sm nd evidence for a major 1 5 ga crust forming event in the central grenville province the majority of gray gneisses from an 80 000 km 2 area in the central quebec grenville province define a sm nd isochron that yields an age of 1 53 0 07 ga major element trace element and initial nd isotopic data all point to a subduction related orogenic source for this terrane it is attributed to a major crustal extraction event that formed a mid proterozoic island arc the age of the terrane agrees with published data from the eastern and western grenville province in newfoundland and ontario respectively we suggest that 1 5 ga are fragments were accreted along much of the length of the laurentian foreland within 100 m y of their formation in an event marked by widespread granitoid plutonism

late quaternary transpressional earthquakes on a long lived intraplate fault a case study of the southern yangsan fault se korea abstract the nne ssw striking yangsan fault in southeastern korea has been regarded as one of the most prominent seismogenic structures in the korean peninsula on the basis of instrumental and historical seismicity and paleoseismic records along the fault zone its seismic behavior is however still uncertain due to long recurrence intervals of strong earthquakes and insufficient historical and geologic records we conducted a detailed paleoseismic investigation including an 8 m deep excavation in order to understand recent earthquake faulting events along the southern yangsan fault our observations indicate that at least two and possibly four dominantly strike slip surface faulting events have occurred along a subsidiary fault in the eastern boundary of the fault valley since the late pleistocene stratigraphic features and osl ages of the stratigraphy exposed in the trenches indicate that the most recent rupture s occurred after 29 2 1 4 ka and the timing of earlier ruptures are constrained to between 70 0 3 7 ka and 29 2 1 4 ka using a contact of the oldest dated unit that has at least 7 5 m of vertical separation we calculate a minimum vertical slip rate during the late quaternary of 0 11 mm yr the minimum horizontal slip rate is presumed to be two times that of the vertical slip rate based on striations observed on clasts next to the fault core we also propose that the late quaternary earthquake faulting kinematics along the yangsan fault expressed as contractional dextral slip with east side up geometry is strongly dependent on a pre existing fault zone architecture with a strike of n10 20 e that dips to the east and the direction of neotectonic maximum horizontal stress ene wsw to e w

characteristics of flow fluctuations in a tide dominated estuary application of triple decomposition technique small tide dominated estuaries are affected by both large scale flow structures manifested as oscillatory residual currents and small scale bed generated turbulence the present understanding of the effects and relative contributions of these factors are inadequate due to limited systematic observations a field study was conducted in a small sub tropical estuary in which high frequency 50 hz turbulence data were recorded continuously for about 48 h a triple decomposition technique was introduced to isolate the contributions of tides slow fluctuations and true turbulence in the flow field a striking feature of the data set was the slow fluctuations which exhibited large velocity amplitudes up to 50 of the tidal amplitude under neap tide conditions the skewness of the fast true turbulence were within the range of 4 and 2 the analysis of the fast fluctuations revealed that variation in the turbulence characteristics are linked with the tidal velocity suggesting that the dispersion and mixing are dependent on some large scale flow properties the results also indicated enhanced mixing associated with the slow fluctuation in the flow field the results provided useful sets of information about the properties of slow and fast fluctuating components and their variations through tidal cycles in a micro tidal estuary

modelling of cohesive sediment transport in a tidal lagoon an annual budget abstract the annual net sediment flux for an enclosed estuary is usually calculated as a residual value in sediment budget studies based mainly on sediment core dating in this study the numerical model mike 21 mt was used to directly model the annual net transport of cohesive sediment for the lister dyb tidal area in the northern part of the european wadden sea the model was calibrated by use of a combination of field data and calibration parameters derived from existing literature the model reproduced the hydrodynamics satisfactorily as well as the concentration level and variation of suspended cohesive sediment concentration net import for the year 2002 was found to be 45 000 t of cohesive sediment corresponding to a mean tidal period import of 64 t which compares to an approximate deposition of 0 1 mg l 1 of the tidal prism gross annual transport through a control cross section of the tidal inlet was 1 million ton meaning that 4 5 of the sediment transported in suspension was on average deposited within the tidal lagoon this net transport was found to be rather constant from tidal period to tidal period thus supporting the theory that the processes of settling and scour lag tidal velocity asymmetry together with sediment floc formation are the controlling processes for import of fine grained sediment to shallow coastal plain estuaries temporary export of sediment from the area occurred during two major wind events in january and february when the maximum loss of sediment during one single tidal period was computed to be 40 000 t which is of the same order as the yearly net import of sediment this indicates that net annual import of cohesive sediment to shallow estuaries may be much more variable than inferred from core dating studies found in literature

aftershock sequence and statistics of the 2017 mw 5 5 pohang south korea earthquake implications of fault heterogeneity and postseismic relaxation

monitoring velocity variations in the crust using earthquake doublets an application to the calaveras fault california we present a technique that greatly improves the precision in measuring temporal variations of crustal velocities using an earthquake doublet or pair of microearthquakes that have nearly identical waveforms and the same hypocenter and magnitude but occur on different dates we compute differences in arrival times between seismograms recorded at the same station in the freqency domain by cross correlation of short windows of signal a moving window analysis of the entire seismograms including the coda gives t the difference in arrival times versus running time along the seismogram the time resolution of the method is an order of magnitude better than the digitization interval the t technique is illustrated with a pair of microearthquakes m 1 7 and 2 0 that occurred before and after the coyote lake california earthquake m 5 9 of august 6 1979 and on the same segment of the calaveras fault that ruptured during the earthquake the coda wave arrivals for some stations are progressively delayed for the second earthquake in the doublet so that its seismogram appears as a stretched version of the earlier event we interpret this systematic variation in t along the coda as a change in the average s velocity in the upper crust in the time interval between the two doublets s wave velocities appear to have decreased by 0 2 in an oblong region 5 10 km in radius at the south end of the aftershock zone

