self similar earthquake triggering bath s law and foreshock aftershock magnitudes simulations theory and results for southern california 1 bath s law the observation that the largest aftershock is on average 1 2 magnitudes smaller than its main shock independent of main shock size suggests some degree of self similarity in earthquake triggering this behavior can largely be explained with triggering models in which the increased triggering caused by larger magnitude events is exactly compensated for by their decreased numbers and these models can account for many features of real seismicity catalogs the bath s law magnitude difference of 1 2 places a useful constraint on aftershock productivity in these models a more general test of triggering self similarity is to plot foreshock and aftershock rates as a function of magnitude m relative to the main shock magnitude mmax of the largest event in the sequence both computer simulations and theory show that these dn dm curves should be nearly coincident regardless of main shock magnitude the aftershock dn dm curves have the same gutenberg richter b value as the underlying distribution but the foreshock dn dm curves have the same b value only for foreshock magnitudes less than about mmax 3 for larger foreshock values the dn dm curve flattens and converges with the aftershock dn dm curve at m mmax this effect can explain observations of anomalously low b values in some foreshock sequences and the decrease in apparent aftershock to foreshock ratios for small magnitude main shocks observed apparent foreshock and aftershock dn dm curves for events close in space and time to m 2 5 to 5 5 main shocks in southern california appear roughly self similar but differ from triggering simulations is several key respects 1 the aftershock b values are significantly lower than that of the complete catalog 2 the number of aftershocks is too large to be consistent with bath s law and 3 the foreshock to aftershock ratio is too large to be consistent with bath s law these observations indicate for southern california that triggering self similarity is not obeyed for these small main shocks or that the space time clustering is not primarily caused by earthquake to earthquake triggering

coastline uplift in oregon and washington and the nature of cascadia subduction zone tectonics coastline deformation resulting from great shallow thrust earthquakes can provide information concerning the paleoseismicity of a subduction zone and thus information on the nature of potential seismicity the cascadia subduction zone is different from most other subduction zones in that it has been quiescent with respect to great earthquakes for at least the past 200 yr the washington oregon coastline also differs from most other coastlines associated with subduction zones in its lack of uplifted holocene shoreline features and low overall rate of late quaternary uplift 0 2 0 6 mm yr the uplift differences suggest that repeated great earthquakes have not occurred along the cascadia subduction zone at least during the late holocene alternatively if the plate interface has generated earthquakes the differences may be explained by longer recurrence intervals for great earthquakes smaller magnitude earthquakes or a mechanism that does not result in uplift of the coastline where expected

normal faulting earthquakes beneath the outer slope of the japan trench after the 2011 tohoku earthquake implications for the stress regime in the incoming pacific plate 1 after the 2011 mw 9 1 tohoku earthquake numerous intraplate earthquakes occurred beneath the outer slope of the japan trench based on ocean bottom seismograph observations these earthquakes occurred in the oceanic crust and uppermost mantle of the pacific plate at depths shallower than about 40 km and had normal faulting focal mechanisms at all depths before the 2011 earthquake normal faulting earthquakes beneath the outer trench slope occurred only at depths shallower than 20 km whereas those at depths of around 40 km had reverse faulting mechanisms these observations suggest that the stress regime in the pacific plate was changed by the 2011 earthquake the tensional stresses that now extend to depths of about 40 km may play an important role not only in the occurrence of large normal faulting earthquakes but also in hydration of the uppermost mantle of the incoming pacific plate prior to the subduction

el mayor cucapah mw 7 2 earthquake early near field postseismic deformation from insar and gps observations el mayor cucapah earthquake occurred on 4 april 2010 in northeastern baja california just south of the u s mexico border the earthquake ruptured several previously mapped faults as well as some unidentified ones including the pescadores borrego paso inferior and paso superior faults in the sierra cucapah and the indiviso fault in the mexicali valley and colorado river delta we conducted several global positioning system gps campaign surveys of preexisting and newly established benchmarks within 30 km of the earthquake rupture most of the benchmarks were occupied within days after the earthquake allowing us to capture the very early postseismic transient motions the gps data show postseismic displacements in the same direction as the coseismic displacements time series indicate a gradual decay in postseismic velocities with characteristic time scales of 66 9 days and 20 3 days assuming exponential and logarithmic decay respectively we also analyzed interferometric synthetic aperture radar insar data from the envisat and alos satellites the main deformation features seen in the line of sight displacement maps indicate subsidence concentrated in the southern and northern parts of the main rupture in particular at the indiviso fault at the laguna salada basin and at the paso superior fault we show that the near field gps and insar observations over a time period of 5 months after the earthquake can be explained by a combination of afterslip fault zone contraction and a possible minor contribution of poroelastic rebound far field data require an additional mechanism most likely viscoelastic relaxation in the ductile substrate

spatial aftershock distribution of the 26 december 2004 great sumatra andaman earthquake in the northern sumatra area 1 in july 2005 about 6 months after the 2004 great sumatra andaman earthquake 20 ocean bottom seismometers were deployed in the northern sumatra area more than 1000 events were identified during the 12 day recording period after relocation the seismicity shows different patterns on each side of the lower splay fault east of this feature and beneath the aceh basin and fore arc the deep earthquakes outline the subduction megathrust fault west of it the aftershocks distribution is strongly influenced by the active n s oceanic fracture zones of the subducted plate two n s trending clusters of 10 to 50 km deep earthquakes observed below the lower wedge are interpreted as reactivated oceanic fracture zones the postseismic activity suggests a significant influence of the n s active fracture zones of the oceanic plate on the toe of the wedge explaining the dextral wrenching of wedge thrusts in the morphology the megathrust fault does not extend to the trench but outcrops east of these active oceanic fractures and seems to merge upward along the lower splay fault where shallow earthquakes are observed

