thrust fault growth and segment linkage in the active ostler fault zone new zealand abstract thrust faulting is a fundamental mode of crustal deformation yet many of the key geometrical attributes of thrust faults and the controls on fault rupture growth and linkage remain poorly resolved numerous surface rupturing thrust faults cut through upper quaternary glacial outwash terraces within the ostler fault zone an active thrust system in the southern alps new zealand we use these deformed marker surfaces to define the three dimensional deformation field associated with their surface expression and to map displacement and length on 40 fault segments displacement transfer across two fault segment arrays occurs in distinctly different styles in one displacement is transferred between en echelon fault segments to produce a smooth linear displacement gradient in the other large scale folding and a population of small faults transfer displacement between two non overlapping fault segments with a residual displacement minimum within the transfer zone size distribution of fault segment length and maximum displacement follow a power law scaling relationship maximum displacement d max scales linearly with and represents 1 of segment trace length l d max l data from the segments of the ostler fault zone display similar scaling to a global fault dataset this similarity is surprising given that the observed displacements along the ostler fault represent only 20 ky of slip on fault segments that are likely to be many times older

aftershocks of the 2010 mw 7 2 el mayor cucapah earthquake reveal complex faulting in the yuha desert california 1 we detect and precisely locate over 9500 aftershocks that occurred in the yuha desert region during a 2 month period following the 4 april 2010 mw 7 2 el mayor cucapah emc earthquake events are relocated using a series of absolute and relative relocation procedures that include hypoinverse velest and hypodd location errors are reduced to 40 m horizontally and 120 m vertically aftershock locations reveal a complex pattern of faulting with en echelon fault segments trending toward the northwest approximately parallel to the north american pacific plate boundary and en echelon conjugate features trending to the northeast the relocated seismicity is highly correlated with published surface mapping of faults that experienced triggered surface slip in response to the emc main shock aftershocks occurred between 2 km and 11 km depths consistent with previous studies of seismogenic thickness in the region three dimensional analysis reveals individual and intersecting fault planes that are limited in their along strike length these fault planes remain distinct structures at depth indicative of conjugate faulting and do not appear to coalesce onto a throughgoing fault segment we observe a complex spatiotemporal migration of aftershocks with seismicity that jumps between individual fault segments that are active for only a few days to weeks aftershock rates are roughly consistent with the expected earthquake production rates of dieterich 1994 the conjugate pattern of faulting and nonuniform aftershock migration patterns suggest that strain in the yuha desert is being accommodated in a complex manner

the influence of salinity and flocculation upon the acquisition of remanent magnetization in some artificial sediments summary a range of redeposition experiments with both magnetite and maghemite grains embedded in kaolinite or quartz has revealed a significant non linear relationship between salinity and the intensity and magnitude of the inclination error of the depositional remanent magnetization drm increasing drm intensities and inclination errors were observed for salinities between 0 1 g l a dramatic reduction in intensity as well as in inclination error appears for salinities above ca 2 g l although there is a negligible effect on intensity of salinity for concentrations above 3 g l a significant inclination error persists over this range of salinities approaching less than 5 at concentrations larger than 30 g l the observed relationships are suggested to reflect mechanisms related to flocculation the results are probably not generally applicable to natural sediments since floc formation in nature usually involves organic compounds

growth of surface breaching normal faults as a three dimensional fracturing process structures along the hopena normal fault of the koae fault system kfs on kilauea volcano hawaii provide a record of fault propagation in three dimensions this fault displays 1 a breached monocline along the scarp 2 a belt of discontinuous echelon fractures along the scarp and past its end 3 a belt of discontinuous fractures on the footwall 4 buckles at the base of the scarp and 5 a belt of discontinuous fractures on the hangingwall that converges towards the end of the fault trace solid mechanics analyses show that this ensemble can be accounted for by the tipline of a normal fault propagating up towards the surface accompanied by antithetic fracturing then intersecting it and propagating laterally normal fault propagation down from the surface cannot account for the observed structures lateral slip occurs along some fractures as a result of local stress changes associated with fault propagation discontinuous fractures at the surface form early above a blind normal fault and continue to develop as a normal fault propagates laterally linkage of the fractures to the fault produces a fault with an irregular trace the discontinuous irregular character of normal fault traces over a broad range of scale is an inevitable consequence of three dimensional fault growth

relay zone geometry and displacement transfer between normal faults recorded in coal mine plans abstract overlap lengths separations and throw gradients were measured on 132 relay zones recorded on coal mine plans throws on the relay bounding fault traces are usually 2 m and individual structures are recorded on only one seam throw gradients associated with relay zones are not always higher than on single faults but asymmetry of throw profiles is diagnostic of relay zones bed geometries around larger faults in opencast mines are used to assess the displacement accommodated by shear in the vertical plane normal to the faults and displacement transfer accommodated by shear in the fault parallel plane three dimensional structure is defined for two relay zones each recorded on five seam plans these relay zones are effectively holes through the fault surfaces and overlap occurs between salients or lobes of the parent fault surfaces lobes initially terminated at tip lines but as the faults grew gradually rejoined the main fault surfaces along branch lines this type of relay zone originates by bifurcation of a single fault surface at a locally retarded tip line and is an almost inevitable result of a tip line irregularity

a statistical simulation of magnetic particle alignment in sediments s u m m a r y sedimentary magnetizations are fundamental to palaeomagnetism but the mechanisms that control remanence acquisition remain poorly constrained observed sedimentary natural remanent magnetizations are often orders of magnitude smaller than the saturation remanent magnetization of the same sediment which indicates inefficient remanence acquisition we present a statistical model based on the vonmises fisher distribution in which magnetic particle reorientations towards an ambient field are considered without representing the physics of the magnetization acquisition process the results provide insights into the nature of sedimentary magnetizations specifically an assemblage of randomly oriented magnetic particles can acquire a high fidelity palaeomagnetic signal with only small rotations in some cases 1 of particles towards the ambient field direction this demonstrates that the action of a geomagnetic torque on individual magnetic mineral particle orientation may be minor and that a weak directional bias on an assemblage of particles could be responsible for the typically observed inefficiency of sedimentary remanence acquisition additionally we demonstrate that weak fields produce sedimentary magnetizations with larger directional uncertainties for natural sediments however these uncertainties appear to be small enough to allow reliable recording of directional geomagnetic field behaviour during periods with weak fields such as palaeomagnetic reversals and excursions

paleomagnetic recording efficiency of sedimentary magnetic mineral inclusions implications for relative paleointensity determinations this study was supported by the national natural science foundation of china grants 41574060 41574063 and 41722402 and the australian research council grants dp120103952 and dp160100805 g a p is supported by a nerc independent research fellowship ne p017266 1 l t acknowledges support from nsf grant ear1547263

creep along the imperial fault southern california from gps measurements 1 in may of 1999 and 2000 we surveyed with global positioning system gps 46 geodetic monuments established by imperial college london in a dense grid half mile spacing along the imperial fault with three additional national geodetic survey sites serving as base stations these stations were previously surveyed in 1991 and 1993 the imperial college sites were surveyed in rapid static mode 15 20 min occupations while the ngs sites continuously received data for 10 h d 1 site locations were calculated using the method of instantaneous positioning and velocities were determined relative to one of the ngs base stations combining our results with far field velocities from the southern california earthquake center scec we fit the data to a simple elastic dislocation model with 35 mm yr 1 of right lateral slip below 10 km and 9 mm yr 1 of creep from the surface down to 3 km the velocity field is asymmetrical across the fault and could indicate a dipping fault plane to the northeast or a viscosity contrast across the fault

