fault death a perspective from actively deforming regions abstract patterns of activity on large faults in regions of distributed continental deformation can change quite rapidly in less than 1 ma such changes include faults becoming permanently or temporarily inactive spatial migration of activity between different faults or faults sets within a deforming region and faults apparently going through episodes of intense activity separated by long quiescent periods greater knowledge of these changes combined with our increasingly detailed understanding of the geometry of large faults have implications for a variety of structural and tectonic issues such as 1 the nature of the interaction between neighbouring faults 2 the link between the discontinuous deformation on faults in the seismogenic upper crust and the more distributed deformation in the aseismic lithosphere beneath and 3 the relation between the instantaneous kinematics and the cumulative finite deformation examples from the active extensional province of central greece are used to illustrate the nature and possible significance of changing fault patterns

source scaling relationship for m 4 6 8 9 earthquakes specifically for earthquakes in the collision zone of taiwan we investigated the source scaling of earthquakes mw 4 6 8 9 mostly from the taiwan orogenic belt and made a global compilation of source parameters to examine the scaling self similarity finite fault slip models 12 dip slip and 7 strike slip using mainly dense strong motion data and teleseismic data from taiwan were utilized seven additional earthquakes m 7 were included for further ex amination of scaling of large events we determined the effective length and width for the scaling study was m0 l 2 and m0 l 3 for the events less than and larger than the seismic moment of 10 20 nm respectively regardless of the fault types suggesting a nonself similar scaling for small to moderate events and a self similar scaling for large events although the events showed variation in stress drops with the exception of three events with high stress drops most of the events had stress drops of 10 100 bars the observed bilinear relation is well explained by the derived magnitude area equation of shaw 2009 when we considered only events with stress drops of 10 100 bars and a seismogenic thickness of 35 km the bilinear feature of the regressed magnitude area scaling holds for ruptured areas up to about 1000 km 2 for our seismogenic thickness of 35 km for the events having rupture areas larger than that the average slip becomes proportional to the rupture length the distinct high stress drop events from blind faults in the western foothill of taiwan yield local high peak ground accelerations pgas when compared to the next generation attenuation model regardless of the relative small magnitudes of these events the high pgas give the region higher seismic hazard potential and thus require special attention for seismic hazard mitigation

a three dimensional fluid controlled earthquake model behavior and implications we describe the behavior of a three dimensional fluid controlled fault model that couples the dominant mechanical effects of fluid within a cellular fault zone with shear stress accumulation from constant plate motion applied at the downward continuation of the fault improvements from a previous model include long term plate motion loading and porosity creation through dilatant slip which allow the model to evolve to its steady state dynamic equilibrium the examined results include slip and slip deficit accumulation pore pressure buildup and release stress states the emergence of seismic scaling relationships and frequency size statistics of model earthquakes we find that asperities develop naturally within the model reflecting the disorganization of the evolving stress state in mohr space the dynamical interaction of shear stress and effective normal stress perturbs the initial uniform stress state to a complex state that produces transient asperity development along the fault these mohr space asperities spontaneously evolve disintegrate reemerge and migrate along the fault plane the general model behavior is independent of the state of the fluid pressure in four examined cases which span the range of possible fault zone overpressures the equilibrium condition is that which occupies all of the available mohr space maximum slip deficits along the fault depend on the degree of fault weakness ranging from about 3 m for a weak fault to over 30 m for a strong fault after 4000 years of model evolution for events that breach the surface the seismic moment scales with the cube of the source dimension mo l3 which reflects the slipped area times the depth extent of the rupture this scaling crosses isolines of stress drop for confined events mo l2 along isolines of stress drop but no general scaling emerges clusters emerge between stress drop versus seismic moment and stress drop versus source dimension with large events converging to average stress drops of about 8 mpa for a weak fault and about 20 mpa for a strong fault

seismic source modeling seismic source modeling is taken to mean the modeling of seismograms to investigate kinematic properties of the earthquake source current trends such as the use of other data types e g geodetic measurements of coseismic deformation and the explicit consideration of source dynamics when modeling seismograms are beginning to blur this definition but i will adhere to it in this review i have divided seismic source modeling into teleseismic regional and near source modeling teleseismic modeling has the advantage of global coverage for earthquakes of magnitude 5 5 and larger but does not provide much more than point source parameters regional distance modeling has the advantage of a more rapid assessment of earthquake source properties but is complicated by relatively complex wave propagation the coverage is also limited to areas of broadband regional networks typically continental areas of developed countries near source modeling has the potential for detailed imaging of source properties but very few earthquakes occur in regions with sufficient instrumentation to allow this i have also included a section on historical earthquakes because of the additional issues that seismologists face in working with pre wwssn data and because of the important issues such as earthquake recurrence that require historical data in addition to reviewing the progress in seismic source modeling during the last four years i have also briefly reviewed some of the progress in understanding earthquake physics and hazards that has come about because of basic research in earthquake source modeling

strike slip earthquakes on quasi vertical transcurrent faults inferences for general scaling relations the recent occurrence of several large strike slip earthquakes provides the opportunity to review and complement available data on the scaling of seismic moment mo with length of rupture l for large earthquakes depending on their tectonic setting and mechanism for strike slip earthquakes on quasi vertical transcurrent faults the mo versus l relation has a significant change of slope around mo 0 6 0 8 1020 n m and for larger earthquakes mo scales linearly with l this is compatible with models where slip is controlled by the width of the fault also it appears to be easier to categorize large earthquakes by their mechanism strike slip on vertical transcurrent fault versus pure thrust normal than their tectonic setting interplate intraplate

geological and seismological analysis of the 13 february 2001 mw 6 6 el salvador earthquake evidence for surface rupture and implications for seismic hazard the el salvador earthquake of 13 february 2001 mw 6 6 caused tectonic rupture on the el salvador fault zone esfz right lateral strike slip surface rupture of the east west trending fault zone had a maximum surface displacement of 0 60 m no vertical component was observed the earthquake resulted in widespread landslides in the epicentral area where bedrock is composed of volcanic sediments tephra and weak ignimbrites in the aftermath of the earthquake widespread damage to houses and roads and the hazards posed by landslides captured the attention of responding agencies and scientists and the presence of surface fault rupture was overlooked additionally the tectonic context in which the earthquake took place had not been clear until mapping of the esfz was completed for the present study we identified several fault segments the distribution of surface ruptures the aftershock pattern and fault rupture scaling considerations that indicate the 21 km long san vicente segment ruptured in the 2001 event static coulomb stress transfer models for the san vicente rupture are consistent with both aftershock activity of the 2001 sequence and ongoing background seismicity in the region at mw 6 6 the 2001 earthquake was of only moderate magnitude yet there was significant damage to the country s infrastructure including buildings and roads and numerous deaths and injuries thus earthquake hazard and risk in the vicinity of the esfz which straddles the city of san salvador with a population of 2 million is high because even moderate magnitude events can result in major damage deaths and injuries in the region

unusual earthquakes in the gulf of alaska and fragmentation of the pacific plate two recent ms 7 6 strike slip earthquakes in the northern gulf of alaska ruptured a composite 250 km long north striking zone in the pacific plate these shocks are attributed to a combination of enhanced tensional stress in the pacific plate seaward of and following the great mw 9 2 alaska earthquake of 1964 and compressional stress resulting from collision of the yakutat terrane with north america the occurrence of these shocks reflects fragmentation of the northeast corner of the pacific plate possibly the initial step in establishing a new plate boundary seaward of the current boundary

the 2002 denali fault and 2001 kunlun fault earthquakes complex rupture processes of two large strike slip events we studied the source processes of two large continental earthquakes the 3 november 2002 denali fault earthquake and the 14 november 2001 kunlun fault earthquake associated with strike slip faulting along ancient sutures we inverted teleseismic p waveforms using a pulse stripping method for multiple time windows with different focal mechanisms and derived composite source models according to our results the 2002 denali fault earthquake began with initial thrusting m w 7 3 along a 40 km long segment of the north northwest dipping susitna glacier fault and later ruptured a 300 km long segment along the denali and totschunda faults with a right lateral strike slip mechanism m w 7 7 in contrast the 2001 kunlun fault earthquake nucleated near an extensional step over with a subevent pair consisting of 30 km long strike slip m w 6 9 event and 40 km long normal m w 6 8 faulting event and later ruptured a 350 km long segment along the kunlun fault with a left lateral strike slip mechanism m w 7 7 both earthquakes propagated primarily unilaterally to the east and released most of their energy along slip patches asperities far from the hypocenter locations we find that both the denali fault and kunlun fault earthquakes had high average rupture velocities of 3 2 km sec and 3 4 km sec respectively we also compared the source properties of these two earthquakes with other strike slip earthquakes for scaling purposes large strike slip earthquakes were classified as interplate oceanic intraplate or continental intraplate events by using this classification the denali fault and kunlun fault earthquakes have an interplate signature that suggests overall weak faulting

earthquake scaling and the strength of seismogenic faults 1 two important and unresolved issues in tectonics and earthquake mechanics are the strength of seismogenic faults and scaling relationships between the seismic moment of an earthquake and the area or length of the rupture these two issues usually treated separately are shown here to be fundamentally related it is shown that the reported scatter in moment area and moment length data of strike slip and dip slip earthquakes is not scatter but instead reflects the strength of the fault that failed relationships that exhibit continuous scaling between small and large earthquakes are derived and demonstrate that fault zone pore pressure is the scaling parameter that collapses the combined catalogs of strike slip and dip slip earthquakes to a single function it is shown that for large earthquakes overpressures vary continuously between hydrostatic and near lithostatic above about 15 km with evidence for a clear transition to near lithostatic pore pressures below this depth these results have significant implications for plate tectonics earthquake source physics and mechanistic seismic hazard assessment

source mechanism of the luzon philippines earthquake of july 16 1990 the luzon philippines earthquake of july 16 1990 with ms 7 8 was generated by left lateral faulting in the central luzon island ground breakage was observed along a linear trace extending 110 km the maximum horizontal offset as measured on the fault was as much as 6 m a fault area of 120 20 km2 was inferred from a field study and aftershock data this event is one of the largest strike slip earthquakes ever recorded in the world for long period surface waveform analysis we used very broadband records from 14 stations of the gdsn geoscope iris and erios networks the centroid moment tensor cmt solution from surface waves represents almost pure left lateral strike slip faulting on a steep fault with strike 155 dip 88 and rake 7 the seismic moment is 3 9 1020 nm 1027 dyn cm which gives mw 7 7 the average dislocation on the fault is 5 4 m and the stress drop is 5 2 mpa 52 bars teleseismic p and sh waves from 14 stations are used to model the spatiotemporal distribution of subevents five subevents are detected in an interval of 44 sec their sequence indicates a bilateral rupture the mean velocity of rupture toward the north is 2 7 km sec the total seismic moment of the subevents is 3 6 1020 nm the largest aftershock ms 6 6 occurred on july 17 near the recognized northern end of the main fault the cmt solution for the aftershock represents a reverse faulting with moment of 6 4 1019 nm mw 6 5 this aftershock was probably caused by compression produced by block motion of the eastern block of the main fault

