enhanced reflectivity of backthrusts in the recent great sumatran earthquake rupture zones in the last five years there have been three great megathrust earthquakes in the sumatra subduction zone and a part of the zone is still locked we have carried out deep seismic reflection surveys along the sw sumatran margin and have imaged backthrusts along four profiles down to 15 20 km depth we find that the seismic images of the backthrusts in the 2004 and 2007 great earthquake ruptured zones are brighter than those in the regions where the subduction zone is still locked we suggest that this enhanced reflectivity is due to the increase of fluid contents along the reactivated backthrusts during or soon after the great earthquakes if this interpretation is valid then the backthrusts observed in the forearc basins could be used to monitor fluid movement from mantle wedge and earthquake precursors before and after an imminent great earthquake in the sumatra locked zone

mechanics of low stress forearcs nankai and cascadia the nankai and cascadia subduction zones have low stress forearcs where the margin normal horizontal compressive stress is similar to or less than the vertical stress except in the accretionary prisms in the absence of active back arc spreading the forearc margin normal stress is controlled mainly by the total shear force along the subduction fault or the plate coupling force and the gravitational force the plate coupling force creates compression and the gravitational force in the presence of margin topography creates lateral tension we give a simple expression that relates the forearc stress to topography and average fault strength with the latter represented by an effective coefficient of friction we also use a finite element model of two converging plates in frictional contact to model the forearc stresses the analyses indicate that a low stress forearc requires not only the subduction fault to be very weak but also the mechanically coupled fault area to be narrow in the downdip direction and shallow in depth for nankai and cascadia where the coupled fault areas are narrow and shallow because of the young and hot subducting plates is about 0 05 or less and in any case less than 0 09 the low fault strength is probably not a unique property of low stress forearcs since the same low values combined with wider and deeper coupled areas can be shown to create large margin normal compression in addition there does not seem to be any relation between subduction earthquake magnitudes and plate coupling forces great earthquakes occur at subduction zones having low stress forearcs such as nankai and cascadia

effects of prestress state and rupture velocity on dynamic fault branching 1 we consider a mode ii rupture which propagates along a planar main fault and encounters an intersection with a branching fault using an elastodynamic boundary integral equation formulation allowing the failure path to be dynamically self chosen we study the following questions does the rupture initiate along the branch does it continue is the extensional or compressional side most favored for branching does rupture continue on the main fault too failure is described by a slip weakening law for which the strength at any amount of slip is proportional to normal stress our results show that dynamic stresses around the rupture tip which increase with rupture velocity at locations off the main fault plane relative to those on it could initiate rupture on a branching fault as suggested by prior work whether branched rupture can be continued to a larger scale depends on principal stress directions in the prestress state and on rupture velocity the most favored side for branching rupture switches from the extensional to the compressional side as we consider progressively shallower angles of the direction of maximum compressive prestress with the main fault simultaneous rupturing on both faults can be activated when the branching angle is wide but is usually difficult for a narrow branching angle due to strong stress interactions between faults however it can be also be activated by enhanced dynamic stressing when the rupture velocity is very near the rayleigh velocity natural examples seem consistent with the simulations that we present

geological evidence for past large earthquakes and tsunamis along the hikurangi subduction margin new zealand abstract the hikurangi subduction margin new zealand has not produced large subduction earthquakes within the short written historic period 180 years and the potential of the plate interface to host large m 7 to great m 8 earthquakes and tsunamis is poorly constrained the geological record of past subduction earthquakes offers a method for assessing the location frequency and approximate magnitude of subduction earthquakes to underpin seismic and tsunami hazard assessments we review evidence of holocene coseismic coastal deformation and tsunamis at 22 locations along the margin a consistent approach to radiocarbon age modelling is used and earthquake and tsunami evidence is ranked using a systematic assessment of the quality of age control and the certainty that the event in question is an earthquake to identify possible subduction earthquakes we use temporal correlation of earthquakes combined with the type of earthquake evidence likely primary fault source and the earthquake certainty ranking we identify 10 past possible subduction earthquakes over the past 7000 years along the hikurangi margin the last subduction earthquake occurred at 520 470 years bp in the southern hikurangi margin and the strongest evidence for a full margin rupture is at 870 815 years bp there are no apparent persistent rupture patches suggesting segmentation of the margin is not strong in the southern margin the type of geological deformation preserved generally matches that expected due to rupture of the interseismically locked portion of the subduction interface but the southern termination of past subduction ruptures remains unresolved the pattern of geological deformation on the central margin suggests that the region of the interface that currently hosts slow slip events also undergoes rupture in large earthquakes demonstrating different modes of slip behaviour occur on the central hikurangi margin evidence for subduction earthquakes on the northern margin has not been identified because deformation signals from upper plate faults dominate the geological record large uncertainties remain in regard to evidence of past subduction earthquakes on the hikurangi margin with the greatest challenges presented by temporal correlation of earthquake evidence when working within the uncertainties of radiocarbon ages and the presence of upper plate faults capable of producing deformation and tsunamis similar to that expected for subduction earthquakes however areas of priority research such as improving the paleotsunami record and integration of submarine turbidite records should produce significant advances in the future

very short term earthquake precursors from gps signal interference based on the 2013 nantou and rueisuei earthquakes taiwan abstract we set up a gps network with 17 continuous gps cgps stations in southwestern taiwan to monitor real time crustal deformation we found that systematic perturbations in gps signals occurred just a few minutes prior to the 2013 nantou ml 6 5 and rueisuei ml 6 4 earthquakes in taiwan the anomalous pseudorange readings were several millimeters higher or lower than those in the background time period these systematic anomalies were found as a result of interference of gps l band signals by electromagnetic emissions ems prior to the mainshocks the ems may occur in the form of harmonic or ultra wide band radiation and can be generated during the formation of mode i cracks at the final stage of earthquake nucleation we estimated the directivity of the likely em sources by calculating the inner product of the position vector from a gps station to a given satellite and the vector of anomalous ground motions recorded by the gps the results showed that the predominant inner product generally occurred when the satellite was in the direction either toward or away from the epicenter with respect to the gps network our findings suggest that the gps network may serve as a powerful tool to detect very short term earthquake precursors and presumably to locate a large earthquake before it occurs nevertheless a direct measurement of ems at the site of the gps array is required in future studies to confirm this hypothesis

chilean megathrust earthquake recurrence linked to frictional contrast at depth fundamental processes of the seismic cycle in subduction zones including those controlling the recurrence and size of great earthquakes are still poorly understood here by studying the 2016 earthquake in southern chile the first large event within the rupture zone of the 1960 earthquake moment magnitude mw 9 5 we show that the frictional zonation of the plate interface fault at depth mechanically controls the timing of more frequent moderate size deep events mw 8 5 we model the evolution of stress build up for a seismogenic zone with heterogeneous friction to examine the link between the 2016 and 1960 earthquakes our results suggest that the deeper segments of the seismogenic megathrust are weaker and interseismically loaded by a more strongly coupled shallower asperity deeper segments fail earlier 60 yr recurrence producing moderate size events that precede the failure of the shallower region which fails in a great earthquake recurrence 110 yr we interpret the contrasting frictional strength and lag time between deeper and shallower earthquakes to be controlled by variations in pore fluid pressure our integrated analysis strengthens understanding of the mechanics and timing of great megathrust earthquakes and therefore could aid in the seismic hazard assessment of other subduction zones the recurrence time of megathrust earthquakes in chile may be controlled by frictional contrasts at depth according to analyses of stress build up and release related to the december 2016 southern chile earthquake

extension of continental crust by anelastic deformation during the 2011 tohoku oki earthquake the role of extensional faulting in the generation of a great tsunami abstract observations of seafloor morphologies and environments made before and after the 2011 tohoku oki earthquake reveal open fissures generated during the earthquake where the fault trace is interpreted on seismic profiles to intersect the seafloor anomalously high heat flow was observed at a landward dipping normal fault in august 2011 five months after the earthquake but by august 2012 heat flow measured at the same station had decreased to close to the background value which suggests that the normal fault ruptured during the 2011 earthquake these seafloor observations and measurements demonstrate deformation that was both extensional and anelastic within the overriding continental plate during the 2011 earthquake seismic profiles as well as seafloor bathymetry data in the tsunami source area further demonstrate that landward dipping normal faults extensional faults collapse the continental framework and detach the seaward frontal crust from the landward crust at far landward from the trench the extensional and anelastic deformation i e normal faulting observed in both seafloor observations and seismic profiles allows the smooth seaward movement of the continental crust seaward extension of the continental crust close to the trench axis in response to normal faulting is a characteristic structure of tsunami source areas as similar landward dipping normal faults have been observed at other convergent plate margins where tsunamigenic earthquakes have occurred we propose that the existence of a normal fault that moves the continental crust close to the trench can be considered one indicator of a source area for a huge tsunami

ball and socket tectonic rotation during the 2013 mw7 7 balochistan earthquake abstract the september 2013 m w 7 7 balochistan earthquake ruptured a 200 km long segment of the curved hoshab fault in southern pakistan with 10 0 2 m of peak sinistral and 1 7 0 8 m of dip slip this rupture is unusual because the fault dips 60 15 towards the focus of a small circle centered in northwest pakistan and despite a 30 increase in obliquity along strike the ratios of strike and dip slip remain relatively uniform surface displacements and geodetic and teleseismic source inversions quantify a bilateral rupture that propagated rapidly at shallow depths from a transtensional jog near the northern end of the rupture static friction prior to rupture was unusually weak 0 05 and friction may have approached zero during dynamic rupture here we show that the inward dipping hoshab fault defines the northern rim of a structural unit in southeast makran that rotates akin to a 2 d ball and socket joint counter clockwise in response to india s penetration into the eurasian plate this rotation accounts for complexity in the chaman fault system and in principle reduces seismic potential near karachi nonetheless these findings highlight deficiencies in strong ground motion equations and tectonic models that invoke anderson byerlee faulting predictions

