity of activity in the early to mid twentieth century and increased activity since a d 1948 whereby large events were followed by subsequent years of continued activity of smaller magnitude patterns of frequency could be attributed primarily to spatiotemporal changes in channel morphology but may also be reflective of changes in transport conditions within the valley this study provides the first regional investigation in the austrian alps and contributes to the documentation of tree responses to geomorphic disturbances in calcareous material

field investigations of the interaction between debris flows and forest vegetation in two alpine fans abstract a key objective in debris flow hazard mitigation is the reduction of the potential depositional area in the fan from this point of view forested areas are able to provide a protective function hindering the flow motion and promoting the surge deposition despite extensive research on alpine forests and their protective functions relatively few studies in the literature have quantitatively focused on the relationship between debris flow depositional features and vegetation in light of the above our research investigates how vegetation characteristics in the fan area interact with debris flow deposition field investigations were carried out in two alpine fans where debris flow events occurred in the summer of 2012 by recording the characteristics of 1567 involved trees and the associated deposit thicknesses this paper provides a data set that contributes to the improvement of the knowledge of these interaction processes the integration of literature findings and the analysis of the collected dataset adds insights into the relationships between tree characteristics and the dynamics of debris flow during the runout path the main results prove the capacity of the forest of uniformly promoting flow energy dissipation presence of high species diversity in debris flow deposits when comparing disturbed and undisturbed forest stands tree mortality largely affecting small diameters

jurassic dextral and cretaceous sinistral movements along the hida marginal belt abstract the hida marginal belt hmb which consists of various kinds of fault bound blocks is located between the continental massif of the hida belt and the mesozoic accretionary complex of the mino belt in central japan detailed field investigation reveals that the hmb had grown through the two different movements i e jurassic dextral and cretaceous sinistral movements the jurassic dextral ductile shear zones run in the southern marginal part of the hida belt and the northern part of the hmb whereas the cretaceous sinistral cataclastic shear zones occur in the southern part of the hmb and the northern marginal part of the mino belt geologic map and field evidence seem to suggest that the jurassic dextral movement form the fault bound blocks of the hmb to form the basic structure of the hida marginal belt i e formation of the proto hmb following the dextral movement the sinistral one restructured the proto hmb to complete the present feature of the hida marginal belt the cretaceous sinistral movement might result in the sinistral collision between the proto hmb and the mino belt

the contribution of geomorphological mapping to sediment transfer evaluation in small alpine catchments the assessment of sediment transfer processes is necessary to understand the hydro geomorphological functioning of small alpine watersheds prone to channelised debris flows because their occurrence often depends on the amount of debris available in the gully systems therefore sediment budgets should be studied through the identification of erosion transport and deposition processes sediment transfer processes were investigated in a small catchment by field measurements and more specifically through the application of a process based geomorphological mapping method the proposed methodology is based on data directly derived from gis analysis using high resolution dem field measurements and aerial photograph interpretations it has been conceived to estimate sediment transfer dynamics taking into account the role of different sediment stores in the torrential system the proposed geomorphological mapping methodology is quite innovative in comparison with most legend systems that are not adequate for mapping comprehensively active and complex geomorphological systems such as debris flow catchments maps representing the various sediment storages and their relationships can be used for hydro geomorphological hazard mitigation

biographical sketch of a giant deciphering recent debris flow dynamics from the ohya landslide body japanese alps abstract debris flow frequency discharge and travel distance are highly catchment dependent and typically controlled by topography hydrological conditions and sediment supply as a consequence detailed and case specific investigations are needed to decipher debris flow histories in order to improve hazard mitigation this study documents past ca 10 years debris flow occurrences originating from the ohya landslide central japan by using a large set of methods including field monitoring repeat airborne lidar orthophoto interpretation and tree ring reconstructions we demonstrate that the different approaches generally agree on the occurrence of debris flows but that mismatches may exist when it comes to the assessment of areas affected by individual events these differences may even exceed the usual errors in precision inherent to each of the methods used in the present case high resolution orthophoto interpretation tends to underestimate areas affected by debris flows especially in the vertical direction in the absence of lateral movement of the channel bed and as a result of shade and areas under trees on the other hand we realize that lidar data cannot necessarily be used to distinguish local changes in topography from noise tree ring analyses can help to improve the temporal resolution of the analysis but may have limitations when it comes to the definition of areas affected by an event because of the point type nature of data we conclude that the best and most complete results are obtained by combining multiple methods to improve the spatial and temporal resolution of past debris flows and to delimit areas affected by individual events

