under what circumstances does a seismogenic patch produce aseismic transients in the later interseismic period whether aseismic transients occur as the next earthquake approaches or not is an important problem in the area of disaster mitigation by geophysical observation we conducted a series of rate state aging law earthquake sequence simulations with inertial effects and revealed that a b direct effect evolution effect is a key parameter controlling the complexity of interseismic behavior in a seismogenic patch interseismically a creep front invades a locked patch if a b 0 4 nucleation takes place as soon as the linear stability of the coherent creep is violated and no significant aseismic transient occurs if a b 0 4 nucleation size is given by the energy balance criterion and if a b 0 6 aseismic transients occur after the violation of linear stability and before the creeping region is able to host the nucleation thus not only a b but also a b must be selected carefully to obtain realistic results in numerical simulations

a slower fault may produce a smaller preseismic moment rate non 1 tf acceleration of moment rate during nucleation and dependency on the background slip rate 1 a recent global study has revealed that seismicity near the hypocenter prior to large earthquakes which could be a proxy for preseismic moment rate accelerates before interplate earthquakes while it rarely does before intraplate earthquakes understanding the amplitude of preseismic deformation is important in assessing the possibility of its detection for a class of rate state friction laws without a characteristic speed related parameter e g aging law and slip law a dimensional analysis has shown that if the moment rate increases more mildly than 1 tf where tf is the time to failure then the amplitude of preseismic moment rate is smaller for a smaller quasistatic slip rate three dimensional numerical simulations have revealed that the aging law yields 1 tf acceleration while the slip law causes milder acceleration if the latter is the case faults with very low long term slip rates e g intraplate faults may have very small preseismic moment rates

the use of sem eds pixe and edxrf for obsidian provenance studies in the near east a case study from neolithic catalhoyuk central anatolia in this paper we evaluate the relative analytical capabilities of sem eds pixe and edxrf for characterizing archaeologically significant anatolian obsidians on the basis of their elemental compositions the study involves 54 geological samples from various sources together with an archaeological case study involving 100 artifacts from neolithic catalhoyuk central anatolia with each technique the artifacts formed two compositional groups that correlated with the east gollu dag and nenezi dag sources the non destructive capabilities of these methods are emphasized albeit with certain analytical limitations in the case of sem eds suggesting important new techniques for near eastern obsidian provenance studies

compositional and temporal investigation of exposed lunar basalts in the mare imbrium region abstract this paper presents an updated stratigraphical and compositional study of the exposed maria within the imbrium basin on the moon clementine multispectral data were employed to derive tio2 and feo wt abundance estimates of potentially distinct basaltic flows additionally nasa lunar orbiter images were used to estimate flow ages using crater count statistics mare imbrium shows evidence of a complex suite of low to high ti basaltic lava units infilling the basin over an 800 million year timescale more than a third 37 of identified mare basalts were found to contain 1 3 wt tio2 two other major mare lithological units representing about 25 of the surface each show tio2 values between 3 5 and 7 9 wt the dominant fraction 55 of the sampled maria contain feo between 16 and 18 wt followed by 27 of maria having 18 20 wt and the remaining 18 14 16 wt feo a crater frequency count for diameters 500 m shows that in three quarters of the sampled mare crater counts range between 3 5 and 5 5 10 2 per km2 which translates according to a lunar cratering model chronology into estimated emplacement ages between 3 3 and 2 5 ga a compositional convergence trend between the variations of iron and titanium oxides was identified in particular for materials with tio2 and feo content broadly above 5 and 17 wt respectively suggesting a related petrogenesis and evolution according to these findings three major periods of mare infill are exposed in the imbrium basin despite each period showing a range of basaltic compositions classified according to their tio2 content it is apparent that at least within these local geological settings the igneous petrogenesis generally evolved through time towards more tio2 and feo rich melts

shear localization in a mature mylonitic rock analog during fast slip highly localized slip zones developed within ductile shear zones such as pseudotachylite bands occurring within mylonitic fabric rocks are frequently interpreted as evidence for earthquake nucleation and or propagation within the ductile regime to understand brittle frictional shear localization processes in ductile shear zones and to relate these to earthquake nucleation and propagation we performed tests with large change in velocity on a brine saturated 80 20 wt mixture of halite and muscovite gouge after forming a mature mylonitic structure through frictional viscous flow the direct effect a on shear strength that occurs in response to an instantaneous upward velocity step is an important parameter in determining the nature of seismic rupture nucleation and propagation we obtained reproducible results regarding low velocity mechanical behavior compared with previous work but also obtained new insights into effects of sudden increases in slip velocity on localization and strength evolution at velocities above a critical velocity vc 20 m s we found that once a ductile mylonitic structure has developed in a shear zone subsequent cataclastic deformation is consistently localized in a narrow zone this switch to localized deformation is controlled by the imposed velocity and becomes most apparent at velocities above vc in addition the direct effect drops rapidly when the velocity exceeds vc this implies that slip can accelerate towards seismic velocities almost instantly and without much loss of fracture energy once vc is exceeded obtaining a measure for vc in natural faults is therefore of key importance for understanding earthquake nucleation and propagation in the brittle ductile transitional regime

obsidian characterization by laser ablation icp ms and its application to prehistoric trade in the mediterranean and the near east sources and distribution of obsidian within the aegean and anatolia for geological studies interest in mass spectrometry with an inductively coupled plasma as an ion source and its association with laser ablation as a sample introduction technique la icp ms has steadily increased during the past few years and is now being developed in other fields such as archaeology after a description of the analytical procedure and the calculation method we show the potential of this technique to characterize almost non destructively archaeological artefacts among the 70 elements that could be routinely analysed by la icp ms with detection limits below the ppm level we choose to determine the more critical ones in order to evaluate the geochemical models of the magmatic process major elements rare earths and some transition elements a detailed survey of cappadocian obsidian flows is given and includes the characterization of nine different sources evidence of complex trade activities is clearly shown by the obsidian tools found at different prehistoric sites from neolithic to bronze age levels in the mediterranean and the near east new results obtained on some archaeological sites located in turkey syria and cyprus are presented they show the importance of cappadocian sources in obsidian trade our results show that la icp ms allows a non destructive analysis of archaeological objects and that it combines the advantage of the different classical methods used to characterize obsidian sources mainly xrf and inaa with high sensitivity and rapidity thus la icp ms appears to be a very powerful analytical tool and at this time this technique is the only one which can non destructively determine such an important number of elements with such low detection limits

