an active deep marine strike slip basin along the north anatolian fault in turkey the tekirdag depression within the marmara sea in the mediterranean region is an active rhomb shaped strike slip basin along the north anatolian fault with a basin floor at a water depth of 1150 m new multichannel seismic reflection data and on land geological studies indicate that the basin is forming along a releasing bend of the strike slip fault and is filled with syntransform sediments of pliocene quaternary age the basin is bounded on one side by the north anatolian fault and on the other side by a subparallel normal fault which forms the steep submarine slope in cross section the basin is strongly asymmetric with the thickness of the syntransform strata increasing from a few tens of meters on the submarine slope to over 2 5 km adjacent to the north anatolian fault seismic sections also show that the slope forming normal fault connects at depth to the north anatolian fault implying that the basin is completely detached from its substratum the whole structure can be envisaged as a huge rather flat negative flower structure the releasing bend of the north anatolian fault responsible for the formation of the basin is flanked by a constraining bend along the constraining bend the syntransform strata are being underthrust implying a recent change in the direction of the regional displacement vector this thrusting is responsible for the uplift of the submarine slope to a height of 924 m possibly by a mechanism of elastic rebound regional geology suggests that most of the syntransform strata are lacustrine with only the topmost few hundred meters consisting of deep marine clays the anomalous present depth of the tekirdag depression is due to reduced quaternary sedimentation coupled with high rates of displacement along the north anatolian fault which amounts to 20 mm yr in the marmara sea region

formation and evolution of the tancheng lujiang wrench fault system a major shear system to the northwest of the pacific ocean abstract in the northwestern peri pacific tectonic belt on the continental margin of east asia there is a series of major faults trending ne nne i e the tancheng lujiang wrench fault system this fault system extends more than 5000 km with a width of 800 1000 km in the continent and a general strike of n30 e on the basis of the results of special research on the major faults and a lot of new information about the fault system the authors discuss early mesozoic triassic jurassic period sinistral transcurrent faulting in the different regions it is suggested that in the eastern continent of east asia the e w trending tectonic pattern of the paleozoic and beginning of the mesozoic appear in the nuclei of the sino korean continent massif and the yangtze continent massif these ancient continent massifs accreted both southwards and northwards which finally led to their collision and suturing to the angura continent massif later this tectonic framework was changed greatly by the tancheng lujiang wrench fault system along which left lateral horizontal displacement of 1000 1500 km took place since the mesozoic the dislocation and deformation of horizontal displacement of the tancheng lujiang fault system produced a series of structures trending ne nne in the continental margin which have greatly transformed the ancient structures of the preceding mesozoic this is an important diktyogenese in the continent of east asia during the horizontal displacement motion of these faults the folds nappes and decollement structures pull apart basins and subductions within the continent occurred in the continent at the same time some large sinistral ductile shear zones of horizontal displacement appeared the depth of the deformed horizon of ductile shear which belongs to simple shear was controlled by the tectonic element and distance away from the continental margin whilst the ductile shear deformation occurred the fault dynamo thermal metamorphism and the fault remelting took place and magma activity appeared within the continent in the mesozoic the fault zones used to be high energy zones and recently became the seismic belts within the continent formation of the tan lu fault system was due to the collision between the southern and northern blocks its large sinistral horizontal displacement in the mesozoic was closely related to the kula plate moving northwards therefore the continent disintegrated by shearing which produced some new terranes the shear edge belt was formed between the continent and ocean the change of relative motion between the continent and pacific ocean plate transformed the tan lu fault system into first extension and then compression clarifying the characteristics of the tan lu fault system is an important key in understanding the evolution of the east asia continent since the mesozoic

structural geometry and evolution of releasing and restraining bends insights from laser scanned experimental models experimental modeling is used to study the geometry and evolution of structures and related secondary faults along releasing bends and offsets and restraining bends on strike slip faults the controls of the relative positions of adjacent strike slip faults on the geometry of the structures and the difference in geometries between bends and offsets are investigated a new method of laser scanning is used to map the geometry and evolution of the structures and related faults the models show that oblique releasing bends connecting approaching faults result in spindle shaped basins whereas transverse bends result in more s shaped or rhomboidal basins offsets result in the distribution of strain over a wider area and a larger number of faults compared with preexisting bends which result in fewer well defined basin bounding faults secondary faults include r r and y riedel shears near the main strike slip faults and oblique normal faults in the center of the basin fault patterns exhibit en echelon geometries with a progressive step down into the deepest parts of the basin symmetric asymmetric and double basins may form in any of the structural settings depending on the slip distribution among faults on the basin margins for restraining bends oblique 45 bends connecting approaching faults result in spindle shaped uplifts whereas transverse or oblique 135 bends connecting overlapping faults result in more rhomboidal or rectangular uplifts the fold trends are at increasingly higher angles with the strike faults for transverse and oblique 135 bends secondary faults include en echelon reverse faults which typically form along the steep limbs of asymmetric uplifts normal faults which are transverse or oblique to the axis of the structure and r r and y riedel shears near the main strike slip faults the aspect ratios of the basins and uplifts increase with increasing displacement on the strike slip faults the results of these models can be used to interpret the structural and fault geometries in surface and subsurface structures formed along strike slip faults

rupture process of the 2002 mw 7 9 denali earthquake alaska using a newly devised hybrid blind deconvolution method this paper investigates the kinematics of the rupture process of the main event of the mw 7 9 denali alaska earthquake of 3 november 2002 a newly devised hybrid blind deconvolution method is applied to deconvolve teleseismic broadband s wave displacement recordings of the earthquake so as to determine the apparent source time functions astfs at 10 stations located around the epicenter the derived azimuthal angle of slip strongly indicates that the event ruptured unilaterally in an east southeasterly direction as determined by the calculated astfs the total duration of the rupture process was about 74 sec based on the images of the static slip dis tribution three slip concentrated areas were located at depths of less than 10 km maximum slip was about 13 4 m centered at 170 km east of the hypocenter and the average slip on the observed rupture area reached 4 1 m one concentrated rupture velocity area located at 160 180 km east of the hypocenter coincided with a slip concentrated area of maximum slip amplitude strongly suggesting that seismic energy was released rapidly a region of the fault along the strike direction with high rupture velocity 80 120 km also had very low levels of slip indicating that this portion of the fault may well have been relatively weak maximum and minimum rupture velo cities were respectively 3 32 and 2 64 km sec while the average rupture velocity was about 2 95 km sec based on the average rupture velocity and the source duration it is suggested that the principal rupture length of the denali fault must have been greater than 210 km

anatomy and evolution of a pull apart basin stellarton nova scotia the stellarton basin is a late paleozoic pull apart basin located close to the meguma avalon terrane boundary in the canadian appalachians at the stepover between the cobequid and hollow strike slip faults the basin contains 3 km of rapidly deposited pennsylvanian clastic sedimentary rocks representing lacustrine and deltaic environments extensively documented through coal related mining and drilling coal seams and oil shales allow stratigraphic correlation within the basin permitting reconstruction of basin subsidence and structural evolution coal seams represent approximately paleo horizontal surfaces thickness variations corrected for tilt and compaction in the most coal rich part of the basin fill show that the south basin margin subsided rapidly during deposition acting as a trap for coarse sediment and allowing coal forming mires to develop in the north abundant soft sediment deformation structures reflect synsedimentary tectonic activity north striking normal faults dissected the basin fill during and soon after deposition early in the diagenetic history contouring of mine plans allows fault heaves to be identified and also shows that both coal seams and faults were folded by east to northeast trending folds consistent with 1 an environment of deformation involving dextral strike slip motion and 2 clockwise rotation of fault blocks during progressive strain later north northeast striking contractional structures within the basin and a positive flower structure at the northwest margin probably represent a transition from transtension to transpression the basin illustrates the role of rotational progressive strain in the reorientation of structures generated during transtension it displays evidence for changes in tectonic style through time from transtension to transpression that may typify basins developed on major strike slip faults