detrital magnetization of laboratory redeposited sediments we conducted several redeposition experiments in laboratory using natural and artificial sediments in order to investigate the role of grain size and lithology on sedimentary remanence acquisition the role of grain size was investigated by using sorted sediment from natural turbidites taking advantage of the magnetic grain size distribution within turbidites we compared redeposition experiments performed with coarse magnetic grains taken from the bottom layers of a turbidite with fine grains from the upper layers of the same turbidite in order to document the magnetization acquired for increasing sediment concentrations that is analogous to increasing depth in the sediment column the samples were frozen at temperatures between 5 and 10 c magnetization acquisition behaved similarly in both situations so that little smearing of the palaeomagnetic signal should be linked to grain size variability within this context other series of experiments were aimed at investigating the influence of lithology we used clay or carbonated sediments that were combined with magnetic separates from basaltic rocks or with single domain biogenic magnetite the experiments revealed that the magne tization responded differently with clay and carbonates clay rapidly inhibited alignment of magnetic grains at low concentrations and therefore significant magnetization lock in occurred despite large water contents perhaps even within the bioturbated layer extension of the process over a deeper interval contributes to smear the geomagnetic signal and therefore to alter the palaeomagnetic record in carbonates the magnetization was acquired within a narrow window of 45 50 per cent sediment concentration therefore little smearing of the ge omagnetic signal can be expected finally experiments on carbonate sediments and biogenic magnetite with increasing field intensities indicate that magnetization acquisition is linear with respect to field intensity altogether the results suggest that sediments with dominant carbonate content should be favoured for records of geomagnetic field changes provided that the minor clay fraction does not vary excessively they confirm the advantage of using cultures of magnetotactic bacteria for redeposition experiments

late quaternary slip rates across the central tien shan kyrgyzstan central asia 1 slip rates across active faults and folds show that late quaternary faulting is distributed across the central tien shan not concentrated at its margins nearly every intermontane basin contains neogene and quaternary syntectonic strata deformed by holocene north south shortening on thrust or reverse faults in a region that spans two thirds of the north south width of the central tien shan slip rates on eight faults in five basins range from 0 1 to 3 mm yr fault slip rates are derived from faulted and folded river terraces and from trenches radiocarbon optically stimulated luminescence and thermoluminescence ages limit ages of terraces and aid in their regional correlation monte carlo simulations that sample from normally distributed and discrete probability distributions for each variable in the slip rate calculations generate most likely slip rate values and 95 confidence limits faults in basins appear to merge at relatively shallow depths with crustal scale ramps that underlie mountain ranges composed of pre cenozoic rocks the sum and overall pattern of late quaternary rates of shortening are similar to current rates of north south shortening measured using global positioning system geodesy this similarity suggests that deformation is concentrated along major fault zones near range basin margins such faults separated by rigid blocks accommodate most of the shortening in the upper crust index terms 8107 tectonophysics continental neotectonics 9320 information related to geographic region asia 8010 structural geology fractures and faults

fluid flow triggered migration of events in the 1989 dobi earthquake sequence of central afar during the august 1989 sequence of earthquakes beneath the dobi graben in central afar principal events including 10 shocks with ml 5 5 propagated 50 km north westwards in 50 h the sequence is analyzed in terms of triggering by propagation of a critical pore pressure wave in a compressible fluid through a fractured medium the macroscopic fluid diffusion tensor d in the crust beneath the graben is estimated its principal eigenvector strikes n115 e nearly parallel to the graben axis with a value it is about 10 times larger than the other two consistent with fissure anisotropy in the graben the order of magnitude of the permeability 10 8 m is compatible with characteristic fissure widths ranging from 1 mm to 3 cm estimating such parameters in other extensional regions might help to understand better the temporal evolution of seismic swarms

constraints on the acquisition of remanent magnetization in fine grained sediments imposed by redeposition experiments the magnetization of sediments is acquired through complex processes involving a large number of physical mineralogical and magnetic parameters despite many attempts the degree to which these processes distort the record of the geomagnetic field as it is archived as a natural remanent magnetization nrm remains poorly documented among many other parameters it is important to evaluate the amount of smoothing inherent to the signal its relation with the field intensity and its variability in the sediment column in order to address these problems we performed new redeposition experiments using carbonate rich ocean drilling program odp site 851 and clay rich odp site 854 sediments we used a dilute solution of gelatin which gels below 20 c thereby allowing mechanical blocking of the magnetic grains we observed two critical results 1 the efficiency of detrital remanent magnetization drm decreases with increasing sediment concentration for a given slurry sediment concentration is defined as c ms ms mh2o where ms and mh2o are the sediment and water mass respectively higher c would then reflect greater compaction lower water content and presumably greater depth in the sediment column this effect reduces drm efficiency nearly to zero for c 50 2 post depositional remanent magnetization pdrm is important for c 50 pdrm is carried by grains covering the entire coercivity spectrum by comparing the mean value of nrm divided by anhysteretic remanent magnetization from the previous magnetostratigraphic study at site 851 with the relevant ratio derived from our redeposition experiments we were able to estimate that pdrm was significant within the depth interval where 44 c 56 if the sediment concentration profile for the uppermost sediment was known at site 851 we could define the transfer function for the deconvolution of the field variations finally the dependence of drm efficiency on c suggests that changes in the thickness of the surface mixed layer would change drm efficiency thus fluctuations in maximum bioturbation depth could possibly cause drm intensity changes regardless of changes in earth s field

depositional remanent magnetization toward an improved theoretical and experimental foundation the first theoretical predictions for the behavior of magnetic particles in water were that sedimentary magnetizations would be fully aligned with the ambient field yet redeposition experiments showed a strong and quasi linear dependence on the external field this empirically observed linearity has served as the fundamental assumption of sedimentary paleointensity studies for decades we present redeposition experiments which suggest instead that the relationship between depositional remanence drm and applied field may frequently be curved for magnetic fields in the range of the earth s numerical simulations using a flocculation model can explain the redeposition data and suggest that drm will be significantly non linear when the flocs are small several microns there is a strong dependence of floc size on salinity particularly in low salinity environments floc size has a profound influence on the efficiency of drm hence low salinity environment may give results with poor reproducibility the size of the floc in which magnetic particles are embedded is not accounted for in current methods of normalization yet is the most important parameter on the bright side however it now seems possible to quantitatively explain paleointensity in sedimentary systems opening the door to absolute paleointensity estimates from sediments whose key parameters of floc size distribution and settling times can be constrained

gis techniques and statistical models in evaluating landslide hazard geographical information systems gis and numerical cartography may greatly facilitate the development and use of statistical models for the assessment of regional landslide hazard from a small drainage basin located in central italy relevant geological and geomorphological factors were collected and processed by applying gis technology in particular modules were used which both generate high fidelity digital terrain models and automatically partition the terrain into main slope units the resulting information was then analysed by discriminant analysis which enabled landslide hazard and risk to be evaluated in each slope unit although not lacking drawbacks the method proved to be a feasible and cost effective approach to landslide susceptibility assessment and mapping

relay ramp forms and normal fault linkages canyonlands national park utah fieldwork within a series of mesoscale grabens in southeast utah has revealed a particularly well exposed system of interlinked extensional faults a series of down faulted grabens are developed within a 460 m thick brittle layer of upper paleozoic sandstone and shale which overlies a ductile layer with a high gypsum content all the major grabens consist of two or more overlapping elements which are composed of fault segments these segments may be hard linked fault surfaces are joined or soft linked fault surfaces are isolated but linked by ductile strain of the rock volume between them in map view relay structures are defined as zones connecting the footwalls and hanging walls of overlapping fault segments representing soft linkage of fault segments in the canyonlands grabens the transfer of displacement between soft linked fault segments is characterized by well de fined dipping relay ramps commonly rotated and extended to accommodate the ductile strain between the overlapping fault segments relay ramps develop as ephemeral structures eventually becoming breached by hard linkage of the fault segments breakdown of ramps by breaching is part of the process of fault growth by segment linkage within the canyonlands graben system four orders of segmentation are present this may be a consequence of different scales of mechanical heterogeneity but evidence from the canyonlands grabens and elsewhere points to a fundamental process of discontinuous fault growth by segment linkage