intense foreshocks and a slow slip event preceded the 2014 iquique mw 8 1 earthquake the subduction zone in northern chile is a well identified seismic gap that last ruptured in 1877 the moment magnitude mw 8 1 iquique earthquake of 1 april 2014 broke a highly coupled portion of this gap to understand the seismicity preceding this event we studied the location and mechanisms of the foreshocks and computed global positioning system gps time series at stations located on shore seismicity off the coast of iquique started to increase in january 2014 after 16 march several mw 6 events occurred near the low coupled zone these events migrated northward for 50 kilometers until the 1 april earthquake occurred on 16 march on shore continuous gps stations detected a westward motion that we model as a slow slip event situated in the same area where the mainshock occurred

modelling of short interval silent slip events in deeper subduction interfaces considering the frictional properties at the unstable stable transition regime summary recent high resolution observations of crustal movements have revealed silent slip events sses with propagation velocities of around 10 15 km d 1 and with intervals of 3 14 months along the deeper parts of the cascadia and nankai subduction zones this study develops 2 d and 3 d models of these short interval sses considering the frictional behaviour that was confirmed experimentally by shimamoto for the unstable stable transition regime to represent this frictional behaviour a small cut off velocity to an evolution effect is introduced in a rate and state dependent friction law when the cut off velocity to the evolution effect is significantly smaller than that to a direct effect steady state friction exhibits velocity weakening at low slip velocities and velocity strengthening at high slip velocities at the deeper cascadia and nankai subduction interfaces the pore pressure is inferred to be high because of the dehydration of materials in the descending plate under conditions where the pore fluid pressure is nearly equal to the lithostatic pressure and the critical weakening displacement is very small short interval sses with propagation velocities and slip velocities of 4 8 km d 1 and 2 4 10 7 m s 1 respectively can be reproduced the propagation velocity of short interval sses is in proportion to the slip velocity the results also show that during the nucleation process of large earthquakes the occurrence of short interval sses becomes irregular because of the accelerated slips that occur at the bottom of the seismogenic zone our results suggest that monitoring of short interval sses might be useful for forecasting the main earthquakes

static coulomb stress load on a three dimensional rate and state fault possible explanation of the anomalous delay of the 2004 parkfield earthquake we perform quasi dynamic modeling of earthquake cycle using laboratory derived rate and state laws of friction on a homogeneous three dimensional fault model we study effects of the static coulomb stress loading on clock advance and clock delay of the subsequent event we carefully investigate dependences of the clock advance on the onset time of the stress load its amplitude areal extent and place of application of the load we find that these dependences are complex being controlled by the actual ongoing slip velocity on the fault especially at the domain of the stress load in particular the stress un load can initiate the occurrence of quasiperiodic creep like episodes which could be associated with episodic increases of microseismicity on real faults such as observed on the locked parkfield segment of the san andreas fault depending on the load parameters including its timing within the earthquake cycle one of such creep like events may trigger the next clock advanced system size earthquake in some cases the nucleation of the main shock can fail and the fault experiences one or several seismic events of smaller magnitudes instead in such a case the next main shock becomes significantly delayed we speculate that such mechanism could have contributed to the extreme delay of the m6 2004 parkfield earthquake indeed the parkfield segment was subject to coulomb stress unload due to the 1983 coalinga nunez earthquakes and then experienced m4 9 events in 1993 1994 when the system size event was expected instead these failed main shock nucleations delayed the parkfield earthquake by another 10 years

quantitative measure of the variation in fault rheology due to fluid rock interactions we analyze friction data from two published suites of laboratory tests on granite in order to explore and quantify the effects of temperature t and pore water pressure pp on the sliding behavior of faults rate stepping sliding tests were performed on laboratory faults in granite containing gouge granite powder both dry at 23 to 845 c lockner et al 1986 and wet pp 100 mpa at 23 to 600 c blanpied et al 1991 1995 imposed slip velocities v ranged from 0 01 to 5 5 m s and effective normal stresses were near 400 mpa for dried granite at all temperatures and wet granite below 300 c the coefficient of friction shows low sensitivity to v t and pp for wet granite above 350 drops rapidly with increasing t and shows a strong positive rate dependence and protracted strength transients following steps in v presumably reflecting the activity of a water aided deformation process by inverting strength data from velocity stepping tests we determined values for parameters in three formulations of a rate and state dependent constitutive law one or two state variables were used to represent slip history effects each velocity step yielded an independent set of values for the nominal friction level five constitutive parameters transient parameters a b1 and b2 and characteristic displacements dc1 and dc2 and the velocity dependence of steady state friction ss ln v a b1 b2 below 250 data from dry and most wet tests are adequately modeled by using the slip law ruina 1983 and one state variable a 0 003 to 0 018 b 0 001 to 0 018 dc 1 to 20 m dried tests above 250 can also be fitted with one state variable in contrast wet tests above 350 require higher direct rate dependence a 0 03 to 0 12 plus a second state variable with large negative amplitude b2 0 03 to 0 14 and large characteristic displacement dc2 300 to 4000 m thus the parameters a b1 and b2 for wet granite show a pronounced change in their temperature dependence in the range 270 to 350 c which may reflect a change in underlying deformation mechanism we quantify the trends in parameter values from 25 to 600 c by piecewise linear regressions which provide a straightforward means to incorporate the full constitutive response of granite into numerical models of fault slip the modeling results suggest that the succeptibility for unstable stick slip sliding is maximized between 90 and 360 c in agreement with laboratory observations and consistent with the depth range of earthquakes on mature faults in the continental crust

earthquakes as multiscale dynamic ruptures with heterogeneous fracture surface energy 1 we propose a model of the wide scale growth of dynamic rupture during an earthquake based on our multiscale simulation of a planar crack in a three dimensional homogeneous elastic space a simple slip weakening law governs the fracture friction processes and its characteristic parameters slip weakening distance and fracture surface energy have multiscale heterogeneous distributions we consider a set of randomly distributed circular patches whose diameter is proportional to the fracture surface energy each patch represents an asperity between irregular fault surfaces and the size number relation of the patches obeys power law statistics we assess rupture propagation from a small instability using a boundary integral equation method with a renormalization technique although most events stop shortly after their initiation some grow triggering neighboring patches of similar size small and large events show statistically self similar properties of rupture growth and stop spontaneously without requiring a special stopping mechanism the rupture velocity locally exceeds the shear wave speed but globally remains subshear speed due to the increase of the average fracture energy as the rupture grows the relation between size and frequency of events is a power law which is explained by the triggering probability between patches as a consequence of statistically self similar random triggering growth we observe a distinct main phase in seismic waves similar to those of natural earthquakes but we cannot estimate the final size of the event from the initial part of the seismic waves if this is true for the real earthquakes predicting the size of a future earthquake would be quite difficult

