determination of space time structure of a deep earthquake source by means of power moments abstract for a planar shear earthquake source with monotonous slip at a given point power moments of the slip rate function provide a useful means of reconstructing a space time source structure in theory even a smoothed source function can be uniformly estimated power moments are linear functions of the processed data we have developed a practical technique for estimating the source power moment of degrees 1 and 2 from the body wave pulses of deep earthquakes the technique is applied to a moderate m b 5 7 event in the fiji islands we determined the source plane elongation direction length and duration values degree of asymmetry and possible rupture velocity most estimates are independent from any particular parametric source model although the haskell aki partly bilateral model agrees well with our observations

rupture dimensions of the 1998 antarctic earthquake from low frequency waves we inverted frequency dependent phase and amplitude measurements from 1st orbit rayleigh waves at global stations for the 1st and 2nd degree polynomial moments of the stress glut rate tensor the higher moments of the slip rate distribution determine the fault plane and approximate rupture dimensions the results show strong rupture propagation to the west with an average velocity of the instantaneous centroid of 3 6 1 km s the rupture had a characteristic length of 178 46 km in the east west direction and a characteristic duration of 48 2 s the results are consistent with unilateral rupture on the east west fault plane of the focal mechanism and rule out significant rupture on the north south nodal plane

contribution of radar interferometry to a two step inversion of the kinematic process of the 1992 landers earthquake we study the rupture process of the 1992 landers earthquake to limit the trade off between slip amplitude and rupture time that affects solutions using only seismological data we adopt a two step approach we first constrain the slip distribution and its uncertainty by independent geodetic data to recover in the second step the temporal details of the rupture propagation the first step consists of an inversion of interferometric data and global positioning system measurements both independently and together to constrain slip distribution on a three segment fault model along both strike and dip direction we use a genetic algorithm to test the uniqueness of the solution and a least squares formulation to find the model which best fits the data we conclude from the results of these geodetic inversions that interferometric data are rich enough to access the slip distribution in the case of the landers earthquake since the surface deformations are more sensitive to shallow slip in our configuration the slip amplitude is better resolved near the surface than at depth the resulting slip distribution is in agreement with geological observations at the surface and confirms the heterogeneous nature of the landers earthquake most of the slip occurs at shallow depths on the homestead valley fault second segment with a maximum value of around 7 m another high slip zone is observed on the johnson valley fault first segment at 8 km depth in the second step we invert strong motion data with the a priori final slip amplitude and its uncertainty deduced from geodetic data to constrain the time history of the rupture process this second step emphasizes a strong variation of the temporal development of the earthquake fast rupture front velocities appear within high slip zones and the rupture slows when it encounters a resistance along the fault on average the rupture front propagates with velocities close to the s wave velocity and terminates about 20 s after initiation the large variations in both slip amplitude and rupture velocity suggest that the rupture process is better described by successively breaking asperities than by a pulse propagating with constant velocity

the seismicity in the eastern marmara sea after the 17 august 1999 izmit earthquake we used seismic stations that we deployed after the izmit earthquake along the shores and islands of the izmit bay cinarcik basin to study the seismic activity that took place after the earthquake in the eastern marmara sea the aftershock distribution indicates the existence of three clusters of activity there in the days that followed the earthquake one of the clusters shows the extension of the e w trending izmit rupture into the eastern marmara sea the seismic activity there clearly outlines the fault plane of the main rupture and shows its termination 35 km beyond the hersek peninsula two other clusters of activity are present in the region one is in the armutlu peninsula and the other one is located a few kilometers southwest of the tuzla peninsula beneath the northern slope of the cinarcik basin the focal mechanism solutions indicate strike slip faulting along the main branch of the izmit rupture and normal faulting within the two swarms the presence of the different mechanisms suggests the existence of slip partitioning in the region a remarkable feature of the aftershock data is the absence of seismicity above 4 km in the marmara sea manuscript received 30 august 2000