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

the role of magnetostatic interactions in sediment suspensions summary the processes that influence a detrital remanent magnetization as well as the physical microscale factors that control formation of a stable post depositional remanent magnetization are still not fully understood previous laboratory studies and statistical numerical approaches have shown the possibility that sediment suspensions can display complex magnetization phenomena such behaviour has been attributed to the effect of magnetostatic interactions in the suspension which could provide one explanation for spurious magnetizations observed in marine sediment cores in laboratory experiments we investigated magnetization decay as a function of time in sediment suspensions produced with varying lithologies and particle concentrations a companion model takes into account the physics of magnetic particle particle interactions brownian motion and hydrodynamic forces to investigate numerically the magnetization behaviour of sediment suspensions when combined the experiments and the numerical models reveal a weak effect of magnetostatic interactions in the natural sediment suspensions which is expressed as an increase in the magnetization decay rate in addition a calculation of effective particle size based on the response of each suspension to brownian motion indicates that the majority of the sedimentary magnetic particles are attached to larger clay particles

role of spherical particles on magnetic field recording in sediments experimental and numerical results abstract we report deposition experiments using spherical glass beads that possess remanent magnetizations stemming from iron impurities 15 g of glass beads with a well characterized size distribution were loaded in two different sets of tubes with diameters of 2 0 and 3 6 cm each tube contains identical column heights of de ionized water thereby allowing us to assess the effect of sediment concentration on the results 352 versus 90 kg m3 g l respectively the tubes were placed in magnetic fields of variable inclination and intensity in a temperature controlled environment the full vector magnetization and sediment accumulation rates were measured upon deposition times ranging from 10 min to 10 days experiments were run in triplicate to evaluate data reproducibility together with the lack of magnetic interaction and the absence of clumping the experiments elucidate an end member scenario of how sediments acquire remanent magnetizations in the absence of flocculation our results show that inclination shallowing in the range of 7 20 for field inclinations of 30 and 60 is indeed possible with solely spherical particles more importantly we observe a field dependence on the inclination error field dependence on the moment acquisition and inclination error both exhibit non linearity which may complicate interpretations of relative paleointensity data in paleomagnetic records a newly developed numerical model whereby particle collision during settling combined with both rolling and slipping translation on the substrate is consistent with the experimental results

near field deformation from the el mayor cucapah earthquake revealed by differential lidar large moment magnitude m w 7 continental earthquakes often generate complex multifault ruptures linked by enigmatic zones of distributed deformation here we report the collection and results of a high resolution nine returns per square meter airborne light detection and ranging lidar topographic survey of the 2010 m w 7 2 el mayor cucapah earthquake that produced a 120 kilometer long multifault rupture through northernmost baja california mexico this differential lidar survey completely captures an earthquake surface rupture in a sparsely vegetated region with pre earthquake lower resolution 5 meter pixel lidar data the postevent survey reveals numerous surface ruptures including previously undocumented blind faults within thick sediments of the colorado river delta differential elevation changes show distributed kilometer scale bending strains as large as 10 3 microstrains in response to slip along discontinuous faults cutting crystalline bedrock of the sierra cucapah

paleoseismic observations along the langshan range front fault hetao basin china tectonic and seismic implications abstract the langshan range front fault lrf is an active holocene normal fault that borders langshan mountain and the hetao basin northwest of the ordos plateau china in this study paleoseismic trenching was undertaken at three sites north south dongshen village tc1 qingshan tc2 and wulanhashao tc3 the paleoevents ed1 ed2 ed3 from tc1 were constrained to 6 0 1 3 9 6 2 0 and 19 7 4 2 ka respectively the single paleoevent eq1 from tc2 was constrained to about 6 7 0 1 ka and the paleoevents ew1 ew2 and ew3 from tc3 were constrained to 2 3 0 4 6 0 1 0 and before 7 0 ka respectively with reference to previous research the holocene earthquake sequence of the lrf can be established as 2 30 2 43 e1 3 06 4 41 e2 6 71 6 80 e3 7 60 9 81 e4 and 19 70 4 20 e5 ka bp events e1 e3 and e4 might have been caused by events with magnitudes of mw 7 6 7 8 that ruptured the entire lrf event e2 might have been smaller magnitude about m7 0 and ruptured only a portion of the fault the vertical slip rate of the lrf at the qingshan site is inferred as 0 9 or 1 4 1 6 mm year in the last 6 8 ka the slip rate at wulanhashao is considered to have been close to but not

the 2010 m w 7 2 el mayor cucapah earthquake sequence baja california mexico and southernmost california usa active seismotectonics along the mexican pacific margin the el mayor cucapah earthquake sequence started with a few foreshocks in march 2010 and a second sequence of 15 foreshocks of m 2 up to m4 4 that occurred during the 24 h preceding the mainshock the foreshocks occurred along a north south trend near the mainshock epicenter the mw 7 2 mainshock on april 4 exhibited complex faulting possibly starting with a m6 normal faulting event followed 15 s later by the main event which included simultaneous normal and right lateral strike slip faulting the aftershock zone extends for 120 km from the south end of the elsinore fault zone north of the us mexico border almost to the northern tip of the gulf of california the waveform relocated aftershocks form two abutting clusters each about 50 km long as well as a 10 km north south aftershock zone just north of the epicenter of the mainshock even though the baja california data are included the magnitude of completeness and the hypocentral errors increase gradually with distance south of the international border the spatial distribution of large aftershocks is asymmetric with five m5 aftershocks located to the south of the mainshock and only one m5 7 aftershock but numerous smaller aftershocks to the north further the northwest aftershock cluster exhibits complex faulting on both northwest and northeast planes thus the aftershocks also express a complex pattern of stress release along strike the overall rate of decay of the aftershocks is similar to the rate of decay of a generic california aftershock sequence in addition some triggered seismicity was recorded along the elsinore and san jacinto faults to the north but significant northward migration of aftershocks has not occurred the synthesis of the el mayor cucapah sequence reveals transtensional regional tectonics including the westward growth of the mexicali valley and the transfer of pacific north america plate motion from the gulf of california in the south into the southernmost san andreas fault system to the north we propose that the location of the 2010 el mayor cucapah as well as the 1992 landers and 1999 hector mine earthquakes may have been controlled by the bends in the plate boundary

a pure dipole analysis of the gondwana apparent polar wander path paleogeographic implications in the evolution of pangea the paleogeography of prebreakup pangea at the beginning of the atlantic spreading has been a subject of debate for the past 50 years reconciling this debate involves theoretical corrections that cast doubt on available data and paleomagnetism as an effective tool for performing paleoreconstructions this 50 year old debate focuses specifically on magnetic remanence and its ability to correctly record the inclination of the paleomagnetic field in this paper a selection of paleopoles was made to find the great circles containing the paleomagnetic pole and the respective sampling site the true dipole pole tdp was then calculated by intersecting these great circles effectively avoiding nondipolar contributions and inclination shallowing in an innovative method the great circle distance between each of these tdps and the paleomagnetic means show the accuracy of paleomagnetic determinations in the context of a dominantly geocentric axial and dipolar geomagnetic field the tdps calculated allowed a bootstrap analysis to be performed to further consider the flattening factor that should be applied to the sedimentary derived paleopoles it is argued that the application of a single theoretical correction factor for clastic sedimentary derived records could lead to a bias in the paleolatitude calculation and therefore to incorrect paleogeographic reconstructions the unbiased apwp makes it necessary to slide laurentia to the west in relation to gondwana in a b type pangea during the upper carboniferous later evolving during the early permian to reach the final a type pangea configuration of the upper permian 2017 american geophysical union all rights reserved

anomalous stress diffusion in earthquake triggering correlation length time dependence and directionality 1 it has been recently suggested that moderate and large earthquakes can be triggered by similarly sized events at very long range here we study the main characteristics of earthquake triggering by determining its correlation length time dependence and directionality the problem is examined at a global level by using the harvard centroid moment tensor catalogue our results show that the correlation lengths depend only weakly on the magnitude thresholds involved no significant systematic triggering is observed for distances greater than the lithospheric thickness 100 150 km and the correlation length magnitude is similar to the seismogenic thickness 10 20 km the mean triggering distance and correlation length both increase with time very slowly compared with what would be expected from a normal diffusion process this is consistent with a clock advance on the failure time based on the constitutive rules for subcritical crack growth following a transient change in the loading stress the power law scaling disappears after a few months a functional form for the probability of triggering as a function of time and distance is proposed on the basis of the properties of near critical point systems the model fits the data well and could be used to calculate conditional probabilities for time dependent seismic hazard due to earthquake triggering an apparent directionality effect that was observed in the data set can be attributed to an artefact of poor depth determination these results do not preclude individual long range triggering with a potential directionality effect but they do rule out a statistical correlation at distances much greater than the thickness of the lithosphere