temporal spatial rupture process of the 1999 chi chi earthquake from iris and geoscope long period waveform data using aftershocks as empirical green s functions a large earthquake m w 7 6 occurred near chi chi taiwan on 20 september 1999 utc and was followed by many moderate size aftershocks in the following days the two largest aftershocks with magnitudes m w 6 1 and 6 2 respectively were used as empirical green s functions egfs to retrieve the source time functions stfs and further image the temporal spatial rupture process of the mainshock for each station two types of stfs were retrieved one from p phases and another from s phases a total of 178 stf individuals were retrieved for source process analysis of the event from the stfs retrieved firstly similarities appeared on the stfs from most stations except that several stfs in special azimuths looked different or odd because of the focal mechanism difference between the mainshock and the egf aftershocks and secondly systematic shape variation with azimuth appeared the analysis of the stfs indicated that this event consisted of two subevents on the average the second event was about 7 sec later than the first one and the first event was about 15 larger than the second one in the moment release rate the total duration time of earthquake rupture process was about 26 sec from the image of the static slip distribution there were two slip concentrated areas on the fault plane and their centers were about 45 km away from each other the maximum slip of about 6 5 m appeared on the northern one the rupture area with the slip greater than 0 5 m was about 80 km long and 60 km wide the maximum stress drop was about 25 mpa 250 bar and the average stress drop on the entire fault was 9 2 mpa 92 bar from the snapshots of the temporal spatial variation of slip and slip rate the rupture initiated at the southern end and stopped at the northern end of the fault which suggested an overall unilateral rupture at a rupture velocity of about 2 5 km sec the depth of the initiation locus was about 20 km the rupture duration times on the subfaults were estimated a good correlation was noticed between the rupture duration time and slip amplitude of the subfaults the larger the slip amplitude the longer the rupture duration time of the subfault the maximum duration time for the subfaults was 16 sec which was about two thirds the total duration time of the earthquake rupture process in the beginning and near the end of the source process the rupture propagated like a self healing pulse of slip manuscript received 21 may 2001

teleseismic time functions for large shallow subduction zone earthquakes broadband vertical p wave records are analyzed from 63 of the largest shallow subduction zone earthquakes which have occurred in the circum pacific in the last 45 yr most of the records studied come from a common instrument the pasadena california benioff 1 90 seismometer propagation and instrument effects are deconvolved from the p wave records using a damped least squares inversion to obtain the teleseismic source time function the inversion has the additional constraint that the time function be positive everywhere the period band over which the time functions are considered reliable is from 2 5 to 50 sec fourier displacement amplitude spectra computed for each of the 1 90 p wave trains indicate spectral slopes measured between 2 and 50 sec of 1 0 to 2 25 with an average value of 1 5 these values assume an average attenuation of t 1 0 the seismic moments derived from the p wave time functions compare well with other published values for earthquakes having moments smaller than 2 5 10 28 dyne cm m w 8 2 because the 1 90 seismometer has little response at very long periods this technique underestimates the moments of the very largest events the time functions are characterized using five parameters 1 spectral slope between 2 and 50 sec 2 roughness of the time function 3 multiplicity of sources 4 pulse widths of individual sources and 5 overall signal duration the 63 earthquakes studied come from 15 subduction zones with a wide range in the ages of subducted lithosphere convergence rates and maximum size of earthquakes comparing the time function parameters with age rate and m w of the subduction zone does not yield obvious global trends however most of the subduction zones do behave characteristically and can be grouped accordingly

empirical green s function study of the january 17 1994 northridge california earthquake the january 17 1994 northridge main shock was analyzed using an empirical green s function approach to estimate the spatial and temporal distribution of fault slip far field source time functions obtained from seismograms recorded by the berkeley digital seismic network bdsn and terrascope stations reveal the distributed nature of the source and the presence of a second large subevent the location of the fault beneath the san fernando valley as well as the updip directivity of the rupture contributed to the locally heavy damage due to this earthquake

rapid creation and destruction of sedimentary basins on mature strike slip faults an example from the offshore alpine fault new zealand abstract seismic reflection profiles and multibeam bathymetric data are integrated to analyse the structure of the 25 km long strike slip dagg basin associated with the marine section of the alpine fault fiordland new zealand the basin is developing in almost 3000 m water depth at a releasing bend whilst contemporaneous transpression results in inversion of its southern end fiord derived glacio marine sediments flooded the basin during the last glaciation and provide a stratigraphic framework for structural analysis geometrical analysis enables an estimation of 450 1650 m of dextral displacement on the alpine fault at the releasing bend since the development of an unconformity estimated to have formed at between 30 and 110 ka this implies a dextral slip rate ranging from a possible minimum of 4 mm yr to the maximum of 35 mm yr constrained by the pacific australian plate motion rate despite total dextral displacement of 480 km on the alpine fault zone and a growth history spanning 15 20 myr this geomorphically well expressed and structurally complex strike slip basin developed and evolved rapidly during the late pleistocene and thus represents only the latest phase in the evolution of the alpine fault upward splaying structures within the fault zone exhibit a rapid spatial evolution in pleistocene strata which may reflect the interactions between high fault slip rate voluminous sedimentation supply inherited structural complexities in the basement rocks and deeper cover sequence and interactions between adjacent faults the present through going releasing bend at the northern end of the basin may have evolved from a more complex pull apart basin that developed between separate segments of the alpine fault the results from dagg basin illustrate the rates at which structural complexities and sedimentary basins can develop within highly active very mature through going continental wrench faults strike slip basins on the scale of 40 80 km 2 on such faults may be ephemeral features that can be developed and destroyed on a time scale of 10 5 10 6 years

transpressive duplex and flower structure dent fault system nw england abstract revised mapping along the dent fault northwest england has improved the resolution of folds and faults formed during variscan late carboniferous sinistral transpression a nne trending east down monocline comprising the fell end syncline and taythes anticline was forced in carboniferous cover above a reactivated precursor to the dent fault within the lower palaeozoic basement the taythes anticline is periclinal due to interference with earlier acadian folds the steep limb of the monocline was eventually cut by the west dipping dent fault the hangingwall of the dent fault was dissected by sub vertical or east dipping faults together forming a positive flower structure in cross section and a contractional duplex in plan view the footwall to the dent fault preserves evidence of mostly dip slip displacements whereas strike slip was preferentially partitioned into the hangingwall faults this pattern of displacement partitioning may be typical of transpressive structures in general the faults of the taythes duplex formed in a restraining overlap zone between the dent fault and the rawthey fault to the west the orientations of the duplex faults were a response to kinematic boundary conditions rather than to the regional stress field directly kinematic constraints provided by the dent and neighbouring variscan faults yield a nnw sse regional shortening direction in this part of the variscan foreland

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

tectonic evolution of the tancheng lujiang tan lu fault via middle triassic to early cenozoic paleomagnetic data the north striking tancheng lujiang tan lu fault is a conspicuous and controversial feature of the eastern asian landscape near the southeast extremity of the fault in anhui province we collected paleomagnetic samples at 17 middle triassic t2 and 10 upper cretaceous k2 to lower cenozoic e1 sites t2 remanent magnetizations are interpreted as primary in two of three areas the three areas are rotated 37 to 137 counterclockwise with respect to the south china block scb reference direction k2 e1 remanent magnetization directions pass regional fold and reversals tests and are not rotated with respect to surrounding areas counterclockwise rotation of t2 strata therefore ended before k2 and is attributed to left lateral shear acting along tan lu during the north china block ncb scb collision in shandong province 700 km north of the anhui sites four areas containing 33 upper jurassic j3 and cretaceous sites have negligible declination differences except for one which has dispersed directions the fold test is inconclusive for this latter area and positive for the other three regional concordance of the j3 e1 paleomagnetic data including paleolatitudes together with observed deformation patterns suggest that an extensional regime prevailed in the late cretaceous and cenozoic euler pole positions that constrain the north south china collision and account for tan lu motion suggest at least 500 km of sinistral shear took place along the fault and either 1 subduction and related ultrahigh pressure uhp metamorphism occurred near the present location of the qinling dabieshan and sulu uhp belts while tan lu acted as a transform fault that connected the two subduction zones or 2 tan lu and sulu were parts of the same transform fault system and no uhp rocks formed in situ at sulu in either case uhp rocks originally exhumed near dabieshan could have been transported by plate capture toward sulu along tan lu after north and south china impacted near dabieshan the tan lu fault grew within the scb as the dabieshan corner indented the scb causing folds in scb cover rocks to conform to the ncb margin late cretaceous to cenozoic reactivation of tan lu with both right lateral strike slip and normal fault motion occurred as the scb extruded east relative to the ncb under the influence of the india asia collision