coseismic slip on shallow decollement megathrusts implications for seismic and tsunami hazard abstract for years many studies of subduction zones and on land fold and thrust belts have assumed that the frontal portions of accretionary prisms are too weak to rupture coseismically and must therefore be fully creeping we present a series of examples both on land and offshore demonstrating that in many cases shallow decollements are capable of large coseismic slip events that rupture to the toes of the fault systems some of these events are associated with ruptures that initiate down dip while others appear to be limited to the frontal shallow portion of the wedge we suggest that this behavior is not limited to the examples described here but rather is common to many perhaps most accretionary wedges and fold and thrust belts around the world indeed there may be many other examples of similar earthquakes where existing data cannot constrain slip at the toe we do not characterize the regions and events described here as unusual as they encompass a wide range of settings this study indicates that there is an urgent need to reevaluate seismic and tsunami hazard in fold and thrust belts and subduction zones around the world allowing for the possibility of shallow decollement rupture

chemical soil surveys at the bremer site dakota county minnesota usa measuring phosphorous content of sediment by portable xrf and icp oes abstract the bremer site lies along the shores of spring lake in southeastern minnesota and excavations in the 1950s uncovered evidence of woodland and mississippian occupation phases in 2011 a new program of systematic survey and excavation began to better understand cultural patterning and diachronic changes at the bremer site the investigations came to include microarcheaological methods including sediment micromorphology and soil chemistry no element has received more archaeological attention than p which can reflect human and animal waste organic refuse burials and ash there has been interest in integrating soil chemistry into the workflow of fieldwork and in the potential of portable analytical instruments to yield data within the timeframe of an excavation season the last few years have seen the rise and proliferation of portable xrf pxrf instruments in archaeological studies the newest generation of pxrf instruments is able to quantify p at low concentrations and our focus here is developing effective methods to do so in archaeological soils and sediments using sediments from the bremer site we evaluate two preparation techniques in order to find which one best balances analytical quality and preparation time to analyze as many specimens as possible during an excavation season it is desirable to identify adequate preparation methods as well as the smallest number of analyses needed to attain reasonable confidence levels regarding repeatability we show that to attain p values with a standard error better than 10 or 20 of the mean one or two analyses per specimen are sufficient in a majority of cases regarding reproducibility we compare the pxrf data to two independent icp oes datasets ultimately these tests aid in establishing methods that enable archaeologically significant pxrf analyses of soil p concentrations even when working far from an analytical laboratory

moving sources a preliminary study of volcanic glass artifact distributions in northeast china using pxrf recent studies have highlighted the long distance transport of obsidian from the paektusan tianchi or baitoushan in chinese volcano on the border between china and north korea to eastern russia and korea but little is known about the role of the local population in the production and movement or exchange of this important raw material this paper addresses this data lacuna by presenting sourcing results of 440 artifacts from 18 late paleolithic sites located in northeast china a portable xrf enabled rapid non destructive characterization of samples the results show that although paektusan obsidian was widely transported throughout northeast asia material from at least three other sources was also used in particular we highlight the significance of basaltic glass artifacts with the same geochemistry as sources found in the primorye region of far east russia in sites from northeast china this result indicates a two way movement of volcanic glass artifacts between primorye and the northeast of china rather than a unidirectional long distance exchange system originating from paektusan volcano

three dimensional earthquake sequence simulations with evolving temperature and pore pressure due to shear heating effect of heterogeneous hydraulic diffusivity 1 a new methodology for three dimensional 3 d simulations of earthquake sequences is presented that accounts not only for inertial effects during seismic events but also for shear induced temperature variations on the fault and the associated evolution of pore fluid pressure in particular the methodology allows to capture thermal pressurization tp due to frictional heating in a shear zone one dimensional 1 d diffusion of heat and pore fluids in the fault normal direction is incorporated using a spectral method which is unconditionally stable accurate with affordable computational resources and highly suitable to earthquake sequence calculations that use variable time steps the approach is used to investigate the effect of heterogeneous hydraulic properties by considering a fault model with two regions of different hydraulic diffusivities and hence different potential for tp we find that the region of more efficient tp produces larger slip in model spanning events the slip deficit in the other region is filled with more frequent smaller events creating spatiotemporal complexity of large events on the fault interestingly the area of maximum slip in model spanning events is not associated with the maximum temperature increase because of stronger dynamic weakening in that area the region of more efficient tp has lower interseismic shear stress which discourages rupture nucleation there contrary to what was concluded in prior studies seismic events nucleate in the region of less efficient tp where interseismic shear stress is higher in our model hypocenters of large events do not occur in areas of large slip or large stress drop

diversity in obsidian use in the prehistoric and early historic middle east abstract the presence of obsidian in the near east has always evoked a response about its exotic nature and origins it was not until 1960s however that this was put onto a scientific footing when colin renfrew and his collaborators began to explore obsidian in turkey and the mediterranean their characterisation of the sources allowed them to attribute artefacts to different sources and suggest models of dispersal and distribution since then considerably more artefacts have been attributed to sources although mostly only small numbers from individual sites this has led to various interpretations of how obsidian was obtained and used new studies have considered least cost path analysis network analysis and agent based modelling increasingly new methods of provenancing of artefacts have also meant that large number of artefacts can be analysed relatively speedily and efficiently portable instruments allow data to be collected outside laboratories avoiding restrictions imposed by export licenses or simplifying work on museum collections here we employ richness and diversity indexes to elucidate some of the patterns in obsidian source use and argue that there are several reasons why the provenancing of large proportions of assemblages will be critical in exploiting the true potential of obsidian studies in the near east even though the initial haphazard small sample approach has been quite effective in sketching out the big picture

the titanium contents of lunar mare basalts lunar mare basalt sample data suggest that there is a bimodal distribution of tio2 concentrations using a refined technique for remote determination of tio2 we find that the maria actually vary continuously from low to high values the reason for the discrepancy is that the nine lunar sample return missions were not situated near intermediate basalt regions moreover maria with 2 4 wt tio2 are most abundant and abundance decreases with increasing tio2 maria surfaces with tio2 5 wt constitute only 20 of the maria although impact mixing of basalts with differing ti concentrations may smear out the distribution and decrease the abundance of high ti basalts the distribution of basalt ti contents probably reflects both the relative abundances of ilmenite free and ilmenite bearing mantle sources this distribution is consistent with models of the formation of mare source regions as cumulates from the lunar magma ocean

