a successful prediction of a strong earthquake in the southwestern hellenic arc by means of the algorithm m8 abstract in an earlier study a current tip time of increased probability has been diagnosed along the southwestern part of the hellenic arc by applying the algorithm m8 in that paper we pointed out that the current tip of duration of five years started at the end of 1986 or at the beginning of 1987 and if the algorithm m8 works reliably then it will be completed by the end of 1992 with an earthquake of a surface waves magnitude in the range 6 0 ms on november 21 1992 an earthquake of ms 6 5 took place in the candidate region in the following we discuss the applicability of the algorithm m8 to delineating critical seismic areas and the necessity of using current tips to focus the attention of multidisciplinary research for evaluating short term precursory phenomena if any

localization of intermediate term earthquake prediction relative seismic quiescence within a region which has already been diagnosed as having entered a time of increased probability tip for the occurrence of a strong earthquake can be used to refine the locality in which the earthquake may be expected to occur a simple algorithm with parameters fitted from the data in northern california preceding the 1980 magnitude 7 0 earthquake offshore from eureka depicts relative quiescence within the region of a ttp the procedure was tested without readaptation of parameters on 17 other strong earthquake occurrences in north america japan and eurasia most of which were in regions for which a tip had been previously diagnosed the localization algorithm successfully outlined a region within which the subsequent earthquake occurred for 16 of these 17 strong earthquakes the area of prediction in each case was reduced significantly ranging between 7 and 25 of the total area covered by the tip

is taiwan the result of arc continent or arc arc collision abstract conventionally it has been accepted that the formation of taiwan results from the collision of the luzon arc with the eurasian continental margin we suggest that taiwan results from the collision of the luzon arc with the former ryukyu subduction zone before the collision the latter extended a few hundred kilometres southwest of its present day termination in the early to middle miocene the subduction became inactive in its southwest portion and the manila trench migrated northeastward giving rise to the formation of the luzon arc the collision started in the late miocene by closing the oceanic domain located between the luzon arc and the former ryukyu arc because the luzon arc moved northwestward with respect to the former ne sw trending ryukyu arc the oblique collision first resulted in the indentation on the south ryukyu arc west of 123 5 e and the narrowing of the corresponding portion of the okinawa trough prior to the uplift of taiwan today the hsuehshan and backbone ranges represent the uplifted portion of the backarc basin and the longitudinal valley corresponds to the suture zone between the former ryukyu and the luzon arcs in this model we propose to link although they are not of the same age two truncated backarc basins the active okinawa trough to the northeast and the former active tainan backarc basin to the southwest the former backarc basin extended from southwest of taiwan to southern japan and could have been initiated near the paleo location of taiwan as early as the eocene oligocene the result of the collision is the truncation of the ancient backarc basin associated with the shortening deformation and uplift of the ancient outer arc and related backarc region which provides the fundamental mechanism of the taiwan mountain building this model is in agreement with a counterclockwise rotation of the portion of taiwan located west of the coastal range belonging to the luzon arc and a clockwise rotation of the south ryukyu arc earthquake focal mechanisms geodetic observations and the distribution of the petrologic and structural features are also consistent with the proposed arc arc collision model

elimination of the overburden response from multicomponent source and receiver seismic data with source designature and decomposition into pp ps sp and ss wave responses this paper shows that betti s reciprocity theorem gives an integral equation procedure to eliminate from the physical multicomponent source multicomponent receiver seismic measurements the effect of the physical source radiation pattern and the response of the physical overburden that is the medium above the receiver plane the physical multicomponent sources are assumed to be orthogonally aligned anywhere above the multicomponent receiver depth level other than the position of the sources no source characteristics are required the method denoted the betti designature elastic demultiple has the following additional characteristics it preserves primary amplitudes while eliminating all waves scattered from the overburden it requires no knowledge of the medium below the receiver level it requires no knowledge of the medium above the receiver level it requires information only of the local density and elastic wave propagation velocities at the receiver level to decompose the physical seismic meas

premonitory seismicity patterns near vancouver island canada abstract the search for premonitory patterns for large seismic events requires an a priori threshold to define them in the area of the explorer and juan de fuca plates the area of vancouver island canada this threshold appears to be m 6 5 the three strongest earthquakes m 6 0 which have occurred since the seismicity catalog has been acceptably complete for m 2 5 are preceded by activation of the earthquake flow in the lower magnitude range in the generalized sense depicted by the algorithm m8 suggested by soviet scientists one event of magnitude 6 0 may have been preceded by activation but two others were not the times of increased probability tip of a strong earthquake occupy about 30 of the total time space domain considered and there are no false alarms this implies a significant similarity between the earthquake flow here and in other regions of the world where algorithm m8 was tested there is a possibility which remains to be tested of anticipating future strong earthquakes in this area with an accuracy of 5 years and 100 km such anticipation could justify some precautionary measures and could be useful for attempts to make short term predictions analysis using patterns of quiescence restrict the location of the anticipated earthquake there is evidence for the coupling of seismicity in the subduction zone with that above it such interaction is a natural consequence of the model of a lithosphere as an assemblage of interacting blocks

comment on barckhausen et al 2014 evolution of the south china sea revised ages for breakup and seafloor spreading abstract we re examined the cessation of the south china sea seafloor spreading by using radioactive dating and fossil assemblage of the eto and the te derived age the youngest available age for the fragment of the south china sea is 15 ma and is more consistent with those suggested by previous studies moreover recent iodp expedition preliminary results suggested that the hemipelagic claystone layer stratigraphically bounded by igneous sequences of massive lava flow rock is early miocene in age therefore the previous interpretations are more inclusive than those provided by barckhasen et al 2014 and indicate that a slow spreading ridge was more plausible to have occurred during the seafloor spreading of the south china sea

mid ocean ridge or marginal basin origin of the east taiwan ophiolite chemical and isotopic evidence the east taiwan ophiolite eto occurs as allochthonous fragments embedded in the plio pleistocene lichi melange in the coastal range of eastern taiwan it is probably the youngest among the known ophiolitic complexes of the world the overall geochemical and isotopic characteristics of the representative rock types are very oceanic and strongly argue for a mid ocean or marginal basin origin of the eto the best criteria include 1 major element compositions 2 ree distribution patterns 3 nd isotopic ratios some have nd 12 4 pb isotopic ratios and 5 the presence and nature of the red shale this conclusion is supported by previous studies of metamorphic evolution of the eto