revitalization of a mature oil bearing basin by a paradigm shift in the exploration concept a case history of bohai bay offshore china abstract the bozhong depression in bohai bay was previously ranked as an unfavorable exploration region due to concerns about reservoir trapping integrity and top seal risks in the mid 1900s a few explorationists began to view the petroleum accumulation conditions more positively they argued that rapid neogene subsidence could have generated a new suite of source potential and that recent continued fault movements may have provided the needed conduits for upward hydrocarbon migration they predicted the existence of lacustrine facies that could supply the needed lateral and top seals for the intensively faulted traps these radical thoughts were gradually formulated into a new concept for the neogene targets this paradigm shift in exploration concepts has since 1995 led to the discovery of nine 9 major oil fields with a combined in place reserves more than double those discovered in the previous thirty 30 years some of these neogene reservoirs appear to be at a dynamic balance between hydrocarbon escape and charge it is speculated that the required driving energy for the charge may have come from earthquake activities

stability of rapid finite fault inversion for the 2014 mw6 1 south napa earthquake local seismograms are useful for rapidly reconstructing kinematic finite fault sources but the results often depend not only on the data coverage but also on uncertainties of parameters e g hypocentral location and fault geometry used as a priori information during the inversion an automatic scheme was applied to offline tests for the 2014 south napa earthquake in the case of retrospective full waveform inversions a network with station spacing of 10 km within the epicentral distance of 30 km is able to provide adequate stable key source parameters if the preestimated hypocenter and fault orientation are accurate of 5 km and 15 respectively in simulated real time inversions the magnitude reaches mw6 0 at 13 s and the slip distribution matches that from the retrospective inversion at about 22 28 s after the origin time of the earthquake these results are meaningful for estimating the lead time of a catastrophic seismic event

early cenozoic two phase extension and late cenozoic thermal subsidence and inversion of the bohai basin northern china abstract the bohai basin is one of a family of early cenozoic extensional basins that lie along the eastern margin of asia from russia to vietnam initial extension was probably triggered by subduction roll back of the oceanic pacific plate from the asian continent there were two phases in the bohai basin s rift history the earlier paleocene early eocene phase resulted in the deposition of the kongdian formation and the fourth lowest member of the shahejie formation in a series of elongate half grabens these half grabens have master faults with a nne ssw orientation secondary normal faults are typically clockwise oblique to the master faults indicating a component of dextral transtension deposition was focused in the west and south of the present basin these rocks are mainly alluvial fan and fluvial red beds the architecture of the basin underwent an important change at ca 43 45 ma middle eocene beginning with the deposition of the third member of the shahejie formation in part these sediments were deposited in the same half grabens as the kongdian formation but the bozhong depression in the central part of the basin originated at this time and became the major depocentre the bozhong depression superficially resembles a pull apart basin it formed when continued transtension of the earlier tertiary fault systems to the east and west created an extensional overlap between them during this phase the basin as a whole had a geometry with elements typical of both pull apart and transtensional basins regional extension in many east asian basins ended at the end of the oligocene probably because of the onset of transpression within eastern asia caused by the collision of australia with the philippine sea plate dextral transpression caused minor inversion of some of the earlier normal faults in bohai but as a whole the basin began to subside in a post rift phase of thermal subsidence that has lasted until the present day

the sticklepath lustleigh fault zone tertiary sinistral reactivation of a variscan dextral strike slip fault dextral strike slip movement on the sticklepath lustleigh fault zone slfz is indicated by displacements of permian and older rocks previous authors have inferred that the main dextral movement which caused these displacements was post permian and noting the presence of small tertiary pull apart basins along the fault zone probably of tertiary age however the geometry of these early tertiary pull apart basins indicates sinistral rather than dextral strike slip movement we present an alternative model for the history of the sticklepath lustleigh fault zone summarized below 1 late variscan strike slip movement with a total displacement of up to 10 km produced the slfz and offset dextrally an earlier variscan thrust 2 extensional reactivation of this thrust led to rapid permo triassic subsidence in the crediton trough and a dextrally offset neighbour the hatherleigh outlier 3 approximately 6 km of early tertiary sinistral movement on the slfz produced small pull apart sedimentary basins and reduced the net dextral offset across the fault 4 in mid tertiary times minor dextral movements on the slfz may have produced reverse faulting on the margins of the tertiary basins

rupture characteristics of the three m 4 7 1992 1994 parkfield earthquakes slip on the san andreas fault was determined for three m 4 7 earthquakes using a tomographic inverse system beroza and spudich 1988 to invert seismic source time functions stfs from s waves stfs were obtained by deconvolving mainshock accelerograms by those from collocated smaller earthquakes accelerograms were from the u s geological survey parkfield small aperture array upsar and from a distributed array of digital accelerometer stations at parkfield eight or nine stfs are used in each of the three inversions stfs are typically symmetrical pulses with a duration of about 0 3 0 5 s in the inversion mainshock rise time was set to 0 05 s and we allowed the rupture time to vary slightly from a constant rupture velocity of approximately 0 85 rupture for all three events which are located in or close to the middle mountain preparation zone or box mmb quickly reaches a local maximum in slip and then propagates outward to peaks ridges or plateaus in the slip distribution slip for the october 20 1992 event located just inside the southern edge of the mmb propagates from an initial spike north and updip along a curving ridge for about 2 km the initial spike continued to grow in the november 14 1993 event located north of the october 20 1992 event just beneath the hypocenter of the 1966 parkfield earthquake which shows little directivity although there is a smaller patch of slip updip and to the south in contrast rupture for the december 20 1994 event located just south of the october 20 1992 event propagated north and slightly updip creating a rough plateau in slip a few kilometers wide on a side directivity for this event also is to the north directivity for all three events points in the approximate direction of the 1966 hypocenter small pulses which comprise a coda are found on the stfs for several seconds after the initial impulsive event several tests based on the assumption that the average of all stfs from upsar for each event is an estimate of the true slip at the source suggest that the codas in the stfs are s waves from a long duration source rather than uncorrected site response an initiation phase is found on the array average for the november 14 1993 and december 20 1994 events these precursory phases are the result of a spike in slip at the hypocenter a value of 2 4 4 mm is obtained for d c the slip weakening distance by interpreting the initial spike as a critical patch the few aftershocks for the october 20 1992 event are distributed to the north and updip of the mainshock but the november 14 1993 event had a strong burst of aftershock activity that propagated to the north of its hypocenter at roughly the same depth aftershocks of the december 20 1994 event are mostly updip the november 14 1993 event had the simplest slip distribution appeared to be the most impulsive and had the most active aftershock sequence and the greatest depth if the eventual parkfield earthquake initiates near the 1966 hypocenter then the directivity of the three events studied here will have pointed to it however it is certainly possible that both the initiation of characteristic parkfield shocks and the directivity of smaller events are controlled by fault properties on a larger scale such as by fault bends or jogs

recent large earthquakes near cape mendocino and in the gorda plate broadband source time functions fault orientations and rupture complexities the northward migration of the mendocino triple junction is associated with complex faulting within the gorda plate and in the convergent zone between the gorda and north american plates this region has experienced substantial recent large earthquake activity and quantification of these faulting processes is essential for understanding the evolution of the triple junction using an empirical green function deconvolution method for teleseismic and regional surface waves and body waves we obtain relative source time functions for the april 25 1992 cape mendocino thrust earthquake m w 7 2 its two large strike slip aftershocks on april 26 1992 m w 6 5 6 6 and two large strike slip events in the gorda plate that occurred july 13 1991 m w 6 8 and august 17 1991 m w 7 1 the removal of propagation effects using empirical green functions provides unusually detailed source rupture information and indicates that all the ruptures are less than 16 s in duration analyzing the directivity effects observed in the source time functions we resolve rupture directions and corresponding fault orientations for the four largest events and place some constraints on the smaller aftershock significant differences in the rupture duration and stress drop are observed between the cape mendocino mainshock and its two largest aftershocks the mainshock which ruptured westward on a shallow dipping plane either on or paralleling the interplate contact between the gorda and north american plates had a smooth 9 s long rupture with a 0 9 4 6 mpa static stress drop the two largest aftershocks occurred within the uppermost mantle of the gorda plate and have more complex ruptures with total durations of 14 15 s and static stress drops of less than 0 3 mpa perhaps reflecting a difference between mantle and crustal earthquakes in this region the aftershocks appear to have ruptured conjugate strike slip faults accounting for differences in their damage patterns the august 17 1991 gorda plate event ruptured a southwest striking fault while the july 13 1991 event ruptured a southeast striking fault with both events relieving north south compression within the deforming gorda plate the existence of multiple active faults in the region constitutes a significant earthquake hazard associated with the complex stress environment of the migrating triple junction