mesoproterozoic and paleoproterozoic crustal growth in the eastern grenville province nd isotope evidence from the long range inlier of the appalachian orogen

field studies of velocity salinity and suspended solids concentration in a shallow tidal channel near tidal flap gates abstract the design and operation of mathematical models of solute mixing and sediment transport in estuaries rely heavily on the provision of good quality field data we present some observations of salinity suspended sediment concentration and velocity at one of the tidal limits of a semi enclosed tidal lagoon in southern england pagham harbour west sussex uk where the natural processes of tidal incursion and solute mixing have been heavily modified as a result of the construction of sea walls dating back to the 18th century these observations made immediately downstream of two parallel tidal flap gates by conductivity temperature depth ctd profiler and also using bed mounted sensor frames to measure velocity at 2 fixed depths have yielded a set of results covering 11 tidal cycles over the period 2002 04 it is clear from the results obtained that over a typical tidal cycle the greatest vertical salinity gradients occur in the 1 2 h immediately after the onset of the flood tide and that subsequently energetic mixing acts to rapidly break down this stratification under moderate to high fresh water flows 0 5 m 3 s the break down in vertical salinity gradient is more gradual while under low fresh water flows 3 s the vertical salinity gradient is generally less pronounced estimates of richardson number during the early flood tide period reveal values that vary rapidly between

crustal formation in the grenville province nd isotope evidence ninety eight new nd isotope analyses are presented for gneissic rocks from the grenville province when combined with over 250 published nd analyses and some unpublished analyses these data can be used to establish a first order crustal formation age map for most of the grenville parautochthon and allochthonous polycyclic belt in particular the geographic extents of a juvenile labradorian arc labradoria and a juvenile 1 5 ga arc quebecia are defined each with an area probably in excess of 100 000 km2 in addition pre 1 75 ga arcs are identified in ontario barilia and labrador makkovikia this work largely fills the last major gap in the continent wide crustal formation age map of the precambrian shield of north america

tectonic and sedimentary evolution of the korean peninsula a review and new view abstract this review focuses on the tectonics and sedimentation of major sedimentary basins and orogenic belts late proterozoic neogene in the korean peninsula the korean peninsula is part of the amuria plate and represents an important link between continental blocks of north and south china and the island arcs of japan the basement rocks exposed in the kyonggi and yongnam massifs consist of 2 7 to 1 1 ga high grade gneiss and schist these massifs are separated by the okchon fold belt which comprises metasedimentary rocks and bimodal meta volcanic rocks the stratigraphy of the okchon group is unclear at present the okchon basin was probably initiated as an intraplate rift prior to the late proterozoic the hwanggangri formation clast bearing phyllite most likely represents deposition by subaqueous debris flows in slope environments of an enclosed basin the stratigraphic relationship between the okchon group and the choson supergroup cambro ordovician of the taebaeksan basin is poorly constrained the choson supergroup unconformably overlies the yongnam massif and consists mainly of carbonate sequence that formed mostly in shallow marine and tidal environments reflecting numerous sea level fluctuations the sequence is disconformably overlain by siliciclastic sequence of pyongan supergroup carboniferous triassic which formed most likely in shallow marine deltaic and fluvial environments the imjingang belt is an east trending fold and thrust zone and consists of metasedimentary rocks and volcaniclastics devonian carboniferous underlain unconformably by proterozoic basement rocks late proterozoic amphibolites of oceanic affinity were metamorphosed at about 8 13 kbar and 630 740 c during the late permian to the early triassic the south vergent contraction and top down to the north normal faulting are suggestive of a suture belt between the north china block sino korea craton and the south china block yangtze craton an extension of sulu belt across the yellow sea entire peninsula experienced strong deformation and metamorphism during the suturing event namely songrim orogeny during this orogenic event the kyonggi massif and the okchon basin accreted to the yongnam massif and taebaeksan basin along the south korean tectonic line running northeast southwest a series of northward trending thrust formed along the boundary zone to the east kaktong and kongsuwon thrusts and others piggyback basins locally developed along the thrust faults forming the taedong group the crustal deformation resumed in the early to late jurassic daebo event under contractional setting dextral ductile shearing associated with thrusting and folding continued in the mid southern part of the peninsula it was due to orthogonal northwestward subduction of the izanagi plate under the asian continent the yongnam massif experienced continuous dextral offset along the honam shear zone in the early cretaceous the izanagi plate began to subduct northward and caused formation of strike slip basins in retroarc setting i e kyongsang basin in the southeastern part and a number of small scale basins in the mid southwestern part of the peninsula small scale alluvial fans and fluvial channel networks formed in the basin margin and were transitional to ephemeral lacustrine systems under semiarid to arid conditions extensive intrusion of granitoids occurred from triassic to early tertiary with a gap between 160 and 100 ma representing continental magmatic arc in the tertiary the southeastern margin of the korean peninsula experienced back arc opening pull apart basins formed in the miocene bounded by the yangsan and hupo faults the yonil group sedimentary fill of the pohang basin comprises more than 1 km thick siliciclastic sequence which represents deposition in fan delta systems on the hanging wall of the yangsan fault thick more than 10 km thick sediments in the ulleung basin margin were deformed in the late miocene due to the northward movement of kyushu block quarternary volcanic events in cheju island represent intraplate hot spots