statistical physics seismogenesis and seismic hazard the scaling properties of earthquake populations show remarkable similarities to those observed at or near the critical point of other composite systems in statistical physics this has led to the development of a variety of different physical models of seismogenesis as a critical phenomenon involving locally nonlinear dynamics with simplified rheologies exhibiting instability or avalanche type behavior in a material composed of a large number of discrete elements in particular it has been suggested that earthquakes are an example of a self organized critical phenomenon analogous to a sandpile that spontaneously evolves to a critical angle of repose in response to the steady supply of new grains at the summit in this stationary state of marginal stability the distribution of avalanche energies is a power law equivalent to the gutenberg richter frequency magnitude law and the behavior is relatively insensitive to the details of the dynamics here we review the results of some of the composite physical models that have been developed to simulate seismogenesis on different scales during 1 dynamic slip on a preexisting fault 2 fault growth and 3 fault nucleation the individual physical models share some generic features such as a dynamic energy flux applied by tectonic loading at a constant strain rate strong local interactions and fluctuations generated either dynamically or by fixed material heterogeneity but they differ significantly in the details of the assumed dynamics and in the methods of numerical solution however all exhibit critical or near critical behavior with behavior quantitatively consistent with many of the observed fractal or multifractal scaling laws of brittle faulting and earthquakes including the gutenberg richter law some of the results are sensitive to the details of the dynamics and hence are not strict examples of self organized criticality nevertheless the results of these different physical models share some generic statistical properties similar to the universal behavior seen in a wide variety of critical phenomena with significant implications for practical problems in probabilistic seismic hazard evaluation in particular the notion of self organized criticality or near criticality gives a scientific rationale for the a priori assumption of stationarity used as a first step in the prediction of the future level of hazard the gutenberg richter law a power law in energy or seismic moment is found to apply only within a finite scale range both in model and natural seismicity accordingly the frequency magnitude distribution can be generalized to a gamma distribution in energy or seismic moment a power law with an exponential tail this allows extrapolations of the frequency magnitude distribution and the maximum credible magnitude to be constrained by observed seismic or tectonic moment release rates the answers to other questions raised are less clear for example the effect of the a priori assumption of a poisson process in a system with strong local interactions and the impact of zoning a potentially multifractal distribution of epicentres with smooth polygons the results of some models show premonitory patterns of seismicity which could in principle be used as mainshock precursors however there remains no consensus on both theoretical and practical grounds on the possibility or otherwise of reliable intermediate term earthquake prediction

source parameter scaling and the cascadia paleoseismic record several approaches to interpreting the cascadia paleoseismic record are used to derive relationships between fault area slip and moment and to compare the results with the scaling relationships determined by somerville et al 2015 for recent subduction zone events in two models ca12a and ca12b taken from goldfinger et al 2012 paleoevents are classified into five characteristic areas ca with the slip during each event estimated based on the time between the event and either the following or the previous event in model ca14 taken from scholz 2014 slip on four characteristic segments is determined from the plate tectonic convergence rate assuming a constant stress drop in model cl introduced in this article the fault length for paleoevents is defined by the along strike length over which the observations have been correlated width and slip are interpolated from model ca14 ca12a and ca12b show large scatter compared with the global compilation because of large variations in slip for a given area models ca14 and cl reproduce the relationship derived for asperities defined as patches in finite fault models with slip 1 5 times the average slip these models can be reconciled with the total area and average slip from somerville et al 2015 by increasing the fault area and decreasing the slip using scaling factors derived from the analysis of recent earthquakes clmod1 or by reducing the slip by a factor of 8 clmod2 clmod1 implies that the paleoearthquake observations are controlled by high slip patches whereas clmod2 implies that much of the plate tectonic convergence is accommodated aseismically a scenario intermediate between clmod1 and clmod2 is considered most likely this study demonstrates the value of using scaling relationships based on modern earthquakes as a tool for evaluating earthquake histories derived from paleoseismic data online material a table summarizing the source parameters for the different models presented in this article to enable figure reproduction figures that summarize the data points used by somerville et al 2015 data points from a new analysis that became available after preparation of the main article ye et al 2016 and results for the turbidite mass model goldfinger et al 2012 for estimating seismic moment

abraded sand volcanoes as a tool for recognizing paleo earthquakes with examples from the cisuralian talchir formation near angul orissa eastern india abstract one of the bedding planes of a sandstone unit belonging to the cisuralian talchir formation is well exposed along the nandir jhor river in eastern india it shows a few dozens of circular structures commonly with diameters of a few decimetres a concentration is found in an area of some 50 m 2 where 12 well developed specimens occur the structures are interpreted as abraded sand volcanoes which interpretation is supported by the occurrence on the same bedding plane of a sand volcano with a diameter of over a meter the concentrated structures thus represent a sand volcano field a phenomenon that has not been recognized earlier in the pre holocene geological record but that in recent times seems always to be related to an earthquake the structures described here might therefore help to recognize earthquakes that occurred in the geological past

implications of the 26 december 2004 sumatra andaman earthquake on tsunami forecast and assessment models for great subduction zone earthquakes results from different tsunami forecasting and hazard assessment mod els are compared with observed tsunami wave heights from the 26 december 2004 indian ocean tsunami forecast models are based on initial earthquake information and are used to estimate tsunami wave heights during propagation an empirical forecast relationship based only on seismic moment provides a close estimate to the observed mean regional and maximum local tsunami runup heights for the 2004 indian ocean tsunami but underestimates mean regional tsunami heights at azimuths in line with the tsunami beaming pattern e g sri lanka thailand standard forecast models developed from subfault discretization of earthquake rupture in which deep ocean sea level observations are used to constrain slip are also tested forecast models of this type use tsunami time series measurements at points in the deep ocean as a proxy for the 2004 indian ocean tsunami a transect of deep ocean tsunami amplitudes recorded by satellite altimetry is used to constrain slip along four subfaults of the m 9 sumatra andaman earthquake this proxy model performs well in comparison to observed tsunami wave heights travel times and inundation patterns at banda aceh hypothetical tsunami hazard assessments models based on end member estimates for average slip and rupture length m w 9 0 9 3 are compared with tsunami observations using average slip low end member and rupture length high end member m w 9 14 consistent with many seismic geodetic and tsunami inversions adequately estimates tsunami runup in most regions except the extreme runup in the western aceh province the high slip that occurred in the southern part of the rupture zone linked to runup in this location is a larger fluctuation than expected from standard stochastic slip models in addition excess moment release 9 deduced from geodetic studies in comparison to seismic moment estimates may gen erate additional tsunami energy if the exponential time constant of slip is less than approximately 1 hr overall there is significant variation in assessed runup heights caused by quantifiable uncertainty in both first order source parameters e g rupture length slip length scaling and spatiotemporal complexity of earthquake rupture

orogenic wedge deformation and potential for great earthquakes in the central andean backarc subduction of the nazca plate beneath south america has driven the growth of the andes mountains subduction has routinely generated earthquakes larger than magnitude 8 0 along the western margin of the mountain belt 1 but the potential size of less frequent earthquakes in the eastern backarc margin is unknown continued support of the high andean plateau at the centre of the andes can be explained only if deformation of the backarc margin is ongoing 2 4 here we present gps data that record surface motions in the subandean ranges that are part of the backarc margin we find that the velocity of surface movement decreases sharply from west to east across the subandean ranges we suggest that a subhorizontal fault underlying the ranges slips freely at depth in the west but is locked for up to 100 km in shallower sections further east analysis of fault scarps formed where the subhorizontal fault intersects the surface indicates that the fault has generated repeated large earthquakes we suggest that rupture of the entire locked section of the fault could generate an earthquake of magnitude 8 7 8 9 we attribute the large seismic potential to the unusual width of the subandean ranges and suggest that deformation of the subandean ranges at a rate unmatched by erosion causes the mountain range to widen the central andean plateau ap is a bilaterally symmetric plateau of 4 000m average elevation fig 1 although ap uplift scenarios are currently debated 5 6 it is generally accepted that the backarc orogenic wedge on the ap s east flank comprising the eastern cordillera ec inter andean zone iaz and subandes sa has contracted by more than 250km since 45myr ago refs 79 wedge deformation has been facilitated by the presence

regional difference in scaling laws for large earthquakes and its tectonic implication we compiled 67 large earthquakes which occurred at and around plate boundaries for the last 140 yrs and classified them into four groups interplate strike slip events intraplate strike slip events underthrust events at island arc subduction zones and underthrust events at continental margin subduction zones for each group of earthquakes we examined relations between seismic moment m 0 fault length l fault width w and average fault slip d and found the following scaling laws in the case of interplate strike slip events the well known l cubed dependence of seismic moment breaks down when l exceeds 30 km because the extent of the seismogenic zone is limited in depth 12 km for large events l 30 km d and m 0 increase with l as d overline delta tau l mu left alpha l beta right and m 0 overline delta tau w l 2 left alpha l beta right respectively where the mean fault width bar w is 12 km and the mean stress drop overline delta tau is 1 8 mpa here and are structural parameters for intraplate strike slip events we obtained nearly the same relations except for significantly higher stress drop 3 1 mpa the difference in stress drop between interplate and intraplate events may be ascribed to the difference in stress accumulation rates and thus the recurrence time of earthquakes in the case of underthrust events at island arc subduction zones we also found the saturation of fault width bar w 120km and the breakaway from the l cubed dependence of m 0 for events larger than l 200 km if we consider the average dip angle of plate boundaries at island arc subduction zones to be 20 30 this indicates that the extent of the seismogenic zone in depth is limited to 40 60 km in the case of continental margin subduction zones on the other hand we could not find the saturation of fault width nor the breakaway from the l cubed dependence of m 0 from the analysis of the present data set w 200 km l 1000 km for sufficiently large earthquakes in general the downward rupture growth is limited to a certain depth due to the existence of a ductile unstressed region which extends under the brittle seismogenic zone since the brittle ductile transition occurs at 300 400 c the difference in the lower limit of the seismogenic zones between tectonically different regions may be attributed to the difference in thermal state there