40ar 39ar dating of strike slip motion on the tan lu fault zone east china abstract ne trending sinistral ductile shear belts in the southern part of the tan lu fault zone east china are exposed along the eastern edge of the northern dabie belt and southern zhangbaling belt three hornblende three phengite and 12 biotite separates from greenschist facies mylonites in the shear belts were dated by the 40ar 39ar method in this study a hornblende plateau age of 143 3 ma is interpreted as representing the time of sinistral motion on the zhangbaling part of the tan lu fault zone seven biotite samples from the same part yield 40ar 39ar cooling ages from 137 to 125 ma a phengite plateau age of 138 8 ma from the eastern edge of the dabie belt is considered as being close to the time of deformation in the tan lu strike slip zone five biotite 40ar 39ar ages from 120 to 110 ma and one phengite age of 121 ma from the same area represent cooling ages after the sinistral faulting it is concluded on the basis of these 40ar 39ar ages that the sinistral ductile shear belts in the southern part of the tan lu fault zone were produced in earliest early cretaceous this sinistral motion on the tan lu fault zone is considered to be related to high speed highly oblique subduction of the pacific plate at this time

4d analogue modelling of transtensional pull apart basins abstract scaled sandbox models were used to investigate the 4d evolution of pull apart basins formed above underlapping releasing stepovers in both pure strike slip and transtensional basement fault systems serial sectioning and 3d volume reconstruction permitted analysis of the full 3d fault geometries results show that very different pull apart basins are developed in transtension compared to pure strike slip both types of models produced elongate sigmoidal to rhomboidal pull apart systems but the transtensional pull apart basins were significantly wider and uniquely developed a basin margin of en echelon oblique extensional faults dual opposing depocentres formed in the transtensional model whereas a single central depocentre formed in pure strike slip in transtension a distinct narrow graben system formed above the principal displacement zones pdzs cross basin fault systems that linked the offset pdzs formed earlier in the transtensional models sequential model runs to higher pdz displacements allowed the progressive evolution of the fault systems to be evaluated in cross section transtensional pull aparts initiated as asymmetric grabens bounded by planar oblique extensional faults with increasing displacement on the pdzs basin subsidence caused these faults to become concave upwards and lower in dip angle due to fault block collapse towards the interior of the basin in addition strain partitioning caused fault slip to become either predominantly extensional or strike slip the models compare closely with the geometries of natural pull apart basins including the southern dead sea fault system and the vienna basin austria

wrench related folding a case study of bohai sea basin china abstract wrench motion is relatively common in basins but often goes undetected because of its subtle structural imprint even so wrench related folding is of significance in petroleum exploration and development based on the riedel shear nomenclature we apply the model of wrench related folding to deformation in the bohai sea basin the folding related to r shears t tensional structural systems t systems and c compressive structural systems c systems in a riedel shear model are discussed the r system related folding results from differential movements between the two sides of fault blocks in map view the fold is oriented 90 2 in the initial deformation stage or more than 90 2 from the principle displacement zone pdz where is the angle of internal friction the t system related folding is related to the rollover of the hanging wall and in map view the fold is initiated at 45 from the pdz in the initial deformation stage the c system related folding is resulted from the compression induced by a wrench action in map view the fold was oriented 45 from initial deformation in the pdz bohai sea basin fold orientations fit our models and the wrench related folds play important roles in oil and gas accumulation

seismic characteristics and identification of negative flower structures positive flower structures and positive structural inversion negative and positive flower structures and positive inverted structures imply specific modes of formation and their distinctive characteristics make them important criteria for the identification of certain structural styles a negative flower structure from the andaman sea consists of a shallow synform bounded by upward spreading strands of a wrench fault that have mostly normal separations paralleling monoclines and oblique en echelon normal faults flank the divergent wrench fault a positive flower structure from the ardmore basin oklahoma consists of a shallow antiform displaced by the upward diverging strands of a wrench fault that have mostly reverse separations en echelon folds are present on either side of this convergent wrench fault flower structures may resemble extensional or contractional fault blocks on individual seismic profiles flower structures are identified by their unique internal fault and fold architecture by their association with a straight and throughgoing zone of deformation and by their lack of a consistent sense of separation or regional upthrown side positive structural inversion at the rambutan oil field south sumatra basin has formed a shallow anticlinorium and has partly uplifted the underlying graben deeper fault segments bounding the graben have retained their normal fault profiles but at shallow levels some of these faults have reverse separations similar changes of separation with depth may be produced by strike slip but sets of faults with listric profiles and nearby blocklike trend patterns identify the inversion as a dip slip event where correlation of reflections is uncertain or deep control is unobtainable positive inverted structures may also resemble contrational fault blocks detached normal fault assemblages and certain negative inverted structures

tectonics of strike slip restraining and releasing bends restraining and releasing bends are common but enigmatic features of strike slip fault systems occurring in all crustal environments and at regional to microscopic scales of observation regional scale restraining bends are sites of mountain building transpressional deformation and basement exhumation whereas releasing bends are sites of topographic subsidence transtensional deformation basin sedimentation and possible volcanism and economic mineralization because restraining and releasing bends often occur as singular self contained domains of complex deformation they are appealing natural laboratories for earth scientists to study fault processes earthquake seismology active faulting and sedimentation fault and fluid flow relationships links between tectonics and topography tectonic and erosional controls on exhumation and tectonic geomorphology this volume addresses the tectonic complexity and diversity of strike slip restraining and releasing bends with 18 contributions divided into four thematic sections 1 a topical review of fault bends and their global distribution 2 bends sedimentary basins and earthquake hazards 3 restraining bends transpressional deformation and basement controls on development 4 releasing bends transtensional deformation and fluid flow

source process of the 4 june 2000 southern sumatra indonesia earthquake source parameters of the 4 june 2000 southern sumatra indonesia earthquake m s 8 0 were estimated from teleseismic body waves recorded by long period seismograph stations of the global seismic network the analysis shows that the earthquake had a mechanism with a strike of 199 a dip of 82 and a rake of 5 and ruptured unilaterally from the northeast to the southwest nearly perpendicular to the java trench the focal mechanism of mainly left lateral strike slip with a small thrust component explains well the reason why no tidal waves were generated by this great earthquake the double couple component of this earthquake was 1 5 10 21 nm the compensated linear vector dipole component was 1 2 10 20 nm and the explosion component was 5 9 10 19 nm the analysis indicates that the source duration was about 16 sec the fault area is about 95 km in length and 60 km in width the average static slip is estimated to be about 11 m and the average static stress drop 90 mpa

identification of wrench faults using subsurface structural data criteria and pitfalls 1 many structures imaged with reflection seismic can resemble a wrench fault system because of the great structural diversity of strike slip faults and the wide range of contractional and extensional features associated with these faults because of these resemblances numerous faults are misidentified as wrench faults by workers using subsurface structural data credible identification requires combinations of profile and map criteria 1 narrow long straight throughgoing solitary master fault or zone of deformation 2 steep to moderate dip of the master fault at depth 3 offset of the top of basement 4 changes in relative upthrown side separation sense and or fault dip direction at depth or along the strike of the master fault 5 narrow fault slices within the master fault zone that steepen and join at depth negative and positive flower structures 6 different separation sense and orientation of relative upthrown side at these fault slices and 7 coeval en echelon flanking structures the identification should be confirmed with other criteria that refute alternative interpretations the main pitfalls to a reliable identification are not considering alternative structural styles and the misinterpretation of features or patterns that superficially resemble wrench systems the profile geometries of basement involved reverse or normal faults particularly those with structural inversion can resemble the single strand of convergent or divergent wrench faults profile geometries of flower structures can be mimicked by narrow contractional horsts or narrow extensional grabens complexly faulted anticlines or synclines splay faults fault zones intruded by salt or shale and overprinted structures pitfalls in interpreting map relationships are possible when structural patterns combine several tectonic influences are controlled by rock anisotropy or include elements hat are not coeval and if the patterns characteristic of other styles are misinterpreted many erroneous identifications of wrench faults can be eliminated by demonstrating that the investigated fault or feature lacks a straight trace lateral length or throughgoing continuity