the location of the allochthon boundary thrust and the archean proterozoic suture in the mattawa area of the grenville province nd isotope evidence abstract over 100 nd isotope analyses are used to map the crustal formation ages of grenville orthogneisses in a 10 000 km 2 area near mattawa on the ontario quebec border lithotectonic terranes with mapped outcrops of eclogite or coronitic metagabbro have nd model ages less than 1 8 ga and are interpreted as fragments of the allochthonous polycyclic belt however large areas of orthogneiss to the north of mattawa have model ages of 1 9 2 9 ga interpreted as archean crust that was extensively plutonised in paleo and mesoproterozoic magmatic events based on this evidence a revised location is proposed for the allochthon boundary thrust abt which passes to the south of the bonfield batholith and mattawa but then trends to the north and is correlated with the lac watson shear zone some allochthonous klippen are identified northwest of the main trace of the abt representing the dissected remains of what was originally a large allochthonous thrust sheet within the parautochthon a major step in depleted mantle model ages is observed in the vicinity of the mattawa fault separating archean and paleoproterozoic crustal blocks this boundary is interpreted as an ancient crustal suture reactivated by faulting associated with the ottawa bonnechere graben it is concluded that nd isotope analysis is a useful technique for detailed mapping of major tectonic boundaries in highly metamorphosed orogenic belts such as the grenville province

recent eruptions at bezymianny volcano a seismological comparison abstract for the past few decades bezymianny volcano has erupted once to twice per year here i examine eight eruptive events between 2006 and 2010 this is the first time period for which proximal or broadband seismic data have been recorded at bezymianny several recurring patterns are demonstrated in advance of eruptions eruptions are generally preceded by 12 36 h of tremor energy elevated by 2 to 3 orders of magnitude locatable earthquake activity is quite erratic in the days before eruptions for eruptions of juvenile magma however the cumulative moment magnitude increases with the repose time since the previous eruption though tenuous this relationship is statistically significant and could improve forecasts of bezymianny eruptions the most energetic eruptions demonstrate increasing multiplet activity in the run up followed by a rapid cessation at the time of eruption when present this behavior marks increasing pressure in the conduit system as degassing eclipses the capacity for venting very long period seismicity 20 s periods accompanies some eruptions these tend to be the same short lived high energy eruptions that exhibit multiplet precursors four eruptions are examined in detail to illustrate the variety in eruption mechanisms lava dome collapses sustained eruptions singular paroxysmal explosions and post explosion lava flows occur in different combinations demonstrating that more than one eruption trigger is regulating bezymianny compared to bezymianny s fifty year modern history recent eruptions have been shorter lived and separated by longer repose times some evidence suggests that these eruptions may be increasingly explosive a speculation that carries significant hazard implications if true however this threat is tempered by solid evidence that the most explosive eruptions are preceded by the clearest precursors suggesting an ability to improve the already excellent eruption forecasts available for bezymianny

estimation of possible maximum earthquake magnitudes of quaternary faults in the southern korean peninsula the korean peninsula is located in the intraplate regime of the eurasian plate and numerous historical and instrumental earthquakes have been recorded among these the largest earthquakes were recorded in and around the gyeongju and ulsan areas in the southeastern part of the korean peninsula we recently reexamined faults in jinhyun and jintee part of the ulsan fault swarm to clarify the average slip rate and the maximum potential magnitude of future earthquakes the jinhyun fault extends to the tabgol fault j t fault and the jintee fault extends to the singye s j fault the faults cut through alluvial fans and are covered by unconsolidated granite washes on tertiary granite all of these faults show reverse sense of motion such that the tertiary granite has been moved upward with a high angle relative to the quaternary sediments most sediment samples from the jinhyun and jintee faults showed quartz osl ages of ca 40 60 ka the calculated vertical slip rate for the jinhyun and jintee faults is in the range of 0 18 0 28 mm y based on maximum earthquake magnitudes calculated from geological survey results as well as historical and instrumental earthquake information the maximum potential magnitudes of future earthquakes in the gyeongju area are estimated to range from 4 6 to 5 6 this suggests that the potential maximum magnitude in the southern korean peninsula is presumably not more than 6

the geon 14 arc related mafic rocks from the central grenville province the late paleoproterozoic to mesoproterozoic ca 1 7 1 2 ga evolution of the active southeastern margin of laurentia terminated with the grenvillian continental collision and the development of a large hot long duration orogen at ca 1 09 0 98 ga as a result much of the hinterland of the grenville province consists of paleoproterozoic and mesoproterozoic rocks mostly preserved as an imbricate stack of high grade gneisses that represent a potential repository of active margin processes this study presents geochronologic geochemical and isotopic analyses of two granulite facies suites of ca 1 45 1 40 ga mafic tholeiites from the canyon domain manicouagan area central grenville province one suite consists of 1439 76 68 ma high feti mafic sills with end values of 0 4 tdm 2 57 2 72 ga indicate derivation from variably depleted to enriched morb type mantle sources probably in an extensional back arc setting before intrusion in a ca 1 5 ga supracrustal metasedimentary sequence the other

the offshore yangsan fault activity in the quaternary se korea analysis of high resolution seismic profiles abstract the nne trending dextral yangsan fault is a 190 km long structure in the korean peninsula traced to the southeastern coast the scarcity of quaternary deposits onland precludes any detailed investigation of the quaternary activity and structure of the yangsan fault using seismic reflection profiling we acquired offshore high resolution seismic profiles to investigate the extension of the yangsan fault and constrain its quaternary activity using stratigraphic markers the seismic profiles reveal a nne trending fault system consisting of a main fault and an array of subsidiary faults that displaced quaternary sequences stratigraphic analysis of seismic profiles indicates that the offshore faults were activated repeatedly in the quaternary the up to the east sense of throw on the main fault and plan view pattern of the fault system are explained by dextral strike slip faulting the main fault when projected toward the korean peninsula along its strike aligns well with the yangsan fault we suggest that the offshore fault system is a continuation of the yangsan fault and has spatial correlation with weak but ongoing seismicity