on claimed ulf seismogenic fractal signatures in the geomagnetic field 1 during the last ten years fractal analysis of ultra low frequency ulf geomagnetic field components has been proposed as one of the most promising tools to highlight magnetic precursory signals possibly generated by the preparation processes of earthquakes several papers claim seismogenic changes in the fractal features of the geomagnetic field some months before earthquakes occur the target of the present paper is to put forth a qualitative investigation on the fractal characteristics of ulf magnetic signatures that previous authors have claimed to be related without doubt to strong earthquakes this analysis takes into account both the temporal evolution of the geomagnetic field fractal parameters reported in previous researches and the temporal evolution of global geomagnetic activity running averages of the geomagnetic indices kp and ap are plotted into the original figures from the previous publications this simple analysis shows that the fractal features of the ulf geomagnetic field are closely related to the geomagnetic activity both before and after the earthquake occurs the correlation between the geomagnetic field fractal parameters and geomagnetic activity is clearly shown over both long and short time scales in light of this the present paper shows that fractal behaviors of previously claimed seismogenic ulf magnetic signatures depend mainly on geomagnetic activity due to solar terrestrial interaction therefore previously reported association with the preparation process of the earthquake is dubious

possible splay fault slip during the 1946 nankai earthquake this paper considers seafloor deformation associated with the 1946 nankai earthquake which occurred in the nankai trough subduction zone off the coast of southwest japan we note that recent high resolution determinations of the slip distribution assumed to be confined to the plate boundary result in a pronounced maximum in seafloor displacement midway between the coast of shikoku and the trough axis we show that this feature could be due to slip on a splay fault rather than the plate boundary such a model for the western part of the slip distribution is able to account for the main features of the tsunamigenic seafloor deformation obtained in previous studies with a maximum slip consistent with the plate convergent rate and history of earthquake recurrence at the nankai trough

viscous accretionary prisms viscoelastic relaxation of the makran accretionary prism following the 2013 baluchistan pakistan earthquake

on the seismogenic increase of the ratio of the ulf geomagnetic field components abstract following the paper by fraser smith et al 1990 many scientists have focused their research on the ulf geomagnetic field pulsations in the hope of finding possible anomalous signals caused by the seismic activity thereafter many papers have reported ulf geomagnetic field polarization ratio increases which have been claimed to be related to the occurrence of moderate and strong earthquakes even if there is no firm evidence of correlation between the polarization ratio increase and seismic events these publications maintain that these anomalous increases are without doubt precursors of pending earthquakes furthermore several researchers suggest that these seismogenic signals may be considered a promising approach towards the possibility of developing short term earthquake prediction capabilities based on electromagnetic precursory signatures on the contrary a part of the scientific community emphasizes the lack of validation of claimed seismogenic anomalies and doubt their association with the seismic activity since earthquake prediction is a very important topic of social importance the authenticity of earthquake precursors needs to be carefully checked the aim of this paper is to investigate the reliability of the ulf magnetic polarization ratio changes as an earthquakes precursor several polarization ratio increases of the geomagnetic field which previous researchers have claimed to have a seismogenic origin are put into question by a qualitative investigation the analysis takes into account both the temporal evolution of the geomagnetic field polarization ratio reported in previous papers and the global geomagnetic activity behaviour running averages of the geomagnetic index k p are plotted onto the original figures from previous publications moreover further quantitative analyses are also reported here nine cases are investigated which include 17 earthquakes in seven cases it is shown that the suggested association between the geomagnetic field polarization ratio increases and the earthquake preparation process seems to be rather doubtful more precisely the claimed seismogenic polarization ratio increases are actually closely related to decreases in the geomagnetic activity level furthermore the last two investigated cases seem to be doubtful as well although a close correspondence between polarization ratio and geomagnetic activity cannot be unambiguously demonstrated

seismic afterslip characterization of the 2010 mw 8 8 maule chile earthquake based on moment tensor inversion 1 on february 27th 2010 a mw8 8 earthquake struck the coast of south central chile rupturing 500 km along the subduction interface here we estimate the amount of seismically released afterslip sra and the mechanisms underlying the distribution of aftershocks of this megathrust earthquake we employ data from a temporary local network to perform regional moment tensor rmt inversions additionally we relocate global centroid moment tensor gcmt solutions assembling a unified catalog covering the time period from the mainshock to march 2012 we find that most 70 of the aftershocks with mw 4 correspond to thrust events occurring on the megathrust plane in areas of moderate co seismic slip between 0 15 and 0 7 fraction of the maximum slip smax in particular a concentration of aftershocks is observed between the main patches of co seismic slip where the highest values of sra are observed 1 7 m on the other hand small events mw 0 85 smax likely related to processes in the damage zone surrounding the megathrust plane our study provides insight into the mechanics of the seismic afterslip pattern of this large megathrust earthquake and a quantitative approach to the distribution of aftershocks relative to coseismic slip that can be used for similar studies in other tectonic settings

detection of ultra low frequency emissions connected with the spitak earthquake and its aftershock activity based on geomagnetic pulsations data at dusheti and vardzia observatories abstract ulf electromagnetic emissions from the spitak armenia earthquake site have been detected observations were carried out at the dusheti and vardzia georgia observatories at distances 120 200 km from the epicentre in a frequency range 0 005 1 hz it is shown that the emission appears several hours before the main shock and some of the powerful aftershocks and is not connected with geomagnetic pulsations of magnetospheric sources

investigating non uniform scaling behavior in ultra low frequency ulf earthquake related geomagnetic signals abstract the scaling properties of the time dynamics of 2000 2001 ulf geomagnetic data in the frequency range between 1 mhz and 10 hz observed at izu peninsula in japan were investigated on the basis of detrended fluctuation analysis dfa which is a powerful method to detect scaling in non stationary time series deviations from uniform power law scaling were identified and quantified our results suggest that a significant non uniform scaling behavior in ulf geomagnetic data could be related to the occurrence of intense seismic clusters these first results could be useful in the framework of short term earthquake prediction

stable isotope geochemistry of organic matter alteration in animikie basin sediments within the thermal aureole of the duluth ccomplex abstract we have determined total organic carbon toc total carbonate carbon tcc and 13 c values for toc in samples from the early proterozoic animikie basin sediments virginia and biwabik iron formations that have been variably metamorphosed by the duluth complex toc values for the variably metamorphosed virginia formation show no systematic variation with distance from the intrusion toc from 0 06 to 2 54 in the biwabik iron formation samples outside the thermal aureole of the intrusion have toc generally below 1 compared to 1 7 6 2 for samples within the thermal aureole this enrichment may reflect extensive remobilization of organic carbon within the thermal aureole however 13 c org values measured for both the virginia and biwabik iron formations within the thermal aureole are not significantly different from those outside the thermal aureole it thus appears that in the iron formation the thermal shock caused by the intrusion induced migration of labile organic carbon that was isotopically similar to the residual kerogen the relatively low tcc in samples within the thermal aureole of the intrusion appear to indicate decarbonation of the iron formation also occurred

electromagnetic emissions during dilating fracture of a rock abstract a lot of experiments on electromagnetic emissions emes have been reported under axial compressive fracture shear fracture indentation fracture and stick slip friction in lab and blasting in situ but there are rare reports on the in lab experimental work on emes during dilating fracture of a rock which is helpful in studying and understanding emes related to slow earthquakes and the earthquakes due to volcanic activities and water level changes of reservoirs therefore in the present paper in order to check whether there are detectable emes during dilating fracture of a rock in lab dilating fracture experiments were conducted the dry cuboid specimens of initially intact granodiorite and limestone were tested inside magnetic field free space mffs at room temperature we arranged evenly 20 eme antennas whose resonance frequencies range from 2 5 khz to 540 khz close to rock specimens our experimental results strongly indicate that detectable emes could generate during dilating fracture of a rock they were recorded only associated with some but not all phases of fracture their waveforms often took on the trend that a peak arrived at first and then attenuated sharply and followed by a series of low amplitude oscillations the electromagnetic em signals after eliminating the effects of eme antennae via deconvolution had the maximum peak to peak amplitudes of about 80 0 mv and 40 5 mv for granodiorite and limestone respectively their main spectral components often concentrated in the band of several khz to 60 khz and of several khz to 280 khz the emission of electrons and charged particles from fracture surfaces and or micro fracture electrification could be possible mechanisms for our experimental results

quantifying offshore fore arc deformation and splay fault slip using drowned pleistocene shorelines arauco bay chile most of the deformation associated with the seismic cycle in subduction zones occurs offshore and has been therefore difficult to quantify with direct observations at millennial time scales here we study millennial deformation associated with an active splay fault system in the arauco bay area off south central chile we describe hitherto unrecognized drowned shorelines using high resolution multibeam bathymetry geomorphic sedimentologic and paleontologic observations and quantify uplift rates using a landscape evolution model along a margin normal profile uplift rates are 1 3 m ka near the edge of the continental shelf 1 5 m ka at the emerged santa maria island 0 1 m ka at the center of the arauco bay and 0 3 m ka in the mainland the bathymetry images a complex pattern of folds and faults representing the surface expression of the crustal scale santa maria splay fault system we modeled surface deformation using two different structural scenarios deep reaching normal faults and deep reaching reverse faults with shallow extensional structures our preferred model comprises a blind reverse fault extending from 3 km depth down to the plate interface at 16 km that slips at a rate between 3 0 and 3 7 m ka if all the splay fault slip occurs during every great megathrust earthquake with a recurrence of 150 200 years the fault would slip 0 5 m per event equivalent to a magnitude 6 4 earthquake however if the splay fault slips only with a megathrust earthquake every 1000 years the fault would slip 3 7 m per event equivalent to a magnitude 7 5 earthquake