bath s law derived from the gutenberg richter law and from aftershock properties 1 the empirical bath s law states that the average difference in magnitude between a mainshock and its largest aftershock is 1 2 regardless of the mainshock magnitude following vere jones 1969 and console et al 2003 we show that the origin of bath s law is to be found in the selection procedure used to define mainshocks and aftershocks rather than in any difference in the mechanisms controlling the magnitude of the mainshock and of the aftershocks we use the etas model of seismicity which provides a more realistic model of aftershocks based on i a universal gutenberg richter gr law for all earthquakes and on ii the increase of the number of aftershocks with the mainshock magnitude using numerical simulations of the etas model we show that this model is in good agreement with bath s law in a certain range of the model parameters

geodynamic evolution of the lithosphere and upper mantle beneath the alboran region of the western mediterranean constraints from travel time tomography an edited version of this paper was published by the american geophysical union copyright 2000 agu see also http www agu org pubs crossref 2000 2000jb900024 shtml http atlas geo cornell edu morocco publications calvert2000 htm

space time etas models and an improved extension for sensitive detection of anomalous seismicity such as quiescence and activation in a given region we need a suitable statistical reference model that represents a normal seismic activity in the region the regional occurrence rate of the earthquakes is modeled as a function of previous activity the specific form of which is based on empirical laws in time and space such as the modified omori formula and the utsu seki scaling law of aftershock area against magnitude respectively this manuscript summarizes the development of the epidemic type aftershock sequence etas model and proposes an extended version of the best fitted space time model that was suggested in ogata ogata y 1998 space time point process models for earthquake occurrences ann inst statist math 50 379 402 this model indicates significantly better fit to seismicity in various regions in and around japan d 2005 elsevier b v all rights reserved

cenozoic active margin and shallow cascades structure cocorp results from western oregon two deep seismic reflection profiles totaling 98 km were recorded by the consortium for continental reflection profiling cocorp in western oregon in 1984 providing some of the first onshore deep seismic reflection data from the forearc and arc of an active convergent margin these data are of lower quality than most cocorp data but when combined with other geological and geophysical data they provide some useful insights into the subduction zone beneath oregon and into extensional structures in the cascades line 1 crossed the eocene sediments and underlying pillow basalts of the coast range and western willamette valley reflections from the willamette valley clearly define the lower and western boundary of flat lying rhythmically bedded eocene sediments these sediments appear to be underlain by as much as 8 km of seismically transparent eocene pillow basalts layered reflections at depths of 8 16 km may indicate a remnant crust upon which the eocene pillow basalts were erupted east dipping reflections at depths of 35 40 km may represent the decollement above the subducting juan de fuca plate oregon line 2 crosses the cenozoic volcanic arc terrains of the western and high cascades interpretation of cocorp seismic data suggests modification of existing models for normal faulting that postulate a symmetric graben or grabens in the cascades of oregon in the high cascades along cocorp oregon line 2 reflections suggest a large gently west dipping half graben with major offset only on the west side of the range the seismic reflection data along with other geological and geophysical data suggest that the high cascades were built on a series of blocks rather than a single graben the blocks were differentially faulted during the pliocene seismic data from the western cascades indicate several normal faults with down to the east offset including a major previously unidentified fault of probable miocene age

lateral variation of the crust in the iberian peninsula new evidence from the betic cordillera abstract new results from a seismic refraction wide angle reflection survey carried out in the betic cordillera in autumn 1989 contribute to a better picture of its deep structure one nw se profile cuts across the iberian massif the external and internal betics the structure of the crust in the iberian massif shows characteristics similar to those found in previous experiments the lower crust is found as a distinct layer 12 km thick with an average velocity of 6 8 km s 1 the moho is found at about 35 km depth this structure extends southeastward until a 3 4 km upwelling of the moho about 30 km north of the present day surface boundary between the external and internal betic units further southeast the moho deepens to 38 km and the lower crust is no longer seismically detected the absence of differentiated lower crust beneath part of the external betics may be related with the mesozoic rifting of the south iberian passive margin instead this absence under the internal betics may be caused by rifting in conjunction with the collisional evolution of the orogen a wnw ese profile lying in the internal betics shows the presence of a prominent reflector at 10 12 km depth this seems to be a widespread feature in the internal betics and may be interpreted as a detachment surface the moho is found at 38 km depth rising strongly in the easternmost betics seismic data suggest a thin crust in the offshore area southwest of malaga probably containing a massive zone of high velocity rocks which is also supported by available geophysical and geological data

copper and manganese in hemipelagic sediments at 21 n east pacific rise diagenetic contrasts abstract relatively rapidly accumulating 7 cm kyr and organic rich 1 5 corg epr sediments near 21 n are characterized by pronounced nitrate reduction in the upper decimetre and by an enrichment of mn and increased fe al ratio in surficial sediments joint consideration of solid phase and pore water data indicates that the distributions of both mn and fe in the sediments are in disequilibrium with their respective pore water profiles precipitation of upward diffusing mn and fe is occurring at present below the enriched horizons producing perched enrichments indicative of non steady state diagenesis consideration of a high resolution 14c age vs depth curve and a decrease toward the interface from 1 51 to 1 37 wt over the top 7 cm of the corg profile suggests that the diagenetic disequilibrium evident for mn and fe may be due to a geologically recent decrease in productivity such a decrease would be manifest in the sediments by a downwardly migrating oxidation front which would progressively erode the mn and fe pore water profiles producing the existing decoupled surface enrichments in contrast to mn the distribution of cu has apparently not been perturbed by non steady state phenomena a first order decrease with depth of the dissolved copper concentration is accompanied by a first order increase in solid phase cu application of a diffusion reaction model to these data predicts a sedimentation rate of 8 cm kyr 1 which agrees well with the 14c determined rate of 7 3 cm kyr 1 implying that the pore water and solid phase distributions are in diagenetic equilibrium available evidence suggests that the major host for non detrital cu in hemipelagic sediments is authigenic nontronite because this phase appears to form slowly there may be a kinetic constraint on the amount of copper which can be incorporated authigenically in rapidly accumulating hemipelagic deposits support for this hypothesis is given by the observed inverse proportionality between the sedimentation rate and the concentration of non detrital cu in surface sediments from at least seven widespread locations in the eastern pacific it is suggested that the variation observed in the salt and caco3 free cu concentration in hemipelagic sediments is a consequence largely of the residence time of sediments at the surface where high dissolved cu concentrations prevail