empirical relationships between aftershock zone dimensions and moment magnitudes for plate boundary earthquakes in taiwan in this study we establish the empirical relationships between the spatial dimensions of the aftershock zones and moment magnitudes m w for the taiwan region the length l and width w of the aftershock zone of an earthquake is measured by the major and minor axes respectively of the ellipse of a two dimensional gaussian distribution of one day aftershocks our data is composed of 649 mainshocks depth 70 km m w 4 0 7 6 between 1990 and 2011 the relationships between aftershock zone dimensions and m w were obtained by least squares method with the corresponding uncertainties estimated by bootstrap our study confirms that aftershock zone dimensions are independent of faulting types and the seismic moment is proportional to l 3 the ratio w l increases slightly with m w and is independent of faulting types together with previous study our results suggest that earthquakes of both small m w 4 0 and large m w 7 0 magnitudes have similar focal zone geometrical parameters by using the m w s relation where the aftershock zone area s is estimated from l and w we also provide an independent examination of the variations in the median stress drop we find that the median stress drops of strike slip earthquakes are higher than those of thrust events moreover the median stress drops are independent of the moment magnitudes for normal and strike slip events but decrease for large thrust events these results are consistent with the latest global observations regardless of faulting types the median stress drop decreases for larger 6 m w 7 6 and relatively deep depth 60 70 km earthquakes online material effect of up dip rupture propagation on estimated maximum slip duration details on teleseismic and geodetic stations and figures of far field displacements temporal change in slip and snapshots of the semblance value distribution

how similar were the 1934 and 1966 parkfield earthquakes bakun and mcevilly 1984 showed that surface waves from the 1934 and 1966 parkfield earthquakes are remarkably similar this observation together with other seismic and geologic data led to the forecast of a repeat of a characteristic parkfield earthquake by 1993 in this paper we model near field geodetic measurements collected before and after the 1934 and 1966 parkfield earthquakes the slip in 1934 on the northwestern half of the rupture is poorly constrained due to the limited station coverage in this part of the rupture near the hypocenter the geodetic measurements permit the two earthquakes to have the same slip distribution on the other hand the data clearly show that the 1966 earthquake ruptured through the right step in the surface trace of the fault while the 1934 earthquake stopped northwest of the step if we assume only that the slip distribution is to some degree smooth we find that the centroid of the 1934 slip distribution could be as much as 10 km northwest of the centroid of the 1966 slip the data are consistent with but do not demand the largest slip in 1934 occurring in a region of low slip in 1966 the geodetically determined moments of the two earthquakes from smooth inversions are indistinguishable m0 4 4 0 4 1018 n m we also examine inversions in which we assume that the two earthquakes start identically and estimate how far down the fault the two earthquakes could have remained the same we find that the 1934 event could have had the same slip as in 1966 up to the fault step the 1934 earthquake must have stopped at the step whereas the 1966 event slipped southeast of the step in this quasi characteristic model m0 of the 1934 quake is only 60 of that in 1966 the difference presumably occurring as afterslip in 1966 if the 1934 geodetic moment was indeed less than in 1966 and the loading rate was constant this observation could explain the early occurrence of the 1934 earthquake

long period surface waves of four western united states earthquakes recorded by the pasadena strainmeter long period surface waves recorded on the north south pasadena strainmeter are used to determine the seismic moments and fault parameters of the 19 may 1940 imperial valley california the 16 december 1954 dixie valley and fairview peak nevada and the 18 august 1959 hebgen lake montana earthquakes synthetic strain seismograms are matched with the observed strainmeter seismograms source parameters from the strainmeter modeling are more consistent with source parameters estimated from geodetic and geologic information than parameters estimated from short period 15 sec body wave data long period surface wave moment estimates agree well with geodetic estimates of moment but are 1 5 to 5 times greater than moments obtained from modeling of teleseismic body waves or geologic information the imperial valley earthquake is best modeled as consisting of 5 point sources along a fault 87 5 km in length with a strike rake and dip of 326 180 and 90 the moment for the earthquake was 4 8 10 19 n m the synthetic seismogram that best models the fairview peak and dixie valley earthquakes assumes that the fairview peak earthquake was twice the size of the dixie valley event moments of 5 9 to 13 10 19 and 3 to 6 5 10 19 n m are obtained for these events a moment of 1 5 10 20 n m is obtained for the hebgen lake earthquake love waves of this earthquake are best modeled by a fault striking 102 although surface faulting produced during the earthquake strikes 130

the thickness of seismogenic layer under the areas surrounding the ordos block northern china a seismic approach was used to calculate the thickness distribution of the seismogenic layer under the block ordos in northern china this block was chosen because of its stability the complicated tectonics around its boundaries and the completeness of the data set several strong earthquakes occurred in this area in the 20th century with the largest one haiyuan m 8 4 1920 in the southwest of the ordos most of the large faults around the ordos are strike slip ones the breaking point i e the saturation of earthquake magnitudes m c of the self similarity from small to large events based on the gutenberg richter relation is calculated under the assumption of the l model which expresses that the offset is proportional to the length of the fault scholz 1982 1990 1994 the thickness w c of the seismogenic layer is directly related to m c to display smoothly the change of the thickness of the seismogenic layer and to ensure the reliability of the results a moving cell of 150 events with a moving step of 0 1 degree was adopted to take advantage of the existing data set the mean value method which is based on the latest complete data information to make the existing data set a complete one was used to extrapolate it so that the data covers the whole time period the results show that the average thickness of the seismogenic layer in the southwest in the northwest and in the east of the ordos is around 30 9 and 17 km respectively the thickness generally decreases from the southwest to the northeast this kind of spatial variation is in agreement with the maximum depth distribution of large amounts of microearthquakes with the correlation coefficient to be about 0 88 and the moho depth

complexity of seismicity due to highly rate dependent friction we study a simple antiplane fault of finite length embedded in a homogeneous isotropic elastic solid in order to understand the origin of seismic source heterogeneity in the presence of nonlinear rate dependent friction all the mechanical properties of the medium and friction are assumed to be homogeneous starting from a heterogeneous initial stress distribution we apply a slowly increasing uniform stress load far from the fault and we simulate the seismicity for more than 20 000 events in some cases the style of seismicity produced by this model is determined by a control parameter which measures the degree of rate dependence of friction for classical friction models with rate independent friction no complexity appears and seismicity is perfectly periodic for weakly rate dependent friction seismicity becomes slightly nonperiodic but most events are still characteristic earthquakes when friction is highly rate dependent seismicity is completely irregular and ruptures of all sizes occur inside the fault highly rate dependent friction destabilizes the healing process producing premature healing of slip and partial stress drop premature healing causes rupture to take the form of narrow propagating slip episodes the so called heaton s 1990 pulses partial stress drop produces large variations in the state of stress which in turn produce earthquakes of different sizes we make the conjecture that all models in which static stress drop is only a fraction of the dynamic stress drop produce stress heterogeneity

scaling of fault parameters for continental strike slip earthquakes the long standing conflict between the predictions of elastic dislocation models and the observation that average coseismic slip increases with rupture length is resolved with application of a simple displacement depth function and the assumption that the base of the seismogenic zone does not result from the onset of viscous re laxation but rather a transition to stable sliding in a medium that remains stressed at or close to failure the resulting model maintains the idea of self similarity for earth quakes across the entire spectrum of earthquake sizes

surface displacements in the 1906 san francisco and 1989 loma prieta earthquakes the horizontal displacements accompanying the 1906 san francisco earthquake and the 1989 loma prieta earthquake are computed from geodetic survey measurements the 1906 earthquake displacement field is entirely consistent with right lateral strike slip on the san andreas fault in contrast the 1989 loma prieta earthquake exhibited subequal components of strike slip and reverse faulting this result together with other seismic and geologic data may indicate that the two earthquakes occurred on two different fault planes

the 23 may 1989 macquarie ridge earthquake a very broad band analysis we use data from the geoscope global seismograph network to determine source parameters for the 23 may 1989 macquarie ridge earthquake by moment tensor inversion of long period surface waves we obtain a seismic moment of 1 8 2 4 1021 n m which makes this the largest seismic event to have occurred worldwide since the 1977 sumba earthquake the focal mechanism shows pure right lateral strike slip motion on a plane parallel with macquarie ridge and the pacific australian plate boundary the mechanism is consistent with the strike slip motion predicted for this area from relative plate motion models we invert broad band teleseismic p and sh waveforms to determine source complexity using the results from the long period analysis as a priori soft constraints the broad band waveforms show that the release of seismic energy was concentrated in the first 30 s of seismic rupture but fault slip continued for more than 60 s lack of directivity in the long period and broad band waveforms indicates that the rupture propagated bilaterally or vertically from the nucleation point

thermal cracking of kerogen in open and closed systems determination of kinetic parameters and stoichiometric coefficients for oil and gas generation abstract the purpose of the study is to compare artificial maturation of kerogens representative of the main types of organic matter kerogen types i ii ii s and iii in open and anhydrous closed pyrolysis systems the generated compounds are fractionated according to their thermal stability into six chemical classes c 1 c 2 c 5 c 6 c 14 c 15 saturates c 15 aromatics and nsos which include resins and asphaltenes in both systems primary cracking of kerogen can be described by two main reactions oil generation together with early gas generation followed by late gas production mass balances obtained in the two pyrolysis systems are reasonably similar although some secondary cracking of the nsos and underestimation of methane potential due to incomplete pyrolysis may occur in the open system kinetic parameters of thermal cracking are derived from experiments in the open system using an optimization procedure which determines a unique frequency factor and a weight distribution of chemical classes for a discrete series of activation energies the resultant frequency factors are checked with those obtained for specific molecular tracers such as n c 12 and n c 24 alkanes generated from kerogens in open and closed systems under isothermal conditions the results show that using a unique frequency factor as determined by optimization is correct for type i ii and ii s kerogens this factor is more questionable however when the distribution of activation energies is very broad such as for type iii coals based on this study a strategy for determination of kinetic parameters on any new source rock sample is proposed