multiple seismo anomalies associated with the m6 1 ludian earthquake on august 3 2014 abstract multiple geophysical parameters including groundwater level water temperature water radon crustal deformation electromagnetic waves and total electron contents tec in the ionosphere are examined together to investigate pre earthquake anomalous phenomena associated with the mw6 1 ludian earthquake on august 3 2014 cross parameter comparison eliminates anomalies that are detected in one parameter only and examine earthquake related phenomena in various fields simultaneously retrieved anomalies show that abnormal decreases of water temperature and radon concentration related to anomalous uplift of groundwater levels appeared about 1 8 days before the earthquake even without contributions from rain significant step like changes are observed from data recorded by strainmeters on july 31 and are consistent with water related anomalies in timing no significant anomalies can be found from electromagnetic data through the preliminary observation in contrast tec appeared positive anomalies 1 3 days before the ludian earthquake although causal mechanisms of the tec anomalies from stressed rocks are not fully understood multiple parameter examination can increase credibility of determination regarding pre earthquake phenomena

magnetic field observations in the near field the 28 june 1992 mw 7 3 landers california earthquake recent reports suggest that large magnetic field changes occur prior to and during large earthquakes two continuously operating proton magne tometers lsbm and ochm at distances of 17 3 and 24 2 km respectively from the epicenter of the 28 june 1992 mw 7 3 landers earthquake recorded data through the earthquake and its aftershocks these two stations are part of a differentially connected array of proton magnetometers that has been operated along the san andreas fault since 1976 the instruments have a sensitivity of 0 25 nt or better and transmit data every 10 min through the goes satellite to the usgs headquarters in menlo park california seismomagnetic offsets of 1 2 0 6 and 0 7 0 7 nt were observed at these sites in comparison offsets of 0 3 0 2 and 1 3 0 2 nt were observed during the 8 july 1986 mt 5 9 north palm springs earthquake which occurred directly beneath the ochm magnetometer site the observations are generally consistent with seismomagnetic models of the earthquake in which fault geometry and slip have the same form as that determined by either inversion of the seismic data or inversion of geodetically determined ground displacements produced by the earthquake in these models right lateral rupture occurs on connected fault seg ments in a homogeneous medium with average magnetization of 2 a m the fault slip distribution has roughly the same form as the observed surface rupture and the total moment release is 1 1 1020 nm there is no indication of dif fusion like character to the magnetic field offsets that might indicate these ef fects result from fluid flow phenomena it thus seems unlikely that these earth quake generated offsets and those produced by the north palm springs earthquake were generated by electrokinetic effects also there are no indications of en hanced low frequency magnetic noise before the earthquake at frequencies be low 0 001 hz

fractal analysis of ulf geomagnetic data associated with the guam earthquake on august 8 1993 this paper presents a fractal analysis of the ulf electromagnetic data obtained at guam observatory during a strong ms 8 0 earthquake occurred on august 8 1993 near the guam island we have already reported the presence of seismogenic ulf emissions for this quake hayakawa et al grl 1996 the chosen period covered four months before and two months after the earthquake it was found that the spectrum of emissions at noon exhibited a power law behavior f which is typical for self organized critical dynamics the slope of the spectrum in the noon sector fluctuates in a range from 2 5 to 0 7 with a tendency to gradually decrease during the process of the earthquake preparation we consider this to be a candidate for a precursory signature the similar effect was found for the night sector we suggest that the focal zone was at the critical stage of self organized criticality process before the quake related to active microfracturing processes followed by the generation of ulf emissions as we detected

active tectonics of the south chilean marine fore arc 35 s 40 s the south chilean marine fore arc 35 s 40 s is separated into four tectonic segments concepcion north concepcion south nahuelbuta and tolten from north to south these are each characterized by their individual tectonic geomorphology and reflect different ways of mechanical and kinematic interaction of the convergent nazca and south american plates splay faults that cut through continental framework rock are seismically imaged in both concepcion segments and the tolten segment additionally the concepcion south segment exhibits prominent upper plate normal faults normal faults apparently relate to uplift caused by sediment underthrusting at depth this has led to oversteepening and gravitational collapse of the marine fore arc there is also evidence for sediment underthrusting and basal accretion to the overriding plate in the tolten segment there uplift of the continental slope has created a landward inclined seafloor over a latitudinal distance of 50 km in the nahuelbuta segment transpressive upper plate faults aligned oblique to the direction of plate motion control the seafloor morphology based on a unique acoustic data set including 90 of bathymetric coverage of the continental slope we are able to reveal an along strike heterogeneity of a complexly deformed marine fore arc which had escaped attention in previous studies that only considered the structure along transects normal to the plate margin

carbon enhanced electrical conductivity during fracture of rocks changes in electrical resistance during rock fracture in the presence of a carbonaceous atmosphere have been investigated using nugget sandstone and westerly granite the experiments were performed in an internally heated gas pressure vessel with a load train that produced strain rates between 10 6 and 10 5 s 1 samples were deformed at temperatures of 354 to 502 c and pressures of 100 to 170 mpa in atmospheres of ar or mixtures of 95 co2 with 5 co or 5 ch4 compositions that are well within the field of graphite stability at the run conditions in experiments using nugget sandstone resistance reached a minimum value when the maximum temperature was achieved and good electrode contact was made the resistance then increased as the experiment continued probably due to dry out of the sample a change in the oxidation state of the fe oxide associated with the cement or destruction of current bearing pathways at approximately 200 mpa end load the rock sample failed plots of load and resistance versus time show several interesting features in one experiment for example as the end load reached about 175 mpa resistance stopped increasing and remained fairly constant for a period of approximately 0 5 hour during loading the end load displayed small decreases that were simultaneous with small decreases in resistance when the end load and the displacement indicated rock failure resistance decreased dramatically from 150 m to 100 m in a single experiment the westerly granite also showed a decrease in resistance during dilatancy the nature and distribution of carbon in the run products were studied by electron microprobe and time of flight secondary ion mass spectroscopy top sims carbon observed by mapping with the former is clearly observed on micro cracks that based on the microtexture are interpreted to have formed during the deformation the tof sims data confirm the electron probe observations that carbon is present on fracture surfaces these observations and experimental results lead to the hypothesis that as microfractures open in the time leading up to failure along a fracture carbon is deposited as a continuous film on the new reactive mineral surfaces and this produces a decrease in resistance subsequent changes in resistance occur as connectivity of the initial fracture network is altered by continued deformation such a process may explain some electromagnetic effects associated with earthquakes

spatiotemporal variation of mantle viscosity and the presence of cratonic mantle inferred from 8 years of postseismic deformation following the 2010 maule chile earthquake

splay fault slip during the mw 8 8 2010 maule chile earthquake splay faults are thrusts that emerge from the plate boundaries of subduction zones such structures have been mapped at several convergent margins and their activity commonly ascribed to large megathrust earthquakes however the behavior of splay faults during the earthquake cycle is poorly constrained because typically these structures are located offshore and are difficult to access here we use geologic mapping combined with space and land geodesy as well as offshore sonar data to document surface fault ruptures and coastal uplift at isla santa maria in south central chile 37 s caused by the 27 february 2010 maule earthquake m w 8 8 during the earthquake the island was tilted parallel to the margin and normal faults ruptured the surface and adjacent ocean bottom we associate tilt and crestal normal faulting with growth of an anticline above a blind reverse fault rooted in the nazca south america plate boundary which slipped during the maule earthquake the splay fault system has formed in an area of reduced coseismic plate boundary slip suggesting that anelastic deformation in the upper plate may have restrained the 2010 megathrust rupture surface fault breaks were accompanied by prominent discharge of fluids our field observations support the notion that splay faulting may frequently complement and influence the rupture of subduction zone earthquakes

ulf geomagnetic anomalies of possible seismogenic origin observed at teoloyucan station mexico in 1999 2001 intermediate and short time analysis abstract the analysis of ulf geomagnetic field measured at teoloyucan station central mexico 11 35 735 w 19 44 45 100 n 2280 m height is presented in an intermediate 15 days and short time scale the day of the eq occurrence in relation to 7 major earthquakes occurred in mexico in 1999 2001 local changes in the fractal dynamics of the magnetic field are found to be important a pronounced fall of the fractal index is frequently observed prior to the main shock the study of the ulf resonant structure recently discovered in the frequencies fr1 10 2 11 1 mhz and fr2 13 6 14 5 mhz reveals changes in their character probably related to the processes of the earthquakes preparation the success of the observation of the mentioned anomalies specially the fractal index decrease strongly depends on how close is the station from the epicenter and what is the magnitude of the earthquake

seismic imaging of a megathrust splay fault in the north chilean subduction zone central andes abstract prominent trench parallel fault systems in the arc and fore arc of the chilean subduction zone can be traced for several thousand kilometers in north south direction these fault systems possibly crosscut the entire crust above the subduction megathrust and are expected to have a close relationship to transient processes of the subduction earthquake cycles with the motivation to image and characterize the structural inventory and the processes that occur in the vicinity of these large scale fault zones we re processed the ancorp 96 controlled source seismic data set to provide images of the faults at depth and to allow linking geological information at the surface to subsurface structures the correlation of the imaging results with observed hypocenter locations around these fault systems reveals the origin and the nature of the seismicity bound to these fault systems active and passive seismic data together yield a picture of a megathrust splay fault beneath the longitudinal valley at mid crustal level which can be observed from the top of the subduction plate interface and which seems to be connected to the precordilleran fault system pfs known at the surface this result supports a previously proposed tectonic model where a megathrust splay fault defines the western altiplano as a crustal scale fault bend fold furthermore we clearly imaged two branches of the uyuni kenayani fault ukf in a depth range between 0 and 20 km in summary imaging of these faults is important for a profound understanding of the tectonic evaluation and characterization of the subduction zone environment for which the results of this study provide a reliable basis

