multi fault rupture and successive triggering during the 2012 mw 8 6 sumatra offshore earthquake 1 on april 11 2012 a mw 8 6 strike slip earthquake struck the northern sumatra offshore region and became the largest intraplate event ever recorded there preliminary study results show a remarkably complex rupture pattern on a fault system manifested by north south trending paleo transform faults and east west striking abyssal hill fabric to image the rupture pattern of the earthquake we back projected teleseismic p wave recordings observed at three regional seismic networks eu au and f net our results indicate that the earthquake ruptured on a conjugate fault system composed of two subparallel wnw ese trending faults and a nne ssw striking fault in between for a duration of at least 120 s the rupture started at the wnw end of the first wnw ese trending fault located at the east of the conjugate fault system and propagated toward ese it then jumped to the second nne ssw trending fault located west of the first fault and first extended sswward and 15 s later nneward after its end on the second fault the rupture jumped onto the third wnw ese trending fault and continued wnwward the static coulomb stress changes calculated from the rupture of the first and then the second faults based on simplified uniform slip models suggest that initiation of the rupture on the second fault could be statically and dynamically triggered by the first fault however the third fault was primarily dynamically triggered by s or even love waves radiated from the southern branch of the second fault

simultaneous rupture along two conjugate planes of the wharton basin earthquake analysis of broadband teleseismic data shows that the 18 june 2000 wharton basin earthquake a moment magnitude 7 8 intraplate event in the region of diffuse deformation separating the indian and australian plates consisted of two subevents that simultaneously ruptured two near conjugate planes this mode of rupture accommodates shortening by a mechanism different from that previously known elsewhere in the region the larger subevent occurred on a fossil fracture zone with a relatively high stress drop of about 20 megapascals showing that large stresses can accumulate in regions of distributed deformation

direct evidence of active deformation in the eastern indian oceanic plate conventional plate tectonics theory postulates that plates only deform on their boundaries to the contrary there is ample evidence of intraplate deformation in the equatorial indian ocean west of the ninetyeast aseismic ridge prior to this study no direct evidence of deforma tion east of the ninetyeast ridge was available we present the results of a multipurpose geo physical cruise showing that intraplate deformation also occurs in this area long at least 1000 km left lateral north south strike slip faults are active and reactivate fossil fracture zones this style of deformation is strikingly different from the east west folds and reverse faults that affect the region west of the ninetyeast ridge contrasting processes of convergence at the northern plate boundaries can account for the two styles of deformation west of the ninetyeast ridge there is a continent continent collision and east of the ridge oceanic lithosphere subducts along the sumatra trench the ninetyeast aseismic ridge therefore appears to be a mechanical border separating two distinct deformed areas

deep seismic reflection images of the wharton basin oceanic crust and uppermost mantle offshore northern sumatra relation with active and past deformation 1 we present deep seismic reflection images along two profiles collected in 2006 in the wharton basin offshore northern sumatra the main profile is located subparallel to the sumatran trench at a distance of 32 66 km faulting of the entire sedimentary section strike slip deformation sometimes accompanied by a dip slip component is imaged over two fracture zones of the extinct wharton spreading center that prior studies have shown to be reactivated as left lateral faults the western fracture zone is associated with a wide region of strong basement topography a difference in crustal thickness of 1 5 km and an age offset of 9 ma the epicenters of the 11 april 2012 mw 8 6 great strike slip earthquake its mw 7 2 foreshock and mw 8 2 aftershock align along this major structure 100 km south of the profile intersection our high quality long offset seismic reflection data also reveal bright dipping reflections extending down to a maximum of 24 km into the oceanic mantle 37 km below sea level apparent dips are mostly 25 35 corresponding to 30 55 along either n s to nne ssw or e w to wnw ese directions which encompass the directions of plate fabric and nodal planes of the mw 8 6 event we suggest that these enigmatic reflections arise from presently inactive dip slip fault planes reaching for the deepest ones to the base of the brittle layer possible origins include extension related to plate bending or an episode of now inactive thrust type deformation reactivating paleonormal faults similar to that taking place in the central indian basin