deformation due to the 17 august 1999 izmit turkey earthquake measured from spot images the geometry of the ruptured areas and the coseismic slip distribution data are key to highlighting the behavior of seismic faults this information is generally retrieved from field investigations and geodetic measurements or synthetic aperture radar sar interferometry here we show that spot images can also be used to accurately map the fault zone and to determine the slip distribution by subpixel correlation of images acquired before and after an earthquake the measured slip includes the contribution of possible distributed shear that might not be clearly expressed in surface ruptures and smoothes out possible along strike variability due to near surface fault complexities we apply the technique to the m s 7 4 1999 izmit earthquake our results reveal a 100 m wide and very linear fault zone that can be traced for 70 km from golcuk to akyazi along which supershear rupture has been inferred the obtained slip distribution compares well with the field measurements and is consistent with ground deformation measured at some distance from the fault zone using sar images very little deformation was accommodated off the main fault plane maximum slip is observed near sapanca lake at a small fault jog that has probably influenced rupture propagation

evidence of nonlinear elasticity of the crust from the mw7 6 manyi tibet earthquake satellite synthetic aperture radar sar interferometry shows that the magnitude 7 6 manyi earthquake of 8 november 1997 produced a 170 kilometer long surface break with up to 7 meters of left lateral slip reactivating a n76 e quaternary fault in western tibet the radar interferometric map reveals asymmetric along strike displacement profiles between the two sides of the surface rupture a pattern that cannot be explained with linear elastic theory this observation suggests that the elastic moduli of the crust in tension and in compression are different because of the presence of cracks in the crust at shallow depth a model indicates that a ratio of 2 between compressive and tensile elastic moduli can account for the observed asymmetry a ratio that is consistent with laboratory and borehole measurements

the surface rupture and slip distribution of the 17 august 1999 izmit earthquake m 7 4 north anatolian fault the 17 august 1999 izmit earthquake occurred on the northern strand of the north anatolian fault zone the earthquake is associated with a 145 km long surface rupture that extends from southwest of duzce in the east to west of hersek delta in the west detailed mapping of the surface rupture shows that it consists of five segments separated by releasing step overs herein named the hersek karamursel golcuk izmit sapanca lake sapanca akyazi and karadere segments from west to east respectively the hersek segment which cuts the tip of a large delta plain in the western end of the rupture zone has an orientation of n80 the n70 80 e trending karamursel golcuk segment extends along the linear southern coasts of the izmit gulf between karamursel and golcuk and produced the 470 cm maximum displacement in golcuk the northwest southeast striking golcuk normal fault between the karamursel golcuk and izmit sapanca segments has 2 3 m maximum vertical displacement the maximum dextral offset along the izmit sapanca lake segment was measured to be about 3 5 m and its trend varies between n80 e and east west the sapanca akyazi segment trends n75 85 w and expresses a maximum displacement of 5 2 m the karadere segment trends n65 e and produced up to 1 5 m maximum displacement the karadere and sapanca akyazi segments form fan shape or splaying ruptures near their eastern ends where the displacement also diminished

new constraints on the rupture process of the 1999 august 17 izmit earthquake deduced from estimates of stress glut rate moments summary this paper illustrates the use of integral estimates given by the stress glut rate moments of total degree 2 for constraining the rupture scenario of a large earthquake in the particular case of the 1999 izmit mainshock we determine the integral estimates of the geometry source duration and rupture propagation given by the stress glut rate moments of total degree 2 by inverting long period surface wave lpsw amplitude spectra kinematic and static models of the izmit earthquake published in the literature are quite different from one another in order to extract the characteristic features of this event we calculate the same integral estimates directly from those models and compare them with those deduced from our inversion while the equivalent rupture zone and the eastward directivity are consistent among all models the lpsw solution displays a strong unilateral character of the rupture associated with a short rupture duration that is not compatible with the solutions deduced from the published models with the aim of understand this discrepancy we use simple equivalent kinematic models to reproduce the integral estimates of the considered rupture processes including ours by adjusting a few free parameters controlling the western and eastern parts of the rupture we show that the joint analysis of the lpsw solution and source tomographies allows us to elucidate the scattering of source processes published for this earthquake and to discriminate between the models our results strongly suggest that 1 there was significant moment released on the eastern segment of the activated fault system during the izmit earthquake 2 the apparent rupture velocity decreases on this segment