the effect of slip variability on earthquake slip length scaling summary there has been debate on whether average slip d in long ruptures should scale with rupture length l o rwith rupture width w this scaling discussion is equivalent to asking whether average stress drop w hich is sometimes considered an intrinsic frictional property of af ault is approximately constant over a wide range of earthquake sizes in this paper we examine slip length scaling relations using a simplified 1 d model of spatially heterogeneous slip the spatially heterogeneous slip is characterized by a stochastic function with a fourier spectrum that decays as k w here k is the wavenumber and is a parameter that describes the spatial smoothness of slip we adopt the simple rule that an individual earthquake rupture consists of only one spatially continuous segment of slip i e earthquakes are not generally separable into multiple disconnected segments of slip in this model the slip length scaling relation is intimately related to the spatial heterogeneity of the slip linear scaling of average slip with rupture length only occurs when is about 1 5 which is a relatively smooth spatial distribution of slip we investigate suites of simulated ruptures with different smoothness and we show that faults with large slip heterogeneity tend to have higher d l ratios than those with spatially smooth slip the model also predicts that rougher faults tend to generate larger numbers of small earthquakes whereas smooth faults may have a uniform size distribution of earthquakes this simple 1 d fault model suggests that some aspects of stress drop scaling are a consequence of whatever is responsible for the spatial heterogeneity of slip in earthquakes

evidence for self similar triangular slip distributions on earthquakes implications for earthquake and fault mechanics we characterize average slip distributions on earthquakes beyond their individual heterogeneity for that we analyze a large number of seismic slip distributions both measured at the surface after earthquakes 44 profiles and derived from slip inversion models 76 models investigating the overall shape of these slip profiles we find that they are roughly triangular both along strike and dip and most of them 70 80 are asymmetric long linear slopes and high slip gradients therefore are the key ingredients to describe earthquake slip profiles the scaling relations between maximum displacement and length or width suggest furthermore that the triangular slip profiles are self similar such slip patterns make earthquakes dominated by one major zone of maximum slip hence one major asperity analyzing the position of hypocenters with respect to these asperities we find that earthquakes nucleate at a distance from them that averages 20 30 of their total length compiling observations on 56 earthquakes we show that this distance i e the asperity size is structurally defined we then compare the earthquake slip profiles to cumulative slip profiles measured on long term faults of various ages and sizes and find that all profiles have a similar shape triangular and asymmetric hence combining data for a large number of earthquakes leads to point out average generic characteristics of the coseismic slip that are similar to those that emerge from the accumulation of events with time on a single fault this suggests that these characteristics result from robust physical properties

why large earthquakes do not nucleate at shallow depths although by definition tectonic earthquakes may nucleate anywhere within the seismogenic layer in almost all cases those earthquakes that become large nucleate near the base of the seismogenic layer because frictional strength and stress drop should increase with depth and in situ stress measurements suggest that the ambient stress increases with depth we have examined spontaneous rupture models with gradients of both average stress drop and average strength relative to ambient stress to determine whether this explains the observed phenomena we report here that ruptures that are nucleated with in the low stress drop shallow regions of the model are inhibited from propagating but those that are nucleated within the high stress drop regions can propagate over the entire fault plane

crustal deformation processes and the stability of the gutenberg richter relationship abstract global and regional surveys of earthquakes show that empirically determined b values of the gutenberg richter distribution are remarkably stable generally limited to values of 1 0 2 here i interpret observations from california new zealand and japan to suggest that the stability of the b value is a manifestation of a physical process specifically the tendency of crustal strains to organize along relatively discrete zones given a portion of the earth9s crust subject to a displacement field displacement is accommodated by a system of fault lengths that obey a power law distribution with continued displacement longer faults develop at the expense of shorter faults and take up an increasingly greater portion of the displacement budget shifts in regional displacement directions lead to reversals of these trends the changes in the ratio of long faults to short faults in a region is thus accompanied by changes in the relationship between fault length and fault slip rate because the recurrence of earthquakes on faults is a function of both fault length and fault slip rate the deformation process may result in a system of feedback that inhibits changes in the b value as fault populations change a corollary to the idea is that the magnitude frequency statistics of seismicity may be attributed to the same physical processes that are responsible for the development of plate tectonic boundaries and the gross spatial distribution of seismicity around the globe

scaling of earthquake rupture growth in the parkfield area self similar growth and suppression by the finite seismogenic layer 1 we propose a new framework on the scaling of earthquake rupture growth time history and we scale the moment rate and the cumulative moment functions of earthquakes over a wide magnitude range mw 1 7 6 0 in parkfield california the moment rate and the cumulative moment functions of the small and medium earthquakes mw 1 7 4 6 are derived by slip inversion analyses with the empirical green s function technique the moment rate functions of the investigated earthquakes except the mw 6 0 event are similar to each other increasing rapidly in the first half growth stage and decelerating in the latter half decline stage in the growth stage the cumulative moment functions are approximated by mo t nm 2 1017 t s 3 independent of the final size of the earthquakes the proportionality of the cumulative moment to the cube of time implies self similarity during earthquake rupture growth in the decline stage the cumulative moment function veers off the common rupture curve the mw 6 0 event also grows along the same rupture curve until 1 s after which the cumulative moment function is proportional to time from the onset itself this is because the finite seismogenic layer limits the vertical extent of dynamic rupture our method and results contribute to our understanding of earthquake source physics especially on earthquake rupture growth processes which may help to improve earthquake early warning techniques

toward a physical understanding of earthquake scaling relations in seismological literature there exist two competing theories the so called w model and l model treating earthquake scaling relations between mean slip and rupture dimension and between seismic moment and rupture dimension the core of arguments differentiating the two theories is whether the mean slip should scale with the rupture width or with the rupture length for large earthquakes in this paper we apply the elastic theory of dislocation to clarify the controversy several static dislocation models are used to simulate strike slip earthquakes our results show that the mean slip scales linearly with the rupture width for small earthquakes with a rupture length smaller than the thickness of the seismogenic layer however for large earthquakes with a rupture length larger than the thickness of the seismogenic layer our models show a more complicated scaling relation between mean slip and rupture dimension when the rupture length is smaller than a cross over length the mean slip scales nearly linearly with the rupture length when the rupture length is larger than a cross over length the mean slip approaches asymptotically a constant value and scales approximately with the rupture width the cross over length is a function of the rupture width and is about 75 km for earthquakes with a saturated rupture width of 15 km we compare our theoretical predictions with observed source parameters of some large strike slip earthquakes and they match up well our results also suggest that when large earthquakes have a fixed aspect ratio of rupture length to rupture width which seems to be the case for most subduction earthquakes the mean slip scales with the rupture dimension in the same way as small earthquakes

scaling relations of earthquake source parameter estimates with special focus on subduction environment abstract earthquake rupture length and width estimates are in demand in many seismological applications earthquake magnitude estimates are often available whereas the geometrical extensions of the rupture fault mostly are lacking therefore scaling relations are needed to derive length and width from magnitude most frequently used are the relationships of wells and coppersmith 1994 derived on the basis of a large dataset including all slip types with the exception of thrust faulting events in subduction environments however there are many applications dealing with earthquakes in subduction zones because of their high seismic and tsunamigenic potential there are no well established scaling relations for moment magnitude and length width for subduction events within this study we compiled a large database of source parameter estimates of 283 earthquakes all focal mechanisms are represented but special focus is set on large subduction zone events in particular scaling relations were fitted with linear least square as well as orthogonal regression and analyzed regarding the difference between continental and subduction zone oceanic relationships additionally the effect of technical progress in earthquake parameter estimation on scaling relations was tested as well as the influence of different fault mechanisms for a given moment magnitude we found shorter but wider rupture areas of thrust events compared to wells and coppersmith 1994 the thrust event relationships for pure continental and pure subduction zone rupture areas were found to be almost identical the scaling relations differ significantly for slip types the exclusion of events prior to 1964 when the worldwide standard seismic network was established resulted in a remarkable effect on strike slip scaling relations the data do not show any saturation of rupture width of strike slip earthquakes generally rupture area seems to scale with mean slip independent of magnitude the aspect ratio l w however depends on moment and differs for each slip type

surface faulting of the 1954 fairview peak ms 7 2 and dixie valley ms 6 8 earthquakes central nevada abstract the 1954 fairview peak earthquake was followed 4 min and 20 sec later by the dixie valley earthquake surface ruptures were distributed among six different faults that define a complex north trending zone 100 km long and over 15 km wide the rupture sequence progressed from south to north the initial event produced a 32 km rupture of right oblique slip along the east dipping fairview fault where the components of right lateral offset and vertical separation reached 2 9 and 3 8 m respectively the northernmost ruptures occurred during the subsequent event along a 46 km portion of the east dipping dixie valley fault where the sense of slip was normal and reached a maximum vertical separation of 2 8 m average surface offset for both events is about 1 2 m the west dipping west gate louderback mountains and gold king faults also ruptured during the earthquake sequence these faults form a complex structural linkage within a 15 km left step that separates the surface traces of the fairview and dixie valley faults the west dipping faults likely played an important role in the redistribution of static stress from the fairview peak earthquake and subsequent triggering of the dixie valley earthquake right lateral offsets of more than a meter occurred along both the west gate and louder back mountains faults slip was limited to normal motion of 1 m or less along the gold king fault the change from right oblique motion along the fairview fault to pure normal motion on the dixie valley fault may reflect the transition from principally northwest extension in the south to more westerly extension in the north alternatively slip at the latitude of the dixie valley fault may be partitioned between pure normal slip along the dixie valley fault and strike slip motion on faults immediately to the west observations of fault dip provide insight to the complex three dimensional geometry of the rupture sequence of particular note a significant section of the dixie valley fault appears to be characterized by dip angles as low as 25 at the surface slip variation or earthquake endpoints do not generally appear to have been influenced by changes in bedrock type we do not observe systematic relations between slip variation and aspects of fault trace geometry such as salients and reentrants yet the relative competence of footwall bedrock appears to have influenced the long term development of large salients and reentrants along both the dixie valley and the fairview faults as well as the style of rupture along the southern portion of the dixie valley fault