the 2012 sumatra great earthquake sequence the equatorial indian ocean is a well known place of active intraplate deformation defying the conventional view of rigid plates separated by narrow boundaries where deformation is confined on 11 april 2012 this region was hit in a couple of hours by two of the largest strike slip earthquakes ever recorded moment magnitudes mw 8 6 and 8 2 broadband seismological observations of the mw 8 6 mainshock indicate a large centroid depth 30 km and remarkable rupture complexity detailed study of the surface wave directivity and moment rate functions clearly indicates the partition of the rupture into at least two distinct subevents to account for these observations we developed a procedure to invert for multiple point source parameters the optimum source model at long period consists of two point sources separated by about 209 km with magnitudes mw 8 5 and 8 3 to explain the remaining discrepancies between predicted and observed surface waves we can refine this model by adding directivity along the wnw ese axis however we do not exclude more complicated models to analyze the mw 8 2 aftershock we removed the perturbation due to large surface wave arrivals of the mw 8 6 mainshock by subtracting the corresponding synthetics computed for the two subevent model analysis of the surface wave amplitudes suggests that the mw 8 2 aftershock had a large centroid depth between 30 km and 40 km this major earthquake sequence brings a new perspective to the seismotectonics of the equatorial indian ocean and reveals active deep lithospheric deformation

simulating the formation and fate of dense water in a midlatitude marginal sea during normal and warm winter conditions 1 dense shelf water production and the deep convection process in the adriatic sea are investigated considering two case studies the first is representative of the present climatic situation whereas the second may be expected in a scenario characterized by mild winter conditions over the basin dense water production and spreading are studied using a high resolution implementation of the massachusetts institute of technology general circulation model that is initialized and forced with realistic conditions this paper provides qualitative and quantitative information on mass transport dense water pathways thermohaline structures and the mixing properties of the basin in the northern adriatic shelf seawater temperature is the key element for winter dense water production because it contributes more relevantly than salinity in determining density in the southern adriatic sea a small amount of dense water that cascades directly into the pit can be formed on the narrow western shelf only during cold winter conditions moreover open ocean deepwater formation occurs in the middle of the southern basin in late winter and spring although only when winter conditions have been sufficiently cold northern adriatic dense shelf water forms a subsurface stream of which the densest part rapidly sinks in the southern pit along the shelf break whereas its lighter part flows southward and reaches the otranto strait the frequent occurrence of mild winter conditions could lead to lower dense water production with a reduced dense water flow from the adriatic sea to the ionian sea and a potential great impact on the eastern mediterranean thermohaline circulation

laboratory earthquakes along inhomogeneous faults directionality and supershear we report on the experimental observation of spontaneously nucleated ruptures occurring on frictionally held bimaterial interfaces with small amounts of wave speed mismatch rupture is always found to be asymmetric bilateral in one direction rupture always propagates at the generalized rayleigh wave speed whereas in the opposite direction it is subshear or it transitions to supershear the lack of a preferred rupture direction and the conditions leading to supershear are discussed in relation to existing theory and to the earthquake sequence in parkfield california and in north anatolia

assessment of archaeological bone and dentine preservation from lazaret cave middle pleistocene in france chemical and structural changes in bones and dentine from cervus elaphus jaws during fossilization were studied by chemical analysis infrared spectroscopy ir and x ray diffraction xrd data were used to discuss the modifications of bones and dentine from the lazaret prehistoric cave nice france which is an important archeologic site of middle pleistocene age fossil bones and dentine mainly consisted of hydroxy carbonate apatite as the primary phase and of calcite as a secondary phase carbonation fluorination and recrystallization processes are shown as more important in bone and dentine than in tooth enamel a good correlation was found between the a cell parameter of apatite and its co3 and fluorine contents in the bones studied fluorine enrichment seems to be related to the permeability of the upper sedimentary levels lazaret fossil bones and dentine are less stable than enamels and their use for dating has to be taken with caution