large scale relocation of two decades of northern california seismicity using cross correlation and double difference methods 1 we simultaneously reanalyzed two decades 1984 2003 of the digital seismic archive of northern california using waveform cross correlation cc and double difference dd methods to improve the resolution in hypocenter locations in the existing earthquake catalog generated at the northern california seismic network ncsn by up to three orders of magnitude we used a combination of 3 billion cc differential times measured from all correlated pairs of events that are separated by less than 5 km and 7 million p wave arrival time picks listed in the ncsn bulletin data were inverted for precise relative locations of 311 273 events using the dd method the relocated catalog is able to image the fine scale structure of seismicity associated with active faults and revealed characteristic spatiotemporal structures such as streaks and repeating earthquakes we found that 90 of the earthquakes have correlated p wave and s wave trains at common stations and that 12 are colocated repeating events an analysis of the repeating events indicates that uncertainties at the 95 confidence level in the existing network locations are on average 0 7 km laterally and 2 km vertically correlation characteristics and relative location improvement are remarkably similar across most of northern california implying the general applicability of these techniques to image high resolution seismicity caused by a variety of plate tectonic and anthropogenic processes we show that consistent long term seismic monitoring and data archiving practices are key to increase resolution in existing hypocenter catalogs and to estimate the precise location of future events on a routine basis

landform vegetation units for investigating the dynamics and geomorphologic evolution of alpine composite debris cones valle dell avio adamello group italy abstract cluster analysis of 245 vegetation plots along 17 transects on alpine composite debris cones in the italian alps allowed us to classify complex mosaics of landforms and plant communities a variety of active and past geomorphic processes mass wasting avalanche activity and running water were responsible for the construction of the debris cones by assessing plant community distribution in the context of the different landform units and geomorphic processes represented in detailed geomorphological maps a sequence of landform vegetation units was identified this approach contributes to the assessment of environmental hazards on the cones and may also be applied in other environmental contexts plant community distribution and development in valle dell avio reflects the frequency and intensity of the processes that built composite alpine debris cones creating environmental gradients and or generating new habitats therefore this patchy landscape allows the preservation of local biodiversity with typical plant communities adapted to particular niches

evidence for enhanced debris flow activity in the northern calcareous alps since the 1980s plansee austria abstract debris flows are among the most important natural hazards the northern calcareous alps with their susceptible lithology are especially affected by a double digit number of major hazard events per year it is hypothesised that debris flow intensity has increased significantly in the last decades in the northern calcareous alps coincident to increased rainstorm frequencies but yet there is only limited evidence the plansee catchment exposes extreme debris flow activity due to the intensely jointed upper triassic hauptdolomit lithology being responsible for most of the debris flow activity in the northern calcareous alps the debris flows feed into a closed sediment system the plansee lake where holocene lateglacial sedimentation rates rates since the late 1940s and recent rates can be inferred accurately using aerial photos and field mapping the temporal and spatial development of eight active debris flow fans is reconstructed in six time intervals from 1947 1952 1971 1979 1987 2000 and 2010 and mean annual debris flow volumes are calculated these are compared with mean holocene lateglacial debris flow volumes derived from the most prominent cone whose contact with the underlying till is revealed by electrical resistivity tomography ert debris flow activity there increased by a factor of 10 from 1947 1952 0 23 0 07 103 m3 yr to 1987 2000 2 41 0 66 103 m3 yr mean post 1980 rates from all eight fans exceed pre 1980 rates by a factor of more than three coinciding with enhanced rainstorm activity recorded at meteorological stations in the northern calcareous alps the frequency of rain storms def 35 mm d has increased in the study area on average by 10 per decade and has nearly doubled since 1921 recent debris flow activity is also 2 3 times higher than mean holocene lateglacial rates the strong correlation between the non vegetated catchment area and the annual debris flow volume might indicate a decadal positive feedback between enhanced rainstorm activity and debris flows here we investigate the temporal and spatial development of debris flow fans to better understand the sensitivity of alpine catchments to heavy rainfall events in the context of climate change