detrital magnetizations from redeposition experiments of different natural sediments abstract we carried out several experiments with carbonate rich and clay rich sediments that were redeposited in plastic cubes or in 1 meter long cylindrical tubes with the aim of investigating the sensitivity of the depositional remanent magnetization drm to various environmental and physical parameters in contrast to previous studies we did not observe any difference in the drm acquired with or without saline water for either kind of sediment taking advantage of a gelatin that fixes the position of particles in suspension we were able to measure the magnetization of suspended sediments within water filled columns and thus to test the degree of alignment of magnetic grains the magnetization of clay rich sediments was not far from saturation but the magnetization was considerably reduced after deflocculation because the large flocs that favored alignment of magnetic grains were destroyed by the deflocculant similarly the large flocs found at the bottom of the deposition tubes also reveal an efficient magnetic alignment in contrast the weak magnetization of the carbonate rich sediments with small flocs yielded accurate and well grouped magnetization directions that were not sensitive to deflocculation only a fraction of magnetic grains was mechanically oriented by the field in this case because of the weak net magnetic moments of the grains embedded within small flocs the drm was constrained by redeposition in plastic cubes performed without gelatin and with different field intensities the drm intensity of the carbonate rich sediments is linearly related to field strength which attests to their suitability for studies of relative paleointensity tests performed with mud from several stratigraphic levels in different marine sediment cores failed to reveal a significant influence of carbonate content on drm which suggests a relatively minor role of lithological changes on records of relative paleointensity

slip accumulation and lateral propagation of active normal faults in afar we investigate fault growth in afar where normal fault systems are known to be currently growing fast and most are propagating to the northwest using digital elevation models we have examined the cumulative slip distribution along 255 faults with lengths ranging from 0 3 to 60 km faults exhibiting the elliptical or bell shaped slip profiles predicted by simple linear elastic fracture mechanics or elastic plastic theories are rare most slip profiles are roughly linear for more than half of their length with overall slopes always 0 035 for the dominant population of nw striking faults and fault systems longer than 2 km the slip profiles are asymmetric with slip being maximum near the eastern ends of the profiles where it drops abruptly to zero whereas slip decreases roughly linearly and tapers in the direction of overall aden rift propagation at a more detailed level most faults appear to be composed of distinct shorter subfaults or segments whose slip profiles while different from one to the next combine to produce the roughly linear overall slip decrease along the entire fault on a larger scale faults cluster into kinematically coupled systems along which the slip on any scale individual fault or fault system complements that of its neighbors so that the total slip of the whole system is roughly linearly related to its length with an average slope again 0 035 we discuss the origin of these quasilinear asymmetric profiles in terms of initiation points where slip starts and barriers where fault propagation is arrested in the absence of a barrier slip apparently extends with a roughly linear profile tapered in the direction of fault propagation

complex multifault rupture during the 2016 mw 7 8 kaikōura earthquake new zealand the 2016 moment magnitude m w 7 8 kaik ura earthquake was one of the largest ever to hit new zealand hamling et al show with a new slip model that it was an incredibly complex event unlike most earthquakes multiple faults ruptured to generate the ground shaking a remarkable 12 faults ruptured overall with the rupture jumping between faults located up to 15 km away from each other the earthquake should motivate rethinking of certain seismic hazard models which do not presently allow for this unusual complex rupture pattern science this issue p eaam7194 1 1 lookup doi 10 1126 science aam7194

superficial simplicity of the 2010 el mayor cucapah earthquake of baja california in mexico the geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation propagation and arrest of seismic ruptures the fault system that runs from southern california into mexico is a simple strike slip boundary the west side of california and mexico moves northwards with respect to the east however the m w 7 2 2010 el mayor cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike slip fault here we use geodetic remote sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake we find that the earthquake produced a straight 120 km long fault trace that cut through the cucapah mountain range and across the colorado river delta however at depth the fault is made up of two different segments connected by a small extensional fault both segments strike n130 e but dip in opposite directions the earthquake was initiated on the connecting extensional fault and 15 s later ruptured the two main segments with dominantly strike slip motion we show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves we conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone

source parameters of the 2016 menyuan earthquake in the northeastern tibetan plateau determined from regional seismic waveforms and insar measurements abstract on january 21st 2016 a ms 6 4 earthquake hit menyuan county qinghai province china the nearest known fault is the leng long ling lll fault which is located approximately 7 km north of the epicenter this fault has mainly shown sinistral strike slip movement since the late quaternary period however the focal mechanism indicates that it is a thrust earthquake which is different from the well known strike slip feature of the lll fault in this study we determined the focal mechanism and primary nodal plane through multi step inversions in the frequency and time domain by using the broadband regional seismic waveforms recorded by the china digital seismic network cdsn our results show that the rupture duration was short within 0 2 s after the earthquake and the rupture expanded upwards along the fault plane based on these fault parameters we then solve for variable slip distribution on the fault plane using the insar data we applied a three segment fault model to simulate the arc shaped structure of the northern lll fault and obtained a detailed slip distribution on the fault plane the inversion results show that the maximum slip is 0 43 m and the average slip angle is 78 8 with a magnitude of mw 6 0 and a focal depth of 9 38 km with the geological structure and the inversion results taken into consideration it can be suggested that this earthquake was caused by the arc shaped secondary fault located at the north side of the lll fault the secondary fault together with the lll fault forms a normal flower structure the main lll fault extends almost vertically into the base rock and the rocks between the two faults form a bulging fault block therefore we infer that this earthquake is the manifestation of a neotectonics movement in which the bulging fault block is lifted further up under the compresso shear action caused by the tibetan plateau pushing towards the northwest direction

full vector model for magnetization in sediments abstract sediments provide a continuous record of past geomagnetic field variations although it is theoretically possible to get both the direction and intensity of the geomagnetic field from sediment records the mechanism is not fully understood previous workers have postulated that flocculation plays an important role in detrital remanent magnetism drm flocs are porous loose and highly fragile aggregates of microscopic clay particles and their behavior in a viscous medium is likely to be different than single particles of magnetic minerals in order to understand the role of flocculation in sediment magnetization we carried out a set of redeposition experiments at different field intensities and a quasi constant field inclination of 45 we present here a simple numerical model of flocculation incorporating both magnetic and hydrodynamic torques to explain the experimental data at small floc sizes drm acquisition is likely to be non linear in field strengths comparable to the earth s but the sediments may be able to record the directions accurately with increasing floc sizes sediments may retain a record of the intensity that is linearly related to the applied field or a direction parallel to the applied field but are unlikely to do both at the same time also the majority of the magnetic particles in the sediments may not be contributing significantly towards the net drm and any bulk normalizing parameter may be unsuitable if the depositional environment has changed over the depositional period

dynamic versus static stress triggering and friction parameters inferences from the november 23 1980 irpinia earthquake this paper concentrates on the problem of fault interaction and earthquake triggering through the 1980 irpinia italy sequence more specifically this paper deals with the problem of the triggering of the second subevent by the mainshock the interaction between the two segments is modeled through a dynamic coulomb failure function the aims of this paper are first to discriminate between the dynamic and the static stress effects on the triggering if these effects exist second to estimate the fault strength relative to the initial state of stress third to determine the parameters of a slip dependent friction law that lead to the observed delay of 20 s numerical simulations show that the critical slip dc may range from 0 03 m up to 1 7 m and that the initial slope of the friction law 0 must be lower than 0 04 m 1 we show that the relative magnitude of the fault strength and the initial state of stress govern the existence and value of a dc lower threshold under which the fault always ruptures before 13 s a close to failure fault is not consistent with a critical slip dc less than 0 8 m whereas small values of dc typically 0 03 m imply a far from failure fault general results concern the effect of a dynamic stress pulse we show that an event can be triggered by a transient stress pulse and that in this case the event can have an initiation duration much longer than the pulse duration we show that it is possible to explain both the triggering and the time delay only with the effect of the transient stress pulse this may explain aftershock triggering even in regions of negative coulomb failure function or long distance triggering of earthquakes by propagating waves