problems encountered in the u th dating of fossil red deer jaws bone dentine enamel from lazaret cave a comparative study with early chronological data previous chronological data such as biochronological data u series and electron spin resonance esr data on stalagmitic flowstone e and samples from the sea deposit b are discussed most of these early studies show a deposition of the archaeological levels c during the oxygen isotopic stage 6 for testing the u th dating the method was applied for the first time to the three tissues bone dentine and enamel from fossil cervus elaphus jaws in order to date directly the archaeological levels of lazaret cave twenty seven bones 21 dentine and 17 enamel samples from 30 jaws and two tibias have been analysed by alpha spectrometry the results show a large range of apparent dates with an open system behaviour for the majority of samples the ages range between 50 and 200 ka the main set of data shows that the ages increase upward in the stratigraphic sequence with low values near the base of the sequence the u th apparent ages of dentine are in better agreement with the ages of their respective enamels than with bones the older the u th ages of the bones the larger the uranium content difference between the bone and dentine samples from the same mandible is observed for some samples from all levels of the continental fill a sequence of episodes of uranium isotope leaching and accumulation has resulted in increased uranium isotope ratios and modified uranium content yielding anomalous ages at lazaret cave u th dating on bone and dentine was not successful but data will be used for esr dating

aftershocks of the 2012 off coast of sumatra earthquake sequence abstract aftershocks of the 2012 off coast of sumatra earthquake sequence exhibit a complex and diffuse spatial distribution the first order complexity in aftershock distribution is clear and well beyond the influence of typical earthquake location uncertainty the sequence included rupture of multiple fault segments spatially separated we use surface wave based relative centroid locations to examine whether at the small scale the distribution of the aftershocks was influenced by location errors surface wave based relative location has delineated precise oceanic transform fault earthquake locations in multiple regions however the relocated aftershocks off the coast of sumatra seldom align along simple linear trends that are compatible with the corresponding fault strikes as estimated for the gcmt catalog the relocation of roughly 60 moderate earthquake epicentroids suggests that the faulting involved in the 2012 earthquake aftershock sequence included strain release along many short fault segments statistical analysis and temporal variations of aftershocks show a typical decay of the aftershocks but a relatively low number of aftershocks as is common for intraplate oceanic earthquakes coulomb stress calculations indicate that most of the moderate magnitude aftershocks are compatible with stress changes predicted by the large event slip models the patterns in the aftershocks suggest that the formation of the boundary and eventual localization of deformation between the indian and australian plate is a complicated process

the use of soil chemistry data to address post mortem diagenesis in bone mineral abstract the soluble and exchangeable ions for a soil profile from the roonka archaeological site lower murray basin south australia are compared with the total elemental content of the soils since the chemical composition of post mortem ionic substitution phases and secondary minerals in archaeological bone will depend on the availability of ions to the soil solution under field conditions it is suggested that models addressing diagenesis in bone employ soluble and exchangeable ions rather than total elemental soil data

solubility profiles of synthetic apatites and of modern and fossil bones abstract strontium has been shown to vary within trophic levels in natural foodwebs so that previous criteria used to identify biogenic strontium in fossils namely consistent differences between herbivores and carnivores may be inappropriate in this article two alternative approaches are explored these include first experimental studies of the behaviour of synthetic apatites in the solubility profile system and second solubility profile studies of fossils from the pleistocene site of swartkrans the synthetic apatite studies show that simple mixtures of apatites dissolve discretely in the system study of swartkrans specimens reveals that while diagenetic sr is clearly present some recoverable sr varies in a manner similar to that seen in modern african foodwebs and is therefore unlikely to be of diagenetic origin