structural and isotopic constraints on fluid flow regimes and fluid pathways during upper crustal deformation an example from the taemas area of the lachlan orogen se australia 1 structural and stable isotope studies of calcite veins and host rocks in a 1000 m thick devonian limestone sequence in the taemas area of the lachlan orogen in se australia indicate that externally derived fluids migrated through the sequence over a protracted interval during folding and associated reverse faulting at temperatures of 200 c the evolution of fluid pathways was governed by growth of fold related and fault related fracture networks at transiently supralithostatic fluid pressures the internal structures of veins indicate growth during repeated cycles of permeability enhancement and sealing systematic increase in 18o of vein calcite upward through the limestone sequence and the presence of an o isotope alteration front in the vein system is related to buffering of fluid compositions by fluid rock reaction during upward migration of overpressured low 18o fluids repeated switching of fractures between high permeability and low permeability states promoted episodic flow and changes in flow paths during progressive deformation a lack of significant migration of the isotopic front during the flow history is consistent with fluid rock interaction being associated with numerous separate pulses of fluid ascending through the percolation network irregular variations in fluid 18o with time during vein growth are interpreted to be driven by repeated changes in reactive path lengths reaction rates and flow rates in a discontinuous flow regime systematic upward changes in vein 18o over an area of 20 km2 requires that on a time averaged basis most of the vein system was hydraulically well connected to the external fluid reservoir and that growth of the fracture network occurred by fluid driven invasion percolation processes repeated failure and sealing events in the fracture system are interpreted to have been driven by episodic migration of fluid pressure waves up through the fracture network possibly in response to deeper level fault rupture events repeatedly breaching an overpressured fluid reservoir

waveform cross correlation based differential travel time measurements at the northern california seismic network we processed the complete digital seismogram database for northern california to measure accurate differential travel times for correlated earthquakes observed at common stations correlated earthquakes are earthquakes that occur within a few kilometers of one another and have similar focal mechanisms thus generating similar waveforms allowing measurements to be made via cross corre lation analysis the waveform database was obtained from the northern california earthquake data center and includes about 15 million seismograms from 225 000 local earthquakes between 1984 and 2003 a total of 26 billion cross correlation measurements were performed on a 32 node 64 processor linux cluster using improved analysis tools all event pairs with separation distances of 5 km or less were processed at all stations that recorded the pair we computed a total of about 1 7 billion p wave differential times from pairs of waveforms that had cross correlation coefficients cc of 0 6 or larger the p wave differential times are often on the order of a factor of ten to a hundred times more accurate than those obtained from routinely picked phase onsets 1 2 billion s wave differential times were mea sured with cc 0 6 a phase not routinely picked at the northern california seismic network because of the noise level of remaining p coda we found that approxi mately 95 of the seismicity includes events that have cross correlation coefficients of cc 0 7 with at least one other event recorded at four or more stations at some stations more than 40 of the recorded events are similar at the cc 0 9 level indicating the potential existence of large numbers of repeating earthquakes large numbers of correlated events occur in different tectonic regions including the san andreas fault long valley caldera geysers geothermal field and mendocino triple junction future research using these data may substantially improve earthquake lo cations and add insight into the velocity structure in the crust

geomorphic coupling between hillslopes and channels in the swiss alps the coupling relationships between hillslope and channel network are fundamental for the understanding of mountainous landscapes evolution here we applied dendrogeomorphic methods to identify the hillslope channel relationship and the sediment transfer dynamics within an alpine catchment at the highest possible resolution the schimbrig catchment is located in the central swiss alps and can be divided into two distinct geomorphic sectors to the east the schimbrig earth flow is the largest sediment source of the basin while to the west the rossloch channel network is affected by numerous shallow landslides responsible for the supply of sediment from hillslopes to channels to understand the connectivity between hillslopes and channels and between sources and sink trees were sampled along the main rossloch stream on the schimbrig earth flow and on the rossloch depositional area geomorphic observations and dendrogeomophic results indicate different mechanisms of sediment production transfer and deposition between upper and lower segments of the channel network in the source areas upper part of the rossloch channel system sediment is delivered to the channel network through slow movements of the ground typical of earth flow shallow landslides and soil creep contrariwise in the depositional area lower part of the channel network the mechanisms of sediment transfer are mainly due to torrential activity floods and debris flows tree analysis allowed the reconstruction of periods of high activity during the last century for the entire catchment the collected dataset presents a very high temporal resolution but we encountered some limitations in establishing the source to sink connectivity at the catchment wide scale despite these uncertainties for decennial timescales the results suggest a direct coupling between hillslopes and neighbouring channels in the rossloch channel network and a de coupling between sediment sources and sink farther downstream with connections possible only during extraordinary events