statistical analysis of ulf seismomagnetic phenomena at kakioka japan during 2001 2010 to clarify and verify the ultralow frequency ulf seismomagnetic phenomena we have performed statistical studies on the geomagnetic data observed at the kakioka kak station japan during 2001 2010 we investigated the energy of ulf geomagnetic signals of the frequency around 0 01 hz using wavelet transform analysis to minimize the influences of artificial noises and global geomagnetic perturbations we used only the geomagnetic data observed at nighttime lt 2 30 a m to 4 00 a m and utilized observations from a remote station kanoya as a reference statistical results of superposed epoch analysis have indicated that ulf magnetic anomalies are more likely to appear before sizable earthquake events es 108 rather than after them especially 6 15 days before the events further statistical investigations show clearly that the ulf geomagnetic anomalies at kak station are more sensitive to larger and closer events finally we have evaluated the precursory information of ulf geomagnetic signals for local sizable earthquakes using molchan s error diagram the probability gain is around 1 6 against a poisson model the above results have indicated that the ulf seismomagnetic phenomena at kak clearly contain precursory information and have a possibility of improving the forecasting of large earthquakes

potential relationships between seismo deformation and seismo conductivity anomalies abstract this study examines the relationships between seismo deformation and seismo conductivity anomalies during two m6 earthquakes that occurred on march 27th and june 2nd 2013 in taiwan the hilbert huang transform is applied on surface displacement data to remove the effects of noise semi annual and annual cycles and the long term plate movements the residual displacements have similar orientations when earthquake related stress accumulates in the crust once the accumulated stress approaches the threshold for fault rupture the orientations of the residual displacements generally become random except in a small region near the epicenter interestingly high conductivity anomalies which can be detected from the 3 component magnetic data via the magnetic transfer function exist in places very close to this small region near the epicenter spatial and temporal correlations between the high conductivity anomalies and the small region of seismo deformation anomalies suggest that electric charges may migrate and become trapped in the region during seismogenic processes due to differential stress accumulation these electric charges form a high conductivity material that affects the parkinson vector of the geomagnetic field

transient electric variations associated with large intermediate depth earthquakes in south aegean abstract a telluric station was installed on crete in the south aegean in order to investigate the existence of transient electric variations before large near intermediate depth earthquakes during the experiment two transient electric variations not correlated with geomagnetic variations were recorded and associated with two time isolated intermediate depth earthquakes with local magnitude m l 5 8 and 4 8 respectively finally a qualitative discussion on the form of the electric signal based on the charge dislocation model is presented

tsunamigenic structures in a creeping section of the alaska subduction zone segments of subduction zones that are capable of generating tsunamigenic earthquakes appear to have characteristic structural configurations these structures include heterogeneous plate interfaces a small wedge of deformed sediment at the toe of the overriding plate the frontal prism and splay faults in the crust of the overriding plate that root within the plate boundary megathrust here we use seismic reflection imaging to show that these features also exist within a creeping segment of the alaska subduction zone the shumagin gap we identify an active crustal scale normal fault system that dips landward and resembles that involved in the 2011 tohoku oki earthquake in japan we also find that the shumagin gap has a small frontal prism a deep water splay fault and that the plate interface here is rough and thinly sedimented we propose that lateral propagation of rupture from a neighbouring segment into the shumagin gap may explain a tsunamigenic earthquake that occurred there in 1788 and that tsunamigenic potential should be considered in hazard assessments for the region our results demonstrate that structural configurations similar to those in tohoku may exist in other subduction zones including within creeping segments or segments with no record of historical megathrust earthquakes but are under recognized identifying similar configurations globally may improve our ability to anticipate regions capable of generating large tsunamis creeping subduction zones are unlikely to generate tsunamigenic earthquakes analysis of a creeping part of the alaskan subduction zone reveals fault structures similar to those in tohoku suggesting it may host large earthquakes and tsunamis

geoelectric signals in china and the earthquake generation process we present original apparent resistivity records for stations located in the chinese provinces of hebei and sichuan along with seismicity patterns fault maps and limited hydrologic data these records are part of a 30 year database of geoelectric signals that have been recorded in china by a nationwide network of more than 100 stations set up by the state seismological bureau of the people s republic of china the database includes the time period during which the m 7 8 1976 tangshan and m 7 2 1976 songpan earthquakes occurred resistivity data recorded in and around the epicentral region of the tangshan event show coherent changes both temporal and in areal distribution years and months before and after the earthquakes a regional change in water table occurred more than 3 years prior to the tangshan earthquake the resistivity and water table signals appear to correlate in the 2 to 3 year period prior to the earthquake rainfall records from the region around tangshan extending to the cities of beijing and tianjin do not appear to account for the resistivity changes regional seismicity and active fault patterns in north china indicate that deformation occurs mainly along the borders of large tectonic blocks the source region for the geoelectric signals appears to lie within a large shear zone at the edge of a tectonic block undergoing rotation the tangshan epicentral area is thus only part of a larger zone of deformation we suggest that dilational strain associated with the opening of fractures may lower resistivity and water table for shallow crustal depths such as those monitored by the chinese geoelectric network dilation and resistivity changes are expected to begin at stress levels well below the peak values of the seismic cycle our study suggests that in some cases the areal extent of geoelectric signals may be significantly larger than that of the eventual earthquake source dimension the chinese geoelectric database offers an opportunity to improve our understanding of possible geoelectric precursors to earthquakes

anomalous behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 there have been many reports on ultra low frequency ulf electromagnetic phenomena associated with earthquakes in a very wide frequency range in this study unusual behaviors of geomagnetic diurnal variations prior to the 2011 off the pacific coast of tohoku earthquake mw9 0 have been reported ratios of diurnal variation range between the target station esashi esa which is about 135 km from the epicenter and the remote reference station kakioka kak about 302 km distant to the epicenter have been computed the results of 10 day running mean of the ratios showed a clear anomaly exceeding the statistical threshold in the vertical component about 2 months before the mega event this anomaly is unique over a 3 year background and the further stochastic test indicates that this anomaly is unlikely a random anomaly which is highly suggestive of correlation with the mega event the original records of geomagnetic fields of the esa station also exhibit continuous anomalous behaviors for about 10 days in the vertical component approximate 2 months prior to the mw9 0 earthquake

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

on the anomalous changes of seismicity and geomagnetic field prior to the 2011 mw 9 0 tohoku earthquake abstract in xu et al 2013 it has just been reported that approximately 2 months prior to the m w 9 0 tohoku earthquake that occurred in japan on 11 march 2011 anomalous variations of the geomagnetic field have been observed in the vertical component at a measuring station about 135 km from the epicenter for about 10 days 4 14 january 2011 here we show that this observation is in striking agreement with independent recent results obtained from natural time analysis of seismicity in japan in particular this analysis has revealed that an unprecedented minimum of the order parameter fluctuations of seismicity was observed around 5 january 2011 thus pointing to the initiation at that date of a strong precursory seismic electric signals activity accompanied by the anomalous geomagnetic field variations starting from this date natural time analysis of the subsequent seismicity indicates that a strong main shock was expected in a few days to one week after 08 40 lt on 10 march 2011

constraining the strength of megathrusts from fault geometries and application to the alpine collision zone abstract using coulomb wedge solutions we show that the effective strength of megathrusts b can be determined from the geometry of out of sequence thrusts cutting through an accretionary or orogenic wedge the method is first tested on central chilean margin for which it yields a frictional strength of b 0 053 0 043 0 024 the inferred value agrees well with previous strength estimates and with the tectonic response of the central chilean wedge to 2010 m w 8 8 maule earthquake we then use the approach to constrain the strength of the collision megathrust of the central european alps 30 20 million years ago we find that the collision megathrust had a strength of b 0 065 0 035 0 026 which is similarly low than the strength of subduction megathrusts the result is integrated into a static force balance model to examine potential implications of a weak megathrust for the alpine orogeny the model results suggest that the alpine megathrust supported a mean maximum elevation of 2 000 m and that growth of the wedge up to this elevation supported a switch from contractional to extensional tectonics in the interior of the alps around 20 ma finally using the example of the himalayas we show how the strength of megathrusts may be also derived from the geometry of crustal ramps which provides a valuable alternative if details on out of sequence thrusts are missing

radio emission associated with rock fracture possible application to the great chilean earthquake of may 22 1960 stress induced piezoelectric fields produce freely propagating electromagnetic radiation when microscopic rock fractures occur in quartz bearing rocks a laboratory study is presented which shows that electromagnetic emissions are produced when microfractures occur in westerly granite a detailed model is presented for the emission process which allows an estimate of the total radiated power from an individual microfracture on the basis of these results a case is presented that an unusual radio emission seen on several widely separated radio astronomy receivers in the northern hemisphere on may 16 1960 was due to a stress induced microfracture along the chilean fault this radio event occurred 6 days prior to the great chilean earthquake of may 22 1960 and may have been a precursor to one of the largest earthquakes of this century