molecular preservation and crystallographic alterations in a weathering sequence of wildebeest bones abstract the changes that occur in bone after the death of an animal are important because they control whether the bone becomes a fossil and what information is retained concerning the original biology of the animal taphonomic study of two 10 year longitudinal samples of wildebeest bones subjected to natural weathering in amboseli park kenya provides evidence for progressive change in both the organic and inorganic components of mammalian bone these changes correspond to weathering stages described on macroscopic structural features the bone samples were subjected to well established techniques of protein extraction from mineralized tissue protein identification by gel electrophoresis and reactivity to antibodies of noncollagenous proteins as well as x ray defractometry of the mineral component both adult and juvenile bones show progressive increase in hydroxyapatite crystal size and increased protein degradation over the 10 year period noncollagenous proteins persist at their original molecular weight in diminished amounts relative to modern controls in the study area 10 years or less of natural surface weathering altered the extractability of collagen indicating peptide and crosslinking cleavage in this protein increased hydroxyapatite crystal size may reflect a tendency of crystals to enlarge in situ once the organic matrix begins to breakdown without the addition of external minerals

the june 2000 mw 7 9 earthquakes south of sumatra deformation in the india australia plate 1 two large mw 7 9 earthquakes occurred on 4 and 18 june 2000 south of sumatra beneath the indian ocean both earthquakes were predominantly left lateral strike slip on vertical n s trending faults that we interpret to be reactivated fracture zones the 4 june enggano earthquake occurred at the edge of the rupture area of the 1833 subduction earthquake the first strike slip subevent within the subducting plate triggered a thrust subevent on the plate interface which comprised at least 35 of the total moment and ruptured se away from the 1833 earthquake the 18 june earthquake in the wharton basin is one of the largest shallow strike slip faulting earthquakes ever recorded a small second subevent with reverse slip is required to fit the body waves the orientation of both subevents in our preferred model is consistent with the current stress field in the region both the june 2000 earthquakes are consistent with recent models of distributed deformation in the india australia composite plate the occurrence of the enggano earthquake implies that the stress field within the indian plate continues to a depth of 50 km in the subducting slab the purely strike slip source model of the wharton basin earthquake obtained by robinson et al 2001 matches the p waves very poorly and fits the s waves no better than our preferred model the strike slip subevents of both earthquakes had few aftershocks and higher stress drops than the subduction thrust subevent of the enggano earthquake this difference is consistent with previous observations of oceanic and subduction earthquakes

tracking the rupture of the 2008 wenchuan earthquake by using the relative back projection method on 12 may 2008 the m w 7 9 wenchuan earthquake occurred along the longmen shan fault in the northwestern sichuan province of china resulting in huge damage as well as loss of human lives rapid estimation of the rupture process is essential for emergency response in this paper the relative back projection method based on nonplane wave array technology was applied to reconstruct the rupture process of this earthquake first the principle of the relative back projection method was briefly introduced then the method was used to obtain the rupture process using the broadband data of 16 stations from the australian national seismic network from the incorporated research institutions for seismology iris data management center the results showed that this earthquake ruptured mostly unilaterally along the longmen shan fault its rupture time was about 98 s rupture length was about 290 km and mean rupture velocity was about 3 0 km s starting from the initial rupture point epicenter 31 00 n 103 32 e the great earthquake ruptured northeastward along the longmen shan fault with two major energy releasing peaks one was located about 50 km northeast of the epicenter at about 20 s after the earthquake began and the other about 140 km northeast at about 50 s which coincided with macrodamage at those two places