late quaternary deformation of marine terraces on the cascadia subduction zone near cape blanco oregon the cape blanco region of south coastal oregon sits on the upper plate of the cascadia subduction zone about 60 70 km east of the base of the continental slope though the region has no historic coseismic deformation late quaternary deposits and landforms show abundant evidence of uplift folding and faulting a set of five late quaternary marine terraces and one uplifted holocene beach berm are preserved in the cape blanco region stratigraphic and altitudinal surveys of these physiographic features combined with several numerical and correlation age determinations permit a reconstruction of tectonic deformation near cape blanco in approximately the last 200 000 years the most cogent aspects of the neotectonics in this part of the cascadia subduction zone are that an east west trending anticline deforms the lower three terraces 80 125 ka as well as accounting for uplift of the holocene storm berm latest movement on the anticline was no more than 2 000 years ago but the anticline also deforms sediments as old as middle miocene the anticline is consistent with a north south principal contraction axis at cape blanco in about the last 100 000 years an older terrace at cape blanco approximately 200 ka is offset by two reactivated faults whose movements prior to the eocene served to suture several terranes to the north american continent tectonic tilting in the older terrace is not consistent with a north south principle axis of contraction but the axis of tilt is parallel to north northwest striking structures developed in the quaternary fold belt offshore on the continental shelf the observed deformation indicates that regional stress in the vicinity of cape blanco in the late quaternary has been accommodated by a variable pattern of strain

comparing foreshock characteristics and foreshock forecasting in observed and simulated earthquake catalogs in this paper we compare the empirical results regarding foreshocks obtained from the japan data with results for synthetic catalogs in order to clarify whether or not the corresponding results are consistent with the description of the seismicity by a superposition of background activity and epidemic type aftershock sequence etas models this question is important because it is still controversially discussed whether the nucleation process of large earthquakes is driven by seismically cascading etas type or by aseismic accelerating processes to explore the foreshock characteristics we first applied the same clustering algorithms to real and synthetic catalogs and analyzed the temporal spatial and magnitude distributions of the selected foreshocks most properties are qualitatively the same in the real data and in synthetic catalogs however we find some quantitative differences particularly in the temporal acceleration spatial convergence and magnitude dependence which also depend on the assumed synthetic catalogs furthermore we calculated forecast scores based on a single link cluster algorithm which could be appropriate for real time applications we find that the japan meteorological agency catalog yields higher scores than all synthetic catalogs and that the etas models having the same magnitude sequence as the original catalog performs better more close to the reality than etas models with randomly picked magnitudes we also find that the etas model that takes account of the triggering effect by small earthquakes below threshold magnitude performs more closely to the reality

lithospheric structure beneath the alboran basin results from 3d gravity modeling and tectonic relevance a three dimensional gravity modeling combined with integrated heat flow and elevation modeling is conducted to map out the crustal and lithospheric mantle thickness in the alboran basin in the westernmost mediterranean a sediment corrected bouguer anomaly has been derived using a depth to the basement map and densities determined from well logs and seismic data the gravity effect of the base of the lithosphere has been removed from the sediment corrected bouguer anomaly to obtain a crustal bouguer anomaly which has been inverted for crustal thickness the resulting lithospheric structure is further constrained by elevation data under the assumption of local isostasy the low residual elevation anomalies obtained 100 m in average suggest that the area is in local isostasy particularly the medium and long wavelength topography features variations in crustal thickness range from 36 km underneath the betic and rif chains to 12 km beneath the easternmost part of the alboran sea basin in the transition to the south balearic basin in western alboran the moho lies at a rather constant depth of 18 km deepening sharply toward the gibraltar strait down to 30 32 km the base of the lithosphere shallows from 140 km depth in the gibraltar strait to 45 km depth in the easternmost alboran sea lithospheric thinning penetrates to the southeastern side of the iberian margin crosscutting topographic highs of the central and eastern betic chain our results favor mantle delamination produced by detachment and subsequent peeling away of the lithospheric mantle rather than convective removal of the lithospheric mantle either by orogenic collapse or detachment and sinking of a lithospheric slab

the relative contribution of accretion shear and extension to cenozoic tectonic rotation in the pacific northwest large cenozoic clockwise rotations defined by paleomagnetic data are an established fact in the pacific northwest and many tectonic models have been proposed to explain them including 1 rotation of accreted oceanic microplates during docking 2 dextral shear between north america and northward moving oceanic plates to the west and 3 microplate rotation in front of an expanding basin and range province stratigraphic onlap relations and local structure indicate that microplate rotation during docking was not a major contributor to the observed rotations coast range structures basin and range extension and paleomagnetic data from middle miocene 15 ma coast range rocks indicate that dextral shear is responsible for at least 40 of the post 15 ma rotation of the coast range and that basin and range extension is responsible for the remainder reconstructions based on extrapolation of this ratio back to 37 and 50 ma are consistent with reconstructions based on paleomagnetic and stratigraphic relations in older rocks and suggest that dextral shear has been a significant contributor to rotation during most of tertiary time changes in the dextral shear rotation rate over the past 50 m y correlate directly with changes in the velocity of the farallon plate parallel to the coast and provide a strong argument for oblique subduction as the driving mechanism continental reconstructions incorporating shear may provide constraints on the rate of extension in the northernmost basin and range region and suggest 17 extension since 15 ma 39 since 37 ma and 72 since 50 ma near latitude 42 n