using tree ring analysis to evaluate intra eruptive lahar activity in the nexpayantla gorge popocatepetl volcano central mexico abstract lahar activity is one of the most important processes capable of mobilizing large volumes of sediment and producing devastating effects on human populations and infrastructure estimating the frequency distribution and climatic controls on lahar activity is necessary for understanding how sediment is mobilized from hillslopes to channels and how the landscape is modified by this type of process in this study we evaluate the intra eruptive lahar activity in the nexpayantla gorge nw of popocatepetl volcano central mexico by using a dendrogeomorphological analysis of growth ring records of abies religiosa trees n 100 based on the identification of 322 growth disturbances gd and field evidences we identify 23 intra eruptive lahars that occurred from 1959 to 2013 by analyzing the lahar chronology and climatic data we observed that 83 of lahar activity coincides with moderate to strong cold and dry phases of el nino southern oscillation based on the seasonal timing of gd we explored the intra annual lahar activity we found that 43 of the lahars occurred in the latewood season from july to october when the mean summer monthly rainfall is 120 mm approximately 37 of lahars occurred during the first heavy rainfalls from march to june which corresponds to the earlywood season the remaining 20 of the lahar activity corresponds to the dormancy period winter season when snowmelt and or occasional strong rainfalls 100 mm day 1 occur the gd indicate that in nexpayantla gorge intra eruptive lahar activity takes place around every two years we also found that the effects of lahars are concentrated around the transitional and depositional zone of nexpayantla gorge

identification of pathways for hydrogen gas migration in fault zones with a discontinuous heterogeneous permeability structure and the relationship to particle size distribution of fault materials previous studies have reported that high concentrations of h2 gas are released from active fault zones experimental studies suggest that the h2 gas is derived from the reaction of water with free radicals formed when silicate minerals are fractured at hypocenter depths during fault activities however the pathways for migration of deep seated fluids to surface are still unknown in this study we performed quick multipoint h2 gas measurements across a fault zone using a portable gas monitor and a hand drill the fault zone studied includes a smectite rich fault core dividing two clearly distinguishable damage zones granite cataclasite and welded tuff fault breccia the measurements show that h2 gas emissions collected in 2 3 h sampling periods from start of measurement range from 320 3 to 446 2 ppm min in the granite cataclasite and 60 5 to 137 8 ppm min in the welded tuff fault breccias negligible quantities of h2 gas could be collected from the fault core particle size distribution analyses of fault rocks indicate that the granite cataclasite tends to be rich in particles that are finer i e less cohesive and easy to disaggregate which leads to the inference that the granite cataclasite has high permeability based on the h2 gas measurements and the particle size distribution analyses the h2 gas is considered to have migrated in permeable damage zones mostly by advection with groundwater multipoint h2 gas measurement will be effective in qualitative delineation of variations in permeability of regional structures

a topographic fingerprint to distinguish alluvial fan formative processes we demonstrate here a topographic fingerprint derived from a 1 m high resolution elevation model dem developed from airborne laser swath mapping alsm that distinguishes between formative processes from surface form in alluvial fans generated through relatively dry debris flows df and those surfaces formed primarily by fluvial sediment transport mf we selected alluvial fans with primarily holocene age surficial deposits along the eastern side of death valley california fans were initially classified in the field into df and mf types largely on the basis of sedimentological characteristics and surface morphometry trend surface analyses were performed on dems of the individual fans in order to remove the long wavelength trends both profile and planimetric from the residual data we found that high resolution surface data distinguishes process information in two ways 1 local relief increases as a function of length scale especially at length scales less than 40 60 m and 2 local relief is significantly higher for debris flow dominated fans than for fluvially dominated fans this fingerprint which is directly related to the dominant surface processes is unavailable from standard 30 m resolution data providing significant support for the acquisition of high quality high resolution data this fingerprint can be used to help calibrate numerical simulations of alluvial fan development and has the potential for similar applications to distinguish between processes of similar landforms on other planetary bodies within our solar system

three dimensional imaging of the p and s wave velocity structure and earthquake locations beneath southwest iceland three dimensional imaging of the p and s wave velocity structure and earthquake locations beneath southwest iceland