earthquake slip distribution a statistical model 1 the purpose of this paper is to interpret slip statistics in a framework of extended earthquake sources we first discuss deformation pattern of the earth s surface from earthquakes and suggest that continuum versus block motion controversy can be reconciled by a model of the fractal distribution of seismic sources we consider earthquake slip statistical distributions as they can be inferred from seismic moment frequency relations and geometrical scaling for earthquakes using various assumptions on temporal earthquake occurrence these distributions are synthesized to evaluate the accuracy of geologic fault slip determinations and to estimate uncertainties in long term earthquake patterns based on paleoseismic data because the seismic moment distribution is a power law pareto a major part of the total seismic moment is released by major earthquakes m 10 19 5 n m moment magnitude m 7 for these large earthquakes the rupture is confined to the upper brittle crust layer we review the various moment frequency and earthquake scaling relationships and apply them to infer the slip distribution at area and site specific regions simulating the seismic moment and strain accumulation process demonstrates that some synthetics can be interpreted as examples of a quasiperiodic sequence we demonstrate the application of the derived slip statistical relations by analyzing the slip distribution and history of the san andreas fault at wrightwood california

on the scaling of slip with rupture length for shallow strike slip earthquakes quasi static models and dynamic rupture propagation we explore whether observations of average surface rupture properties among strike slip earthquakes reflect the underlying mechanics we compare the observed relationship between average slip and rupture length for 27 surface ruptures 18 plate boundary earthquakes and 9 away from transform plate boundaries with predictions from two families of uniform stress drop models purely elastic models with a rupture limiting locking depth predict a nonlinear relationship while a quasidynamic model with no locking depth predicts a linear relationship we explore whether observations of fault slip at the earth s surface distinguish which if either of these two families of models may be favored we find that the data provide insufficient constraints to rule out either a linear or a nonlinear relationship this might arise from uncertainties in the observations or from reasonable but unrecoverable variations in locking depths and uniform stress drops among earthquakes we advance an alternative interpretation that the complexity among the observations is consistent with dynamic rupture models featuring spatially varying stress drops

earthquakes quaternary faults and seismic hazard in california data describing the locations slip rates and lengths of quaternary faults are the primary basis in this work for constructing maps that characterize seismic hazard in california the expected seismic moment m0e and the strength of ground shaking resulting from the entire rupture of each mapped fault or fault segment are estimated using empirical relations between seismic moment m0 rupture length source to site distance and strong ground motions assuming a fault model whereby the repeat time t of earthquakes on each fault equals m0e m0g where the moment rate m0g is proportional to fault slip rate it is observed that the moment frequency distribution of earthquakes predicted from the geologic data agrees well with the distribution determined from a 150 year historical record the agreement is consistent with the argument that the geologic record of quaternary fault offsets contains information sufficient to predict the average spatial and size distribution of earthquakes through time in california the estimates of t for each fault are the foundation for constructing maps that depict the average return period of 0 1g peak horizontal ground accelerations and the horizontal components of peak acceleration peak velocity and the pseudovelocity response at 1 period and 5 damping expected to occur at the level of 0 1 probability during a 50 year period of time a map is also formulated to show the probability that 0 1g horizontal ground accelerations will occur during the next 50 years the maps serve to illustrate the potential value of quaternary fault studies for assessing seismic hazard interpretation of available slip rates indicates that the largest and most frequent occurrence of potentially destructive strong ground motions are associated principally with the san andreas san jacinto calaveras hayward and ventura basin fault zones other regions of similarly high hazard may yet remain unrecognized this inadequacy results primarily from an incomplete data set numerous faults for example are mapped along the coastal region of northern california and within the modoc plateau but relatively few studies relating to fault slip rate are reported a similar problem exists for other stretches of coastal california where marine reflection studies provide evidence of active faulting offshore yet yield little or no information of fault slip rate geological and geophysical field studies can work to remove these deficiencies a concerted effort to locate and define rates of activity on all faults in california is the most promising means to further quantify present levels of seismic hazard in california

aggregate properties of fracture populations abstract empirical studies indicate that the individual attributes of both faults and extension fractures follow power law scaling aggregate properties of fracture populations are important in a variety of problems and can be specified in terms of the scaling parameters of individual fracture attributes development of an expression for an aggregate property requires consideration of a number of independent factors including the topologic dimension of the aggregate property the topologic dimension of sampling and the possibility of scaling changes for fractures that span some mechanically significant layer the riemann zeta function provides an alternative to integration for the analytical and numerical solution of aggregate problems previous work regarding aggregate properties of fracture populations has focused on the strain due to faulting new expressions are developed here for other aggregate properties of interest fracture surface area fracture porosity fracture permeability and shear wave anisotropy a general characteristic of these aggregate properties is that for most values of scaling exponents the aggregate properties are dependent on the size of the sampling domain this implies that the aggregate properties are scale dependent additionally it appears that fracture surface area is concentrated in the smallest fractures of many populations fracture porosity is concentrated in the largest fractures of most populations but not as strongly as fracture permeability which probably derives almost entirely from the largest fractures in populations

tectonics unexpected andean earthquakes great earthquakes along the western subduction zone boundary of the andes mountains in south america are expected measurements of surface motion along the eastern boundary highlight the potential for equally large earthquakes in the east

evidence for different scaling of earthquake source parameters for large earthquakes depending on faulting mechanism scaling relationships between seismic moment rupture length and rupture width have been examined for this purpose the data from several previous studies have been merged into a database containing more than 550 events for large earthquakes a dependence of scaling on faulting mechanism has been found whereas small and large dip slip earthquakes scale in the same way the self similarity of earthquakes breaks down for large strike slip events furthermore no significant differences in scaling could be found between normal and reverse earthquakes and between earthquakes from different regions since the thickness of the seismogenic layer limits fault widths most strike slip earthquakes are limited to rupture widths of between 15 and 30 km while the rupture length is not limited the aspect ratio of dip slip earthquakes is similar for all earthquake sizes hence the limitation in rupture width seems to control the maximum possible rupture length for these events the different behaviour of strike slip and dip slip earthquakes can be explained by rupture dynamics and geological fault growth if faults are segmented with the thickness of the seismogenic layer controlling the length of each segment strike slip earthquakes might rupture connected segments more easily than dip slip events and thus could produce longer ruptures than dip slip events of the same width

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

earthquake scaling fault segmentation and structural maturity abstract slip and length measurements on earthquakes suggest large stress drop variability we analyze an extended set of slip length measurements for large earthquakes m 6 to seek for the possible origin s of this apparent variability we propose that such variability arises from earthquakes breaking a variable number of major fault segments that number depends on the strength of the inter segment zones which itself depends on the structural maturity of the faults we propose new d max l parameterizations based on that idea of multiple segment ruptures in such parameterizations each broken segment roughly scales as a crack while the total multi segment rupture does not stress drop on individual segments is roughly constant only varying between 3 5 to 9 mpa the slight variation that is still observed depends on fault structural maturity more mature faults have lower stress drops than immature ones the new d max l functions that we propose reduce uncertainties with respect to available relationships they thus provide a more solid basis to estimate seismic hazard by integrating fault properties revealed by geological studies

a reappraisal of large earthquake scaling abstract twelve years ago i pointed out that observations indicate that the slip in large earthquakes scales with their length rather than their width as expected from the canonical model romanowicz 1992 has recently argued that more recent data show that the opposite is true which has obliged me to re examine the question i point out here a defining flaw in her analysis in that she allowed mo the moment at the cross over from small to large earthquakes to be a free variable in her curve fitting whereas this parameter can be defined independently when this parameter is independently fixed i find that the up dated data set confirms my earlier conclusion that for large crustal earthquakes m0 scales with l 2 a little over a decade ago i pointed out that obser vations indicate that the slip in large earthquakes scales with their rupture length scholz 1982 several sub sequent papers provided additional data supportive of this view chen and molnar 1983 shimazaki 1986 scholz et al 1986 large earthquakes are defined in this con text as those that rupture the entire seismogenic thick ness w0 and are thus constrained to propagate farther in a horizontal direction only for crustal earthquakes w0 is nearly constant 15 km so this scaling conflicts with conventional models of earthquakes such as dislocation models because they predict that slip scales with width which is invariant for these earthquakes i offered two alternative ways to interpret these observations one is that such conventional w models are correct but that stress drop could no longer be regarded as scale invariant but must scale with fault length as an alternative i sug gested the possibility of what i termed an l model in which slip intrinsically scales with fault length this created a minor crisis in seismology which has yet to be resolved it is no exaggeration to say that my l model suggestion has not attracted a noticeable coterie of admirers nor has my other suggestion and there has been no other model proposed in the interim that ex plains the observed l scaling although heaton 1990 has suggested a way in which length may scale with stress drop a variation of my w model scaling alternative in the face of this an alternative is to question the obser vations which is what romanowicz 1992 has recently chosen to do in her interpretation of an updated data set she concluded that seismic moment m0 scales lin early with rupture length l for large earthquakes which is consistent with w models and implies that slip u is scale invariant for large crustal earthquakes this great discrepancy with the earlier result she implies is due to the presence of superior modern measurements in the updated data set this issue has major implications both practical and theoretical and merits some debate here i present my own reappraisal of the data in which the conclusions are very different reappraisal of the data romanowicz s conclusions were based on a log log plot of m0 versus l for a data set of strike slip earth quakes she showed that the data in this figure could be better fit by two straight lines one with slope 3 in the lower scale range and one with slope 1 in the upper scale range than with a single line of slope 2 for small earth quakes which grow in both dimensions with l w m0 should scale with l 3 for large earthquakes where w has saturated at w0 and growth only occurs in the l di rection m0 should scale with l according to conven tional models hence the problem produced by my ob servation that m0 scales with l 2 for those events superficially then it appears that she has resolved the issue the problem however is that she has allowed the cross over length l which separates small from large earthquakes to be a free variable in her curve fitting ex ercise she thus obtains a cross over moment of 0 6 to 0 8 x 1020 n m which is appropriate for a rupture length of 60 to 70 km by adding an additional free parameter to the curve fitting one would expect a much better fit to be achieved the question is whether such a step is justified if small earthquakes grow with l w then the transition to large earthquakes defined as an event that ruptures the entire seismogenic thickness would be l w0 10 to 20 km for the data being studied this may be checked observationally because large earth quakes almost invariably nucleate near the base of the seismogenic layer das and scholz 1983 it follows that the transition to large earthquakes is at the length at which one begins to consistently see surface ruptures inspec tion of the earthquakes in romanowicz s 1992 figure 215