a new view of integrating stratigraphic and tectonic analysis in south china sea and north borneo basins abstract this review outlines how se asian tectonic and stratigraphic studies could be more closely linked many tectonic papers on the region include comments on stratigraphic evidence and stratigraphic papers often allude to tectonic events but this paper highlights the benefits of a more detailed integration of the two fields of study into a single geological model by using inductive sequence stratigraphic methods supported by geohistory plots the south china sea and north borneo region has been traditionally been divided into provinces each with its own distinct stratigraphy a handicap in merging all the provinces into one geological model has been the inconsistent application of basic biostratigraphy and some examples are given that illustrate that more careful documentation of a complex data set is required in future work the inductive stratigraphic method requires increased analytical work to calibrate seismic data but even on current data an episodic stratigraphic history is indicated and a single tectono stratigraphic framework for the whole region is emerging with a greatly simplified and consistent terminology this review examines the impact of these methods on one important period of transition around the oligo miocene boundary the summary given for the oligo miocene transition questions the viability of the commonly cited slab pull tectonic model as both the historical order of geological events and geographic spread of effects does not fit that model as currently understood

evaluation of elastodynamic interferometric redatuming a synthetic study on salt dome flank imaging summary the recent introduction of novel redatuming techniques based on the principles of timereversed acoustics and source receiver reciprocity has allowed seismic measurements collected on one datum to be extrapolated to another datum under favourable conditions this process can approximately remove the complicated overburden structures without any velocity information we introduce an elastic redatuming scheme for walkaway vertical seismic profiles wvsps based on these principles using p and s wave potentials which are derived from the spatial derivatives of the measured wavefields additional field acquisition is utilized to directly measure these derivatives we test our elastic redatuming scheme on data simulated with an elastic finite difference algorithm the elastodynamic green s functions between multicomponent receivers in a borehole are then extracted from data recorded using multicomponent p and s wave sources at the surface the wavefields are redatumed as four parts two related to the p wave potential and another two related to the s wave potential these parts are migrated separately and form four independent images of the salt dome flank providing a more complete elastic description of the subsurface

virtual seismometers in the subsurface of the earth from seismic interferometry earthquakes often occur in areas that lack an array of seismometers resulting in a scarcity of local measurements from some regions of great geological interest in such regions some earthquakes themselves may be turned into virtual seismometers that are capable of measuring strain caused by passing waves from other earthquakes

testing an earthquake prediction algorithm a test to evaluate earthquake prediction algorithms is being applied to a russian algorithm known as m8 the m8 algorithm makes intermediate term predictions for earthquakes to occur in a large circle based on integral counts of transient seismicity in the circle in a retroactive prediction for the period january 1 1985 to july 1 1991 the algorithm as configured for the forward test would have predicted eight of ten strong earthquakes in the test area a null hypothesis based on random assignment of predictions predicts eight earthquakes in 2 87 of the trials the forward test began july 1 1991 and will run through december 31 1997 as of july 1 1995 the algorithm had forward predicted five out of nine earthquakes in the test area which success ratio would have been achieved in 53 of random trials with the null hypothesis

the temporal and spatial distribution of volcanism in the south china sea region cenozoic magmatism in the south china sea the associated continental margins coastal south china and indochina is reviewed volcanism contemporaneous with rifting and sea floor spreading in the south china sea was very weak in the margins and adjacent areas there was only very limited magmatic activity most probably after the cessation of sea floor spreading the south china sea has non volcanic margins large basement relief caused by extension formed major basins and a continental oceanic transitional zone in the northern margin reflects high crustal rigidity during rifting and drifting the paucity of a magma supply and presence of rigid fault blocks are unfavorable to the mantle flow model previously proposed to account for the opening of the south china sea which was supposedly linked to the escape of indochina induced by indo eurasia collision c 2005 published by elsevier ltd

practical aspects of wavefield separation of two component surface seismic data based on polarization and slowness estimates the processing of multicomponent seismic data carried out individually on the different wavetypes p s and converted waves should result in an improved image of the subsurface we examine the wavefield separation method proposed by cho and spencer we discuss practical aspects related to the separation of interfering waves on two component surface seismic data and illustrate these using synthetic data a sliding spatial window is used for analysis the choice of its width represents a trade off between stabilizing the method in the presence of random noise and ensuring a good spatial resolution no a priori knowledge of the subsurface is required but locally the characteristic parameters of the waves i e horizontal slowness and polarization are assumed to be constant inside the analysis window these parameters are estimated at each frequency but a statistical analysis provides a more robust estimate especially in the presence of random noise this approach also solves the problem of eigenvalue sharing and switching additional smoothing of the estimates according to a model may further improve the results the width of the analysis window may be decreased if the waves inside the data window differ significantly in amplitude the dominant wave in each case is separated from the lower amplitude waves and subtracted from the data this novel iterative approach thereby allows for the isolation of low amplitude events

taiwan orogeny thin skinned or lithospheric collision abstract the taiwan orogeny is young and presently very active it provides an excellent environment for studying ongoing orogenic processes especially since the region is monitored intensively with dense seismological and geodetic networks and new studies aiming at deciphering shallow and deep structures in and around taiwan have been recently conducted or are being planned the available data can be used continually to test critically hypotheses of the taiwan orogeny hypotheses dealing with the mechanics of mountain building are basic to the understanding of taiwan orogeny and are particularly amenable to testing the widely cited thin skinned tectonics hypothesis was formulated to explain mainly the geologic and relatively shallow

how was taiwan created abstract since the beginning of formation of proto taiwan during late miocene 9 ma the subducting philippine ph sea plate moved continuously through time in the n307 direction at a 5 6 cm year velocity with respect to eurasia eu tearing the eurasian plate strain states within the eu crust are different on each side of the western ph sea plate boundary extensional in the okinawa trough and northeastern taiwan versus contractional for the rest of taiwan island the b feature corresponds to the boundary between the continental and oceanic parts of the subducting eurasian plate and lies in the prolongation of the ocean continent boundary of the northern south china sea strain rates in the philippines to northern taiwan accretionary prism are similar on each side of b contractional though with different strain directions perhaps in relation with the change of nature of the eu slab across b consequently in the process of taiwan mountain building the deformation style was probably not changing continuously from the manila to the ryukyu subduction zones the luzon intra oceanic arc only formed south of b above the subducting eurasian oceanic lithosphere north of b the luzon arc collided with eu simultaneously with the eastward subduction of a portion of eu continental lithosphere beneath the luzon arc in its northern portion the lower part of the luzon arc was subducting beneath eurasia while the upper part accreted against the ryukyu forearc among the consequences of such a simple geodynamic model i the notion of continuum from subduction to collision might be questioned ii traces of the miocene volcanic arc were never found in the southwestern ryukyu arc we suggest that the portion of eu continental lithosphere which has subducted beneath the coastal range might include the miocene ryukyu arc volcanoes formed west of 126 e longitude and which are missing today iii the 150 km wide oceanic domain located south of b between the luzon arc and the manila trench above the subducting oceanic eu plate south china sea was progressively incorporated into the eu plate north of b