localized fault slip to the trench in the 2010 maule chile mw 8 8 earthquake from joint inversion of high rate gps teleseismic body waves insar campaign gps and tsunami observations the 27 february 2010 mw 8 8 maule earthquake ruptured 500 km along the plate boundary offshore central chile between 34 s and 38 5 s establishing whether coseismic fault offset extended to the trench is important for interpreting both shallow frictional behavior and potential for tsunami earthquakes in the region joint inversion of high rate gps teleseismic body waves interferometric synthetic aperture radar insar campaign gps and tsunami observations yields a kinematic rupture model with improved resolution of slip near the trench bilateral rupture expansion is resolved in our model with relatively uniform slip of 5 10 m downdip beneath the coast and two near trench high slip patches with 12 m displacements the peak slip is 17 m at a depth of 15 km on the central megathrust located 200 km north from the hypocenter and overlapping the rupture zone of the 1928 m 8 event the updip slip is 16 m near the trench another shallow near trench patch is located 150 km southwest of the hypocenter with a peak slip of 12 m checkerboard resolution tests demonstrate that correctly modeled tsunami data are critical to resolution of slip near the trench with other data sets allowing but not requiring slip far offshore large interplate aftershocks have a complementary distribution to the coseismic slip pattern filling in gaps or outlining edges of large slip zones two clusters of normal faulting events locate seaward along the plate motion direction from the localized regions of large near trench slip suggesting that proximity of slip to the trench enhanced extensional faulting in the underthrusting plate

the influence of bedrock geology on knickpoint development and channel bed degradation along downcutting streams in south central indiana geologic controls on knickpoint development and the mechanics of channel bed degradation were eluci dated by comparison of downcutting streams in south central indiana developed in lithologically homoge neous carbonate units and layered siliciclastic strata knickpoints formed in a single lithologic unit are stepped each step consists of a knickpoint face and tread the height of each step is equal to and controlled by bed thickness spatially knickpoints in homogeneous terrain are limited to jointed strata that dip 1 upstream or 2 downstream at angles less than the channel gradient knickpoints observed in lithologically layered strata are characterized by a single step in which resistant jointed rocks overlie and protect weaker units total knickpoint relief is influenced by thickness of the weaker strata knickpoints in layered siliciclastic strata are spatially limited to bedrock reaches produced by differential rates of channel incision knickpoint distribution is also influenced by joint

origin and evolution of the seattle fault and seattle basin washington analysis of seismic reflection data reveals that the seattle basin washington is markedly asymmetric and consists of 9 10 km of eocene and younger deposits the basin began as a discrete geologic element in the late eocene 40 ma the result of a reorganization in regional fault geometry and kinematics in this reorganization dextral offset on the puget fault south east of seattle stepped eastward and the seattle fault began as a restraining transfer zone north vergent reverse or thrust faulting on the seattle fault forced flexural subsidence in the seattle basin to the north offset on the seattle fault and subsidence of the seattle basin have continued to the present

seismic velocity changes in the epicentral region of the 2008 wenchuan earthquake measured from three component ambient noise correlation techniques 1 we investigate temporal changes of seismic velocity in the epicentral region of the 12 may 2008 mw 7 9 wenchuan earthquake using three component continuous waveforms recorded by a seven station small aperture array we use an ambient noise cross correlation technique to compute the empirical green s function between station pairs from august 2004 to september 2011 our results show no obvious precursory change immediately before the main shock clear coseismic reduction of seismic velocity of up to 0 2 and initial postseismic recovery followed by a long lived velocity reduction the coseismic and postseismic velocity changes are most prominent in the period band of 2 4 s approximate depth of 1 4 km and the velocity changes are smaller in other period bands the seismic velocity in the period band of 1 2 s i e top 2 km correlates well with the water level change of the zipingpu reservoir the observed temporal changes likely reflect damage and healing processes with possible permanent deformation in the upper crust associated with the wenchuan main shock

deep seated flow as a mechanism for the uplift of broad forearc ridges and its role in the exposure of high p t metamorphic terranes forearc systems evolve through the interplay of numerous processes but aside from lateral movements much of the observed variability in morphology can be related to evolution of ductility in the deeper levels of the subduction complex in the eastern aleutian lesser antilles makran and cascade arc trench systems a 50 to 200 km wide forearc ridge is developed along the inboard edge of the subduction complex these forearc ridges did not form until subduction accretion had expanded the arc trench gap to 275 300 km and the near vertical rise of the ridge occurred 50 km or more from the trench slope break the forearc high apparently maintained by accretion at the trench thus these broad forearc ridges are not emergent trench slope breaks the process responsible for uplift is occurring within the subduction complex and the size of the accreted mass is apparently a major factor rheological models assuming frictional sliding laws at shallow levels and power law rheologies at depth predict different behaviors for various parts of a typical large subduction complex the older forearc basement beneath which the inboard part of the subduction complex is emplaced represents a rigid brittle massif that extends 100 150 km from the volcanic arc a prediction supported by seismicity studies in modern convergent margins because of the wet quartz rich lithologies of the subduction complexes however the brittle to ductile transition apparently occurs at depths of 10 20 km within the accreted mass thus in large subduction complexes where the downgoing slab is 40 50 km beneath the inboard edge a significant region at the deeper levels of the subduction complex is apparently capable of flow the predicted zone of ductile deformation is directly beneath the area in which a forearc ridge is generally developed hence we conclude that the broad structural highs of large subduction complexes are dynamically maintained by deep seated flow the character of this flow is uncertain yet it is likely that the stripping of low viscosity partially subducted sediments plays a role and the volume of sediments added by underplating may be the controlling factor in the dynamic uplift of broad forearc ridges kinematically the flow could be a pure shear deformation induced by subhorizontal loading but we prefer the familiar corner flow mechanism because it provides the simplest explanation for the observations the interaction between offscraping at the trench and underplating affects the distribution of mass on the downgoing slab and probably controls uplift rates in broad forearc ridges because of the complexity of the interaction and the observation that modern forearc ridges appear to be rising slowly we conclude that high pressure rocks are only exposed in unusual forearc systems e g systems with either a prolonged period of uplift or large influxes of deep underplated sediment the evolution of ductility plays a major role in the development of forearc morphologies when the subduction complex is small brittle deformation and processes related to accretion at the trench dominate and the classic growth models are applicable however as continued growth of the subduction complex depresses the downgoing lithosphere and increases the arc trench gap the subduction complex becomes ductile at depth and ultimately deep seated flow leads to abrupt uplift along the inboard edge of the subduction complex