small interseismic asperities and widespread aseismic creep on the northern japan subduction interface the canonical model of fault coupling assumes that slip is partitioned into fixed asperities that display stick slip behavior and regions that creep stably we show that this simple asperity model is inconsistent with gps derived deformation in northern japan associated with interseismic coupling on the subduction interface and the transient response to mw 6 3 7 2 earthquakes during 2003 2011 comparisons of gps data with simulations of earthquakes on asperities and associated velocity strengthening afterslip require that afterslip overlaps areas of the fault that ruptured in previous earthquakes including the 2011 mw 9 tohoku oki earthquake whereas about 55 of the plate interface ruptured in earthquakes during 2003 2011 we infer that only 9 of the plate interface was fully locked between earthquakes inferred locked asperities are roughly 25 the size of rupture areas determined by seismic source inversions these smaller asperities are consistent with interseismic strain accumulation in 2009 although more extensive locking is required a decade earlier in 1998

pxrf characterisation of obsidian from central anatolia the aegean and central europe the obsidian sources of central anatolia the aegean and central europe have been studied in detail over the past 50 years various analytical techniques have been employed to discriminate artefacts from each of these and to reconstruct their zones of distribution this paper presents a pxrf method that allows mass sampling of artefacts focusing on three neighbouring regions particularly where these zones overlap successful discrimination of the obsidian source for products could be achieved using three dimensional scatter plots of trace elements rb sr zr pxrf can thus be appreciated as a powerful tool in the region enabling non destructive on site analyses in contexts where the export of artefacts is often difficult if not impossible the ability to rapidly process large assemblages also has major implications for generating data sets of sufficient resolution to transform archaeological interpretation

characterization of new zealand obsidian using pxrf abstract new zealand has some of the most active areas of rhyolitic volcanism in the world and this has produced numerous obsidian sources in the northern half of the north island in total archaeologists have recognized 27 named locations from which obsidian can be obtained scattered across 4 geological source regions shortly after colonization in the late 13th century ad polynesian settlers began transporting this material some thousands of kilometers throughout the country and across the sea in small quantities to distant neighbors in the kermadecs and chatham islands although considerable research has been conducted on obsidian sourcing in new zealand the complexity of geochemical source discrimination and the lack of a practical method of non destructive geochemical analysis has hindered progress we present the results of our use of pxrf to provide geochemical data on new zealand obsidian sources and to compare the use of discriminant analysis and classification tree analysis to discriminate among sources and attribute archaeological samples to sources our research suggests that classification tree analysis is superior to discriminant analysis in sourcing studies a large case study using an important settlement phase site s11 20 from the auckland region demonstrates the utility of the methods and the results support a model of high degrees of mobility and interaction during the early settlement of new zealand

testing the accuracy of portable x ray fluorescence to study aztec and colonial obsidian supply at xaltocan mexico abstract this article demonstrates the accuracy of non destructive portable x ray fluorescence p xrf for the study of obsidian in central mexico obsidian sources were identified for a sample of 103 artifacts from the site of xaltocan which spanned the rise and fall of the aztec empire and the first centuries of spanish colonial rule ad 900 1700 sources were assigned by comparing p xrf measurements with previously published source data and were verified using the standard techniques of laboratory xrf l xrf and instrumental neutron activation analysis inaa additional tests of potentially confounding factors show that neither length of read time presence of surface residue nor incomplete detector coverage due to small artifact size compromised our ability to attribute sources to artifacts concave surfaces did decrease the accuracy of readings because of the greater distance between the artifact and the detector our results provide new insight into the stability of supply networks and markets well into the colonial period as well as the homogenizing tendencies of the aztec market system

episodic slow slip events and rate and state friction 1 there are several ways of generating episodic slow slip events in models of rate and state friction here i explore the possibility that they arise on velocity weakening faults whose length is tuned in some sense unlike spring block sliders which have a unique critical stiffness for instability elastically deformable faults have multiple length scales stiffnesses relevant to nucleation slow slip events occur when the fault is large enough to initiate an event but too small for that event to reach dynamic instability the available window of lengths depends upon the effective fracture energy of the growing nucleation zone for the aging evolution law this fracture energy increases rapidly with slip speed and the range of permissible lengths increases nearly as b b a where a and b are the coefficients of the velocity and state dependence of the frictional strength this range becomes very large for faults that are near velocity neutral a b however existing lab data firmly favor the slip law as a predictor of nucleation style and for this law the effective fracture energy increases much less rapidly with slip speed the range of fault lengths capable of hosting slow slip events in this case seems too small to explain why they are common to so many subduction zones slow slip can be stabilized over an exceedingly large range of fault lengths if the fracture energy increases with slip speed much more rapidly than for the aging law an appealing mechanism is inelastic dilation of the fault zone coupled with pore pressure reduction and diffusive recovery

slow slip slow earthquakes period two cycles full and partial ruptures and deterministic chaos in a single asperity fault abstract the assimilation of geological geophysical and laboratory data in physics based models of fault dynamics promises increasingly realistic simulations of the seismic cycle to assist this effort i explore the dynamics of a single velocity weakening asperity to delineate the relationship between a fault physical properties and the style of faulting during the seismic cycle based on a micro physical model of rate and state friction from a dimensional analysis four non dimensional parameters control the characteristics of slip events and the behavior during the interseismic period including the dieterich ruina rice number ru which is proportional to the ratio of asperity to critical nucleation size w h and rb b a b where a and b control the direct and local evolutionary effects respectively for sufficiently large rb the ru number controls the spectrum of fault slip from periodic slow slip events to aperiodic fast ruptures in finite faults but not in semi infinite faults the transition between these end members includes a bifurcation that involves period two period four period six cycles and deterministic chaos with increasing ru macroscopic fault slip is stabilized as rb vanishes even as ru 1 for finite faults but not for semi infinite faults the transition between slow and fast ruptures for increasing rb includes another type of bifurcation with period two and period four cycles of slow and fast ruptures for 0

scaling of small repeating earthquakes explained by interaction of seismic and aseismic slip in a rate and state fault model because of short recurrence times and known locations small repeating earthquakes present a rare predictable opportunity for detailed field observations they are used to study fault creeping velocities earthquake nucleation stress drops and other aspects of tectonophysics earthquake mechanics and seismology an intriguing observation about repeating earthquakes is their scaling of recurrence time with seismic moment which is significantly different from the scaling based on a simple conceptual model of circular ruptures with stress drop independent of seismic moment and no aseismic slip here we show that a model of repeating earthquakes based on laboratory derived rate and state friction laws reproduces the observed scaling in the model a small fault patch governed by steady state velocity weakening friction is surrounded by a much larger velocity strengthening region long term slip behavior of the fault is simulated using a methodology that fully accounts for both aseismic slip and inertial effects of occasional seismic events the model results in repeating earthquakes with typical stress drops and sizes comparable with observations for a fixed set of friction parameters the observed scaling is reproduced by varying the size of the velocity weakening patch in simulations a significant part of slip on the velocity weakening patches is accumulated aseismically even though the patches also produce seismic events the proposed model supplies a laboratory based framework for interpreting the wealth of observations about repeating earthquakes provides indirect evidence that rate and state friction acts on natural faults and has important implications for possible scenarios of slip partition into seismic and aseismic parts