cenozoic tectonic and stratigraphic development of the central vietnamese continental margin abstract the east vietnam boundary fault zone evbfz forms the seaward extension of the red river shear zone and interacted with the extensional rift systems in basins along the central vietnamese continental margin the structural outline of the central vietnamese margin and the timing of deformation are therefore fundamental to understanding the development of the south china sea and its relation to indochinese escape tectonism and the india eurasia collision this study investigates the structural and stratigraphic evolution of the central vietnamese margin in a regional tectonic perspective based on new 2 d seismic and well data the basin fill is divided into five major oligocene to recent sequences separated by unconformities deposition and the formation of unconformities were closely linked with transtension rifting the opening of the south china sea and late neogene uplift and denudation of the eastern flank of indochina the structural outline of the central vietnamese margin favors a hybrid tectonic model involving both escape and slab pull tectonics paleogene left lateral transtension over the nnw striking evbfz occurred within the song hong basin and the quang ngai graben and over the da nang shelf western phu khanh basin related to the escape of indochina east of the evbfz paleogene ne striking rifting prevailed in the outer phu khanh basin and the hoang sa graben fitting best with a prevailing stress derived from a coeval slab pull from a subducting proto south china sea beneath the southwest borneo palawan region major rifting terminated near the end of the oligocene however late stage rifting lasted to the early miocene when continental break up and seafloor spreading commenced along the edge of the outer phu khanh basin the resulting transgression promoted lower and middle miocene carbonate platform growth on the da nang shelf and the tri ton high whereas deeper marine conditions prevailed in the central part of the basins partial drowning and platform retreat occurred after the middle miocene due to increased siliciclastic input from the vietnamese mainland as a result siliciclastic marine deposition prevailed offshore central vietnam during the pliocene and pleistocene

decomposition of multicomponent sea floor data into upgoing and downgoing p and s waves a method for decomposing multicomponent sea floor measurements into upgoing and downgoing p and s waves is presented we assume that a marine survey employing a marine source in the water layer is conducted over a plane layered medium from recordings of the pressure just above the sea floor and the particle velocity vector just below the sea floor decomposition filters can be determined by plane wave analysis the decomposition filter coefficients depend on the p and s wave velocities and the density at the sea bottom we show how to decompose the multicomponent measurements into upgoing and downgoing p and s vertical traction components vertical particle velocity components and horizontal particle velocity components the decomposition filters are applied with good results to synthetic data modeled in a plane layered medium

inversion of a hyper extended rifted margin in the southern central range of taiwan seismic reflection and wide angle data acquired across south and west of taiwan show that extended to hyper extended continental crust of the chinese continental margin is present more than 200 km south of the shelf and is subducting at the manila trench furthermore crustal scale tomographic velocity models show that this crust is underthrusted to 15 km depth below the accretionary prism where it then is structurally underplated to the base of the prism we document an increasing volume of accreted crust from south to north and in our northern transect high velocity material of the accretionary prism can be directly linked to outcrops of central range basement rocks in map view the central range of taiwan is clearly contiguous with the hengchun peninsula and hengchun submarine ridge to the south accordingly we propose a new model in which the central range forms directly from the accretionary prism including the basement core which originates from subducted and then accreted extended to hyper extended continental crust

crustal scale seismic profiles across the manila subduction zone the transition from intraoceanic subduction to incipient collision 1 we use offshore multichannel seismic mcs reflection and wide angle seismic data sets to model the velocity structure of the incipient arc continent collision along two trench perpendicular transects in the bashi strait between taiwan and luzon this area represents a transition from a tectonic regime dominated by subduction of oceanic crust of the south china sea west of the philippines to one dominated by subduction and eventual collision of rifted chinese continental crust with the luzon volcanic arc culminating in the taiwan orogeny the new seismic velocity models show evidence for extended to hyperextended continental crust 10 15 km thick subducting along the manila trench at 20 5 n along transect t1 as well as evidence indicating that this thinned continental crust is being structurally underplated to the accretionary prism at 21 5 n along transect t2 but not along t1 to the south coincident mcs reflection imaging shows highly stretched and faulted crust west of the trench along both transects and what appears to be a midcrustal detachment along transect t2 a potential zone of weakness that may be exploited by accretionary processes during subduction an additional seismic reflection transect south of t1 shows subduction of normal ocean crust at the manila trench

precursory activation of seismicity in advance of the kobe 1995 m 7 2 earthquake a succession of precursory changes of seismicity characteristic to earthquakes of magnitude 7 0 7 5 occurred in advance of the kobe 1995 m 7 2 earthquake using the japan meteorological agency jma regional catalog of earthquakes the m8 prediction algorithm keilies borko and kossobokov 1987 recognizes the time of increased probability tip for an earthquake with magnitude 7 0 7 5 from july 1991 through june 1996 the prediction is limited to a circle of 280 km radius centered at 33 5 n 133 75 e the broad area of intermediate term precursory rise of activity encompasses a 175 by 175 km square where the sequence of earthquakes exhibited a specific intermittent behavior the square is outlined as the second approximation reduced area of alarm by the mendocino scenario algorithm msc kossobokov et al 1990 moreover since the m8 alarm starts there were no swarms recorded except the one on 9 26 nov 1994 located at 34 9 n 135 4 e time location and magnitude of the 1995 kobe earthquake fulfill the m8 msc predictions its aftershock zone ruptured the 54 km segment of the fault zone marked by the swarm directly in the corner of the reduced alarm area the kobe 1995 epicenter is less than 50 km from the swarm and it coincides with the epicenter of the m 3 5 foreshock which took place 11 hours in advance