risk and return evaluating reverse tracing of precursors earthquake predictions summary in 2003 the reverse tracing of precursors rtp algorithm attracted the attention of seismologists and international news agencies when researchers claimed two successful predictions of large earthquakes these researchers had begun applying rtp to seismicity in japan california the eastern mediterranean and italy they have since applied it to seismicity in the northern pacific oregon and nevada rtp is a pattern recognition algorithm that uses earthquake catalogue data to declare alarms and these alarms indicate that rtp expects a moderate to large earthquake in the following months the spatial extent of alarms is highly variable and each alarm typically lasts 9 months although the algorithm may extend alarms in time and space we examined the record of alarms and outcomes since the prospective application of rtp began and in this paper we report on the performance of rtp to date to analyse these predictions we used a recently developed approach based on a gambling score and we used a simple reference model to estimate the prior probability of target earthquakes for each alarm formally we believe that rtp investigators did not rigorously specify the first two successful predictions in advance of the relevant earthquakes because this issue is contentious we consider analyses with and without these alarms when we included contentious alarms rtp predictions demonstrate statistically significant skill under a stricter interpretation the predictions are marginally unsuccessful

crustal extensional faulting triggered by the 2010 chilean earthquake the pichilemu seismic sequence 1 we report a sequence of crustal quakes that began after the mw 8 8 thrust subduction maule earthquake that affected the central chile margin on 27 february 2010 this activity lasted by several months having the most important events on 11 march 2010 mw 6 9 and mw 7 0 with normal focal mechanisms seismicity shows a rupture oriented along a nw striking and sw dipping normal fault from the surface down to the interplate contact seismicity can be correlated with neotectonics extensional structures similarly oriented in the region which have coexisted with nne ssw reverse faults since the late pliocene even though both have older periods of activity since the paleozoic this crustal rupture would have been triggered by the high coulomb stress change produced by the maule earthquake enhanced by likely fluid presence along weakened zones of the forearc crust as evidenced by high vp vs ratio the occurrence of relevant neotectonic activity in coincidence with short term deformation suggests a relationship with long term tectonic features of this region which would have been acting as a barrier during the interseismic period increasing the strain accumulation and triggering contractional faulting in the crust as well as producing high slip patches during great subduction ruptures favoring triggering of crustal extensional faulting crustal faulting in pichilemu suggests that this kind of events should be considered in seismic hazard analysis despite the absence of historical crustal seismic activity before the maule earthquake

synthetic earthquake catalogs simulating seismic activity in the corinth gulf greece fault system the characteristic earthquake hypothesis is the basis of time dependent modeling of earthquake recurrence on major faults however the characteristic earthquake hypothesis is not strongly supported by observational data few fault segments have long historical or paleoseismic records of individually dated ruptures and when data and parameter uncertainties are allowed for the form of the recurrence distribution is difficult to establish this is the case for instance of the corinth gulf fault system cgfs for which documents about strong earthquakes exist for at least 2000 years although they can be considered complete for m 6 0 only for the latest 300 years during which only few characteristic earthquakes are reported for individual fault segments the use of a physics based earthquake simulator has allowed the production of catalogs lasting 100 000 years and containing more than 500 000 events of magnitudes 4 0 the main features of our simulation algorithm are 1 an average slip rate released by earthquakes for every single segment in the investigated fault system 2 heuristic procedures for rupture growth and stop leading to a self organized earthquake magnitude distribution 3 the interaction between earthquake sources and 4 the effect of minor earthquakes in redistributing stress the application of our simulation algorithm to the cgfs has shown realistic features in time space and magnitude behavior of the seismicity these features include long term periodicity of strong earthquakes short term clustering of both strong and smaller events and a realistic earthquake magnitude distribution departing from the gutenberg richter distribution in the higher magnitude range

bedrock benches and boulder bars floods in the burdekin gorge of australia the burdekin gorge of northeastern australia lies within the seasonal tropics and is characterized by high discharge variability slackwater sediments and paleostage indicators in the gorge record seven large floods that have occurred during the past 1 200 yrs these floods range in magnitude from 11 000 to 30 000 m 3 s 1 and are characterized by large downstream variations in hydraulics the floods generate high values of velocity boundary shear stress and stream power per unit area downstream fluctuations in these variables help to explain the location of boulder bars high flood levees small scale erosional features in the bedrock and the formation of inner channels boulder bars and flood levees form where shear stress and stream power decrease due to channel widening small scale erosional features such as potholes and troughs are best developed at sites of channel constriction and associated increases in shear stress and stream power the development of the inner channel appears to be controlled by complex interactions between bedrock lithology and structure and by flow hydraulics all of the channel features are related to the hydraulics of large floods which therefore are the dominant controls on many aspects of channel morphology in this bedrock gorge