relative paleointensity estimates from magnetic anisotropy proof of concept relative paleointensity data from sedimentary rocks play an important role to decipher the workings of the geodynamo and to correct for atmospheric cosmogenic radionucleide production so it is important to understand how sediments acquire remanent magnetizations and to better assess the quality of relative paleointensity data we present experimental results from sediments deposited in controlled magnetic fields to observe the changes in magnetic anisotropy as a function of applied field strength going from near earth like values to almost full saturation relative paleointensity values followed a very well defined power law through the entire range of applied field intensities magnetic remanence fabrics evolved from oblate with maximum anisotropy axes in the sedimentary plane at low field strengths to prolate with maximum anisotropy axes parallel to the applied field direction at high fields anisotropy of magnetic susceptibility also evolved with field strength but in a much less coherent manner than anisotropy of magnetic remanence the experiments used well characterized natural sediments containing single domain magnetite which made it possible to numerically model the data the model matches the field dependency of both relative paleointensity and magnetic fabric development using a simple assumption that a large proportion similar to 80 of the remanence carriers in the sediments are unable to align with the magnetic field while a small fraction are free to align anisotropy of magnetic remanence thus holds promise to improve and assess relative paleointensity estimates and helps improve theoretical treatment of magnetic recording in sediments c 2019 elsevier b v all rights reserved

rapid zonation of abrupt mass movement hazard part ii applications debris flows landslides and rock falls are severe abrupt mass movement hazards whose recorded occurrence in china has increased markedly in the past two decades with the county and city based data the debris flow hazard zonation for china was accomplished using the rapid zonation of abrupt mass movement hazard rzamh approach whose principles are described in the part i companion paper the entire area of china was classified into five regions with different degrees of hazard landslide and rock fall hazard zonations for china were also presented a sensitivity analysis demonstrated the robustness of the rzamh approach direct validation was made with comparison of the zonation results and historical recordings on occurrence distribution of debris flows the zonations produced by the rzamh approach and other methods were compared by similarity analysis and paired sample t tests for the indirect validation of the accuracy of the rzamh approach

along strike and downdip segmentation of the pamir frontal thrust and its association with the 1985 mw 6 9 wuqia earthquake

dynamics of fault interaction parallel strike slip faults we use a two dimensional finite difference computer program to study the effect of fault steps on dynamic ruptures our results indicate that a strike slip earthquake is unlikely to jump a fault step wider than 5 km in correlation with field observations of moderate to great sized earthquakes we also find that dynamically propagating ruptures can jump both compressional and dilational fault steps although wider dilational fault steps can be jumped dilational steps tend to delay the rupture for a longer time than compressional steps do this delay leads to a slower apparent rupture velocity in the vicinity of dilational steps these dry cases assumed hydrostatic or greater pore pressures but did not include the effects of changing pore pressures in an additional study we simulated the dynamic effects of a fault rupture on undrained pore fluids to test sibson s 1985 1986 suggestion that wet dilational steps are a barrier to rupture propagation our numerical results validate sibson s hypothesis by demonstrating that the effect of the rupture on the undrained pore fluids is to inhibit the rupture from jumping dilational stepovers the basis of our result differs from sibson s hypothesis in that our model is purely elastic and does not necessitate the opening of extension fractures between the fault segments

source complexity of the 1994 northridge earthquake and its relation to aftershock mechanisms we determined the source process of the 1994 northridge earthquake in relation to the aftershock mechanisms to study the source complexity of the mainshock we inverted the p and sh waveforms recorded by the iris and ida iris networks using the method of kikuchi and kanamori 1991 in which the rupture is represented by a series of discrete subevents with varying mechanisms the waveforms show that the rupture consisted of several subevents with about 2 sec in between our solution consists of three subevents with essentially the same mechanism viz strike dip and slip of 130 42 and 116 respectively the first subevent occurred at a depth of about 19 km followed after 2 sec by the second and largest subevent at a depth of 17 km and the third subevent again 2 sec after the second at a depth of about 13 km the total moment from the body waves of this sequence is about 1 1 10 26 dyne cm m w 6 6 with a source duration of 7 sec the large depths of these subevents explain the lack of any surface rupture furthermore the upward propagation of the subevents is consistent with the depth of the hypocenter and the distribution of the aftershocks which are shallower and more northerly than the mainshock hypocenter the aftershocks were analyzed using data from the terrascope network we inverted short period surface waves to determine the moment tensor for 70 events with m w 3 5 the aftershocks can be grouped into three regions based on the mechanisms the eastern part of the aftershock zone where we find thrust events with mechanisms very similar to the main event a central area with predominantly strike slip events and an area to the west where we find oblique thrust events but with more northerly p axes than in the eastern region this distribution suggests that the fault system on which the northridge earthquake occurred is segmented and that the extent of the northridge rupture is controlled by a change in geometry of the fault we find a high stress drop 270 bar for the mainshock we propose that the changes in the fault geometry prevented a slip pulse from propagating thereby causing a high ratio of slip to rupture length

rapid zonation of abrupt mass movement hazard part i general principles hazards caused by mass movement cost many human lives and cause severe damage to property accurate zonation of such hazards provides an important tool for preventive measures previous approaches for mass movement hazard zonation are costly because they require large amounts of data time and labor and are only applicable to specific local areas in this paper a rapid zonation of abrupt mass movement hazard rzamh applicable to large regions is proposed it involves the selection of appropriate zonation principles routes units and indexes that can be used for the classification of reference groups identification of matching groups of test sites evaluation of blank test sites and coalescence of sub regions into specified zonation areas the k means clustering method is used in the classification processes the applicability of the rzamh approach to a large area implies that the number of reference sites required to build the reference groups is not of primary importance as long as the reference sites are representative therefore for large areas the rzamh approach would be more economical than other conventional methods the rzamh approach is probably applicable to all abrupt mass movement hazards including rock falls landslides and debris flows

effects of ph and salinity on the intensity of magnetization in redeposited sediments abstract the intensity of magnetization in redeposited sediments was measured as a function of salinity and ph of the sediment water mixture the intensity was relatively low at high salinity or low ph under these conditions inter particle bonds are enhanced which lead to the formation of larger flocs ferromagnetic minerals magnetite in our sediment are incorporated in the flocs consisting mainly of non magnetic minerals and orientation along an applied field is resisted by the drag proportional to the third power of the diameter of the floc higher intensity is recorded at lower salinity and higher ph when inter particle forces are weaker and floc sizes are smaller the increase of magnetization as a function of ph stops at a ph of about 5 which is the pzc of the edge of illite the dominant non magnetic mineral in our sediment above this ph both the edge and face of the illite grains are negative and there is net repulsion which retards flocculation the interactions between clay particles therefore have a larger effect on the intensity of magnetization than interactions between magnetite and clay this suggests that magnetite is always included in a clay magnetite domain and this domain is the smallest unit that is reoriented by a magnetic field