triggering of earthquake aftershocks by dynamic stresses it is thought that small static stress changes due to permanent fault displacement can alter the likelihood of or trigger earthquakes on nearby faults many studies of triggering in the near field particularly of aftershocks rely on these static changes as the triggering agent and consider them only in terms of equivalent changes in the applied load on the fault here we report a comparison of the aftershock pattern of the moment magnitude mw 7 3 landers earthquake not only with static stress changes but also with transient oscillatory stress changes transmitted as seismic waves that is dynamic stresses dynamic stresses do not permanently change the applied load and thus can trigger earthquakes only by altering the mechanical state or properties of the fault zone these dynamically weakened faults may fail after the seismic waves have passed by and might even cause earthquakes that would not otherwise have occurred we find similar asymmetries in the aftershock and dynamic stress patterns the latter being due to rupture propagation whereas the static stress changes lack this asymmetry previous studies have shown that dynamic stresses can promote failure at remote distances but here we show that they can also do so nearby

fault interactions and triggering during the 10 january 2012 mw 7 2 sumatra earthquake the 10 january 2012 mw 7 2 sumatra earthquake in the wharton basin occurred 3 months before the great mw 8 6 and mw 8 2 earthquakes in the same region which had complex ruptures and are the largest strike slip earthquakes ever recorded teleseismic p wave back projection of the mw 7 2 earthquake images a unilateral rupture lasting 40 s without observable frequency dependency low frequency 0 05 0 3 hz high frequency 0 3 1 hz in addition to radiation bursts during the mw 7 2 main shock coherent energy releases from 50 to 75 s and from 100 to 125 s are observed about 143 km northeast of the main shock rupture and landward of the trench analysis of globally recorded p waves in both 0 02 0 05 hz velocity records and 1 5 hz stacked envelope functions confirms the presence of coherent sources during the time windows the observed energy bursts are likely to be large early aftershocks occurring on or near the subduction interface both dynamic and static triggering could have induced these early aftershocks as they initiated after the surface wave passed by and the coulomb stress perturbations from the mw 7 2 main shock promote earthquakes in the observed locations the earthquake sequence is a clear example of a seaward intraplate strike slip earthquake triggering landward intraplate earthquakes in the same region in contrast to previously reported normal reverse or reverse normal interactions at subduction zones

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

imaging the 2016 mw 7 8 kaikoura new zealand earthquake with teleseismic p waves a cascading rupture across multiple faults the 13 november 2016 mw 7 8 kaikoura new zealand earthquake was investigated using teleseismic p waves backprojection of high frequency p waves from two regional arrays shows unilateral rupture of at least two southwest northeast striking faults with an average rupture speed of 1 4 1 6 km s and total duration of 100 s guided by these backprojection results 33 globally distributed low frequency p waves were inverted for a finite fault model ffm of slip the ffm showed evidence of several subevents however it lacked significant moment release near the epicenter where a large burst of high frequency energy was observed a local strong motion network recorded strong shaking near the epicenter hence for this earthquake the distribution of backprojection energy is superior to the ffm as a guide of strong shaking for future large earthquakes that occur in regions without strong motion networks initial shaking estimates could benefit from backprojection constraints

forecasting the evolution of seismicity in southern california animations built on earthquake stress transfer 1 we develop a forecast model to reproduce the distribution of main shocks aftershocks and surrounding seismicity observed during 1986 2003 in a 300 310 km area centered on the 1992 m 7 3 landers earthquake to parse the catalog into frames with equal numbers of aftershocks we animate seismicity in log time increments that lengthen after each main shock this reveals aftershock zone migration expansion and densification we implement a rate state algorithm that incorporates the static stress transferred by each m 6 shock and then evolves coulomb stress changes amplify the background seismicity so small stress changes produce large changes in seismicity rate in areas of high background seismicity similarly seismicity rate declines in the stress shadows are evident only in areas with previously high seismicity rates thus a key constituent of the model is the background seismicity rate which we smooth from 1981 to 1986 seismicity the mean correlation coefficient between observed and predicted m 1 4 shocks the minimum magnitude of completeness is 0 52 for 1986 2003 and 0 63 for 1992 2003 a control standard aftershock model yields 0 54 and 0 52 for the same periods four m 6 0 shocks struck during the test period three are located at sites where the expected seismicity rate falls above the 92 percentile and one is located above the 75 percentile the model thus reproduces much but certainly not all of the observed spatial and temporal seismicity from which we infer that the decaying effect of stress transferred by successive main shocks influences seismicity for decades finally we offer a m 5 earthquake forecast for 2005 2015 assigning probabilities to 324 10 10 km cells