nd isotope mapping of a pinwarian age composite arc belt in the quebecia terrane of the central grenville province canada abstract there continues to be confusion in the geological community concerning the ages of crustal formation and crustal accretion within the central grenville province of quebec to clarify the geological history of crustal growth in the eastern part of the quebecia terrane sixty new nd isotope analyses are presented from a 60 000 km2 area northwest of baie comeau most samples yield pinwarian nd model ages that suggest them to be derived from juvenile oceanic arc terranes however two large slivers with paleoproterozoic tdm ages attest to the existence of hidden blocks of old crust which divide the area of juvenile pinwarian crust into a composite arc belt of smaller accreted terranes the old crustal blocks probably do not reach the present surface but represent an igneous crustal protolith of younger i type magmatism by comparison with a mesozoic tectonic analogue it is proposed that accreted juvenile arc crust with attached slivers of older crust were rifted away from an active margin to the west and translated eastwards until blocked by the previously accreted labradoria terrane although the quebecia composite arc belt consists of over 95 of pinwarian juvenile arc crust the age of arc accretion was post pinwarian the proposed oblique nature of the accretion process may explain the lack of a major collisional orogen at that time this paper shows the usefulness of large scale nd isotope mapping of precambrian crustal terranes to clarify complex processes of crustal formation and arc accretion

a comparison of nd model ages and u pb zircon ages of grenville granitoids constraints on the evolution of the laurentian margin from 1 5 to 1 0 ga terra nova 24 7 15 2012 abstract concordance and discordance between nd model ages and u pb ages is still widely misunderstood in the geological community in the sw grenville province plutonic orthogneisses often yield tdm ages significantly older than u pb crystallization ages but this can be understood in a model where a series of crustal nd isotope evolution lines departs at intervals from the depleted mantle dm evolution line seven samples with concordant u pb and nd model ages have initial e nd on the dm line attributed to melting of juvenile crust generated in an elzevirian back arc rift zone in contrast plutons with discordant u pb and nd model ages lie near crustal evolution lines defined by suites of basement gneisses on the flanks of the rift zone this study shows that nd data from large suites of geographically constrained undated grey gneiss provide a crustal evolution framework for orogen scale interpretation of more scattered but precisely dated plutons

u pb geochronologic constraints on the crustal evolution of the long range inlier newfoundland the long range mountains of newfoundland expose the northeastern most basement inlier of the appalachian orogen u pb results for two samples of basement gneiss reveal crustal formation ages of 1466 10 ma western brook pond charnockite and 1530 8 ma cat arm road gneiss indicating an affinity with pinwarian magmatism 1510 1450 ma in labrador a third sample of basement gneiss from the cat arm road dam site yielded a minimum formation age of 1631 ma these basement gneisses were intruded by granite plutons during two periods of grenvillian magmatism group i at 1032 1022 ma and group ii at 993 985 ma group i intrusions include the 1032 0 1 5 ma lomond river granite and the 1022 0 2 0 ma lake michel igneous suite group ii intrusions include the 999 4 ma potato hill charnockite 993 7 ma horse chops granite 984 9 1 6 ma cloud river granite and may include the apsy granite the metamorphic history of the long range inlier is complex and three discrete proterozoic metamorphic events can

southern california hypocenter relocation with waveform cross correlation part 1 results using the double difference method we present the results of relocating 327 000 southern california earthquakes that occurred between 1984 and 2002 we apply time domain waveform cross correlation for p and s waves between each event and 100 neighboring events identified from the catalog based on a 3d velocity model to simplify the computation we first divide southern california into five polygons such that there are 100 000 events or less in each region the polygon boundaries are chosen to lie in regions of sparse seismicity we calculate and save differential times from the peaks in the cross correlation functions and use a spline interpolation method to achieve a nominal timing precision of 0 001 sec these differential times together with existing p and s phase picks are input to the double difference program of waldhauser and ellsworth 2000 2002 to calculate refined hypocenters we divide the southern california region into grid cells and successively relocate hypocenters within each grid cell the overall resulting pattern of seismicity is more focused than the previously determined pattern from 1d or 3d models the new improved locations are more clustered in many cases by a factor of two or three and often show clear linear alignments in particular the depth distribution is improved and less affected by layer boundaries in velocity models or other similar artifacts

esr dating of the subsidiary faults in the yangsan fault system korea abstract the yangsan fault system is located near heavy industrial complexes and nuclear power plants in the korean peninsula we carried out esr dating of fault rocks from the wonwonsa and ihwa faults two subsidiary faults of the yangsan fault system esr ages are divided into three groups in order of decreasing confidence multiple plateau esr ages single plateau esr ages and maximum esr ages the wonwonsa fault was reactivated at least 4 times and the ihwa fault at least 2 times within the quaternary period long term cyclic fault activity of some subsidiary faults of the yangsan fault system occurred in the pleistocene and suggests the possibility of continued activity on this fault system

continuous high frequency turbulence and suspended sediment concentration measurements in an upper estuary the present study details new turbulence field measurements conducted continuously at high frequency for 50 hours in the upper zone of a small subtropical estuary with semi diurnal tides acoustic doppler velocimetry was used and the signal was post processed thoroughly the suspended sediment concentration wad further deduced from the acoustic backscatter intensity the field data set demonstrated some unique flow features of the upstream estuarine zone including some low frequency longitudinal oscillations induced by internal and external resonance a striking feature of the data set is the large fluctuations in all turbulence properties and suspended sediment concentration during the tidal cycle this feature has been rarely documented