the rupture mechanism of the coyote lake earthquake of 6 august 1979 inferred from near field data the coyote lake earthquake ml 5 7 occurred within the dense network of seismic instruments of central california and was recorded by numerous accelerograph stations two of these stations located within the fault zone itself provide particularly remarkable records of the rupture process we use these data obtained in the immediate vicinity of the fault and the broadband seismograms recorded at berkeley about 100 km away from the epicenter to infer the velocity of propagation of the rupture the extent of the fractured area the rupture front geometry and other characteristics of the fracture mechanism in order to extract this information from the data we model the earthquake as a propagating dislocation starting at the hypocenter and spreading radially we compute the resulting ground motion at the receiver sites using the discrete wavenumber representation of green s functions bouchon 1981 the results yield a rupture velocity of 2 6 km sec a fault length of about 14 km and a fault slip of 15 to 20 cm they also show that the fault extends to shallower depth than indicated by the aftershocks the most important result is the finding that slip at any given location on the fault takes place in a very short time span and that simple uniform dislocation models give a good description of the rupture process

linking short timescale deformation to long timescale tectonics one of the great successes of plate tectonics has been to provide a link between deformations of the lithosphere observed over widely varying timescales for example the slip between two plates as measured from young magnetic anomalies and hence averaged over the past 1 2 myr has been found1 3to be compatible with estimates obtained from slip during recent earthquakes despite the small time interval covered by the earthquake observations here we start from the idea4 5 that geological deformations are the long term cumulative trace of short term processes such as earthquakes so that the latter can be described as a high frequency noise for the former we return to a theoretical framework6 introduced to model large scale and long term tectonics based on a nonlinear diffusion equation but here explicitly associate the noise term with earthquakes the observed power law relationship between earthquake frequency and magnitude together with an assumption that strain is on average scale independent leads to the prediction that the largest earthquakes will have a gutenberg richter b value of 1 5 as has recently been reported for large mw 7 earthquakes worldwide7

the 1987 1992 gulf of alaska earthquakes abstract we present a study of the 1987 1992 gulf of alaska earthquake sequence using relocated seismicity data together with body wave analysis of selected larger events most of the sequence is located on a n s trending fault directly south of the yakataga seismic gap and consists of four main events of mw 7 2 7 8 7 7 and 6 8 and associated aftershocks the first earthquake is of left lateral strike slip type on an ene wsw trending fault the second event is a right lateral strike slip earthquake on the n s trending fault the fault plane of the third strike slip event was identified as an ene wsw trending fault located to the south of that for the first event in a previous study using body wave analysis we show that though the body wave study cannot unambiguously identify the fault plane the temporal development of the seismicity together with the pattern of aftershock distribution on the conjugate fault suggests that this event also occurred on the n s trending fault and is of right lateral type the seismicity on the conjugate fault is interpreted as being triggered by the increase of the shear stress in the direction of the normal to the fault plane due to the main shock the occurrence of the fourth main shock a right lateral strike slip event in 1992 which itself can be considered an aftershock of the 1987 1988 sequence with epicentres distributed along a n s trending fault favours this conclusion the first three events of the sequence have been described in earlier studies as having too short a rupture length for their seismic moment if the rupture lengths inferred from the aftershock zones in this study are used we find that this is not the case the events in the 1987 1992 sequence lie along magnetic anomaly 13 and related conjugate fracture zones indicating that the oceanic crust is rupturing along pre existing zones of weakness in response to plate boundary stresses at the southern end the seismic activity terminates near a seamount which rises 1 km above an otherwise relatively low relief ocean floor and close to a fracture zone perpendicular to the n s trend of the earthquake sequence suggesting that the n s striking rupture along the n s trending fault is terminated here by a barrier at the northern end the sequence terminates at the alaska trench near the yakataga seismic gap where there is a right lateral offset in the bathymetry along the transition fault this offset also being visible on the gravity map of the region thus this offset has the same right lateral sense as the n s trending strike slip fault planes of three of the main shocks and suggests that though there was no significant seismic activity in this region of the gulf of alaska since 1964 faulting here has been active in the past

analysis of the relationship between seismic moment and fault length for large crustal strike slip earthquakes between 1977 92 we have used an uniform data set to determine the scaling relation between seismic moment m0 and fault length for 34 large crustal strike slip earthquakes in the period 1977 92 the seismic moments used were obtained by the centroid moment tensor analysis the aftershocks of each event were relocated in this study and the fault length estimated from their spatial extent for large events we find that in spite of some scatter in the data the trend of this uni form data set indicates that m0 c 2 our data set does not show any obvious change of slope around m0 6 8 x 102o n m as was seen in a previous non uniform data set in

earthquake size frequency relations from an analytical stochastic rupture model an analytical stochastic model of earthquake rupture is presented although the general formulation makes no a priori self similarity assumption scale independent earthquake size frequency esf statistics emerge from the interaction between fault strength heterogeneity and rupture mechanics the model also gives theoretical derivations for scale dependent esf statistics including gradual frequency saturation for small earthquakes and a continuum of possible transitions in the statistics of large earthquakes a model fault is characterized as a surface composed of a large number of asperities defined as small discrete contact surfaces of finite strength an earthquake rupture grows via successive asperity breaking subevents the probability of rupture to a certain size earthquake or greater is the total product of incremental rupture growth probabilities these are governed by a new asperity failure probability distribution derived as a mixture of weibull distributions by including fracture mechanics the resulting mixture distribution characterized by the scale and shape parameters and is written in terms of the rupture size the important difference between the mixture distribution and the weibull distribution is that the mixture results in power law esf statistics self similarity occurs when material heterogeneity and rupture mechanics are mutually tuned to give 1 frequency saturation for small earthquakes is shown to be a simple consequence of a general aseismic nucleation process the nucleation magnitude m defines the roll off point in esf statistics that occurs when the area of seismic rupture equals the area of precursory aseismic rupture growth by fitting the model to the parkfield earthquake data set m 0 9 is obtained the change in esf scaling for the transition from moderate to large earthquakes depends on the changes in stress at the growing rupture front the northern california earthquake data center seismicity data set is fitted for a transition at magnitude m 5 with 0 4 and 0 75 this result indicates that the change in the esf relation associated with the transition from moderate to large earthquakes in california and nevada is caused by surface rupture accompanied by partial width and slip saturation

a basin modeling study of the jafurah sub basin saudi arabia implications for unconventional hydrocarbon potential of the jurassic tuwaiq mountain formation abstract the middle upper jurassic organic rich carbonate mudrocks of the tuwaiq mountain formation in the jafurah sub basin of the central arabian basin have long been recognized as the source of hydrocarbons trapped primarily in upper jurassic carbonate reservoirs of saudi arabia e g giant ghawar field with the recent development of commercial hydrocarbon production from unconventional reservoirs in north america these organic rich carbonate mudrocks are now recognized as potential shale gas and shale oil plays three conventional source rock intervals the tuwaiq mountain tqmn hanifa and jubaila formations exist within the jurassic petroleum system of the jafurah sub basin the tqmn formation is being evaluated for shale gas and shale oil potential by saudi aramco because the tqmn fm holds excellent unconventional gas characteristics such as high total organic carbon content toc and low clay content and proper maturity window for oil and gas generation five wells representing the first unconventional gas exploration wells drilled in the jafurah sub basin have been selected for 1d and 2d basin modeling work the work was performed to investigate the burial and thermal maturity evolution of the tqmn formation in the jafurah sub basin the maturity of the tqmn formation in the study wells varies from 0 8 to 1 25 vre covering peak oil to wet gas generation stage despite only slight differences in present day burial depths the present day temperature gradients have been calculated to be higher at well locations where the source rock is at higher maturity modeling results suggest that higher temperature gradient areas of the basin probably has higher basement heat flow which leads to satisfactory match between measured and predicted maturity and temperature at present day this increased basement heat flow in areas of higher temperature gradient correspond to the interpreted change in crustal composition most likely granitic basement generating more radiogenic heat the modeling results suggest that tqmn source rocks started generating oil at about 100 ma and they reached the peak oil generation at about 70 ma present day they are in the wet gas generation window in the northern and eastern parts of the jafurah sub basin where the thermal gradients are 28 c km or higher the central and southwestern parts of the sub basin are cooler and here the tqmn source rocks are within the peak oil generation window the warmer parts of the sub basin have higher shale gas potential compared to the cooler parts of the basin we note that proper modeling and estimation of gas content in these source rocks and probably in unconventional resource estimation work in general some skilled modifications in basin modeling parameters are necessary variation of the oil saturation threshold is necessary until a gas saturation level equal to or higher than the gas adsorption capacity of the source rock is obtained otherwise modeling will lead to overestimation of the oil migration out of the source rock and thus the amount of the oil that can be retained and cracked to gas at higher temperatures will be miscalculated therefore the eventual gas content estimations will may be severely underestimated following our basin modeling study we note that improvement of the present day subsurface temperature data will be necessary in the future to estimate the maturity and shale gas potential of the tqmn source rocks in the jafurah sub basin

earthquake scaling relations for mid ocean ridge transform faults 1 a mid ocean ridge transform fault rtf of length l slip rate v and moment release rate can be characterized by a seismic coupling coefficient ae at where ae v is an effective seismic area and at l3 2v 1 2 is the area above an isotherm tref a global set of 65 rtfs with a combined length of 16 410 km is well described by a linear scaling relation 1 ae at which yields 0 15 0 05 for tref 600 c therefore about 85 of the slip above the 600 c isotherm must be accommodated by subseismic mechanisms and this slip partitioning does not depend systematically on either v or l rtf seismicity can be fit by a truncated gutenberg richter distribution with a slope 2 3 in which the cumulative number of events n0 and the upper cutoff moment mc dcac depend on at data for the largest events are consistent with a self similar slip scaling dc ac1 2 and a square root areal scaling 2 ac at1 2 if relations 1 and 2 apply then moment balance requires that the dimensionless seismic productivity 0 0 atv should scale as 0 at 1 4 which we confirm using small events hence the frequencies of both small and large earthquakes adjust with at to maintain constant coupling rtf scaling relations appear to violate the single mode hypothesis which states that a fault patch is either fully seismic or fully aseismic and thus implies ac ae the heterogeneities in the stress distribution and fault structure responsible for relation 2 may arise from a thermally regulated dynamic balance between the growth and coalescence of fault segments within a rapidly evolving fault zone