aseismic slip transients emerge spontaneously in three dimensional rate and state modeling of subduction earthquake sequences 1 to investigate the possible physical mechanisms of recently observed aseismic slip events in the cascadia japan and mexico subduction zones we apply a dieterich ruina rate and state friction law to a three dimensional model of a shallow subduction fault that is loaded by imposed steady plate slip rate far downdip along the thrust interface friction properties are temperature and hence depth dependent such that sliding is stable at depths below about 30 km the system is perturbed into a significantly nonuniform slip mode along strike by introducing small along strike variations in the constitutive parameters a and a b in addition to large heterogeneous earthquake slip at seismogenic depths and associated postseismic transients we found that slip events which have clearly aseismic slip rates emerge spontaneously around the downdip end of the seismogenic zone both transients which start well after a seismic event and those which are triggered by other transients are observed from the simulations the slip velocity depth range and sometimes along strike migration speed of simulated transients are similar to the observations from natural subduction zones unstable stable transitional friction properties near the downdip end of the seismogenic zone are suggested to be an ingredient allowing such transients simulated transients can weaken the locking intensity of the updip seismogenic zone while enhancing that of the transition zone spatial temporal correlation of aseismic transients and nearby seismicity in the guerrero mexico area suggests that transients may signal a period of increased probability for nucleating their high frequency counterparts as damaging subduction thrust events

two mechanism model for frictional sliding of serpentinite room temperature experiments on antigorite serpentinite indicate that at least two mechanisms accommodate frictional sliding of the serpentinite a rate weakening history dependent mechanism which dominates at fast slip velocities and a rate strengthening mechanism with no apparent history dependence which dominates at slow velocities we present a two mechanism model that successfully describes the two types of behavior observed in the friction experimental data without changing the constitutive parameters over the range of experimental conditions multiple mechanisms have been identified in higher temperature experiments by previous workers and may be required for proper representation of all rock types at low slip rates and elevated temperatures

how reliable are our published archaeometric analyses effects of analytical techniques through time on the elemental analysis of obsidians to assess the analytical accuracies and precisions of archaeometric elemental analyses by different techniques a relatively homogeneous material such as obsidian must be studied an assessment of published elemental concentration data from two anatolian obsidian sources shows that while in most cases analytical accuracy is as high as is commonly expected in some cases it is not it also shows that the dispersions of elemental concentration data indicators of analytical precisions coming from modern analytical procedures are akin to the estimated homogeneity of the obsidian based on this latter observation if one has element dispersion data from a single analytical technique with a single source of obsidian as a control data sets that contain multiple but similar sources of obsidian may be differentiated

comparison of xrf and pxrf for analysis of archaeological obsidian from southern peru abstract chemical sourcing is becoming an increasingly important component of archaeological investigation instruments used for elemental analysis generally must be operated in a controlled laboratory environment further many methods require destruction of a small portion of the objects under investigation these facts inhibit the application of chemical sourcing studies in a number of research contexts use of portable non destructive instruments would resolve these issues sixty eight obsidian artifacts from the site of jiskairumoko in southern peru were examined by x ray fluorescence spectrometry xrf and portable x ray fluorescence spectrometry pxrf results were compared for consistency in terms of source determination and individual element concentrations both instruments determined that the same sixty six artifacts derived from the chivay obsidian source and both identified the same two artifacts that could not be assigned to source individual element comparisons showed significant differences but these can be resolved through instrument cross calibration and differences had no bearing on source identification pxrf was found suitable for determining obsidian sources in southern peru and for identifying specimens that require more sensitive analytical methods such as instrumental neutron activation analysis inaa regular use of chivay at jiskairumoko suggests consistent trade relationships developed during the archaic

assessing the applicability of portable x ray fluorescence spectrometry for obsidian provenance research in the maya lowlands recent innovations in portable energy dispersive x ray fluorescence pxrf spectrometry have increased its utility for the geochemical characterization of obsidian artifacts for archaeological provenance research however concerns over the utility of pxrf instrumental analyses have been raised focused on the validity and reliability of the geochemical data produced here we adopt the framework of richard hughes on reliability validity and scale in obsidian sourcing research 1998 whereby reliability addresses instrument stability and issues of measurement while validity pertains to an instrument s ability to discern geochemical source provenance this is done in order to test the utility of pxrf instruments for archaeological provenance research k means cluster analysis was used to test the accuracy of pxrf through statistical comparison of data acquired via laboratory and portable energy dispersive xrf instruments multivariate analysis was employed to demonstrate obsidian source representation at two classic maya archaeological sites in southern belize uxbenka and ek xux and to test the validity of data obtained from a pxrf instrument in answering archaeological research questions pertaining to regional interactions between lowland maya polities results suggest that portable xrf instruments produce internally consistent results however data acquired from a pxrf instrument are not statistically equivalent to other xrf instruments this is to say that while pxrf is not a reliable technique it is valid for questions pertaining to geochemical source representation

physics based scenario of earthquake cycles on the ventura thrust system california the effect of variable friction and fault geometry the ventura thrust system in california is capable of producing large magnitude earthquakes geological studies suggest that the fault geometry is complex composed of multiple segments at different dips thrust ramps dipping 30 50 linked with bed parallel decollements dipping 10 these latter types of gently dipping faults form due to preexisting weaknesses in the crust and therefore have different frictional parameters from thrust ramps the faults also experience different stresses because of how stresses are resolved onto the fault planes here we use a two dimensional fault model to assess how geometry and frictional properties of the ramp decollement system should affect the seismic cycle we test velocity strengthening velocity weakening and conditionally stable decollements and in addition explore how the dip angle of the decollement changes the earthquake behavior a velocity strengthening decollement cannot replicate the through going earthquake ruptures that have been inferred for the ventura fault system we therefore suggest that this and other decollements may be better represented using a velocity weakening or conditionally stable response our results show that minor variations in fault geometry produce slip amounts and recurrence intervals that differ only by 10 20 but do not fundamentally alter the types of earthquakes and interseismic slip we conclude that geological constraints on fault geometry are typically sufficient to produce modeled earthquake sequences that are statistically consistent with paleoseismic records however both frictional parameters along the fault and effective normal stress influence earthquake rupture patterns significantly more research is needed to adequately constrain these quantities in order for earthquake rupture models to work as effective predictors of fault behavior