implications of diagenesis for the isotopic analysis of upper miocene large mammalian herbivore tooth enamel from chad high resolution chemical and textural investigation of upper miocene mammalian tooth enamel from chad using electron microprobe and scanning electron microscope techniques provide direct evidence of extensive diagenetic alteration when compared with some modern and contemporaneous fossil specimens chemical and textural changes in chadian fossil enamel during fossilization include large amounts of secondary fe si mn and al bearing oxides both as coarse precipitation in cracks and permeating the apatite high fluorine contamination i e apatite alteration ca p cl na and mg depletion and sulphur contamination such diagenetic contamination significantly affects the oxygen and carbon isotope analysis of carbonate in apatite altering the delta o 18 and delta c 13 biogenic signals towards more positive values isotopic alteration is however greater for oxygen than for carbon indeed isotopic analysis of the heavily oxide and s contaminated chadian fossil tooth enamel samples on a classical dual inlet multiprep system versus three continuous flow irms mass spectrometers show great differences in both the delta o 18 and delta c 13 values while the multiprep dual inlet approach provides carbon and oxygen isotopic results that are indubitably altered and generally inconsistent with any biological values isotopic analysis on continuous flow systems which automatically filter out contaminating gases allow to attain or at least greatly approach primary isotopic signals some of the chadian fossil enamel samples analysed in this work come from the very important upper miocene tm266 fossil locality that yielded sahelanthropus tchadensis a k a toumai the oldest member of the hominid clade known so far at this site as in others a few or no other environmental proxies than isotopic analysis of biomaterials are available for palaeoenvironmental and palaeoecological reconstructions therefore to obtain reliable environmental information from the time of this ancient hominid recovering uncontaminated biogenic isotopic signals is crucial and from these results it is now technically possible c 2008 elsevier b v all rights reserved

the 2012 mw 8 6 sumatra earthquake evidence of westward sequential seismic ruptures associated to the reactivation of a n s ocean fabric 1 the 11 april 2012 mw 8 6 earthquake offshore sumatra is the largest of the rare great intraplate earthquakes of the instrumental era this major strike slip event occurred in the diffuse zone of deformation that accommodates differential rotation between indian and australian plates we perform a back projection analysis calibrated with well located aftershocks of short period teleseismic p waves recorded by the european array to image the rupture process during the mainshock in complement a love wave analysis is conducted for tracking azimuthal change in the apparent global source duration due to the source spatio temporal extent the combined analysis reveals a complex rupture pattern characterized by three main episodes of energy release the latest being located 370 km west of the epicenter on the ninety east ridge with a delay of 120 s we interpret the 11 april 2012 mw 8 6 offshore sumatra earthquake as a complex westward propagating sequence of dynamically triggered strike slip fault ruptures associated to the reactivation of the inherited nne striking sea floor fabric the dynamic triggering mechanism could result from the interaction between transient surface wave stress perturbations and fluids

stepover rupture of the 2014 mw 7 0 yutian xinjiang earthquake multiple parallel strike slip faults cut through the ashikule basin xinjiang the ashikule basin was struck by an m w 7 0 earthquake on 12 february 2014 to distinguish the causative fault from these parallel faults the rupture process of the earthquake was investigated here we first jointly backprojected teleseismic p wavetrains at alaska european and australian seismic networks to obtain a rupture model next a kinematic finite fault model was derived by inverting teleseismic p waves recorded at the global seismographic network the two rupture models together show that that the earthquake first bilaterally ruptures the northwestward dipping south xiaoerkule fault and then steps over to another parallel xiaoerkule ashikule fault the fault stepover acts as a geometrical barrier during the rupture propagation the rupture at the fault stepover bursts an energy releasing peak in both high and low frequency content the high frequency sources are located at the edge of the shallow low frequency asperity which has an average stress drop of 1 4 mpa the aftershock spatial gap in the northeastern branch of the mainshock indicates that the accumulated strain energy could be all used up inferring that the earthquake has a recurrence period of 160 years electronic supplement 1 figures of waveform comparison and the synthetic test for spatial resolution 1 http www bssaonline org lookup suppl doi 10 1785 0120160099 dc1