probing large intraplate earthquakes at the west flank of the andes estimating the potential for the occurrence of large earthquakes on slow slip rate faults in continental interiors away from plate boundaries is possible only if the long term geological record of past events is available however our knowledge of strong earthquakes appears to be incomplete for thrust faults flanking large actively growing mountain ranges such as those surrounding tibet and the andes mountains we present a paleoseismic study of a prominent fault scarp at the west flank of the andes in santiago chile the evidence demonstrates recur rent faulting with displacement of 5 m in each event with two large earthquake ruptures within the past 17 19 k y and the last event occurring 8 k y ago the fault appears to be ripe for another large earthquake moment magnitude m w 7 5 these results emphasize the potential danger of intraplate continental faults particularly those associated with youthful mountain fronts

comparison between utsu s and vere jones aftershocks model by means of a computer simulation based on the acceptance rejection sampling of von neumann abstract in this research a new algorithm for generating a stochastic earthquake catalog is presented the algorithm is based on the acceptance rejection sampling of von neumann the result is a computer simulation of earthquakes based on the calculated statistical properties of each zone vere jones states that an earthquake sequence can be modeled as a series of random events this is the model used in the proposed simulation contrariwise utsu indicates that the mainshocks are special geophysical events the algorithm has been applied to zones of chile china spain japan and the usa this allows classifying the zones according to vere jones or utsu s model the results have been quantified relating the mainshock with the largest aftershock within the next 5 days which has been named as bath event the results show that some zones fit utsu s model and others vere jones finally the fraction of seismic events that satisfy certain properties of magnitude and occurrence is analyzed

earthquake prediction in seismogenic areas of the iberian peninsula based on computational intelligence abstract a method to predict earthquakes in two of the seismogenic areas of the iberian peninsula based on artificial neural networks anns is presented in this paper anns have been widely used in many fields but only very few and very recent studies have been conducted on earthquake prediction two kinds of predictions are provided in this study a the probability of an earthquake of magnitude equal or larger than a preset threshold magnitude within the next 7 days to happen b the probability of an earthquake of a limited magnitude interval to happen during the next 7 days first the physical fundamentals related to earthquake occurrence are explained second the mathematical model underlying anns is explained and the configuration chosen is justified then the anns have been trained in both areas the alboran sea and the western azores gibraltar fault later the anns have been tested in both areas for a period of time immediately subsequent to the training period statistical tests are provided showing meaningful results finally anns were compared to other well known classifiers showing quantitatively and qualitatively better results the authors expect that the results obtained will encourage researchers to conduct further research on this topic

subducting seamounts and deformation of overriding forearc wedges around japan abstract two subducting seamounts under inner trench slopes have been identified around japan on the basis of magnetic anomalies morphology and geological structure the first one is located under the foot of the inner trench slope at the junction between the japan trench and the kuril trench another one occurs beneath the slope slightly seaward of the tosabae the basement high at the trench slope break along the nankai trough off shikoku the magnetic anomalies of seamount origin are accompanied by the characteristic morphology of a forearc wedge i e a swell landward and a depression seaward the seamounts beneath the inner trench slopes have preserved magnetization showing reasonably consistent directions which suggests that the subducting seamounts have kept roughly their original shapes the morphology of the forearc wedge can be explained by a subducting seamount on the oceanic crust pushing the forearc material forward and upward deformation of the forearc wedge by the subducting seamount extends to the forearc basin the seamounts are stronger and less deformable than the inner slope material and are not offscraped onto inner trench slopes two other examples of deformed inner trench slopes around japan which can be explained by subduction of topographic highs are presented one example is a depression on the foot of the inner trench slope northeast of the junction between the kyushu palau ridge and the nankai trough another one is an area of complex morphology of the inner trench slope along the japan trench around the daiichi kashima seamount

active continental subduction beneath the betic cordillera and the alboran sea p and s wave seismic tomography detect a low velocity anomaly in the upper mantle beneath the betic cordillera and the alboran sea region the anomaly is associated with the intermediate depth seismicity h

adjustments by the charwell river new zealand to uplift and climatic changes major climatic changes and rapid local and regional tectonic movements were common in new zealand during the late quaternary and caused a diversity of adjustments in the drainage basin and piedmont reaches of the charwell river which are separated by the hope fault the onset of semi arid frigid climates during the latest pleistocene probably greatly increased hillslope sediment yields in a periglacial environment and the piedmont reach aggraded as much as 42 m on top of a broad strath with the return of humid mesic climates in the holocene sediment yields decreased as dense forests again mantled the slopes and the piedmont reach degraded as mush as 81 m dating of eleven cut and strath terraces by radiocarbon calibrated weathering rind measurements on greyawake cobbles shows the degradation rates varied greatly during the last 14 ka 1 ka 1000 yr initial degradation rates of 4 m ka 1 increased to 30 m ka 1 by 6 ka ago during a mid holocene climatic optimum since 4 ka ago degradation rates have been only 1 2 m ka 1 comparable to uplift rates in the piedmont reach inferred from marine terrace studies and the river is again cutting a broad strath each broad strath represents equilibrium conditions attained by this powerful stream during interglacial times despite episodes of being overwhelmed by climatically induced sediment yield increases during full glacial climates and having to maintain a long term degradation rate equal to the uplift rate the 75 81 m of degradation since formation of the latest pleistocene fill terrace tread is the sum of the amount of late pleistocene valley floor aggradation and the amount of regional uplift that occurred between the estimated times of major strath formation at about 30 and 0 ka the 39 m of tectonically induced degradation below the pre aggradation strath is sufficiently large that post 30 ka uplift may have doubled holocene degradation rates each of the eleven degradation terraces represents pauses of a few centuries in holocene downcutting brief equilibrium conditions were attained by streambed armoring and concurrent growth of riparian plants both processes progressively increased hydraulic roughness and the shear stresses needed to entrain streambed materials occasional floods possibly from rare cyclones derived from tropical moisture sources destroyed streambed armor and channel downcutting was renewed thus the formation of eleven equilibrium terraces can be accounted for without postulating additional tectonic perturbations or secular climatic changes