the parkfield tremors reveal slow and fast ruptures on the same asperity a tremor source on the san andreas fault produced an unusual sequence of low frequency earthquakes until it was disrupted by the 2004 parkfield earthquake the peculiar recurrence pattern has now been modelled showing that such slip behaviour occurs when the tremor asperity size is close to the critical nucleation size of earthquakes an isolated tremor source on the san andreas fault near parkfield california produces an unusual sequence of low frequency earthquakes which regularly oscillated between recurrence intervals of three and six days until it was disrupted by the 2004 magnitude 6 0 parkfield earthquake after that event the source ruptured every three days only gradually returning to its initial alternating recurrence pattern after two years deepa mele veedu and sylvain barbot have now modelled the mechanism driving the tremor source to form this peculiar recurrence pattern they demonstrate that such slip behaviour can occur when the tremor asperity size is close to the critical nucleation size of earthquakes they also show that changes in pore pressure following the 2004 parkfield earthquake can explain the sudden change and gradual recovery of the recurrence intervals the deep extension of the san andreas fault is believed to be creeping but the recent observations of tectonic tremors from these depths indicate a complex deformation style1 in particular an isolated tremor source near parkfield has been producing a sequence of low frequency earthquakes2 that indicates an uncommon mechanism of stress accumulation and release the tremor pattern regularly oscillated between three and six days from mid 2003 until it was disrupted by the 2004 magnitude 6 0 parkfield earthquake after that event the tremor source ruptured only about every three days but over the next two years it gradually returned to its initial alternating recurrence pattern the mechanism that drives this recurrence pattern is unknown here we use physics based models to show that the same tremor asperity the region from which the low frequency earthquakes radiate can regularly slip in slow and fast ruptures naturally resulting in recurrence intervals alternating between three and six days this unusual slip behaviour occurs when the tremor asperity size is close to the critical nucleation size of earthquakes we also show that changes in pore pressure following the parkfield earthquake can explain the sudden change and gradual recovery of the recurrence intervals our findings suggest a framework for fault deformation in which the same asperity can release tectonic stress through both slow and fast ruptures

a paleogeodetic record of variable interseismic rates and megathrust coupling at simeulue island sumatra an 1100 year long paleogeodetic record of land height change along the simeulue section of the sumatran subduction zone reveals significant variations in vertical motion rates from an 267 year long record we develop models to explain rate variations in the decades before the 1861 2004 and 2005 great earthquakes the record shows that rates accelerated by a factor of 4 to 10 in the decades before the 1861 earthquake one plausible explanation is a significant increase in the depth of interseismic coupling on the sunda megathrust under simeulue despite similarity of the 1861 and 2005 coseismic rupture patterns the pattern of coupling during the decades before the two earthquakes may have been different most gps observations of interseismic deformation at subduction zones span only a decade or two our results highlight the need to treat gps derived coupling maps as only a snapshot of fault conditions that are temporally variable

piecemeal rupture of the mentawai patch sumatra the 2008 mw 7 2 north pagai earthquake sequence the 25 february 2008 mw 7 2 north pagai earthquake partially ruptured the middle section of the mentawai patch of the sunda megathrust offshore sumatra the patch has been forecast to generate a great earthquake in the next few decades however in the current cycle the patch has so far broken in a sequence of partial ruptures one of which was the 2008 event illustrating the potential of the patch to generate a spectrum of earthquake sizes we estimate the coseismic slip distribution of the 2008 event by jointly inverting coseismic offsets from gps and insar we then estimate afterslip with 5 6 years of cumulative gps displacements our results suggest that the estimated afterslip partially overlaps the coseismic rupture the overlap of coseismic rupture and afterslip can be explained conceptually by a simple rate and state model where the degree of overlapping is controlled by the dynamic weakening and the critical nucleation size in the velocity weakening area comparing our rate and state model results with our geodetic inversion results we suggest that the part of the coseismic rupture that does not overlap with the afterslip may represent a velocity weakening region while the overlapping part may represent a velocity strengthening region

reassessment of wd xrf method for obsidian provenance shareable databases abstract the x ray fluorescence technique using peak intensity ratios of trace elements is one of the faster less expensive and less invasive methods for obsidian sourcing moreover xrf peak intensity ratios are particularly useful when the artifact is slightly altered particularly affecting the alkali cations or when its surfaces are covered with a fine film of carbonate deposits formed while the sample was buried the limitation of this technique results from the dimensions of the obsidian samples very small obsidian samples nowadays about 1 cm in size are difficult to measure given the very few x rays emitted by their surface an aluminium holder closed with a very thin mylar polyester film was prepared and the specimen positioned at the centre of the surface of the mylar film was placed in the xrf spectrometer the use of recent technology xrf apparatus equipped with a 4 kw rh anode x ray tube coupled with an accurate measurement of refined x ray characteristic lines that exclude the x ray background contribution of five trace elements rb sr y zr nb made it possible to determine the source geological outcrop of archaeological obsidian samples as little as 7 mm and as light as 40 mg a database of peak intensity ratios background and interference free of five trace elements was produced for obsidian samples from monte arci palmarola lipari pantelleria gyali and melos this database may be used by other laboratories provided the x ray intensity of the trace elements rb sr y zr nb are measured as net intensities that is purified from the contribution of the background and from interelemental interferences a comparison between data obtained with two spectrometers of different generation and differently calibrated confirmed the possibility of obtaining a database that can be shared with other laboratories the proposed xrf method was tested on neolithic obsidians from four apulian sites ripa tetta at lucera palestra ex g i l at foggia pulo di molfetta and grotta di santa barbara at polignano a mare whose source outcrops had been also determined by sem eds

validity of off the shelf handheld portable xrf for sourcing near eastern obsidian chip debris handheld portable xrf hhpxrf has received considerable recent attention in archaeology especially for obsidian sourcing published studies largely suggest a high potential for success hhpxrf though has been met with debate and scepticism concerns fall into three categories 1 low accuracy and precision 2 data correction schemes and calibration and 3 ignorance of fundamental xrf issues such as specimen size limits and morphology effects the result is that archaeological interpretations in hhpxrf based studies are cast into doubt should interpretations be believed if authors did not follow the perceived best practices to address such questions the validity of hhpxrf for near eastern obsidian sourcing was tested under deliberately sub optimal conditions irregular obsidian debitage near the minimum size limits was sourced with a success rate of 94 based on a rank matches to 100 based on a and b rank matches even under conditions chosen to mimic off the shelf operation