challenges in the detection of ionospheric pre earthquake total electron content anomalies peta for earthquake forewarning various studies have investigated the link between seismic activity and ionospheric precursory phenomena many of these retrospective case studies have supported the existence of pre earthquake ionospheric anomalies by examining past earthquake events using a variety of analytical methods based on existing methodologies however the conversion of a retrospective analysis to a prospective forewarning scenario is not a straightforward process the obstacles to its potential adoption stem mainly from assumptions made during data analysis and interpretation in this study several parameters pertaining to existing approaches for the detection of these ionospheric anomalies are highlighted and discussed in particular ionosphere total electron content tec a detailed examination is conducted to understand the roles that each of these parameters play in the detection process and the consequent difficulties when adopting them in a prospective analysis these issues include accounting for variations in ionosphere characteristics owing to different measurement platforms e g ground and space based observations and statistical methods e g standard deviation envelopes used in detecting anomalies furthermore the necessity of excluding space weather contributions in the underlying tec fluctuations poses a challenge in determining the validity of observed ionospheric anomalies the notion of an earthquake preparation zone is also evaluated in the context of the ionosphere along with its implications in a forewarning scenario these issues need to be addressed in current research in order to enable its possible application in earthquake forewarning

estimating coseismic coastal uplift with an intertidal mussel calibration for the 2010 maule chile earthquake mw 8 8 abstract coseismic coastal uplift has been quantified using sessile intertidal organisms after several great earthquakes following fitzroy s pioneer measurements in 1835 a dense survey of such markers may complement space geodetic data to obtain an accurate distribution of fault slip and earthquake segmentation however uplift estimates based on diverse intertidal organisms tend to differ because of few methodological and comparative studies here we calibrate and estimate coastal uplift in the southern segment of the 2010 maule chile earthquake m w 8 8 using 1100 post earthquake elevation measurements of the sessile mussel perumytilus purpuratus this mussel is the predominant competitor for rocky shores all along the pacific coast of south america where it forms fringes or belts distinctively in the middle intertidal zone these belts are centered at mean sea level and their width should equal one third of the tidal range we measured belt widths close to this value at 40 of the sites but overall widths are highly variable due to the unevenness in belt tops belt bases in turn are rather regular belt top unevenness apparently results from locally enhanced wave splash whereas belt base evenness is controlled by predation according to our measurements made beyond the earthquake rupture the belt base is at the bottom of the middle intertidal zone and thus we propose to estimate coastal uplift using the belt base mean elevation plus one sixth of the tidal range to reach mean sea level within errors our estimates agree with gps displacements but differ from other methods comparisons of joint inversions for megathrust slip suggest combining space geodetic data with estimates from intertidal organisms may locally increase the detail of slip distributions

the 2011 magnitude 9 0 tohoku oki earthquake mosaicking the megathrust from seconds to centuries geophysical observations from the 2011 moment magnitude m w 9 0 tohoku oki japan earthquake allow exploration of a rare large event along a subduction megathrust models for this event indicate that the distribution of coseismic fault slip exceeded 50 meters in places sources of high frequency seismic waves delineate the edges of the deepest portions of coseismic slip and do not simply correlate with the locations of peak slip relative to the m w 8 8 2010 maule chile earthquake the tohoku oki earthquake was deficient in high frequency seismic radiation a difference that we attribute to its relatively shallow depth estimates of total fault slip and surface secular strain accumulation on millennial time scales suggest the need to consider the potential for a future large earthquake just south of this event

coastal deformation and great subduction earthquakes isla santa maria chile 37 s isla santa maria at the active margin of south central chile is the result of earthquake related uplift and deformation in the forearc since at least late pleistocene time field mapping dating of key depositional horizons and analysis of seismic refl ection profi les reveal ongoing deformation in this sector of the chilean forearc the 30 km 2 island is located 12 km above the interplate seismogenic zone and 75 km landward of the trench it is situated near the southern termination of the concepcion earthquake rupture segment where charles darwin measured 3 m of coseismic uplift during a m 8 megathrust earthquake in 1835 permanent postearthquake deformation from this earthquake and an earlier event in 1751 is registered by emerged landward tilted abrasion surfaces uplift at 2 m k y and tilting at 0 025 k y of the island have been fairly constant throughout the late quaternary and have resulted in emergence of the island above sea level 31 k y ago the island is composed of a late pleistocene upper tilted surface with two asymmetric tilt domains and holocene lowlands characterized by uplifted and tilted strandlines industry offshore seismic refl ection profi les covering an area of 1800 km 2 and crustal seismicity reveal active reversefault cored anticlines surrounding isla santa maria the principal fault apparently roots in the plate interface thrust these reverse faults in the upper plate result from inversion of late cretaceous to early pliocene normal faults and rift structure of the arauco forearc basin positive inversion of these inherited structures started between 3 6 and 2 5 ma and resulted in continuous shortening rates of 0 8 mm yr the seismic refl ection profi les show that the asymmetric tilt domains and progressive syntectonic sedimentation are linked to the position of the island in the forelimbs of two converging anticlines whereas their backlimbs have been removed by cliff retreat the 2 m uplift contour of the 1835 earthquake is parallel to the strike of active faults and antiforms in the arauco concepcion region the close relation among the asymmetric uplift and tilt of the island modern deformation patterns and reverse faults rooted in the plate interface suggests that slip on the plate interface thrust infl uences localizes and segments surface deformation during large interplate earthquakes furthermore the link between positive inversion of pre existing structures uplift and tilt patterns in the forearc emphasizes the importance of inherited structural fabrics in guiding plate boundary deformation

modelling the connection between earthquake preparation processes and crustal electromagnetic emission abstract the steadily increasing amount of information available today on the natural electromagnetic emission eme of the radio frequency band associated with seismic events raises the problem of the origin of this phenomenon a natural hypothesis is that eme is due to earthquake preparation processes the present paper is concerned with substantiating a model that postulates eme to be caused by cracking of surficial crustal layers in the zone of earthquake preparation the crust is assumed to have ordered hierarchical structure individual elements of that structure are formed of blocks of different scales and obey principles of similarity between the blocks are soft interlayers with a finite strength limit a regular periodic structure with a cubic lattice is studied as a result eme intensity as a function of magnitude is evaluated methodological recommendations are given for organization of field observations of eme in relation to earthquake prediction

dynamic rupture activation of backthrust fault branching we perform dynamic rupture simulations to investigate the possible reactivation of backthrust branches triggered by ruptures along a main thrust fault simulations with slip weakening fault friction and uniform initial stress show that fast propagation speed or long propagation distance of the main rupture promotes reactivation of backthrust over a range of branch angles the latter condition may occur separately from the former if rupture speed is limited by an increasing slip weakening distance towards the junction direction the results suggest a trade off between the amplitude and duration of the dynamic stress near the main rupture front for backthrust reactivation termination of the main rupture by a barrier can provide enhanced loading amplitude and duration along a backthrust rooted near the barrier facilitating its reactivation especially with a high frictional resistance the free surface and depth dependent initial stress can have several additional effects the sign of the triggered motion along the backthrust can be reversed from thrust to normal if a deeply nucleated main rupture breaks the free surface while it is preserved as thrust if the main rupture is terminated by a barrier at depth the numerical results are discussed in relation to several recent megathrust earthquakes in sumatra chile and japan and related topics such as branch feedbacks to the main fault the dynamic view on backthrust fault branching provided by the study fills a gap not covered by quasi static models or observations a specific examined case of antithetic fault branching may be useful for indicating a barrier like behavior along the main fault

megathrust locking and viscous mantle flow induce continental shortening in central andes crustal faults at subduction zones show evidence of activity over geological time but at the scale of earthquake cycle the mechanical behavior of these faults is not fully understood here we construct 2 d viscoelastic models constrained by both horizontal and vertical gps derived interseismic velocities to investigate the contribution and interrelation between subduction zone locking viscous mantle flow and upper plate faulting on surface deformation in central andes main pattern of horizontal velocities can be explained by a combination of locking degree and viscous flow whereas vertical signal is found essential for estimating the locking depth a sharp deformation gradient near the major back arc fault suggests an active interseismic shorting across this structure we further conduct mechanical viscoelastic models with a frictional back arc fault to analyze its displacement and activation conditions our results suggest that the back arc fault is creeping at 3 mm year and its motion is mainly driven by the interseismic viscous mantle flow which spreads plate tectonic stresses broadly across the continent moreover the frictional strength of the back arc fault must be remarkably weak and its mechanics re distributes the interseismic deformation and shortens the continental plate in central andes geological estimates suggest that the long term shortening rate at the back arc fault is 10 mm year suggesting that this structure can accumulate 7 mm year of slip deficit confirming the seismic potential of this structure

results of ultra low frequency magnetic field measurements during the guam earthquake of 8 august 1993 we report the results of measurements of ultra low frequency magnetic noise during a large earthquake ms 7 1 at guam of 8 august 1993 depth 60 km the ulf observing system is located in the guam island about 65 km from the epicenter several distinct features of this analysis are summarized 1 we have proposed rather sophisticated statistical analyses monthly mean standard deviation in order to estimate the wave intensity and polarization i e ratio z h 2 a comparison between the ulf wave activity and kp is useful in distinguishing between the space geomagnetic pulsations and non space emissions 3 then the use of the ratio z h is found to be of essential importance in discrimating the emissions presumably of seismic origin from space plasma waves 4 the statistical analysis of the temporal evolution of this ratio has yielded that it shows a broad maximum only about one month before the earthquake and this suggests that the emissions during this period are very likely to be magnetic precursors 5 the temporal variation of z component is similar to that for the loma prieta earthquake such that it shows a broad maximum ten days two weeks before the earthquake and another increase a few days before the earthquake 6 the emissions presumably associated with the earthquake are of noise like nature and their main frequency is 0 02 0 05 hz with maximum intensity 0 1 nt