predictability in the epidemic type aftershock sequence model of interacting triggered seismicity 1 as part of an effort to develop a systematic methodology for earthquake forecasting we use a simple model of seismicity on the basis of interacting events which may trigger a cascade of earthquakes known as the epidemic type aftershock sequence model etas the etas model is constructed on a bare unrenormalized omori law the gutenberg richter law and the idea that large events trigger more numerous aftershocks for simplicity we do not use the information on the spatial location of earthquakes and work only in the time domain we demonstrate the essential role played by the cascade of triggered seismicity in controlling the rate of aftershock decay as well as the overall level of seismicity in the presence of a constant external seismicity source we offer an analytical approach to account for the yet unobserved triggered seismicity adapted to the problem of forecasting future seismic rates at varying horizons from the present tests presented on synthetic catalogs validate strongly the importance of taking into account all the cascades of still unobserved triggered events in order to predict correctly the future level of seismicity beyond a few minutes we find a strong predictability if one accepts to predict only a small fraction of the large magnitude targets specifically we find a prediction gain defined as the ratio of the fraction of predicted events over the fraction of time in alarms equal to 21 for a fraction of alarm of 1 a target magnitude m 6 an update time of 0 5 days between two predictions and for realistic parameters of the etas model however the probability gains degrade fast when one attempts to predict a larger fraction of the targets this is because a significant fraction of events remain uncorrelated from past seismicity this delineates the fundamental limits underlying forecasting skills stemming from an intrinsic stochastic component in these interacting triggered seismicity models quantitatively the fundamental limits of predictability found here are only lower bounds of the true values corresponding to the full information on the spatial location of earthquakes

stratigraphic architecture shelf edge delta and constraints on the development of the late oligocene to early miocene continental margin prism the pearl river mouth basin northern south china sea abstract the early stage shelf margin prism in the pearl river mouth basin prmb northern south china sea formed from the late oligocene to early miocene comprises a set of shelf edge delta and slope fan wedges of the zhuhai formation and records the development of the continental slope in response to the interaction of sea level change tectonic subsidence and sediment supply based on integrated analysis of seismic well logging and core data the stratigraphic architecture depositional systems and controlling processes are documented the zhuhai formation is a composite sequence bounded by regional unconformity and can be further divided into five sequences cs3 1 cs3 5 the depositional genetic units transgression ascending normal regression and descending forced regression are identified within sequences based on variation in shelf edge trajectories the shelf deltaic clinoforms are characterized by oblique tangential reflections in seismic profiles with a thickness of 100 150 m in contrast the shelf margin delta and slope clinoforms generally are 300 1200 m thick and mainly display as sigmoid or sigmoid tangential seismic reflections the delta deposits usually consist of thick beds of delta front deposits and prodelta slump and deformed sediments and are associated with sandy slope fan systems eleven delta complexes are distinguished by tracking the distribution of the deltaic clinoforms in each sequence and these deltaic deposits tend to extend along their strike direction which may be related to the reworking of strong waves and coastal currents slope fan systems consist mainly of turbidite channel fills frontal splay and debris flow deposits and generally develop along the slope in cs3 3 cs3 5 which may be triggered by steep shelf margin slope and fault activity the stratigraphic pattern of the shelf margin prism and depositional evolution of the deltaic systems from the late oligocene to early miocene were controlled by the interaction of sea level changes sediment supply and tectonic subsidence the ascending trajectory from the cs3 1 30 ma to the top of the cs3 5 indicates that the relative sea level continued to rise generally but the shelf margin prograded basinward rapidly due to the great amount of sediment supply and lower subsidence rate tectonic uplift of the source area and strengthened physical erosion during this period may be the reason for the large sediment supply

times of increased probability of strong earthquakes m 7 5 diagnosed by algorithm m8 in japan and adjacent territories this paper continues to explore the possibility of identifying the times of increased probability tips of occurrence of a strong earthquake by premonitory intermediate term seismic activation in lower magnitude range as defined in the algorithm m8 a tip refers to a 5 year period and an area whose linear size is several times larger than that of an incipient earthquake in the course of the global test of the algorithm we applied it retrospectively to the data from the national earthquake information center worldwide earthquake catalog since the regional japan meteorological agency catalog was unavailable to authors related to the segment of circum pacific belt between latitudes 20 n and 48 n from the south of kuril arc to the taiwan and izu bonin arc the worldwide catalog allows us to diagnose tips for earthquakes above magnitude 7 5 from 1975 on five out of six earthquakes with m 7 5 occurred within the tips diagnosed by the algorithm m8 with a priori fixed parameters the missed earthquake occurred at the final stage of formation of the corresponding tip altogether the tips occupy less than 20 and times of expectation occupy about 8 of the total space time domain considered there are also current tips covering about half of the territory application of the additional algorithm of localization named mendocino scenario indicates that the southern part of the japan trench is an area deserving particular attention the results obtained here by no means constitute the definitive earthquake prediction but merely outline the territories for more detailed and comprehensive analysis if confirmed by regional data the results may be used for implementation of some safety measures and evaluation of other precursors including short term ones

wavefield separation using a volume distribution of three component recordings by making multiple three component 3c measurements around a volume so that the rate of change of the wavefield in all directions can be estimated it is possible to calculate the divergence and the curl of the wavefield which in turns corresponds to p and s waves the volume may be of arbitrary shape but the equations for wavefield separation are simplified if the volume has a known shape such as that of a tetrahedron the dimensions of the volume should be smaller than approximately one fifth of the minimum wavelength of the recorded wavefield a field test was carried out in oman in april 1998 with a lack of distinct p and s waves in the data the technique was instead evaluated on the airwave induced ground motion the airwave arrival was found to consist mainly of vertical motion that decays with depth the wavefield separation technique was successfully tested on this arrival

fast wavefield decomposition of volcano tectonic earthquakes into polarized p and s waves by independent component analysis abstract in the present work a new approach for the analysis of polarization of seismic signals is proposed the method is based on independent component analysis and allows the identification and separation of the basic sources which are naturally polarized into the vertical and horizontal planes the results from the case study of a swarm of volcano tectonic earthquakes occurred at campi flegrei in october 2015 are impressive a clear separation of the p and s wave seismic phases in the time domain is obtained in addition the efficiency of the method in retrieving the polarization parameters is demonstrated by the comparison with other standard techniques the presented approach provides wavefield decomposition and polarization analysis in a single step thus avoiding a priori cumbersome filtering procedures and segmentation of the signals it is useful for discriminating and analysing different seismic phases and can be applied to a variety of volcanic and tectonic signals therefore it can strongly support all the studies on propagation and source mechanism moreover due to its fastness and robustness this stand alone tool can be routinely used in the volcano monitoring practice