source pulse enhancement by deconvolution of an empirical green s function observations of the earthquake source time function are enhanced if path recording site and instrument complexities can be removed from seismograms assuming that a small earthquake has a simple source its seismogram can be treated as an empirical green s function and deconvolved from the seismogram of a larger and or more complex earthquake by spectral division when the deconvolution is well posed the quotient spectrum represents the apparent source time function of the larger event this study shows that with high quality locally recorded earthquake data it is feasible to fourier transform the quotient and obtain a useful result in the time domain in practice the deconvolution can be stabilized by one of several simple techniques in this paper the method is implemented and tested on high quality digital recordings of aftershocks of the jan 9 1982 miramichi new brunswick earthquake in particular seismograms from a jan 17 aftershock 017 13 33 gmt local mag 3 5 exhibit path or site effects which complicate the determination of source parameters after deconvolution the apparent far field source of this event is a simple pulse in displacement with duration 0 07 second for both p and s

cenozoic evolution of the tan lu fault zone east china constraints from seismic data abstract the tan lu fault zone tlfz is a continental scale strike slip fault zone in the east china that contains rich and significant information about the mesozoic cenozoic evolution of eastern asia it experienced a long term and complex superimposed deformation characterized by mesozoic sinistral and cenozoic dextral motions the fault has a well documented mesozoic sinistral displacement history but its cenozoic history is poorly known in this study based on the observations of the interrelationships of fault kinematics fault geometry and concomitant sedimentation the cenozoic evolution of the tlfz is constrained by abundant seismic data from oil fields numerous bends along the cenozoic master fault sensitively record changes in the stress field during strike slip motion taking into account the cenozoic evolution of the bohai bay basin east china the evolutionary history of these strike slip bends is investigated and the results indicate that dextral motion along the tlfz began at about 40 ma furthermore the cenozoic evolutionary history of the tlfz is suggested to include an extensional deformation with a possible weak sinistral shear from 65 to 40 ma from 40 to 0 ma dextral motion occurred due to a change in the subduction direction of the pacific plate relative to the eurasian plate causing the fault to experience dextral shear with a component of extensional deformation dextral motion was most intense from 40 to 25 ma and then the dextral direction may have suddenly changed from a nearly ne sw trend to a nearly n s trend at around 25 ma dextral motion was relatively enhanced again after 12 ma and was particularly strong after 5 ma episodic and ephemeral thrusting deformation might have occurred during the quaternary the cumulative cenozoic dextral displacement of the tlfz is far smaller than its mesozoic sinistral strike slip displacement may be no more than 21 km

investigation of the rupture process of the 28 june 1992 landers earthquake utilizing terrascope abstract displacement seismograms recorded by terrascope for the 28 june 1992 landers earthquake m w 7 3 are deterministically modeled using a forward point source summation technique although the data set is sparse it was possible to robustly determine important rupture parameters such as gross slip distribution rupture velocity rise time and total source duration the relatively simple approach lends itself to rapid application following large earthquakes provided that a catalog of green9s functions appropriate for the region is available the fault used in the modeling of the landers mainshock has a length of 70 km along strike and a width of 15 km along dip a model was found in which the distribution and amplitude of slip at the surface matches the observed surface slip and provides a very good level of fit to the seismic data seismically the landers earthquake is characterized as two subevents the peak slip of the first subevent is 10 km north of the epicenter and the second is 40 km northwest along strike from the epicenter the seismic moment is distributed as 2 10 26 dyne cm to the first and 6 10 26 to the second subevent respectively it was assumed in our modeling that the distribution of seismic moment along strike was the same at all depths this assumption implies that slip at depth is 69 of that at the surface as a result of differences in the material properties in the velocity model the sensitivities of the source model to rupture velocity and dislocation rise time were examined a rupture velocity of 2 9 km sec 80 of the shear wave velocity and a rise time of 1 to 3 sec were found to satisfy the data the rise time is only a fraction of the total source process time of 24 sec and implies that slip on the fault occurred within a narrow band 3 to 10 km at any instant during the rupture

the effect of convergence angle on the kinematic evolution of strain partitioning in transpressional brittle wedges insight from analog modeling and high resoluiton digital image analysis 1 using analog modeling aided by digital image analysis dpiv we constrained the long term kinematic evolution of strain partitioning in transpressional brittle wedges as a function of convergence angle we ran a series of dry quartz sand experiments representing highly oblique continent continent collision convergence angles of 4 to 30 the digital image analysis provided high resolution constraints on the long term kinematic evolution of these wedges which could be subdivided in distinct kinematic stages comprising 1 an initial distributed strain stage and 2 an oblique wedge stage before 3 the stage of strain partitioning is reached thus we document the evolution of different deformation stages from a single plate tectonic boundary condition in addition the relationship between convergence angle kinematic stages and wedge geometry including fault dips and fault hierarchy was established the modeling results show that smaller convergence angles lead to steeper faults besides for a constant convergence angle the proshears that evolved during the strain partitioning stage were less steep than those formed during the oblique wedge stage the fault slip vector on individual fault segments was derived from the dpiv data set for each time increment quantifying the magnitude and orientation of slip on fault segments during the different kinematic stages in addition in the 7 5 and 15 models rotation of the slip vector by up to 40 was observed on a single proshear during the strain partitioning stage these observations allow to some degree a validation of existing analytical models of strain partitioning in particular the assumption of steady state

tectonic characteristics of the central segment of the tancheng lujiang fault zone shandong peninsula eastern china abstract the tancheng lujiang fault zone tlfz in the central segment in the shandong peninsula eastern china is composed of four major faults called f1 f4 from east to west forming a 50 km wide zone detailed field study demonstrates that neogene volcanic and sedimentary strata quaternary deposits and topographic surfaces cover the fractured zones of faults f3 and f4 and are not deformed or displaced the same rocks and surfaces on faults f1 and f2 however are clearly displaced the geological and seismological data show that the f1 and f2 are presently active as a major seismic zone in eastern china whereas the f3 and f4 have been inactive since the neogene fabrics of foliated cataclastic rocks generated in the fracture zones show left lateral strike slip on the f3 and f4 between cretaceous and neogene time and high angle reverse or normal faulting with a dextral component on faults f1 and f2 in late quaternary time field evidence and analysis of the fabrics of fault related rocks reveal the changes of shear sense and activity of faults f1 f4 of the central segment of the tlfz from cretaceous to quaternary time in the shandong peninsula

the dynamics of a one dimensional fault in the presence of friction summary the tearing and healing of a one dimensional crack in a solid in the presence of external tectonic forces pre stress static friction cohesion and dynamic friction is investigated it is found that cohesive forces have a strong influence on the velocity of rupture the velocity of rupture is always less than or equal to the velocity of sound the extension of the crack ceases either when the crack enters a region with too high a cohesive force or when the difference between the tectonic stress and the dynamical shear stress becomes negative over a substantial region of space for one simple model a high displacement high energy release event has been found while in another model of the same fault length a low displacement low energy release event with the same stress drop takes place the difference between the two models is in the mode of healing and in particular whether the fault breaks out at the free surface of the earth

analog models of restraining stepovers in strike slip fault systems scaled sandbox models have successfully simulated the geometries and progressive evolution of antiformal pop up structures developed in a weak sedimentary cover above restraining stepovers in offset sinistral strike slip fault systems in rigid basement models were run both with and without synkinematic sedimentation which was added incrementally to cover the growing antiformal structures vertical and horizontal sections of the completed models permit the full three dimensional 3 d structure of the pop ups to be analyzed in detail three representative end member experiments are described 30 underlapping restraining stepovers 90 neutral restraining stepovers and 150 overlapping restraining stepovers the experimental pop ups are typically sigmoidal to lozenge shaped antiformal structures having geometries that are dependent on both the stepover angle and stepover width in the underlying basement faults underlapping restraining stepovers typically form elongate lozenge shaped pop ups 90 neutral restraining stepovers produce shorter squat rhomboidal pop ups and overlapping restraining stepovers produce sigmoidal antiformal pop ups trans pop up cross fault systems are characteristic at large displacements on the basement fault system above the offset principal displacement zones the pop ups are commonly small narrow positive flower structures whereas in the stepover region they widen out and become markedly asymmetric this pop up asymmetry switches across the center of the stepover where the pop ups are largely symmetical maximum rotations measured within the central highly uplifted region of the pop ups increase from 7 counterclockwise for the underlapping 30 stepovers to 14 counterclockwise for the neutral 90 stepovers to 16 counterclockwise for the overlapping 150 stepovers in models where no synkinematic sediments were added during deformation the pop up structures are bound by convex flattening upward oblique slip reverse fault systems that link downward to the offsets in the basement fault system in contrast in the begin page 234 experiments where synkinematic sediments were added incrementally during deformation the pop ups are formed by oblique slip reverse faults that steepen upward into the synkinematic strata with the formation of fault propagation growth folds the analog models are compared with natural examples of pop up structures and show strong similarities in structural geometries and stratal architectures these models may provide structural templates for seismic interpretation of complex contractional structures in offset strike slip fault systems