dynamic deformation of the accretionary prism excites very low frequency earthquakes 1 we have detected anomalous very low frequency earthquakes within the accretionary prism along the nankai trough southwestern japan centroid moment tensor inversion analysis reveals that the earthquake hypocenters are distributed at 10 km depth above the upper surface of the subducting philippine sea plate and within 50 70 km landward of the trough axis the focal mechanisms indicate reverse faulting their hypocenters are distributed beneath a deformation zone of an accretionary prism in sea floor topography these observations suggest that the occurrence of very low frequency earthquakes is related to numerous reverse fault systems within the accretionary prism and that the earthquakes reflect the dynamics of deformation within this accretionary prism

new tectonic divisions of the grenville province southeast canadian shield on the basis of geological geophysical and geochronological data the grenville province has been divided into three first order longitudinal belts the parautochthonous belt pb allochthonous polycyclic belt apb and allochthonous monocyclic belt amb these are set apart by three first order tectonic boundaries the grenville front gf allochthon boundary thrust abt and monocyclic belt boundary zone mbbz the belts are subdivided into terranes based on internal lithological character the gf separates the archean to proterozoic foreland northwest of the orogen from reworked equivalents to the southeast continuous at the scale of the orogen its main characteristic is that of a crustal scale contraction fault the pb although less clearly identified along the length of the orogen in most places represents upgraded and tectonically reworked rocks of the adjacent foreland the boundary between the pb and the apb to the southeast the abt is most clearly delineated in the eastern half of the province it is the locus of major crustal delamination along which high grade mostly middle proterozoic polycyclic terranes were tectonically transported northwest toward and onto the pb the amb comprises two separate areas underlain by the wakeham supergroup and what is currently known as the grenville supergroup respectively its basal contact the mbbz is a decollement zone of variable kinematic significance between older polycyclic rocks and tectonically overlying monocyclic rocks this first order zonation implies a tectonic polarity to the grenville province superimposed on which are second order features evident from contrasting tectonic styles and radiometric ages these characteristics are consistent with a diachronous or oblique collisional model for the grenville orogen

forward waveform modelling procedure for 1 d crustal velocity structure and its application to the southern korean peninsula summary we propose a full grid search procedure for broad band waveform modelling to determine a 1 d crustal velocity model the velocity model can be more constrained because of the use of broad band waveforms instead of traveltimes for the crustal phases although only a small number of event station pairs were employed despite the time consuming nature of the full grid search method to search the whole model parameter space the use of an empirical relationship between the p and s wave velocities can significantly reduce computation time the proposed method was applied to a case in the southern korean peninsula broad band waveforms obtained from two inland earthquakes that occurred on 2007 january 20 mw 4 6 and 2004 april 26 mw 3 6 were used to test the method the three layers over half space crustal velocity model of the p and s wave velocities was estimated comparisons of waveform fitness between the final model and previously published models demonstrate advancements in the average value of waveform fitness for the inland earthquakes in addition 1 d velocity models were determined for three distinct tectonic regions namely the gyonggi massif the okcheon belt and the gyeongsang basin which are all located inside the study area a comparison between the three models demonstrates that the crustal thickness of the southern korean peninsula increases from nw to se and that the lower crustal composition of the okcheon belt differs from that of the other tectonic regions

styles of proterozoic crustal growth on the southeast margin of laurentia evidence from the central grenville province northwest of lac st jean quebec the southeast margin of laurentia was a very long lived active continental margin part of whose history is recorded in the grenville province of the canadian shield within this province nd isotope mapping can be used to define the boundaries between terranes with a variety of crustal formation ages and can also distinguish between crustal growth by oceanic and continental arc magmatism the former gives rise to large terranes with homogeneous nd isotope signatures and well defined boundaries whereas the latter leads to areas with heterogeneous nd isotope signatures one of the best examples of continental arc magmatism in the grenville province is provided by the region northwest of lac st jean quebec eighty new nd isotope analyses are used along with aeromagnetic data to divide this area into three blocks bounded by abrupt changes in nd model age the western block consists almost exclusively of tonalitic grey gneisses with archean model ages the eastern block is composed almost exclusively of

nd isotope mapping of allochthonous grenvillian klippen evidence for widespread ramp flat thrust geometry in the sw grenville province abstract over sixty new nd isotope analyses are used to constrain the extent of several small grenvillian lithotectonic domains that form erosional outliers of the grenvillian allochthonous polycyclic belt the identification of these tectonic klippen when combined with previous mapping of large nappes shows that the allochthonous polycyclic belt forms a mid upper crustal sub horizontal thrust sheet that was transported to the nw over the archean proterozoic parautochthon this thrust sheet was corrugated by folding and dissected by erosion leaving the klippen as synformal remnants nd isotope mapping of these remnants when coupled with seismic reflection data from the lithoprobe programme suggests that these thrust sheets were exhumed on relatively steep crustal scale ramps before transportation to the nw on sub horizontal shear zones this type of thrust geometry previously observed in the central eastern grenville province was termed ramp flat geometry by rivers et al 2012 re examination of lithoprobe seismic data for the georgian bay transect shows that reflectors under the parry sound klippe have a synformal character in the mid crust suggesting that this is also part of an undulose sub horizontal thrust sheet exhumed on a steep crustal scale ramp rather than the previous model of a very long ramp with low inclination hence we argue that the georgian bay section has a geometry resembling the ramp flat trajectory of the allochthon boundary thrust previously discerned elsewhere in the grenville province