rifting and magmatism in the northeastern south china sea from wide angle tomography and seismic reflection imaging we present a new travel time tomography velocity model and seismic reflection images that delineate the rift architecture and magmatic features of the rifted margin in the northeastern south china sea these data reveal moderately stretched crust 25 km thick along the continental shelf and thin but laterally variable crustal thickness in the distal margin along the continental slope crust rapidly thins to 4 km in a basin characterized by tilted fault blocks that sole into a low angle detachment strain was localized to a degree within the highly stretched basin but failed to progress to breakup and seafloor spreading crust in the distal margin is 12 15 km thick few extensional structures are apparent in the distal margin but seismic velocities are suggestive of highly thinned and magmatically intruded continental crust the magmatic features we interpret include volcanic zones at the top of the basement that deform or disrupt overlying postrift strata sills intruded into the postrift sedimentary section and a high velocity 6 9 7 5 km s lower crustal layer that we take to be magmatic underplating or pervasive lower crustal intrusions these features primarily occur in the distal margin and may have been emplaced during postrift seafloor spreading the postrift magmatism may have been induced by convective removal of continental lithosphere following breakup and the onset of seafloor spreading in the south china sea

major unconformities termination of extension events and associated surfaces in the south china seas review and implications for tectonic development abstract the distribution of unconformities and end of cenozoic rifting events in the south china seas scs reflects both the modes of rift development and the effects of driving mechanisms continental rifting began in the eastern basins during the paleocene and propagated westwards to the vietnam basin margin in the late eocene continental breakup around 32 28 ma caused a regional reduction or cessation in extensional activity particularly affecting basins furthest from the spreading centre basins in the slope and deepwater area north of the spreading centre exhibit reduced fault activity until 21 20 ma propagation of oceanic crust westwards between 25 and 23 ma and termination of seafloor spreading sometime between 20 5 and 16 ma affected fault activity in the qiongdongnan and nam con song basins in the phu khanh basin and south in the dangerous grounds area extension continued until about 16 ma ending at the red unconformity the end of seafloor spreading around 20 5 ma reflects loss of extensional driving force as thinned continental crust entered the nw borneo subduction zone controversially a key component of the driving force maybe attributed to slab pull a transitional period of about 5 7 my between the onset of subduction of continental crust and final jamming of the subduction zone deep regional unconformity dru is inferred the last pulse of extension was focussed in the western scs and terminated around 10 5 ma detailed understanding of proto south china seas development remains uncertain and controversial

reply to chang et al 2014 evolution of the south china sea revised ages for breakup and seafloor spreading abstract chang et al introduce some new lines of evidence for an end of seafloor spreading in the south china sea not before 15 ma however we find strong indications that their interpretation is not conclusive the origin of the east taiwan ophiolite from the scs as assumed by chang et al is not in agreement with recent studies which find continental crust in the deep water domain of the northeastern south china sea the age dating of the east taiwan ophiolite is based on one single k ar age of questionable accuracy the calculation of te derived ages leaves a thermal rejuvenation of the oceanic crust in the south china sea by post spreading volcanism out of consideration biostratigraphically determined ages of sediments recovered directly above igneous crust of the south china sea during iodp 349 drilling expedition are inconclusive so far the final key to unlocking the spreading history of the scs will be the ar ar age dating of the basaltic rocks recovered during iodp expedition 349

decomposition of multicomponent seismic data into primary p and s wave responses1 inversion of multicomponent seismic data can be subdivided in three main processes 1 surface related preprocessing decomposition of the multicomponent data into primary p and s wave responses 2 prestack migration of the primary p and s wave responses yielding the angle dependent p p p s s p and s s reflectivity of the subsurface 3 target related post processing transformation of the reflectivity into the rock and pore parameters in the target this paper deals with the theoretical aspects of surface related preprocessing which consists of two steps 1 decomposition of the multicomponent data pseudo p and s wave responses into true p and s wave responses 2 elimination of the surface related multiple reflections and conversions

seismicity based earthquake forecasting techniques ten years of progress abstract earthquake fault systems interact over a broad spectrum of spatial and temporal scales and in recent years studies of the regional seismicity in a variety of regions have produced a number of new techniques for seismicity based earthquake forecasting while a wide variety of physical assumptions and statistical approaches are incorporated into the various methodologies they all endeavor to accurately replicate the statistics and properties of both the historic and instrumental seismic records as a result the last ten years have seen significant progress in the field of intermediate and short term seismicity based earthquake forecasting these include general agreement on the need for prospective testing and successful attempts to standardize both evaluation methods and the appropriate null hypotheses here we differentiate the predominant approaches into models based upon techniques for identifying particular physical processes and those that filter or smooth the seismicity comparison of the methods suggests that while smoothed seismicity models provide improved forecast capability over longer time periods higher probability gain over shorter time periods is achieved with methods that integrate statistical techniques with our knowledge of the physical process such as the epidemic type aftershock sequence etas model or those related to changes in the b value for example in general while both classes of seismicity based forecasts are limited by the relatively short time period available for the instrumental catalog significant advances have been made in our understanding of both the limitations and potential of seismicity based earthquake forecasting there is general agreement that both short term forecasting on the order of days to weeks and longer term forecasting over five to ten year periods is within reach this recent progress serves to illuminate both the critical nature of the different temporal scales intrinsic to the earthquake process and the importance of high quality seismic data for the accurate quantification of time dependent earthquake hazard

near surface seismic properties for elastic wavefield decomposition estimates based on multicomponent land and seabed recordings accurate knowledge of the seismic material properties in the immediate vicinity of the receivers represents a prerequisite for elastic wavefield decomposition we present strategies for estimating the elastic material properties for both land and seabed multicomponent seismic data the proposed scheme for land data requires dense multicomponent geophone configurations which allow spatial wavefield derivatives to be explicitly calculated the required information can be obtained with four three component surface geophones positioned at the corners of a square and a fifth geophone buried at a shallow depth below the center of the square the technique yields local estimates of the near surface p and s wave velocities but the density cannot be constrained using a similar approach for four component three orthogonal components of particle velocity plus pressure seabed recordings allows the p and s wave velocities as well as the density of the seafloor to be estimated in this case the proposed scheme does not require buried geophones and it is applicable to multicomponent data recorded in routine seabed surveys compared to existing techniques the new method allows the elastic seafloor properties to be more accurately determined and it does not rely critically on the inclusion of large offset data numerical tests indicate that the proposed schemes are robust and yield accurate results provided that the signal used for the inversion contains sufficient horizontal energy and can be clearly identified and separated from other signals although the schemes are designed for application on the first arrivals they are in principle applicable to any data window containing isolated p or s arrivals the proposed scheme is successfully applied to a seabed data set acquired in the north sea in contrast the application on a multicomponent land data set was unsuccessful because of strong receiver to receiver variations in amplitude and phase probably caused by differences in coupling and instrument response