the temporal and spatial evolution of the 19 september 1985 michoacan earthquake as inferred from near source ground motion records abstract a frequency domain inversion technique is employed to image the rupture process of the 19 september 1985 michoacan mexico earthquake a linear system is derived from the elastodynamic representation theorem and is solved for the spatial slip velocity distribution in the frequency bandwidth 0 0 to 0 32 hz the temporal behavior of slip velocity on the fault plane is then recovered by fourier synthesis model complexity is penalized by seeking a solution that propagates with the most nearly constant rupture velocity and that produces the most nearly constant spatial slip distribution at 0 hz the inversion of surface static displacements as inferred from strong motion recordings of the guerrero accelerograph array gives an estimate of the static offset on the fault plane coastal uplift data inferred from the mortality of intertidal organisms bodin and klinger 1986 is also used to further constrain the spatial slip distribution a low frequency image of the rupture process of the earthquake has been obtained using full space green9s functions two areas of large slip amplitude are discernible one located downdip of the reported hypocenter and the other updip of the projection on the fault plane of station la union their separation is approximately 100 km assuming that full space green9s functions underestimate static offset values at the surface of a half space by a factor of 0 5 the inferred seismic moment is 10 6 10 27 dyne cm 90 per cent of which is released in these two areas sustaining the largest slip the total inferred rupture duration is approximately 56 sec from the hypocenter the rupture front proceeds with an average velocity estimated at 2 8 km sec there are indications of bilateral propagation both from the hypocentral area and from an area surrounding the projection on the fault plane of the strong motion station la union an upper bound on rupture duration at the two principal subevents is 8 sec

syn collisional transform faulting of the tan lu fault zone east china origin of the continental scale tan lu fault zone tlfz east china remains controversial about 550 km sinistral offset of the dabie orogenic belt dob and sulu orogenic belt sob is shown along the ne nne striking tlfz syn collisional sinistral ductile shear belts in the tlfz have been identified thirteen phengite bulk separates from the mylonites were dated by the 40ar 39ar method they gave cooling ages of the 198 181 ma for the shear belts along the eastern margin of the dob and 221 210 ma from the western margin of the sob distribution of the foreland basin deposits suggests that sinistral offset of the dob and sob by the tlfz took place prior to deposition of the upper triassic strata the marginal structures around the dob and sob support syn collisional faulting and indicate anticlockwise rotation of the dob during the displacement the folding and thrust faulting related to crustal subduction coeval with the tan lu faulting is older than the foreland basin deposition related to the orogenic exhumation several lines of evidence demonstrate that the tlfz was developed as a syn collisional transform fault during latest middle to earliest late triassic time when the dob and sob experienced crustal subduction of the south china block scb eastward increase of the crustal subduction rates is believed to be responsible for the sinistral transform faulting

rupture characteristics and tomographic source imaging of ml 3 earthquakes near anza southern california the rupture characteristics of several ml 3 earthquakes near anza california are determined from time domain analysis of path corrected displacement pulses these pulses are corrected for propagation effects apparent attenuation scattering site resonance using the waveforms of adjacent small events ml 2 1 as empirical green s functions the earthquakes studied occurred during two swarm sequences near cahuilla in an area characterized by swarm activity at shallow depth 5 km the data consist of seismograms recorded by the anza seismic network a high dynamic range local array with digital telemetry the waveforms of adjacent small events ml 2 1 are deconvolved from those of the ml 3 events to yield the source time functions of the larger earthquakes the ml 3 earthquakes display a variety of rupture modes similar to those reported for large shocks but over much shorter time scales and distances events with single and multiple ruptures are observed relative locations of the subevents are obtained from azimuthal differences in the time separation of pulses in the deconvolved displacement waveforms some events as small as ml 2 4 display unilateral rupture propagation as manifested by azimuthal variations in the pulse widths of the deconvolved displacement pulses a tomographic back projection technique is applied to the deconvolved displacement pulses to image the slip velocity on the fault as a function of time after nucleation and distance along the fault using a one dimensional fault model the tomographic inversion for one of the events ml 2 4 reveals a unilateral rupture with rupture velocity about equal to the shear wave velocity vs and fault length of 300 m a similar inversion for an ml 3 7 event resolves two subevents separated by about 200 m and yields an average rupture velocity of 0 8vs these rupture velocities are similar to those reported for large earthquakes indicating that rupture velocity is independent of seismic moment down to 3 1 1019 dyn cm the smallest event studied there are clear variations in pulse width for neighboring events with similar seismic moments implying significant differences in static stress drops factor of five variations in stress drop 11 61 bars are calculated for events within 200 m of each other thus the stress and or strength along this fault zone varies considerably over distances of hundreds of meters

neogene quaternary postrift tectonic reactivation of the bohai bay basin eastern china bohai bay basin located in eastern china is considered a cenozoic rifted basin the basin is atypical in terms of its neogene quaternary postrift subsidence history in that it experienced intensive tectonic reactivation rather than the relative tectonic quiescence experienced during this stage by most rift basins this neogene quaternary tectonic reactivation arose principally in response to two tectonic events 1 activity on a dense array of shallow faults and 2 accelerated tectonic subsidence that occurred during the postrift stage these two events were neither strictly temporally nor spatially equivalent the dense array of shallow faults form a northwest southeast trending belt in the central part of the basin with displacement induced by the reactivation of older northeast and northwest trending basement faults and an associated substantial component of strike slip displacement occurring after 5 3 ma the intensive reactivation of these faults contributed to the atypically accelerated rate of postrift tectonic subsidence of the basin that commenced ca however this was not the sole cause of this accelerated tectonic subsidence a combination of geological activity deep within the crust led to the buildup of intraplate stresses and this combined with ongoing thermal subsidence acted as an additional contributory factor that drove unusually high rates of subsidence for this basin this episode of accelerated postrift tectonic reactivation resulted in conditions favorable for hydrocarbon accumulation

shear wave splitting and earthquake forecasting seismic shear wave splitting sws monitors the low level deformation of fluid saturated microcracked rock we report evidence of systematic sws changes recorded above small earthquakes monitoring the accumulation of stress before earthquakes that allows the time and magnitude of impending large earthquakes to be stress forecast the effects have been seen with hindsight before some 15 earthquakes ranging in magnitude from an m1 7 seismic swarm event in iceland to the ms7 7 chi chi earthquake in taiwan including a successfully stress forecast of a m5 0 earthquake in sw iceland characteristic increases in sws time delays are observed before large earthquakes which abruptly change to deceases shortly before the earthquake occurs there is a linear relationship between magnitudes and logarithms of durations of both increases and decreases in sws time delays before large impending earthquakes however suitably persistent swarms of small earthquakes are too scarce for routine stress forecasting reliable forecasting requires controlled source cross hole seismics between neighbouring boreholes in stress monitoring sites sms it would be possible to stress forecast damaging earthquakes worldwide by a global network of sms in real time

three types of flower structures in a divergent wrench fault zone flower structures are typical features of wrench fault zones in conventional studies two distinct kinds of flower structures have been identified based on differences in their internal structural architecture 1 negative flower structures characterized by synforms and normal separations and 2 positive flower structures characterized by antiforms and reverse separations in addition to negative and positive flower structures in this study a third kind of flower structure was identified in a divergent wrench fault zone a hybrid characterized by both antiforms and normal separations negative flower structures widely occur in divergent wrench fault zones and their presence indicates the combined effects of extensional and strike slip motion in contrast positive and hybrid flower structures occur only in fault restraining bends and step overs a hybrid flower structure can be considered as product of a kind of structural deformation typical of divergent wrench zones it is the result of the combined effects of extensional compressional and strike slip strains under a locally appropriate compressional environment the strain situation in it represents the transition stage that in between positive and negative flower structures kinematic and dynamic characteristics of the hybrid flower structures indicate the salient features of structural deformation in restraining bends and step overs along divergent wrench faults including the coexistence of three kinds of strains i e compression extension and strike slip and synchronous presence of compressional i e typical fault bend fold and extensional normal faults deformation in the same place hybrid flower structures are also favorable for the accumulation of hydrocarbons because of their special structural configuration in divergent wrench fault zones