on the sources and uses of obsidian during the paleolithic and mesolithic in poland abstract eighty six obsidian artifacts from twenty paleolithic and mesolithic archaeological sites in poland were analyzed using non destructive energy dispersive x ray fluorescence edxrf analysis and assigned to parent geological obsidian source chemical type results of the study the first country wide survey of its kind support the conclusion that the geological source of obsidian remained largely unchanged for thousands of years that obsidian use appears to have been minimal throughout the paleolithic and mesolithic regardless of distance to source that obsidian artifacts were used to perform the same functions as their non obsidian flint and radiolarite counterparts and that the distinct visual properties of volcanic glass may have contributed to its recognition as unique and exotic in different social contexts

initial source evaluation of archaeological obsidian from the kuril islands of the russian far east using portable xrf obsidian artifacts recently have been recovered from 18 archaeological sites on eight islands across the kuril island archipelago in the north pacific ocean suggesting a wide ranging distribution of obsidian throughout the island chain over the last 2 500 years although there are no geologic sources of obsidian in the kurils that are known to have been used prehistorically sources exist in hokkaido japan and kamchatka russia the southern and northern geographic regions respectively from which obsidian may have entered the kuril islands this paper reports on the initial sourcing attempt of kuril islands obsidian through the analysis of 131 obsidian artifacts data from this research were generated through the application of portable xrf technology and are used to address research questions concerning prehis toric mobility exchange and social networking in the kuril islands

variability of earthquake nucleation in continuum models of rate and state faults and implications for aftershock rates using two continuum models of rate and state faults one with a weaker patch and the other with rheological transition from steady state velocity weakening to velocity strengthening friction we simulate several scenarios of spontaneous earthquake nucleation plausible for natural faults investigate their response to static shear stress steps and infer the corresponding aftershock rates overall nucleation processes at weaker patches behave similarly to theories based on spring slider models with some notable deviations in particular nucleation and aftershock rates are affected by normal stress heterogeneity in the nucleation zone nucleation processes at rheological transitions behave differently producing complex slip velocity histories nonmonotonic responses to static stress changes and aftershock rates with pronounced peaks and seismic quiescence for such processes positive stress steps sometimes delay nucleation of seismic events by inducing aseismic transients that relieve stress and postpone seismic slip superposition of the complex aftershock response for spatially variable stress changes results in omori s law for a period of time followed by seismic quiescence such behavior was observed at the base of the seismogenic zone near the 1984 morgan hill earthquake we show that the computed aftershock rates are linked to unperturbed slip velocity evolution in the nucleation zone and construct simplified analytical scenarios that explain some features of the response the qualitative differences that we find between the two nucleation models indicate that aftershock response of rate and state faults to static stress changes would depend on the conditions under which nucleation occurs on natural faults and may be different from predictions based on spring slider models

spontaneous and triggered aseismic deformation transients in a subduction fault model 1 aseismic deformation transients can emerge as a natural outcome of the rate and state friction processes revealed in laboratory fault sliding experiments when that constitutive formulation is applied to model subduction earthquake sequences transients can arise spontaneously for certain effective stress variations with depth we show that if interstitial fluids are present and pore pressure is near lithostatic around and downdip from the frictional stability transition transients with recurrence intervals of 1 year are predicted on the basis of laboratory friction parameters and their temperature hence depth variations the recurrence interval decreases with and reaches 14 months when is 2 3 mpa dimensional analysis and numerical studies show that the fault response primarily depends on a parameter w h here the high pore pressure zone extends distance w updip from the stability transition and h is the stable patch size for steady sliding evidence that such fluid conditions may actually be present is independently provided by the occurrence of nonvolcanic tremors as apparent responses to extremely small stress changes and by petrological constraints on expected regions of dehydration for the shallow dipping subduction zones where transients are observed transient sequences can also be triggered by a modest one time step like interseismic stress perturbation on the subduction fault due to nearby earthquakes or to pore pressure changes e g during episodes of metamorphic fluid release properties of triggered transients and future thrust earthquakes depend on the interseismic time when the perturbation is introduced its relative location along the subduction fault and its magnitude

elastodynamic analysis for slow tectonic loading with spontaneous rupture episodes on faults with rate and state dependent friction we present an efficient and rigorous numerical procedure for calculating the elastodynamic response of a fault subjected to slow tectonic loading processes of long duration within which there are episodes of rapid earthquake failure this is done for a general class of rate and state dependent friction laws with positive direct velocity effect the algorithm allows us to treat accurately within a single computational procedure loading intervals of thousands of years and to calculate for each earthquake episode initially aseismic accelerating slip prior to dynamic rupture the rupture propagation itself rapid post seismic deformation which follows and also ongoing creep slippage throughout the loading period in velocity strengthening fault regions the methodology is presented using the two dimensional 2 d antiplane spectral formulation and can be readily extended to the 2 d in plane and 3 d spectral formulations and with certain modifications to the space time boundary integral formulations as well as to their discretized development using finite difference or finite element methods the methodology can be used to address a number of important issues such as fault operation under low overall stress interaction of dynamic rupture propagation with pore pressure development patterns of rupture propagation in events nucleated naturally as a part of a sequence the earthquake nucleation process earthquake sequences on faults with heterogeneous frictional properties and or normal stress and others the procedure is illustrated for a 2 d crustal strike slip fault model with depth variable properties for lower values of the state evolution distance of the friction law small events appear the nucleation phases of the small and large events are very similar suggesting that the size of an event is determined by the conditions on the fault segments the event is propagating into rather than by the nucleation process itself we demonstrate the importance of incorporating slow tectonic loading with elastodynamics by evaluating two simplified approaches one with the slow tectonic loading but no wave effects and the other with all dynamic effects included but much higher loading rate

multiple slow slip events during a foreshock sequence of the 2014 iquique chile mw 8 1 earthquake to obtain a precise record of the foreshock sequence before the 2014 iquique chile mw 8 1 earthquake we applied a matched filter technique to continuous seismograms recorded near the source region we newly detected about 10 times the number of seismic events listed in the routinely constructed earthquake catalog and identified multiple sequences of earthquake migrations at speeds of 2 10 km d both along strike and downdip on the fault plane updip of the main shock area in addition we found out repeating earthquakes from the newly detected events likely indicating aseismic slip along the plate boundary fault during the foreshock sequence these observations suggest the occurrence of multiple slow slip events updip of the main shock area the final slow slip event migrated toward the main shock nucleation point we interpret that several parts of the plate boundary fault perhaps experienced slow slip causing stress loading on the prospective largest slip patch of the main shock rupture