earthquake locations in southern california obtained using source specific station terms we relocate 297 400 events recorded by the southern california seismic network scsn between 1975 and 1998 using spatially varying station terms to improve relative location accuracy our method uses existing scsn p and s picks a smooth one dimensional velocity model and an iterative grid search approach based on the l1 norm we apply empirical corrections for three dimensional structure by computing station timing corrections that continuously vary as a function of source position station terms for each event are obtained by smoothing the residuals from nearby events using a natural neighbor delaunay tessellation of the seismicity and then iterating until a stable set of locations and station terms is achieved our approach achieves relative location accuracy comparable locally to master event methods but can be applied uniformly over large regions median estimated standard errors for our final locations are 328 m in horizontal position and 741 m in depth our locations exhibit much less scatter particularly in depth than those of the scsn catalog and a greater tendency to align into linear and planar features suggestive of fault structures our results appear comparable to and in some cases better than previous scsn relocation studies using joint hypocenter velocity inversion techniques plots of daytime versus nighttime events permit discrimination between clusters of natural and artificial seismicity we observe no simple relationship between the maximum depth of seismicity and surface geology

an integrated approach for hazard assessment and mitigation of debris flows in the italian dolomites abstract this paper shows the results of research on a debris flow occurring on 4 september 1997 in the territory of cortina d ampezzo dolomites italy where it caused a significant threat owing to the intense urban development typical of several alpine valleys the event which affected the talus fans at the foot of mt pomagagnon near the village of fiames blocked the state road no 51 alemagna and after sparing some houses barred the course of the torrent boite and formed an impoundment this debris flow aroused great concern among local authorities and the belluno civil engineers board therefore the construction of embankments for protecting the buildings threatened by the debris flow was started immediately this area was studied in detail during this research in order to identify the hazard situations of the whole slope the investigations made use of an integrated approach including historical geomorphological geostructural meteorological pedological and forest management aspects furthermore assessments of the debris volumes potentially removable in the source area were carried out the geomorphological evolution of the area was reconstructed pinpointing the morphological changes occurring in the past 45 years taking into account the increased frequency and magnitude of recent events and considering the location of roads and buildings in the accumulation area the risk conditions were analysed in order to identify a risk zonation and to propose mitigation measures

relative geomagnetic paleointensity of the brunhes chron and the matuyama brunhes precursor as recorded in sediment core from wilkes land basin antarctica abstract paleomagnetic and rock magnetic investigation was performed on the 35 m long md03 2595 cado coring adelie diatom oozes piston core recovered on the continental rise of the wilkes land basin east antarctica analysis of the characteristic remanent magnetization chrm inclination record indicates a normal magnetic polarity for the uppermost 34 m of the sequence and a distinctive abrupt polarity change at the bottom of the core this polarity change which spans a 27 cm thick stratigraphic interval represents a detailed record of the matuyama brunhes m b transition and it is preceded by a sharp oscillation in paleomagnetic directions that may correlate to the m b precursor event paleomagnetic measurements enable reconstruction of geomagnetic relative paleointensity rpi variations and a high resolution age model was established by correlating the cado rpi curve to the available global reference rpi stack indicating that the studied sequence reaches back to ca 800 ka with an average sedimentation rate of 4 4 cm ka orbital periodicities 100 ka and 41 ka were found in the chrm inclination record and a significant coherence of chrm inclination and rpi record around 100 ka suggests that long term geomagnetic secular variation in inclination is controlled by changes in the relative strength of the geocentric axial dipole and persistent non dipole components moreover even if the relatively homogeneous rock magnetic parameters and lithofacies throughout the recovered sequence indicates a substantial stability of the east antarctic ice sheet during the middle and late pleistocene influence of the 100 ka and 41 ka orbital periodicities has been detected in some rock magnetic parameters indicating subtle variations in the concentration and grain size of the magnetic minerals linked to orbital forcing of the global climate

spatio temporal stress states estimated from seismicity rate changes in the tokai region central japan abstract since unprecedented large scale silent slip was detected by gps in 2001 in the tokai region evaluating whether such movement is uniquely connected to the expected tokai earthquake or repeatedly occurs in this area becomes vitally important because of short history of gps observations and the limited areal coverage surrounding the suruga trough we take advantage of continuously recorded seismicity that is presumed to be sensitive to the deformation at seismogenic depth together with the well maintained nied earthquake data we employ the seismicity to stress inversion approach of rate state friction to infer the spatio temporal stress changes in and around the presumed hypocentral zone of the future tokai earthquake mapping stress changes inverted from microseismicity year by year we find that the stress under lake hamana the western expected future tokai source has been decreasing since 1999 during which the gps data showed a normal trend of plate coupling in contrast stresses in the surrounding regions are calculated to have increased by transfer from lake hamana region we interpret that this continuous process is associated with the 2000 2004 tokai slow slip event the characteristic patterns related to aseismic stress release are also identified in the early 1980s and during 1987 1989 when slow events are inferred to have occurred on the basis of conventional geodetic measurements revisiting the seismotectonics and taking into account the mechanical implications of the inversion results we argue that the transition zone situated between a deep stable creeping zone and a locked zone undergoes episodic creep and plays an important role in the transfer of stress to the locked zone consequently even though we speculate that the current 2000 to present day silent slip event might be one of the repeating events the inferred enlargement of the stress releasing area is significant and possibly raises the likelihood of the next tokai earthquake

fault segmentation new concepts from the wasatch fault zone utah usa the question of whether structural segment boundaries along multisegment normal faults such as the wasatch fault zone wfz act as persistent barriers to rupture is critical to seismic hazard analyses we synthesized late holocene paleoseismic data from 20 trench sites along the central wfz to evaluate earthquake rupture length and fault segmentation for the youngest 3 ka and best constrained earthquakes differences in earthquake timing across prominent primary segment boundaries especially for the most recent earthquakes on the north central wfz are consistent with segment controlled ruptures however broadly constrained earthquake times dissimilar event times along the segments the presence of smaller scale subsegment boundaries and areas of complex faulting permit partial segment and multisegment e g spillover ruptures that are shorter 20 40 km or longer 60 100 km than the primary segment lengths 35 59 km we report a segmented wfz model that includes 24 earthquakes since 7 ka and yields mean estimates of recurrence 1 1 1 3 kyr and vertical slip rate 1 3 2 0 mm yr for the segments however additional rupture scenarios that include segment boundary spatial uncertainties floating earthquakes and multisegment ruptures are necessary to fully address epistemic uncertainties in rupture length we compare the central wfz to paleoseismic and historical surface ruptures in the basin and range province and central italian apennines and conclude that displacement profiles have limited value for assessing the persistence of segment boundaries but can aid in interpreting prehistoric spillover ruptures our comparison also suggests that the probabilities of shorter and longer ruptures on the wfz need to be investigated

a rational method for estimating maximum discharge of a landslide induced debris flow a case study from southwestern china this paper presents a rational method for estimating the maximum discharge of a landslide induced debris flow the method has five basic principles or steps a to identify and measure representative bends and straight zones along a channel through which a debris flow went down b to evaluate peak debris flow velocity in the bends c to assess peak debris flow velocity in the straight channel zones d to use the peak velocities to estimate the distribution of peak discharge along the entire channel and e to find the maximum velocity and discharge of the debris flow the method is illustrated with a case study of a landslide induced debris flow at a mountainous region near chengdu southwestern china the results show that the peak debris velocity was between 2 4 and 4 7 m s 1 and the peak debris discharge was between 6 7 and 35 7 m 3 s 1 the peak discharge initially increased at the upper portion of the channel then decreased at the lower portion indicating that the upper channel experienced erosion but the lower channel experienced deposition the location with the maximum debris flow discharge corresponds to the point where the volume of the debris flow started to decrease the method presented in this paper can help to prevent or mitigate debris flow hazards c 2006 elsevier b v all rights reserved

are hydrodynamic shape effects important when modelling the formation of depositional remanent magnetization recent conceptual models have attributed the weak depositional remanent magnetizations observed in natural sediments to flocculation processes in the water column magnetic particles included into flocs have not only to rotate themselves into alignment with the geomagnetic field but also the larger particles to which they are attached making remanence acquisition an inefficient process alignment is hindered further when the magnetization vectors of the particles in any given floc partially cancel reducing the overall magnetic torque existing numerical simulations of flocculation effects on depositional remanence formation have been limited to spherical bodies with translational and rotational motion acting independently of each other in the case of non spherical flocs the translational and rotational motion are coupled and such bodies will describe a complex trajectory through the water column calculations will be presented that show the torque exerted on a non spherical floc by the surrounding water can be orders of magnitude greater than the magnetic torque non spherical flocs will therefore align less efficiently with the geomagnetic field and hydrodynamic effects may play an important role in controlling the magnitude of sedimentary remanence