archaean basic volcanism in the eastern goldfields province yilgarn block western australia abstract petrographic petrological and geochemical studies have demonstrated the presence of three distinctive basic volcanic suites in the eastern goldfields province yilgarn block western australia these are termed the high magnesian series basalts hmsb the low magnesian series basalts lmsb and the siliceous high magnesian series basalts shmsb the hmsb and shmsb constitute differentiation series which contain both high mgo 9 5 14 wt and low mgo the hmsb and lmsb were derived from source mantle regions which were variably depleted in the incompatible elements archaean komatiites were derived from similarly depleted source regions and it is argued that the main petrogenetic difference between these three volcanic suites was the degree of partial melting from which they were derived the depleted nature of the source regions may have been induced by earlier small degree source mantle regions of the shmsb were variably enriched in the incompatible elements and water and parental magmas of the shmsb were derived from moderately hydrous conditions of partial melting the relative proportions of each basalt suite varies considerably between the layered successions examined for example the basic volcanics overlying the komatiites at kambalda are shmsb while the footwall volcanics consist predominantly of hmsb with subordinate lmsb however the norseman succession where no ultramafic volcanics are known to occur is comprised mainly of lmsb with a smaller proportion of hmsb

higher degree moment tensor inversion using far field broad band recordings theory and evaluation of the method with application to the 1994 bolivia deep earthquake summary we present a method to estimate parameters of the extended earthquake source using higher degree moment tensors at 27 centroid locations we show that a taylor series expansion of green s functions around a single centroid is not accurate enough when working with seismic wave periods and wavelengths in the range of the rupture duration and spatial extent of the fault respectively introducing a grid of 27 centroid locations on the fault and using higher degree moment tensors we are able to model adequately body and surface waves with periods and wavelengths smaller than the rupture duration and fault dimensions under simplifying assumptions an iterative inversion scheme is coded to estimate parameters of planar haskell type faults realistic inversion examples for deep and shallow earthquakes show that uni and bidirectional rupture models rupture direction fault and auxiliary plane and kinematic source dimensions and can be constrained with teleseismic body and or surface waves the application to the deep bolivia event indicates a subhorizontal fault plane unidirectional rupture to the north is slightly preferred the rupture duration of 25 s and fault dimensions of 47 25 km agree well with the estimates for the main pulse moment release given in other studies

triggered slip observations of the 17 august 1999 izmit turkey earthquake using radar interferometry we use synthetic aperture radar interferometry insar to map the displacement field of the 17 august 1999 izmit earthquake which largely conforms to that predicted for an elastic upper crust we determine the earthquake source parameters and show that slip continues farther west than the mapped fault ruptures we also show that additional sub surface displacements occurred on parallel strands of the north anatolian fault zone we argue that this was caused by changes in static stress accompanying the mainshock or by the dynamic release of regional stresses

determination of stress glut moments of total degree 2 from teleseismic surface wave amplitude spectra abstract a special case of the seismic source where the stress glut tensor can be expressed as a product of a uniform moment tensor and a scalar function of spatial coordinates and time is considered for such a source a technique of determining stress glut moments of total degree 2 from surface wave amplitude spectra is described the results of application of this technique for the estimation of spatio temporal characteristics of the georgian earthquake 29 04 91 are presented

predominance of unilateral rupture for a global catalog of large earthquakes the manner in which an earthquake rupture propagates across a fault reflects both the initial properties of the fault and the dynamical stresses produced by the rupture we quantify the propagation of an earthquake rupture using the second moments of the earthquake space time distribution in particular the second moments provide a simple way to differentiate between approximately bilateral and predominantly unilateral ruptures we determined the second moments for a catalog of m w 7 earthquakes that have occurred since 1994 the results show that approximately 80 of large shallow ruptures are predominantly unilateral our result agrees well with strong motion inversions from previous studies on moderate and large earthquakes the predominance of unilateral propagation in large earthquakes is explained by a simple characteristic earthquake model in which large events rupture an entire structurally defined fault segment and nucleation points are uniformly distributed along the fault the predominance of unilateral rupture may also be enhanced by the dynamic stress field produced by contrasts in the elastic properties between the two sides of plate boundary faults manuscript received 16 november 2001