hierarchical asperity model for multiscale characteristic earthquakes a numerical study for the off kamaishi earthquake sequence in the ne japan subduction zone 1 we develop a numerical model to simulate the occurrence of multiscale characteristic earthquakes in the off kamaishi area of the northeast japan subduction zone a notable feature of these earthquake sequences is that microearthquakes occur during the later half of interseismic period between two successive m 4 9 characteristic earthquakes which we call moderate earthquakes we introduce a microasperity the rupture area of the microearthquakes with a significantly smaller nucleation size than the size of a hyper asperity the rupture area for moderate earthquakes in contrast the nucleation size in the rest of the hyper asperity which we call a conditional asperity is set to be comparable to the spatial size of the hyper asperity such a hierarchical asperity model successfully reproduces the observed earthquake sequences the simulation results show that both microearthquakes and moderate earthquakes nucleate at the microasperity the stress level in the conditional asperity determines whether a rupture terminates just outside the microasperity or propagates out into the conditional asperity

new investigations of the golludag obsidian lava flows system a multi disciplinary approach abstract the golludag obsidian lava flow system is relatively complex more than ten different obsidian outcrops and knapping workshops have been identified around this volcano their importance for long and short distances obsidian supply has already been demonstrated one of the main problem encountered when studying the golludag obsidian flows is the great chemical similarity of some of them the use of the geochemical approach to solve the problems of obsidian trade around the golludag is therefore insufficient a multi disciplinary program joining archaeology geochemistry and geomorphology was thus started to understand the relationships between the different obsidian flows and to draw the pattern of the golludag obsidian trade our archaeological and geomorphologic approach will help us to understand which obsidian outcrops were available during the palaeolithic and neolithic periods also our geomorphologic approach linked to intensive geochemical analyses will help us to understand the spatial variability of the geochemistry of the obsidian outcrops lithic technology will also give information about the different knapping methods used at the workshops

interaction of slip on asperities numerical simulation of seismic cycles on a two dimensional planar fault with nonuniform frictional property 1 numerical simulation is conducted to understand the variety of frictional sliding on a plate interface and complex recurrence of earthquakes a planar square fault in an infinite uniform elastic medium is considered and the frictional stress on the fault is assumed to obey a rate and state dependent friction law nonuniformity in a frictional constitutive parameter is introduced on the model fault on the fault plane one or two circular patches with velocity weakening frictional property are surrounded by velocity strengthening areas unstable slip may occur for velocity weakening friction and aseismic sliding occurs for velocity strengthening friction velocity weakening patches correspond to asperities because intense seismic slip may occur there simulation results indicate that episodic aseismic slip events slow earthquakes occur when the velocity weakening patch size is close to the critical size of earthquake nucleation propagation of postseismic sliding on the velocity strengthening region follows an earthquake at a velocity weakening patch when the postseismic sliding reaches another velocity weakening patch an earthquake may be triggered at the patch resulting in a double earthquake the time delay between two events of the double earthquake increases with the distance between the two velocity weakening patches or the degree of velocity strengthening in the region between the patches when the distance between the two velocity weakening patches is long an earthquake at one patch does not directly cause an earthquake at the other patch in these cases complex earthquake recurrence may appear due to the interaction between ruptures at the two patches and the recurrence interval of earthquakes and coseismic slip is not constant at each velocity weakening patch

episodic slow slip events in the japan subduction zone before the 2011 tohoku oki earthquake abstract we describe two transient slow slip events that occurred before the 2011 tohoku oki earthquake the first transient crustal deformation which occurred over a period of a week in november 2008 was recorded simultaneously using ocean bottom pressure gauges and an on shore volumetric strainmeter this deformation has been interpreted as being an m6 8 episodic slow slip event the second had a duration exceeding 1 month and was observed in february 2011 just before the 2011 tohoku oki earthquake the moment magnitude of this event reached 7 0 the two events preceded interplate earthquakes of magnitudes m6 1 december 2008 and m7 3 march 9 2011 respectively the latter is the largest foreshock of the 2011 tohoku oki earthquake our findings indicate that these slow slip events induced increases in shear stress which in turn triggered the interplate earthquakes the slow slip event source area on the fault is also located within the downdip portion of the huge coseismic slip area of the 2011 earthquake this demonstrates episodic slow slip and seismic behavior occurring on the same portions of the megathrust fault suggesting that the faults undergo slip in slow slip events can also rupture seismically

large nucleation before large earthquakes is sometimes skipped due to cascade up implications from a rate and state simulation of faults with hierarchical asperities 1 does a large earthquake have a large quasi static preparation a hierarchical asperity model in which a large tough patch patch l contains smaller fragile patches patch s enables a large earthquake to start with only small preparation because of cascade up rupture growth we realized such a model in a rate and state framework by heterogeneous distributions of the state evolution distance and its consequences are investigated by earthquake sequence simulations focus is put on elementary processes the interaction between two scales one patch l containing one patch s is simulated with their size ratio as a parameter if patch s is larger than the nucleation size of patch l the system falls into a limit cycle consisting of only one earthquake that starts with patch s nucleation and grows dynamically to rupture entire patch l if patch s is considerably smaller than the nucleation size of patch l small earthquakes never dynamically cascade up and the large earthquakes are initiated by large quasi static nucleation in between large earthquakes start in various ways by large nucleation dynamic cascade up or delayed cascade up in the final stage of quasi static nucleation the preseismic moment release rate increases roughly inversely proportional to the time to failure tf with its amplitude depending on the nucleation size for a patch s rupture to cascade up strength in the adjacent region must have been reduced manifested by a higher creep velocity before the patch s nucleation starts following 1 tf acceleration large nucleation sometimes has a precursory small earthquake characterized by larger afterslip than nonprecursory ones

three dimensional boundary integral modeling of spontaneous earthquake sequences and aseismic slip 1 fault processes involve complex patterns of seismic events and aseismic slip this work develops a three dimensional 3 d methodology for simulating long term history of spontaneous seismic and aseismic slip on a vertical planar strike slip fault subjected to slow tectonic loading our approach reproduces all stages of earthquake cycles from accelerating slip before dynamic instability to rapid dynamic propagation of earthquake rupture to postseismic slip and to interseismic creep including aseismic transients we use the developed 3 d methodology to study interaction of fault slip with a small patch of higher normal stress over long term slip history for uniform initial prestress dynamic rupture is significantly affected by the stronger patch in the first simulated event but not in subsequent ones the change in behavior is due to redistribution of shear stress by prior slip which demonstrates that distributions of fault strength and stress are related and illustrates the importance of simulating long slip histories even in studies of dynamic rupture despite no long term effect on dynamic rupture the small patch of higher normal stress influences nucleation processes and hence long term slip patterns in the model comparison of the fully dynamic simulations and a widely used quasi dynamic approach shows that the quasi dynamic approach modifies long term slip patterns in addition to resulting in much smaller slip velocities and rupture speeds during dynamic events we show that the response of quasi dynamic formulations with reduced radiation damping terms can be scaled to match the results of the standard quasi dynamic formulation and hence cannot improve the comparison