low frequency magnetic field measurements near the epicenter of the ms 7 1 loma prieta earthquake the authors report the results of measurements of low frequency magnetic noise by two independent monitoring systems prior to the occurrence of the m sub s 7 1 loma prieta earthquake of 17 october 1989 their measurements cover 25 narrow frequency bands in the more than six decade frequency range 0 01 hz 32 khz with a time resolution varying from a half hour in the ulf range 0 01 10 hz to one second in the elf vlf range 10 hz 32 khz the ulf system is located near corralitos about 7 km from the epicenter the elf vlf system is located on the stanford campus about 52 km from the epicenter analysis of the elf vlf system is located on the stanford campus about 52 km from the epicenter analysis of the elf vlf data has revealed no precursor activity that they can identify at this time however the ulf data have some distinctive and anomalous features first a narrow band signal appeared in the range 0 05 0 2 hz around september 12 and persisted until the appearance of the second anomalous feature which consisted of a substantial increase in the noise background starting on 5 october and covering almost the entire frequency range of the ulf system third there was an anomalousmore dip in the noise background in the range 0 2 5 hz starting one day ahead of the earthquake finally and perhaps most compelling there was an increase to an exceptionally high level of activity in the range 0 01 0 5 hz starting approximately three hours before the earthquake there do not appear to have been any magnetic field fluctuations originating in the upper atmosphere that can account for this increase further while the systems are sensitive to motion seismic measurements indicate that there were no significant shocks preceding the quake thus the various anomalous features in the data and in particular the large amplitude increase in activity starting three hours before the quake may have been magnetic precursors less

splay fault branching along the nankai subduction zone seismic reflection profiles reveal steeply landward dipping splay faults in the rupture area of the magnitude m 8 1 tonankai earthquake in the nankai subduction zone these splay faults branch upward from the plate boundary interface that is the subduction zone at a depth of approximately 10 kilometers approximately 50 to 55 kilometers landward of the trough axis breaking through the upper crustal plate slip on the active splay fault may be an important mechanism that accommodates the elastic strain caused by relative plate motion

experimental study on characteristics of surface potential and current induced by stress on coal mine sandstone roof abstract rocks generate voltage and current when subjected to load hence the study of their characteristics is critical to the prevention and management of mine dynamic disasters and their secondary impacts to investigate the characteristics of surface potential and current induced by stress on coal mine sandstone roof an experimental scheme for determining the mechanical electrical characteristics of rocks is constructed the aforementioned system tests the evolution rules of current and voltage generated by the coal mine sandstone roof at different loading rates the formation mechanism and coupling rules with mechanical properties of sandstone are also analysed experimental results show that although loading rates may differ the variations of pressure stimulated current psc and pressure stimulated voltage psv curves are similar throughout the loading process the psc is divided into three stages rapid growth slow growth and peak on the other hand the psv curve exhibits a double peak characteristic the loading rate changes the current and voltage growth rates and peak values when combined with mechanical properties it can be observed that the psc is related to the effective elastic modulus whereas the psv is related to micro crack and macro crack events in rocks the current and voltage generated by the coal mine sandstone roof subjected to load are consistent with stress the mechanical electrical properties of sandstone indicate that the change processes in the psc and psv result from the coupling effects of various mechanisms in the compaction stage these are mainly caused by the piezoelectric effect of sandstone in the elastic plastic deformation stage they are primarily generated by the electric dipoles formed by micro cracks in the sandstone fracture deformation stage the change processes are mainly caused by the crack tip discharge this study provide an experimental basis and practical results that reflect the microscale process and electrical precursors of sandstone fracturing

results of ulf magnetic field measurements near the epicenters of the spitak ms 6 9 and loma prieta ms 7 1 earthquakes comparative analysis the characteristics of the ulf magnetic field emissions measured at two magnetic observatories in the republic of georgia prior to and after the ms 6 9 earthquake that occurred near spitak armenia on december 7 1988 are compared with the apparently similar emissions associated with the ms 7 1 earthquake that occurred near loma prieta california on october 17 1989 the main features of the spitak measurements according to observations made at the dusheti station 128 km to the spitak epicenter as compared with the loma prieta measurements which were made at corralitos california 7 km to the loma prieta epicenter are the following 1 the intensity of ulf background activity started growing 3 to 5 days before the spitak earthquake whereas the corresponding increase in activity began 12 days before the loma prieta earthquake 2 a substantial ulf emission burst was recorded at dusheti starting 4 hours prior to the main shock a similar large burst of ulf activity commenced 3 hours before the loma prieta event and continued until the occurrence of the main shock 3 ulf activity remained high for about two weeks after the spitak earthquake and for several months after the loma prieta earthquake 4 ulf noise bursts were observed 1 to 6 hours before powerful aftershocks at spitak during the period of enhanced activity but there was no conclusive link between the ulf noise at corralitos and the after shocks a major difference in the ulf activity preceding the two earthquakes is a difference in amplitude 0 2 nt at spitak and 5 nt at loma prieta but this is easily explained as being caused by the different distances of the observation stations from the epicenters

tsunamis and splay fault dynamics 1 the geometry of a fault system can have significant effects on tsunami generation but most tsunami models to date have not investigated the dynamic processes that determine which path rupture will take in a complex fault system to gain insight into this problem we use the 3d finite element method to model the dynamics of a plate boundary splay fault system we use the resulting ground deformation as a time dependent boundary condition for a 2d shallow water hydrodynamic tsunami calculation we find that if the stress distribution is homogeneous rupture remains on the plate boundary thrust when a barrier is introduced along the strike of the plate boundary thrust rupture propagates to the splay faults and produces a significantly larger tsunami than in the homogeneous case the results have implications for the dynamics of megathrust earthquakes and also suggest that dynamic earthquake modeling may be a useful tool in tsunami research

geomagnetic variations possibly associated with the pisco earthquake on 15 august 2007 peru abstract on 15 august 2007 pisco earthquake magnitude 8 0 hit the central coast of peru near the magdas ancon anc station geomagnetic data from anc and other reference stations have been analyzed to detect any signature related to this great earthquake results indicate the presence of annual geomagnetic variations in the vertical component at anc and huancayo hua stations in the vicinity of the epicenter of pisco earthquake these variations have a quasi sinusoidal waveform with amplitudes of about 10 and 5 nt for anc and hua stations respectively they appeared clearly during the period preceding the onset of the pisco earthquake especially at anc station by using hua eusebio eus and kourou kou as reference stations in the vicinity and away from the epicenter of pisco earthquake a clear disappearance of the diurnal variation of the vertical component was observed at anc station during the day of earthquake moreover the pisco earthquake and another earthquake on 29 march 2008 near anc station were found to occur concurrently with the depressions in the polarization ratio z h of pc 3 10 45 s amplitude such anomalous variations appear to be a result of changes in the crustal stress field and the lithospheric conductivity in the studied region

anatomy of the andean subduction zone three dimensional density model upgraded and compared against global scale models summary we present an upgraded version of a previously published 3 d density model of the andean subduction zone between 18 s and 45 s this model consists of 3 d bodies of constant density which geometry is constrained by independent seismic data and is triangulated from vertical cross sections these bodies define the first order morphology and internal structure of the subducted nazca slab and south american plate the new version of the density model results after forward modelling the bouguer anomaly as computed from the most recent version of the earth gravitational model egm2008 the 3 d density model incorporates new seismic information to better constrain the geometry of the subducted slab and continental moho cmh and has a trench parallel resolution doubling the resolution of the previous model as an example of the potential utility of our model we compare the geometry of the subducted slab and cmh against the corresponding global models slab1 0 and crust2 0 respectively this exercise demonstrates that although global models provide a good first order representation of the slab and upper plate crustal geometries they show large discrepancies up to 40 km with our upgraded model for some well constrained areas the geometries of the slab lithosphere asthenosphere boundary below the continent cmh and intracrustal density discontinuity that we present here as supporting information can be used to study andean geodynamic processes from a wide range of quantitative approaches

simple crack models explain deformation induced by subduction zone megathrust earthquakes following the 2010 maule and 2011 tohoku earthquakes many studies have examined the relation between megathrust earthquakes and subsequent deformation here we apply simple models based on mode ii shear cracks including approximated effects of the free surface to study induced deformation during coseismic and early postseismic stages we distinguish between buried and surface ruptures represented by a full crack and a half crack model respectively we adopt an analogy based approach to interpret the half crack model from well known results of the full crack model which is also validated by our numerical simulations with transferable knowledge between the two models we provide easy ways to understand 1 the contrasting deformation patterns in the frontal wedge of the overriding plate between buried ruptures and surface ruptures 2 the correlation between triggered outer rise normal faulting and surface ruptures and 3 the similar deformation patterns for both buried and surface ruptures toward the down dip end with a preference for normal faulting in the overriding plate and for reverse faulting in the subducting plate these model outcomes are consistent with several recent observations on aftershocks and veins in a paleoaccretionary wedge we further investigate some important transient features during rupture propagation which show that a transition from compressional to extensional deformation in the frontal wedge of the overriding plate is possible even during a single rupture event our work provides alternative views for understanding various aspects of subduction zone megathrust earthquakes and raises the issue of important transient features that were typically ignored in previous studies