nd isotope mapping of the allochthon boundary thrust on the shores of georgian bay ontario significance for grenvillian crustal structure and evolution nearly 50 new nd isotope analyses are presented for the shawanaga region of georgian bay ontario to study crustal evolution in the grenvillian central gneiss belt depleted mantle t dm nd model ages are used to map a major grenvillian tectonic boundary the allochthon boundary thrust abt which in the shawanaga area separates gneisses with t dm ages above and below 1 65 ga this is lower than the 1 8 ga age cut off observed further north and is attributed to a southward increase in mesoproterozoic magmatic reworking of an original palaeoproterozoic continental margin causing a progressive southward decrease in nd model ages between shawanaga island and franklin island nd isotope mapping yields an abt trajectory that closely matches published geological mapping and passes within 100 m of four retrogressed eclogite bodies typically associated with the thrust boundary this validation of the method gives confidence in the mapped trajectory south of snake island where sparse outcrop inhibits lithological mapping the new results suggest that published 1 7 1 9 ga t dm ages in the lower go home domain of the central gneiss belt further south are also indicative of parautochthonous crust hence we propose that the main ramp of the abt is located in the immediate hangingwall of the go home domain much further south than generally recognized this has important implications for the large scale crustal structure of the sw grenville province suggesting that the abt ramp has a similar curved trajectory to the grenville front and the central metasedimentary belt boundary thrust

precise tremor source locations and amplitude variations along the lower crustal central san andreas fault 1 we precisely locate 88 tremor families along the central san andreas fault using a 3d velocity model and numerous p and s wave arrival times estimated from seismogram stacks of up to 400 events per tremor family maximum tremor amplitudes vary along the fault by at least a factor of 7 with by far the strongest sources along a 25 km section of the fault southeast of parkfield we also identify many weaker tremor families which have largely escaped prior detection together these sources extend 150 km along the fault beneath creeping transitional and locked sections of the upper crustal fault depths are mostly between 18 and 28 km in the lower crust epicenters are concentrated within 3 km of the surface trace implying a nearly vertical fault a prominent gap in detectible activity is located directly beneath the region of maximum slip in the 2004 magnitude 6 0 parkfield earthquake

turbulence characteristics of a small subtropical estuary during and after some moderate rainfall in natural estuaries scalar diffusion and dispersion are driven by turbulence in the present study detailed turbulence measurements were conducted in a small subtropical estuary with semi diurnal tides under neap tide conditions three acoustic doppler velocimeters were installed mid estuary at fixed locations close together the units were sampled simultaneously and continuously at relatively high frequency for 50 hours the results illustrated the influence of tidal forcing in the small estuary although low frequency longitudinal velocity oscillations were observed and believed to be induced by external resonance the boundary shear stress data implied that the turbulent shear in the lower flow region was one order of magnitude larger than the boundary shear itself the observation differed from turbulence data in a laboratory channel but a key feature of natural estuary flow was the significant three dimensional effects associated with strong secondary currents including transverse shear events the velocity covariances and triple correlations as well as the backscatter intensity and covariances were calculated for the entire field study the covariances of the longitudinal velocity component showed some tidal trend while the covariances of the transverse horizontal velocity component exhibited trends that reflected changes in secondary current patterns between ebb and flood tides the triple correlation data tended to show some differences between ebb and flood tides the acoustic backscatter intensity data were characterised by large fluctuations during the entire study with dimensionless fluctuation intensity ib ib between 0 46 and 0 54 an unusual feature of the field study was some moderate rainfall prior to and during the first part of the sampling period visual observations showed some surface scars and marked channels while some mini transient fronts were observed

mesoproterozoic basement of the lac st jean anorthosite suite and younger grenvillian intrusions in the saguenay region quebec structural relationships and u pb geochronology

nd isotopes and the origin of 1 9 1 7 ga penokean continental crust of the lake superior region nd isotopic data on 26 samples demonstrate the origin of the early proterozoic crust of the penokean orogen the three major components are 1 the marquette range supergroup a predominantly miogeoclinal continental margin sequence deposited before 1 85 ga on archean basement 2 ca 1 88 ga felsic metavolcanic rocks of the wisconsin magmatic terrane to the south of evolved island arc affinity and 3 1 87 1 76 ga granitoids that intrude the metavolcanic rocks initial nd values for the metavolcanic rocks of the magmatic terrane range between 0 0 and 2 4 and t dm ages between 1 9 and 2 2 b y the volcanic rocks primarily represent new crustal material that had only a limited archean input probably through mixing of subducted sediments into the magma source area nd t values for sedimentary rocks in the lower part of the marquette range supergroup indicate an archean source most likely the 2 7 ga superior province to the north on the other hand the sedimentary rocks in the upper part of the marquette range supergroup graywackes of the upper michigamme formation have initial nd values between 0 8 and 1 5 indicative of an early proterozoic source these graywackes probably are foredeep deposits derived from the volcanic rocks of the wisconsin magmatic terrane to the south thus the time of deposition of the upper michigamme formation dates the final convergence of the wisconsin magmatic terrane with the continental margin the granitoids of the wisconsin magmatic terrane have a wide range of nd t values from 4 5 to 4 0 they represent mixtures of variable amounts of new crustal material and recycled archean detritus the more negative nd t values occur in samples close to the northern boundary of the wisconsin magmatic terrane which is marked by a mylonitic shear zone the niagara fault zone we suggest that the miogeoclinal lower marquette range supergroup rocks having an archean nd signature became involved in magma genesis close to the collisional boundary whereas increasingly lesser amounts of this older material were available for mixing farther away from the suture the 1 9 1 7 ga penokean events involved major growth of new crust from the mantle