improved tests reveal that the accelerating moment release hypothesis is statistically insignificant 1 we test the hypothesis that accelerating moment release amr is a precursor to large earthquakes using data from california nevada and sumatra spurious cases of amr can arise from data fitting because the time period area and sometimes magnitude range analyzed before each main shock are often optimized to produce the strongest amr signal optimizing the search criteria can identify apparent amr even if no robust signal exists for both 1950 2006 california nevada m 6 5 earthquakes and the 2004 m9 3 sumatra earthquake we can find two contradictory patterns in the pre main shock earthquakes by data fitting amr and decelerating moment release we compare the apparent amr found in the real data to the apparent amr found in four types of synthetic catalogs with no inherent amr when spatiotemporal clustering is included in the simulations similar amr signals are found by data fitting in both the real and synthetic data sets even though the synthetic data sets contain no real amr these tests demonstrate that apparent amr may arise from a combination of data fitting and normal foreshock and aftershock activity in principle data fitting artifacts could be avoided if the free parameters were determined from scaling relationships between the duration and spatial extent of the amr pattern and the magnitude of the earthquake that follows it however we demonstrate that previously proposed scaling relationships are unstable statistical artifacts caused by the use of a minimum magnitude for the earthquake catalog that scales with the main shock magnitude some recent amr studies have used spatial regions based on hypothetical stress loading patterns rather than circles to select the data we show that previous tests were biased and that unbiased tests do not find this change to the method to be an improvement the use of declustered catalogs has also been proposed to eliminate the effect of clustering but we demonstrate that this does not increase the statistical significance of amr given the ease with which data fitting can find desired patterns in seismicity future studies of amr like observations must include complete tests against synthetic catalogs that include spatiotemporal clustering

inversion of p and sv waves from multicomponent offset vertical seismic profiles downgoing waves in multicomponent vsp experiments are used to obtain seismic p and s wave velocities as a function of depth and angle of incidence if p and sv waveforms do not overlap in time at the depth of interest local velocities of the medium are obtained by separate analysis of these events the apparent velocity of the event p or sv is computed from the moveout across several neighboring depth locations the angle of incidence of the same event is computed from the particle motion hodogram within an appropriately chosen time window then the local medium velocity p wave or s wave depending on the chosen event is given by the apparent velocity multiplied by the cosine of the angle of incidence layer interfaces with reasonably sharp velocity contrasts are efficient p wave to sv wave converters even at moderate angles of incidence in offset vsp experiments converted sv waves are generated with varying strengths at practically all depths consequently the converted sv waveforms partially o

volumetric wavefield recording and wave equation inversion for near surface material properties volumetric recording of the seismic wavefield implies that the local receiver group or array approximately encloses a volume of the earth we show how volumetric recording can be used to measure several spatial derivatives of the wavefield by making use of the full elastic wave equation the free surface condition on elastic wavefields and derivative centering techniques analagous to lax wendroff corrections used in synthetic finite difference modeling these derivative estimates can be inverted for p and s velocities in the near surface directly beneath the receiver group the quantities estimated are the effective velocities of the p and s components experienced by the wavefield at any point in time hence the velocity estimates may vary with both wave type and wavelength the estimates may be useful to aid statics estimation and are exactly the effective velocities required for separation of the wavefield into p and s and up and down going components

crustal accretion in the manila trench accretionary wedge at the transition from subduction to mountain building in taiwan abstract new marine seismic reflection and coincident wide angle ocean bottom seismometer data acquired offshore taiwan provide high resolution constraints on the crustal structure of an incipient mountain belt during the earliest stage of arc continent collision the new seismic reflection image and travel time tomography velocity model show evidence for crust of the distal southern chinese continental margin being subducted eastward beneath the manila trench and underplated to the accretionary wedge before collision with the southern chinese continental shelf the distal margin crust consists of highly extended continental crust interspersed with volcanic bodies and a high velocity lower crustal layer of likely magmatic intrusions the distal margin crust is 10 14 km thick outboard of the trench but thins to 6 km thick beneath the lower slope of the manila trench accretionary wedge along the lower slope of the accretionary prism we image westward verging imbricate thrusts and folded strata up to 10 km thick a sharp decrease in bathymetry marks the transition from lower to upper slope where we observe a fast 6 0 km s seismic velocity anomaly at the base of the wedge that we interpret as structurally underplated crust from the distal continental margin our results support a model of arc continent collision in taiwan where the accretionary wedge is first thickened by structural underplating of distal margin crust prior to collision with the continental shelf the crustal rocks exposed throughout the central range in taiwan may be similarly derived from subducted and structurally underplated crust from the highly extended distal continental margin

evolution of the south china sea revised ages for breakup and seafloor spreading abstract the continental breakup which gave way to the formation of the oceanic south china sea scs basin began in the latest cretaceous in the northeastern scs and propagated in southern and western direction over a long period of time possibly more than 40 m y the seafloor spreading history of the south china sea has been interpreted in different ways in the past and the debate over the correct timing of the major tectonic events continues we review the different models that have been published and present a revised interpretation of seafloor spreading anomalies based on three datasets with documented high quality which cover all of the scs but the northernmost and southernmost parts we can precisely date the onset of seafloor spreading in the central part of the scs at 32 ma after a ridge jump at 25 ma spreading also began in the southwestern sub basin and spreading ended at 20 5 ma in the entire basin followed by a phase of magmatic seamount formation mainly along the abandoned spreading ridge spreading rates vary from 56 mm yr in the early stages to 72 mm yr after the ridge jump to 80 mm yr in the southwestern sub basin we find indications for a stepwise propagation of the seafloor spreading from northeast to southwest in segments bounded by major fracture zones seafloor spreading ended abruptly probably because the subduction zone along the eastern and southern boundary of the scs of which today the manila trench remains was blocked by collision with a continental fragment possibly the northern part of palawan or a part of the dangerous grounds

a plane wave decomposition for elastic wave fields applied to the separation of p waves and s waves in vector seismic data we describe a method to decompose a two dimensional 2 d elastic wave field recorded along a line into its longitudinal and transverse parts that is into compressional p waves and shear s waves separation of the data into p waves and s waves is useful when analyzing vector seismic measurements along surface lines or in boreholes the method described is based on a plane wave expansion for elastic wave fields and is illustrated with a synthetic example of an offset vertical seismic profile vsp in a layered elastic medium