new constraints on slip rates of the fodongmiao hongyazi fault in the northern qilian shan ne tibet from the 10 be exposure dating of offset terraces abstract the fodongmo hongyazi fault fhf is a major thrust of northeastern tibet bounding the qilian shan it accommodates crustal shortening across this region and has produced a strong historical earthquake until now the slip rate has been poorly constrained limiting our understanding of its role in the accommodation of deformation across this region in this paper faulted terraces at two sites on the western and middle segments of the fhf were mapped with satellite imagery and field observations chronological constraints are placed on the ages of displaced river terraces at these sites using terrestrial cosmogenic nuclide tcn exposure dating these ages combined with offsets measured from spot 6 dem s yield average vertical slip rates of 1 3 0 1 mm yr for the western segment since 207 ka and 0 9 0 1 mm yr since 46 ka for the middle segment these data suggest that the fhf accommodates 15 20 of the total shortening across the qilian shan 5 5 7 mm yr in addition comparisons of our data with published slip rates along the northern qilian thrust fault zone show that the fastest tectonic uplift occurs along the western portion of the northern qilian shan this is consistent with estimates deduced from geomorphology the western portion of the qilian shan is mainly controlled by compressional deformation produced by the northward movement of the northeastern tibetan plateau while the eastern qilian shan is mainly controlled by the eastward extrusion of material along the left lateral haiyuan strike slip fault

scales of structural heterogeneity within neotectonic normal fault zones in the aegean region abstract structural heterogeneities within neotectonic normal fault zones in the aegean region are important controls on the geomorphic expression of their uplifted footwall blocks contrasting fault rocks and slip plane phenomena corrugations comb fractures slip parallel fractures and pluck holes are responsible for mesoscopic inhomogeneities within fault scarps along strike disruptions in the continuity of fault scarps step over zones step up zones step down zones footwall cross faults and hangingwall cross faults are products of perturbations in slip plane geometry or intersections with transverse faults large scale variations in range front morphology reflect contrasting patterns of deformation within fault zones some major fault zones and many minor fault zones are characterized by a migration of the active slip plane towards the hangingwall resulting in a distributed network of high angle faults and a range front which is stepped in profile the presence of a localized mass of uneroded bedrock hangingwall salients protruding from the hangingwall of some major fault zones results in intense deformation along a principal slip plane and a range front which is ramp like in profile as a consequence of structural heterogeneities within neotectonic normal fault zones fault scarps and range fronts in the aegean region are subject to a temporally and spatially variable pattern of degradation

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

a reassessment of post depositional remanent magnetism preliminary experiments with natural sediments abstract realignment of magnetic grains below the sediment water interface is thought to impart a post depositional remanent magnetization pdrm however there is little convincing evidence in the published literature that pdrm is the dominant mechanism by which sediments become magnetized we report here preliminary results from two kinds of laboratory experiments designed to investigate whether post depositional reorientation of magnetic particles is likely to occur in nature in the first experiment we monitored changes in the magnetization of natural sediments in response to changing laboratory fields our results are inconsistent with post depositional reorientation of magnetic particles in a second experiment we put live worms in a multi core tube with the original sediment water interface intact remagnetization was only observed in samples taken from a mound of fecal pellets formed at the surface these pellets had been suspended by a worm and redeposited in the laboratory field the other samples which were not resuspended but nonetheless bioturbated by the worms showed no change in magnetization our preliminary results do not support the hypothesis that post depositional reorientation occurs in natural undisturbed sediments below the sediment water interface

calibration of geomagnetic paleointensity data based on redeposition of sedimentary rocks abstract a new express method for redeposition of sedimentary rocks is proposed the method may be used for calibration of the ancient geomagnetic field intensity data obtained using sedimentary rocks the results of testing of the method for assessment of the intensity of ancient geomagnetic field using redeposition on the modern sediments formed in different climatic zones are presented it is shown that the error of a single determination of the magnetic field intensity on the contemporary marine sediments does not exceed 20 the results of determination of the ancient geomagnetic field intensity from sedimentary rocks available to date are summarized the average values of the paleointensity in the late cretaceous early jurassic late jurassic triassic permian late and early carboniferous obtained from sedimentary and thermomagnetized rocks has been compared it is revealed that sedimentary and thermomagnetized rocks have similar potentials for the assessment of the dynamics of the late paleozoic mesozoic paleointensity

rupture terminations and size of segment boundaries from historical earthquake ruptures in the basin and range province abstract the fault segmentation method is commonly used to estimate the potential earthquake size segment boundaries play an important role in arresting earthquake ruptures from event to event in the basin and range province earthquake rupture terminations are commonly associated with structural discontinuities but not all structural discontinuities have the capability to terminate an earthquake rupture the size of structural discontinuities with respect to the rupture length and displacement may play an important role in controlling rupture termination studies of the geometric pattern of seven well documented historical earthquake ruptures in the basin and range province reveal three important relationships between rupture termination and the size of structural discontinuities firstly terminations of normal faulting earthquakes are often associated with structural discontinuities at least for the five historical ruptures studied in this paper secondly the sizes of structural discontinuities at the end of earthquake rupture zones are generally the largest among the structural discontinuities within the rupture zone thirdly there appears to be a trend that larger earthquake ruptures are stopped by larger structural discontinuities the size of structural discontinuities that stopped the earthquake seems to scale with the length and displacement of earthquake surface rupture

evidence of complex faulting near the huangcheng shuangta fault gansu china from the 11 may 2012 mw 4 8 sunan earthquake we determined the mainshock source parameters relocated aftershocks and modeled broadband waveforms from 14 stations within 300 km of the 11 may 2012 m w 4 8 sunan earthquake the focal mechanism determined by the cut and paste method is predominantly strike slip with a component of thrust and occurred at a depth of 5 1 km the shallow focal depth likely contributed to the strong shaking in the epicentral area the strike and dip of nodal plane i are consistent with the strike and dip of the huangcheng shuangta fault which may have hosted the devastating 1927 m s 8 0 gulang earthquake and the surface trace for which is 2 km northeast of the sunan epicenter we used the double difference location method to relocate aftershocks and found that they occurred at depths from 4 to 7 km on a well defined plane dipping to the northwest this plane closely corresponds with nodal plane ii of our focal mechanism the dip of the relocated aftershocks is consistent with the dip of nodal plane ii therefore this earthquake likely occurred on a secondary fault in a region undergoing transpression which indicates that deformation is not restricted to the huangcheng shuangta fault

shallow seismogenic zone detected from an offshore onshore temporary seismic network in the esmeraldas area northern ecuador for a given site many factors control the seismic risk earthquake magnitude hypocentral distance rupture mechanism site effects and site vulnerability are among the most important this article deals with one of these factors the depth of the seismogenic zone in the northern ecuadorian subduction system beneath a highly vulnerable site the city of esmeraldas and its industrial complex the ecuadorian oil refinery and shipping terminal to address this problem we analyzed data from a three weeks passive seismological experiment conducted in the spring of 1998 using 13 ocean bottom seismometers and 10 portable land stations a preliminary interpretation of wide angle data obtained in the fall of 2000 in the manta area 100 km south of the study area unambiguously indicates the presence of a velocity inversion in the ecuadorian margin velocity structure this velocity inversion is characterized by a shadow zone of 1 s on the record sections and is interpreted as the result of a velocity contrast between the upper plate structure and the sedimentary and basaltic layer ii of the subducted oceanic nazca plate one dimensional velocity models are deduced from these wide angle data and are used for earthquake location in the esmeraldas area this highly improved the hypocentral parameter determinations the updip limit of the seismogenic zone is found at a depth of 12 km 35 km eastward of the trench and the depth of the seismogenic zone below the esmeraldas city is found at 20 km this shallow depth of the seismogenic zone dramatically increases the seismic hazard of the area