fault slip analysis of quaternary faults in southeastern korea abstract the quaternary stress field has been reconstructed for southeast korea using sets of fault data the subhorizontal direction of the maximum principal stress 1 trended ene and the direction of the minimum principal stress 3 was nearly vertical the stress ratio 2 3 1 3 value was 0 65 two possible interpretations for the stress field can be made in the framework of eastern asian tectonics 1 the hmax trajectory for southeast korea fits well with the fan shaped radial pattern of maximum principal stress induced by the india eurasia collision thus we suggest that the main source for this recent stress field in southeast korea is related to the remote india eurasia continental collision 2 the stress field in korea shows a pattern similar to that in southwestern japan the origin for the e w trending hmax in japan is known to be related to the mantle upwelling in the east china sea thus it is possible that quaternary stress field in korea has evolved synchronously with that in japan we suggest further studies gps and in situ stress measurement to test these hypotheses

seismotectonics and fault structure of the california central coast abstract i present and interpret new earthquake relocations and focal mechanisms for the california central coast the relocations improve upon catalog locations by using 3d seismic velocity models to account for lateral variations in structure and by using relative arrival times from waveform cross correlation and double difference methods to image seismicity features more sharply focal mechanisms are computed using ray tracing in the 3d velocity models seismicity alignments on the hosgri fault confirm that it is vertical down to at least 12 km depth and the focal mechanisms are consistent with right lateral strike slip motion on a vertical fault a prominent newly observed feature is an 25 km long linear trend of seismicity running just offshore and parallel to the coastline in the region of point buchon informally named the shoreline fault this seismicity trend is accompanied by a linear magnetic anomaly and both the seismicity and the magnetic anomaly end where they obliquely meet the hosgri fault focal mechanisms indicate that the shoreline fault is a vertical strike slip fault several seismicity lineations with vertical strike slip mechanisms are observed in estero bay events greater than about 10 km depth in estero bay however exhibit reverse faulting mechanisms perhaps reflecting slip at the top of the remnant subducted slab strike slip mechanisms are observed offshore along the hosgri san simeon fault system and onshore along the west huasna and rinconada faults while reverse mechanisms are generally confined to the region between these two systems this suggests a model in which the reverse faulting is primarily due to restraining left transfer of right lateral slip

waveform relocated earthquake catalog for southern california 1981 to june 2011 we determine a new relocated catalog hys catalog 2011 for southern california from 1981 through june 2011 about 75 3 of the hypocenters are calculated with absolute and differential travel time picks and 24 7 could be relocated only by using absolute travel time picks with 3d or 1d velocity models the total catalog consists of more than 502 000 earthquakes in the region extending from baja california in the south to coalinga and owens valley in the north the catalog consists of three m 7 1 m 7 2 and m 7 3 mainshocks their foreshocks and aftershocks and background seismicity caused by tectonic and other processes in the southern california crust hypocenters in the new relocated catalog exhibit tighter spatial clustering of seismicity than does the routinely generated catalog and the depth distribution is tighter and reflects the thickness of the seismogenic zone more accurately compared to the standard catalog the relocated hypocenters are more easily related to other data sets such as mapped late quaternary faults

lateral variation in the source parameters of earthquakes in the korean peninsula to elucidate the seismic characteristics of earthquakes in the korean peninsula we investigated seismic source parameters of 651 earthquakes that occurred between 2001 and 2014 with magnitudes greater than 1 9 we estimated the seismic moment corner frequency and stress drop of an event from s wave source spectra comparison of our estimates with the results of previous studies confirmed the reliability of our findings breakdown in the self similarity of an earthquake source may occur at around a seismic moment of 1021 dyn cm as suggested by previous studies although nonnegligible variation still appears in the corner frequency of low magnitude events we also found that earthquakes in two regions near pyongyang and on the western margin of the east sea sea of japan occurred with low stress drops these regions have distinctively higher seismicity than other regions the largest earthquake m w 6 2 in the korean peninsula in the past century occurred in the low stress drop region near pyongyang the western margin of the east sea reportedly has earthquake focal mechanisms that differ from those of earthquakes in other regions in the peninsula therefore we suggest that lateral variation in stress drops in the korean peninsula could be related to the distinctive seismic characteristics in these regions

infragravity currents in a small ria estuary amplified coastal edge waves abstract observations are presented of estuarine infragravity oscillations in a very small estuary the ria de santiuste northern spain that discharges into a bay time scale calculations and measurements indicate that the most likely source of amplified infragravity waves within the estuary are coastal edge waves which appear to be resonating between the headlands of the bay and onshore offshore seiching of waters that may be resonating between the beach and the bay s seaward limit infragravity waves in the estuary have a narrow power dominant periodicity range of 4 3 4 8 min generally only very weak waves and at other periodicities occur within the tidal river when it is unaffected by the tide although infragravity water level amplitudes are small in the tidal river typically 0 01 m during high water the corresponding velocity amplitudes are significant typically 0 1 m s 1 despite the occurrence of high runoff conditions during these measurements within the estuary and close to the mouth near bed salinity shows considerable variability that is a consequence of salt wedge oscillations with periodicities that are within the range of 4 3 4 8 min model results for simulated neap to spring high water water levels show that wave periodicities in the range 3 5 4 5 min correspond approximately to 3 4 resonances the model also indicates that an effect of low runoff is to greatly enhance resonant behaviour within the estuary such that water level amplitudes of 0 02 m at the mouth can produce wave currents as fast as 0 4 m s 1 within the estuary compared with 0 1 m s 1 during high runoff