seismotectonics of the ibero maghrebian region abstract a study of the seismotectonics of the ibero maghrebian region is presented as deduced from main geological features seismicity and focal mechanism data the hypocentral distribution of shallow intermediate depth and deep earthquakes is analyzed the direction of the stress distribution is inferred from the focal mechanism of 24 selected events a seismotectonic framework summarizing these results together with the main geological features shows that a nw se general direction of horizontal compressive stresses is present in the region with a localized zone of horizontal tensions in the betics and the alboran sea the presence of intermediate depth and deep earthquakes is tentatively explained as caused by two consecutive processes of subduction

earthquake triggering by migrating slow slip initiated by m8 earthquake along kuril trench japan 1 evidence of a slow slip temporally ahead of the m7 earthquake doublet that occurred in november december 2004 offshore of eastern hokkaido japan was registered in continuous gps measurements the gps data suggest that a slow slip around a forthcoming rupture zone on the plate boundary triggered these earthquakes this slow slip episode was itself triggered by the m8 tokachi earthquake of september 2003 this is a demonstration of the geodetic visualization of the mechanism of a triggering of a subsequent earthquake caused by a preceding large earthquake the geodetic data will improve the reliability of the warning of an occurrence of a subsequent earthquake after a large one that is currently dependent on only co seismic static stress increase

refinement of a technique for determining rock mass strength for geomorphological purposes use of a field technique recently devised by selby for the measurement of rock mass strength has resulted in the understanding of the relationship between rock mass strength and slope form it is suggested that the accuracy of rock mass strength assessments may be enhanced by further subdividing the rating scales for intact rock strength and the spacing of partings the relationship between rock mass strength and gradient is reformulated using southern african data and statistically based confidence limits for identifying strength equilibrium slopes are proposed

high pressure metamorphism and uplift of the olympic subduction complex the discovery of the critical assemblage lawsonite quartz calcite indicates that a significant part of the cenozoic olympic subduction complex of northwestern washington state formed by underplating at a depth of about 11 km the deep structural level exposed in this area is attributed to the presence of a 10 km high arch in the underlying juan de fuca plate we postulate that this arch was formed when the southern cordilleran coastline swung westward as a result of middle miocene to recent extension in the basin and range province

seismicity near the slip maximum of the 1960 mw 9 5 valdivia earthquake chile plate interface lock and reactivation of the subducted valdivia fracture zone understanding the processes behind subduction related hazards is an important responsibility and major challenge for the earth sciences few areas demonstrate this as clearly as south central chile where some of the largest earthquakes in human history have occurred we present the first observation of local seismicity in the villarrica region 39 40 s based on a temporary local network of 55 stations installed from the chilean coast into the argentinian back arc for one year while consistent with the chilean national catalog ssn our results allow us to observe smaller magnitudes with a completeness of about 2 0 and image the geometry of the wadati benioff zone from the chile trench down to 200 km offshore a gap in interplate seismicity is observed in the region of the 1960 valdivia earthquake slip above the interface two offshore seismicity clusters possibly indicate ongoing stress relaxation in the subducting nazca plate we find a prominent seismicity cluster along the extrapolated trace of the oceanic valdivia fracture zone vfz the seismicity cluster is observed between 70 and 130 km depth and comprises mainly strike slip events it indicates weakening and reactivation of the major vfz by dehydration of oceanic crust and mantle interpreting the subducted vfz section as a localized reservoir of potential fluid release offers an explanation for the villarrica volcanic complex that is located above the reactivated vfz and shows the highest volcanic activity in south america crustal seismicity is observed near puyehue volcano which recently started to erupt june 2011 key points we observe local seismicity near the 1960 valdivia maximum slip region the subducted valdivia fracture zone is reactivated by fluid release the seismogenic zone is free of seismicity events occur at faults and volcanoes

stress origins and earthquake potentials in cascadia focal mechanism solutions for shallow earthquakes throughout the cascadia plate system indicate that the primary regional stress is northerly compression even though the juan de fuca plate generally is thought to be subducting n50 e this compressional stress is pervasive throughout the gorda juan de fuca explorer plate system and much of the adjoining section of north american plate modeling using a discrete element code shows that this stress primarily is due to the pacific plate being driven into the gorda block and juan de fuca plate at the mendocino and blanco fracture zones this plate collision causes compression of the offshore plate system northward through the 45 w trending vancouver island and leads to transfer of northerly compression into the overriding plate the northerly compression in the cascadia plate system has caused large crustal earthquakes in the regions of vancouver and northern california and may be capable of causing large earthquakes also in and offshore of washington and oregon several independent lines of evidence confirm that the cascadia subduction interface is coupled strongly and that subduction primarily must be accompanied by significant earthquakes rather than occurring aseismically for numerous earthquakes within the subducted plate focal mechanisms indicate extensional stresses that trend downdip these earthquakes reflect plate extension that is due to sinking of the more deeply subducted plate and to plate motion being resisted at the shallow subduction interface the slab pull force of the sinking plate also can lead to earthquakes at the shallow subduction interface and the potential exists for m 7 5 8 0 subduction earthquakes to occur at segments of the subduction boundary at washington and vancouver and less frequently so at segments of the subduction boundary at oregon the in plate driving forces of the offshore cascadia plate system do not appear to contribute significantly to regional stresses stresses and earthquakes at the cascadia province primarily result from the action of the pacific plate on the gorda juan de fuca explorer plate system a transfer of this action into the overriding north american plate and the independent sinking and slab pull force of the subducted oceanic lithosphere