wavefield separation using densely deployed three component single sensor groups in land surface seismic recordings surface seismic data are usually acquired by placing receivers on the earth s free surface this is exactly the surface at which all up coming wave energy is reflecting and converting into down going energy so the wavefield recorded is the sum of up coming down going reflected and down going converted waves in order to anaylze upcoming from the reservoir energy only e g for true amplitude analysis it is necessary to separate and remove all down going waves from the recorded data we present a new approach for wavefield separation of land surface seismic data based on receiver groups with densely deployed single sensor recordings by converting vertical spatial derivatives to horizontal derivatives using the free surface condition the methodology only requires locally dense measurements of the wavefield at the free surface to calculate all spatial derivatives of the wavefield these can in turn be used to compute divergence giving p wave potential and curl giving s wave potential of the wavefield at the free surface the effects of the free surface are removed through an up down separation step using the elastodynamic representation theorem this results in infinite spatial filter expressions that are appropriate for homogeneous media the filter for p waves depends on both p and s velocity at the receivers whereas the s wave filters only depend on the s velocity these velocities can be estimated using the techniques in the companion paper by curtis and robertsson in this issue spatially compact filters are chosen to approximate the analytical filter expressions the filters are designed so that they can be applied within a densely deployed spatially limited group of three component 3c receivers by assuming that the earth is locally homogeneous no significant variations within the near surface region of the group wavefield separation can be carried out also in areas with significant statics variations over the survey area in particular the simplest approximate expression for p waves consists of two terms the first term corresponds to divergence in the presence of the free surface scaled by a material constant the second term is a time derivative of the recorded vertical component scaled by a material constant hence the first term is a correction that is added to the traditional p interpretation the second term which improves accuracy for incidence angles other than normal incidence the proposed methodology is tested on synthetic data by comparing traditional p sections to those obtained using the new methodology we demonstrate that a significant improvement in amplitudes and phases of arrivals is obtained using the new methodology by using the simplest possible filter which only involves first order derivatives in time and space we obtained sufficiently accurate results up to incidence angles of around 30 away

times of increased probability of earthquakes of ml 5 5 in greece diagnosed by algorithm m8 an attempt is made to explore the possibility of identifying the times of increased probability tips of occurrence of earthquakes with ml 5 5 by premonitory intermediate term seismic activation in lower magnitude ranges as defined in the algorithm m8 a tip refers to a 5 year period and an area whose length is several times greater than that of an incipient earthquake this algorithm has been already tested retrospectively for the strongest earthquakes of magnitude greater than or equal to 7 0 which have occurred in greece since 1973 in the present study the same algorithm is also applied retrospectively by considering smaller earthquakes of local magnitude ml greater than or equal to 5 5 the obtained results show that ten out of eleven events with m 5 5 which took place in greece and surrounding region from january 1 1977 till december 31 1990 occurred within the tips diagnosed by the algorithm m8 retrospectively only the thessaloniki earthquake of june 20 1978 did not occur within tip the m8 algorithm failed in four cases namely those that occurred in regions for which our catalogue was not complete altogether the tips occupy less than 25 and times expectation about 8 of the total space time considered there is also a current tip started at the end of 1986 or at the beginning of 1987 for the south southwestern part of thehellenic arc indicating that this area deserves particular attention if the algorithm m8 works reliably then this tip will be filled by the end of 1992 this result by no means constitute the definitive earthquake prediction but merely outline a territory for more detailed and comprehensive analysis

perturbation analysis of an explicit wavefield separation scheme for p and s waves dense spatial recording patterns of three component 3c receivers allow for direct wavefield decomposition through explicit calculation of divergence and curl of the recorded elastic wavefield since this approach is based upon the observation of small phase shifts it requires highly accurate deployment of the receiver configurations to study the feasibility of a recently proposed p s wave separation scheme we systematically assess the effects of position and orientation errors of one or several geophones within the recording pattern on technique performance we find that realistic deployment errors can significantly affect estimates of the divergence and curl of particle velocity the errors induced by mispositioned or misoriented geophones differ for each of the geophones that make up a pattern moreover the inaccuracies vary with the angle of incidence potentially affecting analysis procedures applied to the data at a later stage such as amplitude variation with offset avo based on a relative

multiple ophiolite generation preserved in the northern philippines and the growth of an island arc complex abstract although all oceanic arcs grow through the addition of subduction generated magmas the geology of the northern philippines demonstrates that a major contribution to arc crustal growth can come from repeated episodic intra arc back arc and or fore arc oceanic crust generation with subsequent preservation of the basic ultrabasic units in the arc complex at least five episodes of oceanic crust generation are represented in the northern philippines by preserved ophiolitic sequences and recent intra arc seafloor spreading each episode is distinct in age as confirmed by modern dating techniques with the ages ranging from pre jurassic to quaternary although the philippines is widely regarded as an amalgamation of allochthonous terranes a review of the available data shows that there is currently no compelling evidence that these ophiolites are of exotic origin and that they have been tectonically accreted to the philippine arc complex rather the evidence suggests that most and possibly all of the ophiolites were generated as back arc fore arc or intra arc crust within the philippine arc complex hence there is a close spatial association of several ophiolitic terranes of diverse ages spanning 150 myr that formed as part of the arc complex such an association may have arisen from episodic generation of oceanic crust during periods of local extension in a suprasubduction zone setting which has experienced changing and possibly overlapping subduction from the east and west sides in the current reference frame disruption of the ophiolitic basement terranes has been and continues to be effected primarily by wrench faulting this style of arc growth has implications for the paleotectonic interpretation of ancient ophiolite arc terranes in continents and the petrologic evolution of island arcs