magnetic paleointensity stratigraphy and high resolution quaternary geochronology successes and future challenges abstract magnetic paleointensity stratigraphy is used to detect variations in the strength of earth s ancient magnetic field paleointensity studies have demonstrated that a dominantly dipolar geomagnetic signal can be recorded in a globally coherent manner in different types of sediments and in non sedimentary archives including ice core records and marine magnetic anomaly profiles the dominantly dipolar nature of geomagnetic paleointensity variations provides a global geophysical signal that has come to be widely used to date quaternary sediments despite the many successful applications of paleointensity assisted chronology the mechanisms by which sediments become magnetized remain poorly understood and there is no satisfactory theoretical foundation for paleointensity estimation in this paper we outline past successes of sedimentary paleointensity analysis as well as remaining challenges that need to be addressed to place such work on a more secure theoretical and empirical foundation we illustrate how common concepts for explaining sedimentary remanence acquisition can give rise to centennial to millennial offsets between paleomagnetic and other signals which is a key limitation for using paleointensity signals for geochronology our approach is intended to help non specialists to better understand the legitimate uses and limitations of paleointensity stratigraphy while pointing to outstanding problems that require concerted specialist efforts to resolve

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

behavior of the superstition hills fault during the past 330 years we have investigated the recent prehistoric behavior of the superstition hills fault by examining its effect on the beach deposits of ancient lake cahuilla excavation of these sediments in three dimensions where they are cut by the fault has enabled determination of total offset since the latest highstand of the lake about 330 years ago as of 3 march 1988 total dextral offset was 1106 50 mm about 609 mm of this amount can be attributed to one or more slip events before 1987 the remaining slip occurred during the moderate earthquake of 24 november 1987 and as subsequent aftercreep additional aftercreep here might produce a total of 1210 100 mm for that event thus if afterslip continues according to our prediction slip associated with the penultimate seismic slip event on the superstition hills fault was only about half of the co seismic slip and predicted afterslip associated with the 1987 earthquake this difference established at a single site on the fault may reflect a larger size for the 1987 event than for its predecessor we calculate that the slip rate of the superstition hills fault zone averaged over the past 330 years is between about 2 and at least 6 mm yr at this site during this time the average interval between large surface slip events on the superstition hills fault has been between about 150 and 300 years the pre 1987 slip event documented in our excavations could have occurred at any time between a d 1660 and about a d 1915 these results are significant for understanding earthquake recurrence and patterns of earthquakes in the imperial and coachella valleys

the kazova basin an active negative flower structure on the almus fault zone a splay fault system of the north anatolian fault zone turkey abstract the kazova basin is located within the almus fault zone afz a splay fault system of the north anatolian fault zone in the central pontides turkey it is a 0 7 10 km wide 60 km long wedge shaped right lateral strike slip depression bounded by the mercimekda i camdere fault set in the north and the tokat fault set in the south the kazova basin is superimposed on pre pliocene basement rocks while its basin fill comprises the pliocene to lower quaternary kizkayasi and cerci formations and quaternary alluvials the mercimekda i camdere and tokat fault sets of the afz the basin margin faults of the kazova basin have a considerable amount of normal separation and show a divergent character here the kazova basin is interpreted as an active negative flower structure where the combination of normal movement extension along the different segments of the afz and the oblique extension between its branching splays resulted from a natural response to the anticlockwise rotation along the afz are suggested basin forming mechanism this kind of basin is first from turkey although different types of strike slip basins such as fault wedge pull aparts composite pull aparts are widely represented and well known

latest pleistocene to holocene thrusting recorded by a flight of strath terraces in the eastern qilian shan ne tibetan plateau

formation of segmented normal faults a 3 d perspective the interpretation of fault kinematics from geometric data is an essential step in developing an understanding of the growth of fault systems constraints on fault geometry are however often restricted to 2 d maps or cross sections in this article we consider the extent to which kinematic interpretations of faulting benefit from a 3 d rather than 2 d geometrical perspective concentrating on relay zones and segmented normal fault arrays we suggest that very different interpretations of their evolution arise from the recognition that the propagation directions of faults and fault segments will rarely be contained within the inspection plane of 2 d data a 3 d perspective favours an interpretation in which the segments of a fault array are kinematically interrelated from their initiation individual segments in such systems may link into a single fault surface out of the plane of inspection or may be unconnected in 3 d we argue that this interpretation which conflicts with the often suggested model of incidental overlap of originally isolated faults should be the preferred model for the generation and growth of segmented normal fault arrays

five short historical earthquake surface ruptures near the silk road gansu province china five historical earthquakes m 7 have occurred along the hexi corridor at the northeastern margin of the tibetan plateau since a d 180 these are the a d 180 gaotai earthquake m 7 5 the 1609 hongyazi earthquake m 7 25 the 1927 gulang earthquake m 8 0 the 1932 changma earthquake m 7 6 and the 1954 shandan earthquake m 7 3 they are predominantly reverse slip except for the 1932 changma and the 1954 shandan earthquakes the changma earthquake is char acterized by left lateral faulting with a reverse component while the shandan earth quake by right lateral faulting with a normal component fieldinvestigationsindicatethatthelengthofthesurface rupturezoneisonly28km for the a d 180 earthquake 11 km for the 1609 earthquake 23 km for the 1927 earth quake and 5 1 km for the 1954 earthquake much shorter than that predicted using an empirical equation between moment magnitude mw surface rupture length srl coseismic displacement d maximum displacement md average displacement ad and mode value combined displacement statistic mvcds mw 5 91 0 609logsrl dfor strike slip faults mw 5 81 0 653logsrl dfor reverse faults and mw 6 93 0 82logad mvcdsfor all faults this may be common for reverse faulting earthquakes worldwide and suggests that trying to estimate magnitudes of past earthquakes from one type of even the most recent surface rupture data is unreliable and the empirical equations between magnitude coseismic slip and surface rupture length should be applied with caution to seismic hazard assessment on active thrust faults

global survey of aftershock area expansion patterns we developed an objective method to define the aftershock areas of large earthquakes as a function of time after the main shock the definition is based upon the amount of energy released by aftershocks the spatial distribution of the energy release is first determined and is contoured the 1 day aftershock area is defined by a contour line corresponding to the energy release level of 10 15 6 ergs 100 km 2 day the 10 day 100 day and 1 y aftershock areas are similarly defined by contour lines corresponding to 10 14 8 10 14 0 and 10 13 5 ergs 100 km 2 day respectively we also define the expansion ratios at time t by the ratio of the aftershock area at t to that at 1 day using this method we study the aftershock area expansion patterns of 44 large m s 7 5 and five moderate shallow earthquakes which occurred from 1963 to 1980 each aftershock sequence is examined at four different times i e 1 day 10 days 100 days and 1 y after the main event we define the aftershock area expansion ratios and e by s 100 s 1 and l 100 l 1 respectively here s t and l t are the area and the length of the aftershock area respectively at time t our study suggests that a distinct regional variation of aftershock area expansion patterns is present it is strongly correlated with the tectonic environment in general the subduction zones of the mariana type have large expansion ratios and those of the chilean type have small expansion ratios some earthquakes that occurred in the areas of complex bathymetry such as aseismic ridges tend to have large expansion ratios these results can be explained in terms of an asperity model of fault zones in which a fault plane is represented by a distribution of strong spots called the asperities and weak zones surrounding the asperities the rupture immediately after the main shock mostly involves asperities after the main rupture is completed the stress change caused by the main shock gradually propagates outward into the surrounding weak zones this stress propagation manifests itself as expansion of aftershock activity in this simple picture if the fault zone is represented by relatively large asperities separated by small weak zones chilean type then little expansion of aftershock activity would be expected on the other hand if relatively small asperities are sparsely distributed mariana type significant expansion occurs the actual distribution of asperities is likely to be more complex than the two cases described above however we would expect that the expansion ratio is in general proportional to the spatial ratio of the total asperity area to the fault area