complex source process of the 17 august 1999 izmit turkey earthquake broadband teleseismic p wave data at epicentral distances of 30 90 are inverted to retrieve the complex source process of the 17 august 1999 izmit earthquake a comparison of the waveforms of the mainshock with those of the aftershocks suggests a spatially complex rupture process having a duration of more than 45 sec inversion and modeling of broadband p waveforms are performed in this time window incorporating a priori field observations of coseismic displacements both single point and multiple point source representations are determined we found that the rupture process can be divided into at least three steps in the first step rupture initiated from the hypocenter and extended bilaterally along the e w striking fault with an almost pure right lateral strike slip motion the eastern portion of the rupture front passed through the sapanca lake and stopped around akyazi whereas the western portion stopped near hersek this step lasted for 22 23 sec releasing a total moment of 1 43 1020 n m the dislocation was concentrated briefly at two areas one near golcuk and the other between the sapanca lake and akyazi slip in these two areas was concentrated in the upper 10 km of the crust after 1 2 sec a second source started possibly initiating on an underwater fault west of hersek although its rupture lasted for almost 20 sec its moment release was very low just 0 17 1020 n m another 8 9 sec later the easternmost fault segment between akyazi and the area west of duzce was triggered with a rupture lasting for more than 15 sec producing little energy in the short period band with slip concentrated in a zone extending vertically 25 km to the surface and with a moment of 0 61 1020 n m manuscript received 22 september 2000

seismic imaging of the 1999 izmit turkey rupture inferred from the near fault recordings we use near fault accelerograms to infer the space time history of rupture on the fault during the izmit earthquake the records show that the ground displacement and velocity near the fault were surprisingly simple rupture propagated toward the west at a velocity of about 3 km s and toward the east at a remarkably high average velocity of 4 7 km s over a distance of about 45 km before decelerating to about 3 1 km s on the eastern segment slip on the fault is particularly large down to a depth of 20 km on the central portion of the fault where it reaches about 7 m slip is large also below 10 km on the eastern fault segment and this may have contributed to the loading of shear stress on the duzce fault on the western fault segment large slip seems confined to shallow depths

experimental study on lateral pile soil interaction of offshore tetrapod piled jacket foundations in sand recently tetrapod piled jacket tpj foundations have shown considerable promise in offshore developments due to the increases in power capacity and water depth for offshore wind turbines this p

coseismic and postseismic fault slip for the 17 august 1999 m 7 5 izmit turkey earthquake we use global positioning system gps observations and elastic half space models to estimate the distribution of coseismic and postseismic slip along the izmit earthquake rupture our results indicate that large coseismic slip reaching 5 7 meters is confined to the upper 10 kilometers of the crust correlates with structurally distinct fault segments and is relatively low near the hypocenter continued surface deformation during the first 75 days after the earthquake indicates an aseismic fault slip of as much as 0 43 meters on and below the coseismic rupture these observations are consistent with a transition from unstable episodic large earthquakes to stable fault creep sliding at the base of the seismogenic zone

the 1999 izmit earthquake sequence in turkey seismological and tectonic aspects the izmit duzce earthquake sequence is the largest sequence recorded by modern digital networks in the history of turkish earthquakes the m w 7 4 izmit mainshock occurred at 29 967 e and 40 729 n and 13 km depth at 00 hr 01 min 38 7 sec utc on 17 august 1999 and was preceded by at least eight immediate foreshocks of magnitude m l 3 0 aftershock locations show that a large region has become seismically very energetic following the mainshock and that most of the aftershock zone developed quickly in the first 3 days the distribution of the aftershocks illuminates numerous seismotectonic structures associated with the various branches of the north anatolian fault naf in the aftershock zone the seismicity pattern defines a rupture plane that extends about 80 km east and 75 km west of the mainshock epicenter confirming bilateral rupture during the mainshock the western aftershock activity is almost entirely located offshore extending along the axis of the izmit bay we show that the westernmost extent of the mainshock rupture reached the offshore region just 10 km south of the princes islands the dominance of strike slip motion is one of the main characteristics of the izmit sequence a number of significant aftershock clusters occur off the inferred mainshock rupture plane the spatial and temporal occurrence of these clusters show that they are triggered by the complex redistribution of stresses and dynamic strains imposed by the dislocation of the mainshock the focal mechanisms of the events located in the western end of the rupture zone show both strike slip and normal faulting mechanisms we infer that the yalova cluster was triggered by the mainshock the dominance of the normal faulting mechanisms supports the notion that dynamic extensional strains played a major role in triggering this cluster four events located off the princes islands indicate similar source mechanisms characterized by right lateral strike slip motion parallel to the strike of the northern boundary fault nbf and local trend of aftershock distribution this observation leads to a first order seismotectonic evidence that the nature of the nbf which is known to be a transtensional feature at the surface is dominated by strike slip motion at depth the coexistence of strike slip and extensional seismotectonic features in the sea of marmara highlights the importance of strain partitioning amongst shallow transtentional structures accommodating north south extension and deeper structures associated with the naf accommodating east west right lateral shear manuscript received 22 september 2000