large extensional aftershocks in the continental forearc triggered by the 2010 maule earthquake chile summary the mw 8 8 maule earthquake occurred off the coast of central chile on 2010 february 27 and was the sixth largest earthquake to be recorded instrumentally this subduction zone event was followed by thousands of aftershocks both near the plate interface and in the overriding continental crust here we report on a pair of large shallow crustal earthquakes that occurred on 2010 march 11 within 15 min of each other near the town of pichilemu on the coast of the o higgins region of chile field and aerial reconnaissance following the events revealed no distinct surface rupture we infer from geodetic data spanning both events that the ruptures occurred on synthetic sw dipping normal faults the first larger rupture was followed by buried slip on a steeper fault in the hangingwall the fault locations and geometry of the two events are additionally constrained by locations of aftershock seismicity based on the international maule aftershock data set the maximum slip on the main fault is about 3 m and consistent with field results the onshore slip is close to zero near the surface satellite radar data also reveal that significant aseismic afterslip occurred following the two earthquakes coulomb stress modelling indicates that the faults were positively stressed by up to 40 bars as a result of slip on the subduction interface in the preceding megathrust event in other words the pichilemu earthquakes should be considered aftershocks of the maule earthquake the occurrence of these extensional events suggests that regional interseismic compressive stresses are small several recent large shallow crustal earthquakes in the overriding plate following the 2011 mw 9 0 tohoku oki earthquake in japan may be an analogue for the triggering process at pichilemu

generation of ulf electromagnetic emissions by microfracturing microfracturing electrification is discussed as a possible explanation of ulf electromagnetic emissions observed before and after earthquakes using a space time simple model of microfracture progression it is possible to compare theoretical results and observed results with special reference to the intensity spectrum and temporal development of ulf magnetic field variations

long period analysis of the 2016 kaikoura earthquake abstract the recent m w 7 8 kaikoura new zealand earthquake involved a remarkably complex rupture propagating in an intricate network of faults at the transition between the alpine fault in the south island and the kermadec tonga subduction zone we investigate the main features of this complicated rupture process using long period seismological observations apparent rayleigh wave moment rate functions reveal a clear northeastward directivity with an unusually weak rupture initiation during 60 s followed by a major 20 s burst of moment rate to further explore the rupture process we perform a bayesian exploration of multiple point source parameters in a 3 d earth model the results show that the rupture initiated as a small strike slip rupture and propagated to the northeast triggering large slip on both strike slip and thrust faults the kaikoura earthquake is thus a rare instance in which slip on intraplate faults trigger extensive interplate thrust faulting this clearly outlines the importance of accounting for secondary faults when assessing seismic and tsunami hazard in subduction zones

hidden holocene slip along the coastal el yolki fault in central chile and its possible link with megathrust earthquakes megathrust earthquakes are commonly accompanied by increased upper plate seismicity and occasionally triggered fault slip in chile crustal faults slipped during and after the 2010 maule m8 8 earthquake we studied the el yolki fault eyof a transtensional structure midways the maule rupture not triggered in 2010 we mapped a holocene coastal plain using lidar which did not reveal surface ruptures however the inner edge and shoreline angles along the coastal plain as well as 4 3 4 0 ka intertidal sediments are back tilted on the eyof footwall block documenting 10 m of vertical displacement these deformed markers imply 2 mm yr throw rate and dislocation models a slip rate of 5 6 mm yr for the eyof in a 5 m deep trench the holocene intertidal sediments onlap to five erosive steps interpreted as staircase wave cut landforms formed by discrete events of relative sea level drop we tentatively associated these steps with coseismic uplift during eyof earthquakes between 4 3 and 4 0 ka the maule earthquake rupture may be subdivided into three subsegments based on coseismic slip and gravity anomalies coulomb stress transfer models predict neutral stress changes at the eyof during the maule earthquake but positive changes for a synthetic slip distribution at the central subsegment if eyof earthquakes were triggered by megathrust events their slip distribution was probably focused in the central subsegment our study highlights the millennial variability of crustal faulting and the megathrust earthquake cycle in chile with global implications for assessing the hazards posed by hidden but potentially seismogenic coastal faults along subduction zones

high precision slip distribution of the 1944 tonankai earthquake inferred from tsunami waveforms possible slip on a splay fault abstract inversion of tsunami waveforms is a well established technique for estimating the slip distributions of subduction zone earthquakes with some of the most detailed results having been obtained for earthquakes in the nankai trough sw japan the present study although it uses a method and tsunami waveform data set almost identical to previous study aims to improve on previous work by using a more precise specification of initial conditions for the calculation of tsunami green s functions specifically we incorporated four improvements in the present study 1 we used a realistic plate model based only on seismic survey results and assumed it to be the fault plane of the 1944 tonankai earthquake 2 the smallest subfaults consistent with the long wavelength approximation were used in the tsunami inversion analysis 3 we included the effect of horizontal displacement of the ocean bottom on tsunami generation and 4 we performed a checkerboard resolution test as obtained in previous studies a zone of high slip 2 0 m was resolved off the shima peninsula however the more precise calculation of tsunami green s functions has revealed additional detail that was not evident in previous studies which we demonstrate is resolvable and correlates with the position of known faults in the accretionary prism while there was little or no slip near the trench axis in the eastern part of the rupture zone there was up to 1 5 m of slip resolved within 30 km of the trough axis in the western part along the coast of the kii peninsula this troughward slip zone coincides with the position of a large splay fault mapped in multichannel reflection surveys furthermore it is also clear that the upper edge of the enshu fault off shima and atsumi peninsulas is consistent with the up dip limit of slip in the eastern part of our model we tested the possibility that slip occurred on the former splay fault instead of on the plate interface during the 1944 tonankai earthquake and find that slip on this splay fault is also consistent with the data although we cannot distinguish whether slip was dominant on the splay fault or on the plate interface we further suggest that the position of the enshu fault may be determined by the subduction of topographic highs and that such faults may have an important influence on the up dip rupture limit of the 1944 tonankai and potentially other subduction zone earthquakes

seismomagnetic effect generated by the october 1989 ml 7 1 loma prieta california earthquake a differentially connected array of proton magnetometers operated within the epicentral region of the october 18 1989 ml 7 1 loma prieta earthquake for 12 years from 1974 to 1986 the closest magnetometer station was located 7 3 km from the epicenter of the earthquake and within 3 km of the site where anomalous ulf magnetic noise measurements were observed following the earthquake the magnetometers were reinstalled with sensors replaced in the original undisturbed sensor holders comparison of pre 1986 total intensity magnetic field data with data obtained during the months following the earthquake indicate local offsets of about 1 nt may have been generated at stations nearest the epicenter tests on other continuous differenced data from 1983 to present indicate that offsets determined could be biased by as much as 0 7 nt the offsets can be approximately fit with a simple seismomagnetic model of the earthquake for which 1 9 m of right lateral and 1 3 m of dip slip southwest side up occurred on a fault patch between 6 km and 18 km deep and 45 km long the total rock magnetization is assumed to be 1 5 a m since the offset has persisted following the earthquake an alternate explanation in terms of electokinetic effects is unlikely even though transient ground water flow occurred following the earthquake comparison of pre 1986 and similar post seismic total magnetic field noise does not indicate any change caused by aliasing of ulf 0 01 hz 10 hz magnetic noise in the vicinity of the loma prieta earthquake

revisiting viscoelastic effects on interseismic deformation and locking degree a case study of the peru north chile subduction zone viscoelastic effects potentially play an important role during all phases of the earthquake cycle in subduction zones however most current models neglect such effects in the interseismic deformation pattern here we use finite element method fem models to investigate the control of viscoelasticity on interseismic deformation and to highlight the pitfalls of interpreting the data with purely elastic models for both the forward and inverse problems our results confirm that elastic models are prone to overestimating the interseismic locking depth a crucial parameter for estimating the maximum possible earthquake magnitude the application of the viscoelastic model improves the fit to the interseismic deformation especially in the inland area additionally we construct 3 d fem models constrained by geophysical and gps data and apply our methodology to the peru north chile subduction zone our results indicate that viscoelastic effects contribute significantly to the observed gps data the signals interpreted as back arc shortening in the elastic model can be alternatively explained by viscoelastic deformation which in turn dramatically refines the interseismic locking pattern in both dip and strike directions our viscoelastic locking map exhibits excellent correlation with the slip distributions of previous earthquakes especially the recent 2014 mw 8 1 iquique earthquake the incorrect elastic assumptions affect the analysis of interseismic deformation with respect to slip deficit calculations our results thus suggest that it is necessary to thoroughly reevaluate existing locking models that are based on purely elastic models some of which attribute viscoelastic deformation to different sources such as microplate sliver motions

frictional discharge plasma and seismo electromagnetic phenomena abstract although several mechanisms of precursory electromagnetic emissions of earthquakes have been proposed there has been no in situ observation of electromagnetic phenomena occurring at the frictional contacts during rock frictions from an experiment simulating the motion of an asperity on a fault surface we report the generation of photon emissions around frictional contacts between natural rock minerals spectroscopic analysis clarified that the photon emissions are caused by dielectric breakdown of ambient gases electric discharge plasma due to frictional electrification the plasmas were found to occur under normal stress of 4 mpa and sliding speed of 10 2 m s this indicates that plasma generations do not require high normal stresses needed to fracture rocks and sliding speeds as high as seismic rates 1 m s thus frictional discharges could occur at microscopic asperities at the onset of the slips of earthquakes and might be one of the sources of the seismo electromagnetic emission

ulf electromagnetic precursors for an earthquake at biak indonesia on february 17 1996 ulf electromagnetic emissions associated with a large earthquake occurred at biak island indonesia at 5h 59m ut on february 17 1996 magnitude mw 8 2 and depth 20 km from usgs catalog have been investigated on the basis of ulf magnetic observations at two stations biak and darwin in australia about 1 200 km apart though a simple analysis of magnetic field intensity horizontal and vertical magnetic field components at both stations was found to be closely correlated with geomagnetic kp activity a detailed analysis of the difference of h and z components at the two stations the polarization analysis z h and fractal analysis frequency spectrum slope at these two stations has yielded that the ulf emissions in the frequency range from 5 mhz to 30 mhz about 1 5 1 0 months before the quake are likely to be a precursory signature of the quake with its intensity on the order of 0 2 0 3 nt