zinc isotopes in late pleistocene fossil teeth from a southeast asian cave setting preserve paleodietary information stable carbon and nitrogen isotope ratios of collagen from bone and dentin have frequently been used for dietary reconstruction but this method is limited by protein preservation isotopes of the trace element zinc zn in bioapatite constitute a promising proxy to infer dietary information from extant and extinct vertebrates the 66zn 64zn ratio expressed as 66zn value shows an enrichment of the heavy isotope in mammals along each trophic step however preservation of diet related 66zn values in fossil teeth has not been assessed yet here we analyzed enamel of fossil teeth from the late pleistocene 38 4 13 5 ka mammalian assemblage of the tam hay marklot thm cave in northeastern laos to reconstruct the food web and assess the preservation of original 66zn values distinct enamel 66zn values of the fossil taxa 66zncarnivore

multiarray rupture imaging of the devastating 2015 gorkha nepal earthquake sequence a rapid robust multiarray backprojection method was applied to image the rupture pattern of the 2015 gorkha nepal mw7 8 main shock and its mw7 3 aftershock backprojected teleseismic p wave trains from three regional seismic arrays in europe australia and alaska show that both earthquakes ruptured unilaterally and primarily eastward with rupture speeds potentially decreasing with depth the rupture of the main shock first extended eseward at 3 5 km s over 120 km with later rupture propagation further downdip on the eastern segment at 2 1 km s the aftershock ruptured the fault se of the main shock s ruptured plane it began to rupture updipward for 20 km at a speed around 1 2 km s then it may have accelerated to 3 5 km s for the next 50 km the apparent depth dependent rupture speeds of the two earthquakes may be caused by along dip heterogeneities in fault strength with a higher stress concentration on the updip part of the nepalese main himalayan thrust

indian ocean actively deforms according to plate tectonics plates are rigid and deform only at narrow boundaries but studies have shown that intraplate deformation can occur in continental plates in her perspective deplus discusses recent evidence for active deformation in the indian ocean offering a rare opportunity to study intraplate deformation of oceanic lithosphere

earthquake in a maze compressional rupture branching during the 2012 mw 8 6 sumatra earthquake seismological observations of the 2012 moment magnitude 8 6 sumatra earthquake reveal unprecedented complexity of dynamic rupture the surprisingly large magnitude results from the combination of deep extent high stress drop and rupture of multiple faults back projection source imaging indicates that the rupture occurred on distinct planes in an orthogonal conjugate fault system with relatively slow rupture speed the east southeast west northwest ruptures add a new dimension to the seismotectonics of the wharton basin which was previously thought to be controlled by north south strike slip faulting the rupture turned twice into the compressive quadrant against the preferred branching direction predicted by dynamic coulomb stress calculations orthogonal faulting and compressional branching indicate that rupture was controlled by a pressure insensitive strength of the deep oceanic lithosphere