quaternary uplift astride the aseismic cocos ridge pacific coast costa rica the pacific coast of costa rica lies within the central american forearc and magmatic arc region that was created by northeastward subduction of the cocos plate beneath the caribbean plate at the middle america trench from the peninsula de nicoya south eastward toward the peninsula de osa and the peninsula de burica on the panamanian border the middle america trench loses its physiographic expression where it intersects the aseismic cocos ridge interaction between subduction of the buoyant aseismic cocos ridge and the overriding caribbean plate is invoked to explain the variation in rates of vertical crustal uplift along a coastal transect from nicoya to burica the pliocene and pleistocene stratigraphic record and holocene marine terraces and beach ridge complexes indicate that maximum rates of crustal uplift have occurred on the peninsula de osa immediately landward of the aseismic cocos ridge crustal uplift rates decrease northwest toward the peninsula de nicoya and to a lesser extent southwest toward the peninsula de burica the late quaternary stratigraphy on the peninsula de osa is subdivided into two major chronostratigraphic sequences from groupings of radiocarbon dates crustal uplift rates calculated from these sequences systematically decrease from 6 5 to 2 1 m ka north east across the peninsula deformation of the peninsula is modeled as uplifted and down to the northeast tilted fault blocks with an angular rotation rate of 0 03 to 0 06 per thousand years although less well constrained crustal uplift rates on the peninsula de nicoya 200 km to the northwest of the peninsula de osa vary from 1 m ka for pliocene and pleistocene sediments to 2 5 m ka for holocene marine terraces in the quepos region 100 km to the northwest of the peninsula de osa calculated uplift rates derived from incision of late quaternary fluvial terraces range from 0 5 to 3 0 m ka on the peninsula de burica only 60 km to the southwest of the peninsula de osa calculated uplift rates range from 4 7 m ka for a late holocene marine terrace to 1 2 m ka for post late pliocene deep sea sediments the variations in calculated uplift rates on the peninsula de osa constrain a dynamic model for subduction of the cocos ridge and the resulting uplift of the overriding caribbean plate deflection of the caribbean plate is modeled using various effective elastic thicknesses as the response of an elastic plate to the buoyant force of the subducted cocos ridge because the shape of the subducted end of the cocos ridge is unknown two scenarios are evaluated 1 a radially symmetric ridge with a slope similar to the slope of the flanks of the ridge and 2 a ridge where the subducted end was truncated by the panama fracture zone the best fit model utilizes a truncated ridge that has been subducted during the past 0 5 m y 50 km beneath the overriding caribbean plate which has an effective elastic thickness of 5 km the model predicts that the highest uplift rate should be 3 7 m ka and occur on the southwest coast of the peninsula de osa the rate of uplift slows considerably to the northeast and indicates that the peninsula de osa is tilting to the northeast which agrees with observations in that region the predicted uplift rate attributed to aseismic ridge subduction also decreases along the coast both north and south of the peninsula de osa resulting in little uplift that can be attributed to cocos ridge subduction in the northwestern portions of the peninsula de nicoya

triggering of the 1999 mw 7 1 hector mine earthquake by aftershocks of the 1992 mw 7 3 landers earthquake 1 there is strong observational evidence that the 1999 mw 7 1 hector mine earthquake in the mojave desert california was triggered by the nearby 1992 mw 7 3 landers earthquake many authors have proposed that the landers earthquake directly stressed the hector mine fault our model of the landers aftershock sequence however suggests there is an 85 chance that the hector mine hypocenter was actually triggered by a chain of smaller earthquakes that was initiated by the landers main shock we perform our model simulations using the monte carlo method based on the gutenberg richter relationship omori s law bath s law and assumptions that all earthquakes including aftershocks are capable of producing aftershocks and that aftershocks produce their own aftershocks at the same rate that other earthquakes do in general our simulations show that if it has been more than several days since an m 7 main shock most new aftershocks will be the result of secondary triggering these secondary aftershocks are not physically constrained to occur where the original main shock increased stress this may explain the significant fraction of aftershocks that have been found to occur in main shock stress shadows in static coulomb stress triggering studies

late quaternary stream incision and uplift in the forearc of the cascadia subduction zone western oregon documentation of a latest pleistocene earliest holocene episode of strath formation and fluvial aggradation in the oregon coast range provides a datum from which long term bedrock stream incision rates are determined variations in long term incision rates probably reflect cumulative differential uplift in the forearc of the cascadia subduction zone although factors such as bedrock and climatic controls and isostatic adjustments to erosion obscure the precise relationship between surface uplift and stream incision patterns of differential incision are most striking near the latitude of newport where a steep gradient divides a region of higher rates 0 6 0 9 mm yr in the northern coast range from a region of lower rates 0 1 0 3 mm yr in the central coast range the steep incision gradient is nearly coincident with abrupt changes in marine terrace 80 125 kyr uplift rates the locations of quaternary faults and the southern flank of a saddle of low historic 40 70 years uplift the exact causes of these variable patterns of incision uplift are unknown analogies with uplift patterns in other subduction zones and comparisons with other neotectonic data in the region indicate that patterns of differential incision probably are caused by variations in permanent strain accumulation along the cascadia subduction zone such variations may be related to differences in seismic moment release during individual earthquakes to changes in plate geometry or rates of wedge accretion to segmentation of earthquake ruptures and or to deformation on active structures in the north american plate and accretionary wedge