regional stress field as determined from electromagnetic radiation in a tunnel abstract the paper presents the results of electromagnetic radiation emr measurements in the feuerberg tunnel in southwest germany emr is associated with small scale fracturing processes the measured numbers of emr impulses are shown to be proportional to shear stresses from the correlation of emr and shear stresses along the long axis of the tunnel orientations and magnitudes of the horizontal principal stresses are determined the major horizontal principal stress is 3 6 0 3 mpa and has an azimuth of 143 6 the minor principal horizontal stress is 2 1 0 3 mpa zones in the tunnel are located where low shear stresses occur because vertical overburden and horizontal stresses are equal in these zones also minimum radiation was detected a possible stress accumulation close to a fault is suggested by higher emr values in a part of the tunnel orientations and magnitudes of the horizontal principal stresses which are derived from the measurements of emr correlate well with conventional stress measurements it is suggested that the cross section measuring method described in the study is used to determine regional stress fields as well as to investigate endangered zones with high stresses in underground facilities which may be critical with regard to stability

constructing forearc architecture over megathrust seismic cycles geological snapshots from the maule earthquake region chile we present new field structural data from the chilean coastal cordillera located above the northern and central parts of the interplate contact ruptured by the a d 2010 m w 8 8 maule earthquake the northern study area contains the northwest striking pichilemu normal fault an intraplate structure reactivated after the megathrust event by crustal earthquakes up to m w 7 0 the structural style of this region is dominated by kilometer scale normal faults that have been active at least throughout the quaternary the orientations of these main faults define three structural systems 1 northeast and 2 northwest striking margin oblique faults and 3 north to north northeast striking margin parallel faults from north to south these three systems vary in their predominant occurrence starting with bimodal orientations of groups 1 and 2 followed by predominantly single north to north northeast orientations of group 3 reverse faults coexist in time and space with the normal structures but are scarce and display variable apparently random orientations the shallow crustal normal faults including the pichilemu fault show a persistent kinematic history probably spanning thousands of subduction seismic cycles though historically smaller in magnitude than those of the triggered normal faults interseismic forearc thrust events were recorded above the rupture area prior to the maule earthquake the quaternary reverse faults identified in our study regions may be preserving interseismic slow strain rate permanent deformation signature in the structural grain analogous observations along the a d 2011 tohoku earthquake rupture in japan imply that such a link between the short and long term deformation patterns of the forearc is not exclusive of the maule earthquake region

re os isotopic variations in carbonaceous pelites hosting the duluth complex implications for metamorphic and metasomatic processes associated with mafic magma chambers abstract previous mineralogic and isotopic studies of sulfide mineralization in the 1 1 ga duluth complex have suggested that sulfur and possibly metals have been derived from proterozoic sedimentary country rocks the re os isotopic system offers great potential in the evaluation of crustally derived metals in magmatic ore forming processes but an understanding of the mechanisms that could cause isotopic variations in country rock contaminants is a prerequisite a suite of sulfidic and carbonaceous pelitic rocks of the virginia formation country rock to the duluth complex ranging from unmetamorphosed through strongly recrystallized and partially melted xenoliths have been analyzed for their os isotopic composition sulfide mineral separates mainly pyrrhotite kerogen graphite isolates and whole rocks were analyzed whole rocks kerogen and graphite from metamorphosed samples plot between 1 85 ga and 1 1 ga chondritic reference isochrons sulfide separates from all metamorphosed samples plot nearer the chondritic 1 1 ga reference isochron and require exchange with a fluid or melt characterized by a chondritic os isotopic composition potentially derived from the duluth complex devolatilization and partial melting may perturb isotopic systematics when accompanied by the loss of re and os bearing fluids these processes could in part explain the scatter in isotopic values found in kerogen and metamorphosed whole rocks however metasomatic addition of os via interaction with a fluid or melt is required to explain the sulfide isotopic ratios and is consistent with sulfide minerals being more susceptible to os exchange with a fluid than kerogen the relative ease with which pyrrhotite may be reset during fluid interaction as well as the variable degrees of exchange shown by kerogen graphite suggest that a knowledge of the petrologic and isotopic evaluation of country rocks is necessary before a meaningful assessment of the isotopic variations found in igneous rocks or associated ore deposits can be undertaken

splay fault triggering by great subduction earthquakes inferred from finite element models we have investigated the influence that megathrust earthquake slip has on the activation of splay faults using a 2 d finite element method fem taking into account the effects of gravity and variations in the frictional strength properties of splay faults we simulated both landward dipping and seaward dipping splay fault geometries and imposed depth variable slip distributions of subduction events our results indicate that the two types of splay fault exhibit a similar behavior with variations in frictional properties along the faults affecting only the seismic magnitude the triggering process is controlled by a critical depth megathrust slip concentrated at depths shallower than the critical depth will favor normal displacement while megathrust slip concentrated at depths deeper than the critical depth is likely to result in reverse motion our results thus provide a useful tool for predicting the activation of secondary faults and may have direct implications for tsunami hazard research

modeling megathrust earthquakes across scales one way coupling from geodynamics and seismic cycles to dynamic rupture abstract taking the full complexity of subduction zones into account is important for realistic modelling and hazard assessment of subduction zone seismicity and associated tsunamis studying seismicity requires numerical methods that span a large range of spatial and temporal scales we present the first coupled framework that resolves subduction dynamics over millions of years and earthquake dynamics down to fractions of a second using a two dimensional geodynamic seismic cycle sc method we model 4 million years of subduction followed by cycles of spontaneous megathrust events at the initiation of one such sc event we export the self consistent fault and surface geometry fault stress and strength and heterogeneous material properties to a dynamic rupture dr model coupling leads to spontaneous dynamic rupture nucleation propagation and arrest with the same spatial characteristics as in the sc model it also results in a similar material dependent stress drop although dynamic slip is significantly larger the dr event shows a high degree of complexity featuring various rupture styles and speeds precursory phases and fault reactivation compared to a coupled model with homogeneous material properties accounting for realistic lithological contrasts doubles the amount of maximum slip introduces local pulse like rupture episodes and relocates the peak slip from near the downdip limit of the seismogenic zone to the updip limit when an sc splay fault is included in the dr model the rupture prefers the splay over the shallow megathrust although wave reflections do activate the megathrust afterwards

effects of thermal maturation on stable organic carbon isotopes as determined by hydrous pyrolysis of woodford shale acquiring crude oils that have been expelled from the same rock unit at different levels of thermal maturation is currently not feasible in the natural system this prevents direct correlation of compositional changes between the organic matter retained in a source rock and its expelled crude oil at different levels of thermal maturation alleviation of this deficiency in studying the natural system requires the use of laboratory experiments natural generation of petroleum from amorphous type ii kerogen in the woodford shale may be simulated by hydrous pyrolysis which involves heating crushed rock in contact with water at subcritical temperatures 374 c four distinct stages of petroleum generation are observed from this type of pyrolysis 1 pre oil generation 2 incipient oil generation 3 primary oil generation and 4 post oil generation the effects of thermal maturation on the 13c values of kerogen bitumen and expelled oil like pyrolysate from the woodford shale have been studied through these four stages of petroleum generation similar to the natural system the kerogens isolated from the pyrolyzed rock showed no significant change in 13c this suggests that the 13c value of kerogens may be useful in kerogen typing and oil to source rock correlations 13c values of bitumens extracted from the pyrolyzed rock showed an initial decrease during the incipient oil generation stage followed by depletion during the primary and post oil generation stages this reversal is not favorable for geochemical correlation or maturity evaluation saturated and polar components of the bitumen show the greatest 13c variations with increasing thermal maturation the difference between the 13c of these two components gives a unidirectional trend that serves as a general indicator of thermal maturation and is referred to as the bitumen isotope index bii 13c values of the expelled pyrolysates show a unidirectional increase with increasing thermal maturation the constancy and similarity of 13c values of the aromatic components in the expelled pyrolysates and bitumens with increasing thermal maturation encourages their use in oil to oil and oil to source rock correlations isotopic type curves for expelled pyrolysates indicate that they may be useful in oil to oil correlations but have a limited use in oil to source rock correlations

study of directivity effect on electromagnetic emissions in the hf band as earthquake precursors preliminary results on field observations abstract this work focuses on the use of electromagnetic emissions em in the hf band as a warning event for earthquakes em at hf components 41 mhz and 46 mhz were monitored and recorded from eight field stations in greece and correlated with seismological events directivity effect raised since em emissions at specific station locations were correlated to earthquake events from prescribed regions em recordings during 1999 were used and by visual inspection were associated to most of the earthquake events greater than 5r using these observations a novel algorithm based on the ratio of short term to long term signal average together with a prediction rules set derived from 1999 s em emissions study were developed to combine results from several field stations performance of the system was promising but was dependent on the geographic area of interest overall performance for earthquakes events of magnitude greater than 5 7 r was 75 of seismic events were correctly predicted by em activity while 25 were not predicted

theory of time dependent rupture in the earth at a velocity x which is a well defined function of k this propagation is stable and quasi static and is referred to as subcritical crack growth we shall use the terms stable quasistatic and subcritical to mean propagation at velocities much less than the sonic velocities of the medium this behavior results from stress induced corrosion at the crack tip the principal corrodent for the present application being h20 this behavior has been firmly established in the laboratory for mode i tensile cracks in a wide variety of materials ineluding silicates and silicate glasses see cholz 1968a 1972a martin 1972 wiederhorn and bolz 1970 atkinson 1979 lawn and wilshaw 1975 knott 1973 the form of the relationship between k and x does not vary significantly with the material only the parameters in the law vary as an example we show in figure 1 data on subcritical crack growth in quartz after atkinson 1979 the empirical relationship is found to take the form