plausibility of long distance electrotelluric precursors to earthquakes a systematic analysis of the plausibility of different classes of models which could account for low frequency precursory electrotelluric signals observable at large distances from a large earthquake is carried out first we consider linear models for which either a stationary electrical field is generated by a current dipole in the source volume or a static deformation field results from a precursory strain in the source volume linearly inducing a streaming potential effect near the electrode in the former case only the conjunction of very favorable circumstances may lead to an electrical field larger than 10 mv km at more than 100 km with the constraint that no anomaly exceeds a few volts per kilometer in the source area it indeed requires a powerful electrical dipole current 104 a length 1 km which might be produced by a streaming potential effect associated with the connection of nonhydrostatic fluid reservoirs pore pressure difference up to 100 mpa a two dimensional channeling of the electrical currents from the source to the electrode area which would result from high conductivity horizontal layers and finally a local amplification factor of typically 100 near the electrodes which might be produced by a narrowing of the conductive channel for an elastic long distance interaction an electric field of 10 mv km at a distance 10 times the source length 100 km away from a m 6 earthquake requires a precursory deformation larger than the coseismic deformation if no strong local amplification is considered alternatively nonlinear models are proposed and discussed assuming that the crust is stuffed with small scale local instabilities fractures and nonhydrostatic fluid reservoirs among which a number are close to their instability threshold these instabilities may follow their own evolutionary process inducing sporadic fluid flow and hence streaming potential effect in the vicinity of the electrodes without any relation to a remote tectonic activity however these instabilities may be sensitive to very small changes in the stress field and hence be triggered by the elastic precursory deformation of a remote seismic source this requires that the precursory deformation near the instability is at least larger than the tidal strain 10 7 this necessary condition is met at a distance of up to 10 times the source dimension when the precursory strain source is only 10 of the coseismic deformation provided that the strain source is double the size of the seismic fault itself this model could account for the absence of self potential anomalies related to the earthquake itself as a large proportion of the available instabilities could have been swept away by the precursory strain furthermore with such a model a precursory strain in the source area could induce a detectable change in the background seismic activity over a vast area which may give a new interpretation of the times of increased probability observations for short distances the triggering of fluid instabilities by strain perturbation and the associated streaming potential effect may well be a promising model for explaining low frequency electric and magnetic precursors

times of increased probability of large earthquakes ms 7 5 along the mexican subduction zone abstract using the method of pattern recognition of infrequent events we explore the possibility of identifying the times of increased probability tip of occurrence of large earthquakes ms 7 5 along the mexican subduction zone a tip refers to a 5 year period within which a strong earthquake has a high probability of occurrence we analyzed the seismicity for the regions of chiapas eastern oaxaca 91 97 w region 1 western oaxaca guerrero 97 102 w region 2 and michoacan colima jalisco 102 106 w region 3 for the time interval 1970 1991 with the national oceanic and atmospheric administration seismic catalog as the source data the premonitory intermediate term seismic activation to identify a tip was measured using the algorithm m8 three out of the five earthquakes of ms 7 5 that occurred during the studied period are diagnosed by algorithm m8 and for the region 3 segment a tip is identified that will end between 1994 and 1996 we consider the area between the western colima gap and the jalisco region 103 7 106 0 w as the zone where the forecast earthquake has a higher than usual probability of occurrence our results by no means constitute a definitive earthquake prediction but suggest the need for detailed seismic analysis and the study of other geophysical precursors along the colima jalisco segment

separation of p and s waves in combined p and sv observations with vertical and in line horizontal geophones recognition and separation of the individual p and s arrivals may form a considerable problem due to the geophone receiving characteristics p and s waves are observed on both horizontal and vertical geophones a new method of separating p and s waves is presented that inverts the geophone records for the receiving characteristics thereby separating the two wavetypes the filter coefficients are determined from the near surface p and s wave velocity and from the geometry of the geophone groups the p s separation filter was tested on synthetic data with good results even ps and sp converted reflections which are completely coinciding for horizontal reflectors could be well separated the filter appears to be stable and to have low sensitivity to noise in the data or to errors in the near surface p and s wave velocity the filter is superior to other separation methods which were applied to the same dataset for comparison this method can also be applied to vsp data

crustal structure and inferred rifting processes in the northeast south china sea abstract taiger project deep penetration seismic reflection profiles acquired in the northeastern south china sea scs provide a detailed view of the crustal structure of a very wide rifted continental margin these profiles document a failed rift zone proximal to the shelf a zone of thicker crust 150 km from the shelf and gradually thinning crust toward the cob spanning a total distance of 250 300 km such an expanse of extended continental crust is not unique but it is uncommon for continental margins we use the high quality images from this data set to identify the styles of upper and lower crustal structure and how they have thinned in response to extension and in turn what rheological variations are predicted that allow for protracted crustal extension upper crustal thinning is greatest at the failed rift uc 7 5 but is limited farther seaward uc 1 2 we interpret that the lower crust has discordantly thinned from an original 15 17 km to possibly less than 2 3 km thick beneath the central thick crust zone and more distal areas this extreme lower crustal thinning indicates that it acted as a weak layer allowing decoupling between the upper crust and the mantle lithosphere the observed upper crustal thickness variations and implied rheology lower crustal flow are consistent with large scale boudinage of continental crust during protracted extension

an optimization of using the m8 algorithm for prediction of major m7 0 earthquakes in the iranian plateau the casualties and financial losses caused by large earthquakes have led to an awareness of prediction importance of such earthquakes the earthquake prediction is divided into four categories long term intermediate term short term and immediate the m8 algorithm is one of the intermediate term middle range prediction algorithms primarily used to predict earthquake of magnitude 8 or more and is applied later for smaller magnitudes the iranian plateau is less exposed to earthquake with magnitude 8 or more and it is observed that the seismicity rate in this region is generally low thus the original m8 is not suitable for applying in this region the objective of this study is to modify the m8 algorithm for prediction of major m7 0 earthquakes in the iranian plateau the major earthquake of magnitude 7 or more in the iranian plateau from 1975 to 2018 is considered as the target earthquakes the hit rate times 1 minus alarm rate is defined as objective function and the particles swarm optimization meta heuristic algorithm is used to maximize it the optimum m8 could predict 14 out of 17 large earthquakes in the iranian plateau while occupying 31 7 of the spatio temporal space as the alarm the results show that by employing an optimization algorithm we can modify the m8 algorithm for efficient prediction of the target magnitudes less than 8 in the regions with low seismicity rate

testing an earthquake prediction algorithm the 2016 new zealand and chile earthquakes the 13 november 2016 m7 8 54 km nne of amberley new zealand and the 25 december 2016 m7 6 42 km sw of puerto quellon chile earthquakes happened outside the area of the on going real time global testing of the intermediate term middle range earthquake prediction algorithm m8 accepted in 1992 for the m7 5 range naturally over the past two decades the level of registration of earthquakes worldwide has grown significantly and by now is sufficient for diagnosis of times of increased probability tips by the m8 algorithm on the entire territory of new zealand and southern chile as far as below 40 s the mid 2016 update of the m8 predictions determines tips in the additional circles of investigation cis where the two earthquakes have happened thus after 50 semiannual updates in the real time prediction mode we 1 confirm statistically approved high confidence of the m8 msc predictions and 2 conclude a possibility of expanding the territory of the global test of the algorithms m8 and msc in an apparently necessary revision of the 1992 settings