high precision earthquake location and three dimensional p wave velocity determination at redoubt volcano alaska 1 redoubt volcano alaska poses significant volcanic hazard to the cook inlet region and overlying flight paths during and following the most recent eruption in 1989 1990 the alaska volcano observatory deployed up to 10 seismometers to improve real time monitoring capabilities at redoubt and continues to produce an annual earthquake catalog with associated arrival times for this volcano we compute a three dimensional p wave velocity model using double difference tomography combined with waveform cross correlation techniques to identify families of similar earthquakes and increase earthquake location precision at redoubt absolute and differential times for well constrained events are used to simultaneously invert for hypocenter location and p wave velocity structure shot and earthquake arrival times recorded by temporary stations deployed on redoubt in july 1991 supplement the catalog picks double difference tomography reduces uncertainties associated with absolute and relative earthquake locations and provides a clearer picture of three dimensional velocity heterogeneity all redoubt data available through november 2005 are relocated through the three dimensional model and we investigate seismicity associated with the 1989 1990 eruption and compare cross correlation coefficients to identify similar earthquakes within the catalog waveform similarity is high at redoubt especially during the eruptive phases and event families include long period shallow summit hybrid and both shallow summit and midcrust level volcano tectonic earthquakes we do not resolve a low velocity feature in the three dimensional p wave model that can be interpreted as a source magma chamber and prefer the idea of an interconnected body of dikes and sills as the source of magma erupted in 1989 1990

nd isotope mapping of the grenvillian allochthon boundary thrust in algonquin park ontario over 50 new nd isotope analyses are presented for high grade orthogneisses from algonquin park and surrounding region to map major grenvillian thrust boundaries nd model ages display a consistent

large scale relocation of two decades of northern california seismicity using cross correlation and double difference methods 1 we simultaneously reanalyzed two decades 1984 2003 of the digital seismic archive of northern california using waveform cross correlation cc and double difference dd methods to improve the resolution in hypocenter locations in the existing earthquake catalog generated at the northern california seismic network ncsn by up to three orders of magnitude we used a combination of 3 billion cc differential times measured from all correlated pairs of events that are separated by less than 5 km and 7 million p wave arrival time picks listed in the ncsn bulletin data were inverted for precise relative locations of 311 273 events using the dd method the relocated catalog is able to image the fine scale structure of seismicity associated with active faults and revealed characteristic spatiotemporal structures such as streaks and repeating earthquakes we found that 90 of the earthquakes have correlated p wave and s wave trains at common stations and that 12 are colocated repeating events an analysis of the repeating events indicates that uncertainties at the 95 confidence level in the existing network locations are on average 0 7 km laterally and 2 km vertically correlation characteristics and relative location improvement are remarkably similar across most of northern california implying the general applicability of these techniques to image high resolution seismicity caused by a variety of plate tectonic and anthropogenic processes we show that consistent long term seismic monitoring and data archiving practices are key to increase resolution in existing hypocenter catalogs and to estimate the precise location of future events on a routine basis

implications of intermittent turbulent bursts for sediment resuspension in a coastal bottom boundary layer a field study in the western yellow sea china abstract previous experiments carried out in the laboratory flumes and open channels have shown that close to the wall sediment resuspension is largely dominated by a sequence of intermittent powerful and large scale motions called coherent structures or burst cycle which mainly account for reynolds stress generation however the difficulties in simultaneously measuring the fluctuations of velocities and sediment concentration close to the seabed during the field observations inhibit the further understanding of this laboratory discovery in the marine regime in the present paper field data sets collected within a coastal bottom boundary layer bbl in the western yellow sea are examined comprehensively to reveal the relationships between coherent structures and sediment resuspension the following results are obtained 1 the bulk of turbulent sediment flux c w is accomplished by ejection 56 and sweep 42 events while contributions coming from outward and inward interactions are negligible 2 wall turbulence containing coherent structures vertically transport momentum more efficiently than suspended sediments 3 spectral scaling of sediment concentration reveals that two types of suspended sediment clouds with different sizes were existent during the peak flood the large size particle clouds contain coarse sediments locally resuspended from seabed whereas the smaller particle clouds consist of silts and clays and act as washload advected from jiaozhou bay and yellow sea by tidal flows 4 wavelet transform can provide a more intuitive way to study and visualize the relationship between the burst cycle and sediment suspension and the results clearly show that the intermittent reynolds stress generation is accompanied by intense sediment resuspension

partitioned fault movement and aftershock triggering evidence for fault interactions during the 2017 mw 5 4 pohang earthquake south korea

isotopic mapping of the allochthon boundary thrust in the grenville province of ontario canada abstract nd isotope analyses of orthogneissic rocks were conducted in the vicinity of the allochthon boundary thrust abt in the central gneiss belt of ontario canada gneisses from the parautochthonous belt have relatively homogeneous nd isotope signatures with an average tdm model age of 1 91 ga consistent with an origin as an accreted paleoproterozoic arc terrane barilia orthogneissic rocks from the overlying allochthonous belt have a wider range of model ages from 1 46 to 1 79 ga consistent with a more complex geological history that may involve reworking of sedimentary material in a long lived ensialic arc algonquia the isotopic boundary between these terranes represented by the abt is consistent with the distribution of distinct types of metabasic rock previously used as a criterion for recognising rocks of the allochthonous and parautochthonous belts of the grenville province however the location of the abt proposed on the basis of isotopic analysis has been modified from that of other workers because nd isotopes provide a much more detailed tool for mapping the original zone of convergence thrusting between allochthonous and parautochthonous terranes with distinct crustal formation ages the isotopic boundary is also supported by field based mapping of high strain zones in critical areas other mapped shear zones may represent later extensional structures with lesser geological significance