kerogen asphaltene sulfur relationships in sulfur rich monterey oils abstract monterey oils in the santa maria basin onshore and offshore are generally low maturity oils because of low thermal exposure relatively shallow burial for short times they are generated as heavy high sulfur oils because of the composition of the unusual type ii source kerogens which are exceptionally rich in organic sulfur 8 14 these high sulfur kerogens which we designate type ii s appear to generate oil at significantly lower thermal exposures than ordinary type ii kerogens with less than 6 s in contrast to common type ii kerogens which generate oil largely by cleavage at oxygen bridge groups and carbon carbon bonds eliminating co2 h2o and hydrocarbon fragments type ii s kerogens have an additional complement of weak bonds associated with bound sulfur the preferential cleavage at weak sulfur linkages tends to produce larger fragments leading to high initial amounts of asphaltenes resins and sulfur rich aromatics together with smaller amounts of saturated hydrocarbons elemental analyses of monterey kerogens and asphaltenes clearly support the concept that the asphaltenes are essentially fragments of kerogen cleaved sufficiently to be soluble or peptized in this heavy oil system solubilization of asphaltenes is attributed to their interactions with the abundant resins and aromatics this sysstem is sufficiently stable under source and reservoir conditions to allow expulsion and migration for reasonable distance without significant fractionation or changes in gross properties initial asphaltenes have essentially the same atomic h c ratios as the source kerogen but have significantlyy lower o c ratios and slightly lower s c ratios the n c ratios are nearly the same for kerogens and their derived asphaltenes with increasing maturity the h c ratios in asphaltenes decrease much like maturation changes in kerogen the s c ratio also decreases significantly however the o c ratios initially low in asphaltenes and n c ratios increase slightly due to material balance caused by other losses these element composition and atomic ratio relationships allow some important inferences concerning source kerogen composition from analysis of asphaltenes alone this can be useful when potential source rock samples are not available for analysis and or when a choice between alternate source rock possibilities must be made

loading mechanism and scaling relations of large interplate earthquakes we have done a numerical simulation of tectonic loading at transform plate boundaries with a lithosphere asthenosphere coupling model subject to steady relative plate motion in this model a seismic fault is represented by a locked patch with a finite length on an infinitely long vertical dislocation surface cutting the entire lithosphere through the numerical simulation we have obtained the following results stress accumulation on the fault is partly due to viscous drag at the base of the lithosphere base loading and partly due to dislocation pile ups at horizontal edges of the fault edge loading if the viscosity of the asthenosphere is less than 1018 pa s the base loading is not effective since its rate exponentially decays very soon if the viscosity of the asthenosphere is greater than 1020 pa s both types of loading are effective and then the stress accumulation rate in the early stage of loading is formally written as d dt vpl a bl where vpl is a rate of relative plate motion and l is a fault length when the fault length l is small the effect of edge loading the second term is dominant and the stress accumulation rate is in proportion to the inverse of l when the fault length l is large the effect of base loading the first term becomes dominant and the stress accumulation rate is independent of l it is well known that the general l cubed dependence of seismic moment m0 breaks for large interplate earthquakes this break in the moment length relation can be ascribed to difference in loading mechanism between small and large earthquakes from the results of numerical computation if interplate earthquakes have the same stress drop regardless of their fault lengths we may derive a l squared dependence of m0 for large interplate earthquakes and a linear l dependence of m0 for very large interplate earthquakes

the macquarie ridge earthquake of 1989 summary a study of the seismicity on the central portion of the macquarie ridge before and after the 1989 may 23 macquarie ridge earthquake mw 8 2 and the solution of the inverse problem to obtain the moment release time history during the earthquake are presented the aftershock study shows that there were remarkably few and small aftershocks on the main fault the aftershocks were distributed along a 220 km portion of the india australia pacific plate boundary and indicate that the motion was bilateral on a vertical fault in addition the earthquake reactivated a 175 km section of a fault to its west which had been dormant since at least 1964 and 44 per cent of the aftershocks occurred on this feature moreover the largest aftershocks in the five month period following the event occurred not on the main fault plane but on the reactivated one based on available bathymetry gravity and magnetic anomaly data from the region this reactivated feature is interpreted as being an old oceanic fracture zone and hence a pre existing zone of weakness the aftershock distribution and their focal mechanisms are interpreted in terms of the tectonics of the region and suggest that a triangular piece of crust to the west of the macquarie ridge is being squeezed to the north and west the centroid moment tensor solution was obtained using both gdsn and geoscope data simultaneously it shows that the motion was primarily strike slip on a vertical fault with a moment of mo 1 5 x lo2 n m and a centroid depth of 19 5 km the moment release distribution and time history were obtained by inversion of broad band body waves recorded digitally by the gdsn and geoscope networks the rupture is found to be bilateral with the propagation first starting towards the north east and a few seconds later towards the south west the moment release was low in the hypocentral area with the higher areas of moment located towards the north east and south west of this the average rupture speed was approximately the shear wave speed no simple relation between the moment release pattern and the distribution of aftershocks on the fault plane was found instead the aftershock distribution is seen to be dominated by the intersection of the reactivated fault and the main fault plane with most aftershocks occurring to the north of this intersection

aftershock zones of large shallow earthquakes fault dimensions aftershock area expansion and scaling relations summary we determine the aftershock areas from relocated hypocentres for 64 dip slip and eight strike slip earthquakes in the period 1977 1996 together with those for three recent earthquakes the 1998 antarctic plate earthquake the 1999 izmit turkey earthquake and the 2000 wharton basin earthquake we also include the data for 27 strike slip earthquakes from pegler das 1996 we find that the location of the hypocentre is essentially random along strike for both strike slip and dip slip earthquakes subduction zone earthquakes appear to initiate more frequently towards the down dip edge of the fault whereas the non subduction zone dip slip earthquakes do not have any preferred depth of initiation the aftershock zones of subduction zone earthquakes often expand substantially along strike and up dip but far less in the down dip direction whereas those for non subduction zone earthquakes do not expand significantly in either the up or the down dip direction subduction zone thrust earthquakes have larger and more numerous aftershocks than earthquakes in all other tectonic settings for strikeslip earthquakes we find that slip increases at least linearly with length for dip slip earthquakes we find that the ratio of length to width increases systematically with length for lengths 40 km indicating that there is some restriction on fault width slip is found to be proportional to length over the moment range 10 17 nm m0 3r10 21 nm

changes in frequency size relationship from small to large earthquakes the constant b value observed in frequency magnitude distributions of earthquakes has been taken as an indication of self similarity at all magnitudes hence earthquake properties should scale uniformly in the same way from small to large earthquakes it has often been observed however that the seismic moment released in small earthquakes scales differently with rupture length than it does for large events1 2 where the crossover between small and large events is defined at a rupture dimension equal to the down dip width of the seismogenic zone a possible explanation for this contradiction is that frequency size distributions are biased by small earthquakes small events dominate most global earthquake catalogues because of the short time period covered another source of bias in size distributions is the saturation of earthquake magnitudes for large events here we correct biases in calculations of b values and present evidence for a change in b value in frequency size distributions we find that a break in self similarity from small to large earthquakes occurs at a point where the dimension of the event equals the down dip width of the seismogenic layer

scaling of intraplate earthquake recurrence interval with fault length and implications for seismic hazard assessment consensus indicates that faults follow power law scaling although significant uncertainty remains about the values of important parameters combining these scaling relationships with power law scaling relationships for earthquakes suggests that intraplate earthquake recurrence interval scales with fault length regional scaling data may be locally calibrated to yield a site specific seismic hazard assessment tool scaling data from small faults those that do not span the seismogenic layer suggest that recurrence interval varies as a negative power of fault length due to uncertainties regarding the recently recognized changes in scaling for large earthquakes it is unclear whether recurrence interval varies as a negative or positive power of fault length for large faults those that span the seismogenic layer this question is of critical importance for seismic hazard assessment

on moment length scaling of large strike slip earthquakes and the strength of faults 1 several large strike slip earthquakes have occurred in various tectonic settings in the past 5 years adding well documented data to the global collection of moment and length estimates for such earthquakes based on this augmented dataset we reexamine the controversial issue of scaling of seismic moment with length of rupture we find that the global dataset of large strike slip earthquakes follows a bi modal distribution most oceanic and or intraplate strike slip earthquakes have stress drops that are 5 times larger than interplate continental ones when distinguishing these two classes the scaling is compatible with that predicted by simple dislocation theory

scaling differences between large interplate and intraplate earthquakes a study of large intraplate earthquakes with well determined source parameters shows that these earthquakes obey a scaling law similar to large interplate earthquakes in which m 0 l 2 or u l where l is rupture length and u is slip in contrast to interplate earthquakes for which 1 10 5 for for the intraplate events 6 10 5 which implies that these earthquakes have stress drops about 6 times higher than interplate events this result is independent of focal mechanism type this implies that intraplate faults have a higher frictional strength than do plate boundaries and hence that faults are velocity or slip weakening in their behavior this factor may be important in producing the concentrated deformation that creates and maintains plate boundaries

on scaling of earthquake faults abstract scaling relations among seismic moment m 0 average displacement rupture width w and rupture length l of earthquake faults are studied mainly using the data base of earthquake source parameters compiled by wells and coppersmith 1994 results show that seismic moment scales with rupture length approximately as m 0 l 2 rupture width is independent of rupture length for large earthquakes average displacement relates to rupture length approximately as l and the average displacement is independent of rupture width consequently the l model proposed by scholz 1982 is more appropriate than the w model suggested by romanowicz 1992 to describe the scaling of earthquake faults

size distributions for large and small earthquakes small and large earthquakes obey different scaling laws and inhabit distinct populations both characterized by power laws with different exponents when considering earthquakes on a single fault or fault segment the one large earthquake that occurs during a seismic cycle is discontinuous with the population of small earthquakes here it is shown that these two observations together with the scaling laws are self consistent when proper account is taken of the size distribution of faults

scaling relations of strike slip earthquakes with different slip rate dependent properties at depth abstract empirical observations suggest that earthquake stress drop is generally constant to investigate the effect of rupture width on earthquake scaling relations we analyze synthetic seismicity produced by a 3d vertical strike slip fault model using two different profiles of frictional slip rate behavior below the seismogenic zone within the rate and state framework a relatively abrupt transition of the a b profile from velocity weakening to strengthening at the base of the seismogenic crust produces increasing slip and stress drop with increasing event size choosing a smoother transition allows large earthquakes to propagate deeper leading to similar slip length scaling but constant stress drop scaling our numerical experiments support the idea that the maintenance of constant stress drop across the entire range of observed earthquake magnitudes may be achieved by allowing coseismic slip to rupture to depths below the seismogenic layer