reading a 400 000 year record of earthquake frequency for an intraplate fault our understanding of the frequency of large earthquakes at timescales longer than instrumental and historical records is based mostly on paleoseismic studies of fast moving plate boundary faults similar study of intraplate faults has been limited until now because intraplate earthquake recurrence intervals are generally long 10s to 100s of thousands of years relative to conventional paleoseismic records determined by trenching long term variations in the earthquake recurrence intervals of intraplate faults therefore are poorly understood longer paleoseismic records for intraplate faults are required both to better quantify their earthquake recurrence intervals and to test competing models of earthquake frequency e g time dependent time independent and clustered we present the results of u th dating of calcite veins in the loma blanca normal fault zone rio grande rift new mexico united states that constrain earthquake recurrence intervals over much of the past 550 ka the longest direct record of seismic frequency documented for any fault to date the 13 distinct seismic events delineated by this effort demonstrate that for 400 ka the loma blanca fault produced periodic large earthquakes consistent with a time dependent model of earthquake recurrence however this time dependent series was interrupted by a cluster of earthquakes at 430 ka the carbon isotope composition of calcite formed during this seismic cluster records rapid degassing of co2 suggesting an interval of anomalous fluid source in concert with u th dates recording decreased recurrence intervals we infer seismicity during this interval records fault valve behavior these data provide insight into the long term seismic behavior of the loma blanca fault and by inference other intraplate faults

the 2012 mw 8 6 indian ocean earthquake deep nucleation on a listric like fault abstract the 2012 mw 8 6 indian ocean earthquake the largest instrumentally recorded strike slip event has been described as a westward rupture on orthogonal faults that are part of the original oceanic fabric of the region reported estimates of its depth vary from 10 to 45 km while the maximum depth of its inferred rupture extends to 50 60 km the complexity of the earthquake is undeniable both in terms of fault geometry and rupture propagation with debates on the geometry of the causative faults results from recent seismic surveys enable a fresh look at the earthquake fault geometry nucleation depths and lithospheric rheology in the present study these new findings are incorporated into 22 forward models using a revised velocity structure and n s geometries that flatten with depth the rupture initiation is modeled in the uppermost mantle 25 30 km as well as in the upper mantle at 45 km the latter of which is 15 20 km below the commonly accepted values of maximum depth for frictional failure our study shows that the westward directionality of wave propagation is achieved for strike slip failure on a listric like fault in contrast to subvertical geometries as previously suggested this propagation is persistent for a strike slip failure only for events nucleating at upper mantle depths 45 km rather than for those set to originate at depths between 25 and 30 km however for a dip slip failure the westward propagation is found to be consistent at both nucleation depths on a listric like fault this study highlights a deep nucleation within the lithospheric mantle for the 2012 mw 8 6 earthquake that could be due to strain localization induced by fluid rock interaction and or mineral transformation crystallization near the 680 c isotherm at 45 km depth 1 4 gpa which correlates with deep serpentinization on faults

a diffuse plate boundary model for indian ocean tectonics it is suggested that motion along the virtually aseismic owen fracture zone is negligible so that arabia and india are contained within a single indo arabian plate divided from the australian plate by a diffuse boundary the boundary is a zone of concentrated seismicity and deformation commonly characterized as intraplate the rotation vector of australia relative to indo arabia is consistent with the seismologically observed 2 cm yr of left lateral strike slip along the ninetyeast ridge north south compression in the central indian ocean and the north south extension near chagos

the april 2012 indian ocean earthquakes seismotectonic context and implications for their mechanisms the 11 april 2012 earthquakes m w 8 6 and m w 8 2 were sourced within the northern wharton basin in the northeastern part of the indo australian diffuse plate boundary this unusually active oceanic intraplate region has generated many large earthquakes in the past most of which are believed to have occurred by strike slip motion triggered by the nw se oriented compressional stresses acting across the indian and australian plates in the aftermath of the 2004 megathrust earthquake along the nearby sunda trench increased seismicity in the northern wharton basin is attributed to the stress transfer from the sumatra andaman plate boundary models proposed for the april 2012 earthquakes differ somewhat in details but partly attribute their complex rupture to the reactivation of pre existing structures these structures include previously mapped n s trending fracture zones within the northern wharton basin and e w lineations across the ninetyeast ridge in this paper we review the regional tectonics and past seismicity on the indo australian plate in order to understand the seismotectonic setting of the april 2012 indian ocean earthquakes c 2014 elsevier b v all rights reserved