seasonality variations in the central mediterranean during climate change events in the late holocene abstract holocene rapid climate change rcc events such as the little ice age lia are thought to have influenced average annual temperatures only marginally but to have affected winter temperatures relatively strongly with summer temperatures relatively unaffected reconstructing climate change at a seasonal resolution is crucial to fully capture holocene climate variability mediterranean climate is highly seasonal being influenced by the subtropical high pressure belt in summer and the mid latitude westerlies combined with outbreaks of polar winds in winter we identified events of high and low detrital input to the gulf of taranto central mediterranean sea anticipated to be linked to humid and dry conditions respectively and thereby potentially reflecting seasonal contrasts these events represent the bronze age ba roman humid period rhp medieval climate anomaly mca lia and present day and were selected for the analysis of single specimen globigerinoides ruber white carbonate chemistry mg ca 18o and 13c the dynamic range found for these parameters for the measured single individuals in the most recent interval reflects the present day seasonal contrasts in temperature and precipitation albeit with a bias towards the summer season these results are compared with high resolution 15 years sample sea surface temperature sst and bottom water temperature bwt reconstructions based on the 18o of g ruber white and mg ca of benthic foraminifer hyalinea balthica although the seasonal temperature contrast remains relatively stable significant winter cooling is observed during the ba and lia connections between high latitude climate winter conditions and low latitude climate summer conditions appear not straightforward during rcc events this results in changes in the moisture balance and in shifts in seasonal dominance between rccs during the lia winter like conditions cold and humid prevail throughout the year in contrast winters are dry and cold during the ba and are accompanied by dry and warm summers suggesting year round aridity and a relatively high seasonal temperature contrast this could have had a profound impact on early agriculture in southern italy

seismogenic strike slip faulting and the development of the north china basin the actively subsiding north china sedimentary basin is associated with an unusually high level of seismic activity this oil and gas producing basin has been the site of nine large m 7 destructive earthquakes since 1600 a d an analysis of faulting during the tangshan earthquake sequence which includes some of the largest shocks that have occurred in this basin during the past 400 years showed that the dominant pattern of deformation during this sequence was associated with displacement on right stepping right lateral strike slip faults a large amount of subsidence 1 0 1 5 m occurred in pull apart regions between steps of the north northeast nne trending strike slip faults the directivity of the p wave radiation pattern and the distribution of aftershocks of the bohai gulf earthquake of july 18 1969 also indicate strike slip faulting on planes of similar nne trend together with the four largest shocks of the hsingtai sequence in 1966 earthquakes with right lateral slip on nne trending faults account for about two thirds of the seismic moment released in this region for the past 100 years the average regional strain due to seismic slip has a dominant component of dextral simple shear on nne striking planes that is approximately twice as large as north south extension or east west shortening based on a combination of published field and borehole data the dominance of horizontal dextral simple shear over subsidence seems to have begun no later than the mid pliocene and the total amount of extension over the entire basin is only about 20 30 this pattern of deformation the spatially variable heat flow values the scattered locations of rapid deposition of quaternary sediments and the fluctuating rate of sedimentation in space and time during the neogene in this basin are difficult to explain by pure extension and thermal subsidence we propose that these observations and the shape of the whole north china basin that of a lazy z are a consequence of pulling apart associated with right lateral movement on the nne trending strike slip fault systems and that the basin as a whole has formed and evolved as a composite pull apart basin due to right lateral slip on numerous right stepping faults since the eocene

source process of the 1990 gonghe china earthquake and tectonic stress field in the northeastern qinghai xizang tibetan plateau the m s 6 9 gonghe china earthquake of april 26 1990 is the largest earthquake to have been documented historically as well as recorded instrumentally in the northeastern qinghai xizang tibetan plateau the source process of this earthquake and the tectonic stress field in the northeastern qinghai xizang plateau are investigated using geodetic and seismic data the leveling data are used to invert the focal mechanism the shape of the slipped region and the slip distribution on the fault plane it is obtained through inversion of the leveling data that this earthquake was caused by a mainly reverse dip slipping buried fault with strike 102 dip 46 to ssw rake 86 and a seismic moment of 9 4 1018 nm the stress drop strain and energy released for this earthquake are estimated to be 4 9 mpa 7 4 10 5 and 7 0 1014 j respectively the slip distributes in a region slightly deep from nww to see with two nuclei i e knots with highly concentrated slip located in a shallower depth in the nww and a deeper depth in the see respectively

automatic imaging of earthquake rupture processes by iterative deconvolution and stacking of high rate gps and strong motion seismograms by combining the complementary advantages of conventional network inversion and backprojection methods we have developed an iterative deconvolution and stacking ids approach for imaging earthquake rupture processes with near field complete waveform data this new approach does not need any manual adjustment of the physical empirical constraints such as restricting the rupture time and duration and smoothing the spatiotemporal slip distribution therefore it has the ability to image complex multiple ruptures automatically the advantages of the ids method over traditional linear or nonlinear optimization algorithms are demonstrated by the case studies of the 2008 wenchuan and 2011 tohoku earthquakes for such large earthquakes the ids method is considerably more stable and efficient than previous inversion methods additionally the robustness of this method is demonstrated by comprehensive synthetic tests indicating its potential contribution to tsunami and earthquake early warning and rapid response systems it is also shown that the ids method can be used for teleseismic waveform inversions for the two major earthquakes discussed here the ids method can provide without tuning any physical or empirical constraints teleseismic rupture models consistent with those derived from the near field gps and strong motion data

extensional fault arrays in strike slip and transtension abstract sedimentary basins developed under conditions of strike slip or transtension are subject to significant rotational strains yet faults developed in such regimes are commonly explained using simplified models that ignore rotation the heaves of extensional faults developed provide a means of quantifying this rotation for ideal strike slip simple shear the apparent stretch due to fault heaves can be related simply to shear strain at shear strains above 1 0 previously formed extensional faults begin to show inversion as reverse faults becoming fully inverted at 2 0 in transtensional basins the apparent stretch is related in addition to the initial orientation of the faults which may itself be related to the incremental strain in the stellarton basin of nova scotia canada fault heaves and orientations can be measured from subsurface mine plans measurements of these quantities indicate that strain was only mildly transtensional with a small the measurement of fault heaves potentially provides detailed information on strain wherever strike slip or transtensional basins have been explored in detail by seismic or other subsurface methods

a time domain inversion technique for the tempo spatial distribution of slip on a finite fault plane with applications to recent large earthquakes in the tibetan plateau a time domain inversion technique is proposed to invert for the tempo spatial distribution of slip on an earthquake fault plane this technique is based on the idea that a finite fault plane can be divided into several subfaults each of which can be treated as a point source and that the source time function stf of the finite fault is the weighted sum of the stfs of all the subfaults this technique is applied to deduce the source processes of three recent large earthquakes in the qinghai xizang tibetan plateau the 1990 april 26 gonghe qinghai earthquake ms6 9 ruptured on a fault plane with a strike of 113 a dip of 68 and a rake of 89 the fault has a length of 45 km a width of 15 km and a total moment release of 9 4 1018 n m the rupture initiated at the wnw end of the fault and propagated unilaterally towards the ese end of the fault in total the rupturing lasted for 45 s and was divided into two episodes the first 9 s long and the second 16 s long with 20 s quiescence in between there are two distinct rupture regions nuclei on the fault plane these two nuclei with maximum slips of about 62 and 55 cm are about 25 km apart in the wnw ese direction the 1996 february 3 lijiang yunnan earthquake ms7 0 has a focal mechanism with a strike of 157 a dip of 48 and a rake of 102 the earthquake fault is about 45 km with a width of 20 km and a total moment release of 9 8 1018 n m the total duration of the rupture was 16 s is divided into two episodes the first 8 5 s long and the second 7 5 s long the inverted final slip distribution of the lijiang earthquake also shows two nuclei one nucleus with a maximum slip of 40 cm is located on the nnw portion of the fault at a shallower depth and the other with a maximum slip of 50 cm is located on the sse portion of the fault at a greater depth the 1997 november 8 mani xizang tibet earthquake ms7 9 has a focal mechanism with a strike of 250 a dip of 88 and a rake of 19 and a moment release of 3 4 1020 n m the total duration of the rupture was about 15 s the inverted final slip distribution of the mani earthquake shows three nuclei on the fault plane the first nucleus with a maximum slip of 956 cm is located at the wsw end of the fault at 10 km in depth the second with a maximum slip of 743 cm is located at the ene end of the fault 55 km away from the wsw end of the fault and at 35 km depth the third with a maximum slip of 1060 cm is about 30 km away from the wsw end of the fault and at about 40 km depth these three nuclei form a total rupture area of about 70 km in length and 60 km in depth