surface traces of the minnivellir rettarnes and tjorvafit seismic faults in the south iceland seismic zone segmentation lengths and magnitude of related earthquakes abstract accurate gps mapping and field measurements have been carried out along the surface traces of three n s right lateral historical and prehistorical seismic strike slip faults in the south iceland seismic zone the minnivellir tjorvafit and rettarnes faults we used these data and those previously collected on the selsund and leirubakki faults to characterise the faulting behaviour this study illustrates a characteristic multi scale segmentation including from the longer to the smaller fault elements i fault corresponding to the total length of the seismic fault ii fault segments iii arrays of fractures and iv individual fractures the most distinctive feature of such right lateral fault is its left stepping en echelon arrangement at various scales with push up structures accommodating the motion in the relay zones this study also highlights the role of the nature and thickness of the uppermost layer lava flow thin or thick grassy soil with respect to the type and length of fractures at the surface our mapping reveals complex fault geometry which however is consistent with the general left lateral transform behaviour of the south iceland seismic zone some left lateral conjugate fault branches are present along these major right lateral faults and participate to the deformation the estimation of the strike slip offsets 1 3 2 m based on the analysis of push up structures allow to infer the total rupture lengths 45 70 km for these faults and to estimate the magnitudes 7 0 7 2 of the related earthquakes bringing confirmation that events significantly larger than those of june 2000 ms 6 6 have occurred in the sisz which plays an important role for the seismic hazard assessment

source parameters of the 1 october 1995 dinar turkey earthquake from sar interferometry and seismic bodywave modelling abstract the 1 october 1995 m s 6 1 dinar earthquake ruptured a 10 km section of the nw se dinar civril fault there are discrepancies between the published source parameters from seismic data with seismic moments in disagreement by over a factor of two we use both sar interferometry and seismic bodywave modelling to determine earthquake source parameters an interferogram generated from ers 1 2 sar imagery spanning the event and separated by 5 months is used to derive source parameters by a downhill simplex inversion with multiple monte carlo restarts we model the displacements in the satellite line of sight initially using uniform slip on a rectangular dislocation in an elastic half space the resultant model fault plane agrees in strike and location with the observed surface break but systematic residuals exist in the line of sight deformation field resulting in a r m s residual of 20 mm in the interferogram the residuals are reduced if the depth distribution of slip is allowed to vary spatially in four segments along a continuous fault plane our best fitting solution with a r m s misfit of 8 mm reveals two distinct areas of slip on the fault plane strike 145 dip 49 rake 270 a main rupture slipping by 1 44 m between depths of 1 and 8 km becoming deeper to the se and matching the observed surface rupture and an along strike continuation to the nw of the same fault plane but between depths of 8 and 13 km and not associated with a surface break the total geodetic moment 4 5 0 1 10 18 nm is more than twice as large as published seismic moments based on the inversion of p waveforms alone but close to the harvard cmt moment 4 7 10 18 nm we use sh waveforms in addition to the p waves used previously to determine an alternative seismic source mechanism sh waves constrain the depth to be shallower than solutions based on p waves alone agreeing with the depths from the interferometric inversion and resulting in a larger moment 3 1 0 4 10 18 nm than the previous bodywave estimates 2 2 1 10 18 nm the cmt moment reduces in magnitude to a similar size 3 3 10 18 nm if the centroid depth and fault dip are constrained to the values determined from bodywave modelling and interferometry thus the geodetic moment is 40 bigger than the moment determined from seismology

scaling of the shear rupture process from nucleation to dynamic propagation implications of geometric irregularity of the rupturing surfaces a series of systematic high resolution laboratory experiments have been performed on the nucleation of propagating slip failure on preexisting faults having different surface roughnesses to demonstrate how the size scale and duration of shear rupture nucleation are affected by geometric irregularity of the rupturing surfaces on the basis of the experimental results it has been discussed theoretically how consistently scale dependent physical quantities inherent in shear rupture are scaled the experiments led to conclusive results that the nucleation process consists of two phases phase i an initial quasi static phase and phase ii a subsequent accelerating phase and that the nucleation process is greatly affected by geometric irregularities on the rupturing surfaces in phase i the rupture grows at a slow steady speed which is independent of the rupture growth length l in contrast during phase ii the rupture develops at accelerating speeds v which increase with an increase in l obeying a power law v vs l c n where vs is the shear wave velocity c is the characteristic length representing the geometric irregularity of the fault surfaces and and n are constants 8 87 10 29 and n 7 31 scale dependency of scale dependent physical quantities including the nucleation zone size and its duration is commonly ascribed to scale dependency of the slip dependent constitutive law parameter dc which is in turn governed by c it has been discussed that a unified comprehension can be provided for shear rupture of any size scale if the constitutive law for shear rupture is formulated as a slip dependent law

comment on on scaling relations for large earthquakes by b romanowicz and j b rundle from the perspective of a recent nonlinear diffusion equation linking short time deformation to long time tectonics

magnitude distributions and slip scaling of heterogeneous seismic sources abstract a series of numerical experiments have been conducted to explore effects of strength heterogeneity and rupture propagation upon the average slip and magnitude distributions of earthquakes alternative rupture processes were represented by two possible sets of rules controlling rupture propagation ruptures were run on faults having strong patches that break to form subevents with various assumed stress drops the subevents have a truncated power law size distribution the rules controlling rupture propagation in combination with the subevent stress drop have a strong effect upon the magnitude distribution the most realistic rupture model favors ruptures whose length and width are comparable and produces an increase in b value for events above magnitude 7 5 magnitude distributions similar to observations of global seismicity are produced by models with subevents that have a stress drop near 100 mpa the relationship between seismic moment and rupture area also agrees with observations of events not from subduction zones when the same model that fits the global magnitude distribution is adapted for a narrower fault width

seismic moment frequency relation for shallow earthquakes regional comparison we determine the parameter values for the seismic moment frequency relation using flinn engdahl s regionalization of global seismicity and the harvard centroid moment tensor data the earthquake size distribution is approximated by the gamma law a version of the gutenberg richter distribution with an exponential taper at the maximum moment there is no statistically significant variation of the fj value the analog of the b value for all seismic regions except for the midocean ridge systems for the latter regions fj 0 93 whereas for all other zones fj 0 63 the maximum moment mxg can be statistically evaluated only for subduction zones treated as a whole mxg 10 21 2 x 10 22 newton m which corresponds to the worldwide mxg value for other regions as well as for single subduction zones mxg is determined by comparing the number of events in each zone with the seismic moment rate calculated on the basis of the nuvel 1 model of plate motion for subduction zones we obtain the estimate of mxg which agrees with the statistical value giving evidence that most tectonic deformation is released by earthquakes we test the hypothesis that no statistically significant variation in mxg occurs in subduction and continent collision zones the hypothesis cannot be rejected with available data for the midocean ridges the mxg estimate cannot be unambiguously determined it is quite possible that the estimate is significantly biased because only a small part of tectonic deformation at the ridges is released by earthquakes these results have importance in evaluating seismic risk and may also lead to developing a physical theory for earthquake generation

comparison of earthquake scaling relations derived from data of the instrumental and preinstrumental era estimates of surface rupture displacement and magnitude for crustal earthquakes from the preinstrumental era pre 1900 tend to be greater than the corresponding estimates derived from modern scaling relations we investigate this tendency using an expanded and updated version of the earthquake dataset of wells and coppersmith 1994 to fit regression relations of moment magnitude on surface rupture length and rupture area and average surface displacement on surface rupture length separate relations are fitted to preinstrumental and instrumental data and the results compared to the equivalent relations of wells and coppersmith we find that our relations for instrumental data remove some but not all of the differences between the preinstrumental data and the relations of wells and coppersmith we attribute the remaining differences largely to natural censoring of surface displacements less than about 1 m and surface rupture lengths less than about 5 km from the dataset for the preinstrumental era because regressions constructed from similarly censored instrumental data are indistinguishable from the preinstrumental regressions since the regressions for our censored instrumental data i e restricted to moderate to large earthquakes are different from regressions for our complete dataset of instrumental earthquakes and from the regressions of wells and coppersmith both with a larger proportion of small to moderate earthquakes the results may indicate that large earthquakes have different scaling relationships from those of smaller earthquakes

note on scaling of peak ground acceleration and peak ground velocity with magnitude summary the theoretical scaling of near field peak ground acceleration and peak ground velocity with moment magnitude mw is found using an l model of rupture this scaling matches well with the magnitude scaling of recent attenuation relations

displacement and geometrical characteristics of earthquake surface ruptures issues and implications for seismic hazard analysis and the process of earthquake rupture there now exist about three dozen historical earthquakes for which in vestigators have constructed maps of earthquake rupture traces accompanied by de scriptions of the coseismic slip observed along the fault strike the maps and slip distributions are compiled here to place observational bounds on aspects of seismic hazard analysis and fault mechanics analysis leads to an initial statistical basis to predict the end points of rupture and the amount of surface slip expected at sites along the strike during earthquakes on mapped faults the observations also give support to the ideas that there exists a process zone or volume of about 3 4 km in dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes to this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike online material maps of surface ruptures digitized values and curve fits to surface slip distributions and notes and references for tables 1 and 2

influence of depth focal mechanism and tectonic setting on the shape and duration of earthquake source time functions source time functions of 255 moderate to great earthquakes obtained from inversions of teleseismic body waves by tanioka and ruff 1997 and coworkers were compared in a systematic way they were scaled to remove the effect of moment and to allow the direct comparison and averaging of time function shape as well as duration time function durations picked by tanioka and ruff 1997 are proportional to the cube root of seismic moment if moments from the harvard centroid moment tensor catalog are used the average duration of scaled time functions is shorter and the average shape has a more abrupt termination for deeper events than shallower ones with a distinct change occurring at 40 km depth the complexity of the time functions as quantified by the number of subevents appears to decrease below 40 km depth furthermore among events shallower than 40 km the average duration of scaled time functions is shorter and their average shape has a more abrupt termination 1 for events with strike slip focal mechanisms compared to thrust events and 2 for the few thrust events associated with an intraplate setting compared to the majority associated with an interplate subduction boundary in each of these cases events in more technically and seismically active settings have a longer duration and a more gradual termination this can be interpreted in terms of lower stress drops and or slower rupture velocities at active plate boundaries suggesting that fault rheology depends on slip rate and may evolve as total fault slip accumulates furthermore differences in average time function shape and duration associated with different subduction zones suggest that differences exist in the rheology on the plate boundaries at the various subduction zones supporting data table is available via web browser or via anonymous ftp from ftp kosmos agu org directory append username anonymous password guest subdirectories in the ftp site are arranged by paper number information on seraching and submitting electronic supplements is found at http www agu org pubs esupp about html