source parameters and tectonic origin of the 1996 june 1 tianzhu mw 5 2 and 1995 july 21 yongden mw 5 6 earthquakes near the haiyuan fault gansu china summary the 1996 june 1 tianzhu mw 5 2 ms 4 9 and the 1995 july 21 yongden mw 5 6 ms 5 4 earthquakes are the two largest events recorded in the last 10 years between the 1990 october 20 ms 5 8 and the recent 2000 june 6 ms 5 6 earthquakes near the tianzhu seismic gap on the haiyuan fault in northeastern tibet we use frequency time analysis ftan to extract the fundamental modes of love and rayleigh waves from digital records a joint inversion of their amplitude spectra and of p wave first motion polarities is then performed to calculate the source parameters focal mechanisms depths and seismic moments of these two ms 5 earthquakes such a joint inversion is tested for the first time we use iris and geoscope network records for period ranges of 20 40 s for the former event and 35 70 s for the latter the inversion of the tianzhu earthquake yields nodal planes with strike dip and slip of 282 72 and 3 and 191 87 and 162 respectively a focal depth around 12 km and a seismic moment of 0 56 1017 n m consistent with the harvard cmt calculation and the alignment and depths of the aftershocks recorded by a local network we propose two possible tectonic interpretations for this off fault event the solution for the yongden earthquake is consistent with a thrust with strike dip and slip of 105 45 and 75 respectively a focal depth around 6 km and a seismic moment of 2 4 1017 n m also in agreement with the harvard cmt mechanism the distribution of the aftershocks recorded by a regional network and the general tectonic setting that we refine

joint inversion of insar and teleseismic data for the slip history of the 1999 izmit turkey earthquake the slip history of the izmit earthquake is investigated by jointly inverting sar and teleseismic data with a multi segment variable slip finite fault model surface offsets are used as an added constraint the highest slip values 5 to 7 m of right lateral displacement are associated with a strong central asperity surrounding the hypocenter the bilateral breaking of this main asperity which lasted about 10 sec dominates the source time function from the golcuk izmit area to lake sapanca a relatively good correspondence is observed between slip at depth and at the surface but farther to the west and to the east slip tends to be confined to the near surface slip in the easternmost part of the rupture duzce segment is not well resolved our analysis finds the insar and teleseismic data to be compatible and complementary this study shows the potential of the joint inversion of both data sets for a rapid determination of the spatio temporal history of large earthquakes

teleseismic inversion for the second degree moments of earthquake space time distributions summary determining detailed descriptions of the space time distribution of an earthquake s rupture using only teleseismic data is often a difficult and non unique process however a description of an earthquake that goes beyond a point source is often needed for many seismotectonic problems we have developed a method that inverts measurements of the shifts in traveltime and amplitude of various seismic phases at global stations for the second degree polynomial moments of an event s space time distribution our values for the second moments of the 1995 mw 8 0 jalisco mexico thrust event correspond to a characteristic rupture length of 121t10 km along strike a characteristic rupture width of 76t11 km downdip a characteristic duration of 29t2 s and a direction of rupture propagation along the strike of the subduction zone to the nw for the 1995 mw 7 2 gulf of aqaba earthquake our estimates of the second moments correspond to a characteristic rupture length of 53t2 km a characteristic duration of 12t1 s and rupture propagation to the ne along the strike of the dead sea transform our estimates of the first and second moments agree well with values from local seismic and geodetic networks for both the jalisco and aqaba events we are able to resolve the fault plane ambiguity associated with the events moment tensors using our estimates of the second spatial moment