the influence of basement faults during extension and oblique inversion of the makassar straits rift system insights from analog models analog models were used to investigate the influence of cross trending basement faults on inverted rift systems similar to those located in the makassar straits multilayer models composed of sand silicone putties and a silicone plasticine mixture were constructed so that laterally offset rift basins would form on either side of a preexisting basement fault transfer zones comprising a series of en echelon normal faults that connect downward with the basement fault formed to link the laterally offset rift basins during the extension phase subsequent oblique inversion of the models resulted in a general progression starting with broad folding followed by the development of small scale inversion anticlines associated with reactivated rift faults to thrust faulting and finally to the formation of cross trending wrench faults rift fault reactivation and wrench fault development were prominent in the transfer zones because of the orientation of the constituent faults oblique to the shortening direction and their connection with the underlying basement fault the addition of an intrasedimentary detachment layer which represents a thick overpressured shale present in the vicinity of the economically important mahakam delta allowed gravitational collapse and extensional faulting to occur on structural highs the cross trending basement fault was again the locus for inversion structures both above and below the detachment layer in the latter case which may have influenced the distribution of petroleum in the region

rupture directivity and slip distribution of the m 4 3 foreshock to the 1992 joshua tree earthquake southern california details of the m 4 3 foreshock to the joshua tree earthquake were studied using p waves recorded on the southern california seismic network and the anza network deconvolution using an m 2 4 event as an empirical green s function corrected for complicated path and site effects in the seismograms and produced simple far field displacement pulses that were inverted for a slip distribution both possible fault planes north south and east west for the focal mechanism were tested by a least squares inversion procedure with a range of rupture velocities the results showed that the foreshock ruptured the north south plane similar to the mainshock the foreshock initiated a few hundred meters south of the mainshock and ruptured to the north toward the mainshock hypocenter the mainshock m 6 1 initiated near the northern edge of the foreshock rupture 2 hr later the foreshock had a high stress drop 320 to 800 bars and broke a small portion of the fault adjacent to the mainshock but was not able to immediately initiate the mainshock rupture

variable slip rupture model of the great 1923 kanto japan earthquake geodetic and body waveform analysis abstract the available geodetic and teleseismic data sets for the 1923 kanto earthquake m s 8 1 have been combined into a joint inversion for both temporal and spatial slip variations we assumed an initial faulting model to be consistent with the geometry determined by kanamori 1971 on the basis of first motion data aftershock area and the amplitude of surface waves at teleseismic distances and also to enclose the slipped area estimated by matsu9ura et al 1980 from the geodetic data employed here we then inverted for a heterogeneous distribution of slip of the fault plane the leveling routes and triangulation stations used consisting of 225 bench marks and 31 triangulation points are from matsu9ura et al 1980 we chose to first determine the overall static slip distribution by inverting the geodetic data alone we then proceeded to gradually increase the importance of the teleseismic data always requiring a good fit to the geodetic leveling and horizontal displacements in this way we could provide a constraint on the overall static slip characteristics from the geodetic data and provide stability for the teleseismic inversion yet determine the degree of slip heterogeneity and time history most suitable for matching the waveform data and for simulating strong ground motions our analysis yields a seismic moment of 7 to 8 10 27 dyne cm m w 7 8 to 7 9 with a maximum slip of approximately 8 m the most concentrated slip is in the shallow central and western portion of the fault the location of the concentrated slip on the fault plane has important consequences for the amplitude duration and frequency content of the resulting ground motions as documented by takeo and kanamori 1993

seismic reflection imaging of a major strike slip fault zone in a rift system paleogene structure and evolution of the tan lu fault system liaodong bay bohai offshore china the tan lu fault system in the liaodong bay bohai offshore china affords an exceptional opportunity to document the structural features of a major strike slip fault using two and three dimensional seismic reflection data as well as evolution of a strike slip fault developed coeval with a rift system the fault zone displays a relatively straight throughgoing trace longitudinally bisecting the rift valley it consists of positive and negative flower structures and en echelon folds in the south bay and three parallel flower structure systems northward the middle fault bifurcates northward into two semiparallel vertical fault strands to the north the west strand bends clockwise and merges with the east strand the stepping pattern and orientation of en echelon structures indicate right lateral sense and about n10 35e azimuth of slip the fault apparently accrued about 30 40 km 20 25 mi of post early eocene slip based on the current distribution of deformation zones and depocenters tan lu fault segments with clockwise and counterclockwise orientation relative to the regional slip direction are characterized by divergent and convergent structures i e restraining and releasing bends respectively waning of rifting eliminated the cause of a major restraining bend putting an end to development of associated convergent structures in the south bay area near the central north bay deformation occurred along major normal faults related to the basin rifting although a prominent feature reflecting regional strain partitioning the tan lu fault apparently was not a major factor in the paleogene opening of the liaodong bay basin and the larger north china rift basin

tan lu fault system and its significance in oil accumulation in the central liaodong bay subbasin bohai bay basin china the tan lu fault system in the central liaodong bay subbasin bohai bay basin has complex structural characteristics and its tectonism during the cenozoic is an important factor in oil accumulation three dimensional seismic data were used to document the structural features and evolution of the system variations in source rock occurrence oil catchment area and faulting intensity were comprehensively evaluated to discuss the heterogeneity of oil occurrence along the system detailed analysis of the seismic data indicates a right lateral slip for the tan lu fault system transpression and transtension occur on two branches of the tan lu fault with different orientations indicating a likely slip azimuth that is between the two orientations i e 30 35 the strike slip began at the middle stage of deposition of the shahejie formation and reached its climax during deposition of the first and second members of the dongying formation to date the slip is still continuing in the transpressional system the lower strata on opposite sides of the strike slip fault were shortened and folded whereby the upper strata were stretched and normal faulted as a result a negative flower structure developed immediately above a positive flower structure strain distribution in this system is similar to that in a classic fold moderate tectonic deformation could enlarge the oil catchment area benefiting oil accumulation weak or intense deformation is unfavorable for commercial oil accumulation because of a small oil catchment area and poor oil preservation respectively

structural records of the late cretaceous cenozoic extension in eastern china and the kinematics of the southern tan lu and qinling fault zone anhui and shaanxi provinces pr china abstract our study of the late cretaceous cenozoic extension in eastern china is a kinematic analysis of faults 1500 striated fault data 175 stress solutions at 90 sites that has permitted us to separate stress fields belonging to six tectonic events a wnw ese extension 1 has affected eastern china from the campanian to the late palaeocene early ypresian under this extension the qinling qlfz and southern tan lu stlfz fault zones have been dextral transtensional fault zones a first transpressional event 2 nne ssw shortening has occurred during the late ypresian lower lutetian the qlfz and the stlfz have been dextral transpressional fault zones a ne sw extension 3 has affected the weihe graben during the palaeogene after a second transpressional event 4 the ne sw extension 5 has been rejuvenated during the late miocene and the qlfz has been a normal fault zone again and the stlfz a sinistral transtensional fault zone synrift subsidence has occurred in the weihe graben the second transpressional event 4 wnw ese shortening has occurred during the late oligocene early miocene during a period of uplifting and exhumation at that time the stlfz and the qlfz have become sinistral transpressional fault zones a period of extension 6 has taken place during the late pliocene quaternary the extensional direction has trended nnw sse during this event the qlfz has been a sinistral transtensional fault zone and the stlfz a dextral transtensional fault zone these results are compared with those previously published in order to evaluate the regional significance of these tectonic events

single station decomposition of seismograms for subevent time histories we have adapted an iterative lseast squares inversion with positivity constraints to the problem of deconvolving the recordings of a small earthquake from the recordings of a large composite earthquake the inversion uses an f test to minimize the number of non zero amplitudes or subevents in the solution set by requiring each added subevent to reduce the variance significantly we apply this inversion to the analysis of strong motion recordings of a set of moderate sized 4 0m l 6 4 aftershocks of the 1976 friuli earthquake