problems in identifying the effects of structure and critical state in a soil with a transitional behaviour this work shows that some soils with an intermediate behaviour between clays and sands do not have a unique compression line as has also been pointed out by martins et al it has been shown here that a unique critical state line could not be determined for the remoulded soil although the results shown here are for a reconstituted residual soil similar behaviour in compressibility has been found in silts and mixtures of sand and kaolin however it has been found that the critical state framework can be applied using a family of parallel critical state lines depending on the initial specific volume one of the questions raised by this work is how the effects of structure can be quantified if the intrinsic properties of the remoulded material are not unique the compression and critical state lines of the remoulded material are not only non unique but also of a distinctly different gradient from the natural material

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

inversion of complex body waves ii abstract after our previous paper we developed a method to deconvolve body waves into a multiple shock sequence we first consider a general case where a rupture process consists of subevents with arbitrary source parameters and next a special case where a source process consists of subevents with two different fault mechanisms a simple criterion to check the significance of solution is given by a statistical consideration on the estimated values the method is applied to two large earthquakes the 1976 tangshan earthquake and the 1976 east turkey earthquake in both cases the earthquake sources consist of major strike slip events and minor thrust events the total seismic moments of the major events are comparable to the values obtained by surface wave analyses the 1968 borrego mountain earthquake is also analysed by the same method for comparison a single mechanism solution results in a good waveform match and no significant secondary mechanism is required for this event

detrital zircon u pb geochronology of the magog group southern quebec stratigraphic and tectonic implications for the quebec appalachians

finite fault inversion of dinsar coseismic displacement of the 2009 l aquila earthquake central italy 1 we define the geometric and kinematic characteristics of the fault activated during the mw 6 3 6 april 2009 l aquila earthquake from the modeling of envisat and cosmo skymed the first ever x band interferogram inverted for a coseismic dislocation study dinsar interferograms our best fit solution for the main shock is represented by a normal fault 16 km long and 12 km wide with a small right lateral component dipping 47 sw with a maximum slip of 90 cm although the seismic dislocation probably ended at 1 km depth the updip projection of the fault plane corresponds to the northern segment of the mapped paganica s demetrio fault where alignment of surface breaks was observed in the field the absence of this fault in existing seismic source catalogues suggests that an improved approach involving detailed surface and subsurface geological and geophysical investigations is needed for a better assessment of the seismic hazard at the local scale

lower silurian subduction related volcanic rocks in the chaleurs group northern new brunswick canadageological survey of canada contribution no 2008 0166 contribution to natural resources canada s targeted geoscience initiative 3 2005 2010 early silurian volcanic and subvolcanic rocks are preserved in the lower part of the chaleurs group at two locations in northern new brunswick at quinn point mafic to intermediate rocks are hosted by sedimentary rocks of the weir formation and at pointe rochette a bed of felsic tuff occurs near the base of the weir these rocks are interpreted as the first evidence in new brunswick of magmatism associated with late ordovician early silurian subduction of tetagouche exploits back arc oceanic crust at quinn point mafic rocks include a thick basaltic flow or sill and intermediate to mafic cobbles in overlying conglomerate beds the in situ mafic rocks and the conglomerate clasts are chemically alike and display subduction related affinities on tectonic discrimination diagrams at pointe rochette fine grained felsic tuff contains elevated th and u and depleted high field strength elements consistent with a subduction influenced setting although rare earth element ree abundances are low and the re

monotonic and cyclic behavior of two calcareous soils of different origins the behavior of two calcareous soils goodwyn gw and ledge point lp is studied through a series of monotonic and cyclic triaxial tests these two soils are selected because they represent two extreme formation conditions in terms of their depositional environments physical characteristics and grain strength the experimental investigation included isotropic compression tests to high stress levels undrained monotonic shearing tests and undrained cyclic shearing tests under one way and two way loading conditions tests were performed on samples with different initial conditions the experimental results show that although the overall qualitative stress strain behavior of both gw and lp soils is similar to that of other silicious soils significant quantitative differences are observed between the two soils and also between calcareous and silicious soils especially in terms of volumetric reduction during compression monotonic and cyclic shear strength and the strain required to mobilize the strength this paper explores the mechanical behavior of the two calcareous soils and highlights the similarities and differences between their behavior and also between calcareous and silicious soils

mechanical properties of sand silt and clay containing tetrahydrofuran hydrate 1 the mechanical behavior of hydrate bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes drilling and coring operations and the analysis of certain small strain properties of these sediments for example seismic velocities this study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 mpa confining pressure on sand crushed silt precipitated silt and clay specimens with closely controlled concentrations of synthetic hydrate the results show that the stress strain behavior of hydrate bearing sediments is a complex function of particle size confining pressure and hydrate concentration the mechanical properties of hydrate bearing sediments at low hydrate concentration probably 50 of pore space the behaviorbecomesmoreindependentofstressbecausethehydratescontrolbothstiffnessand strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination cementing particles together and filling the pore space the cementation contribution to the shear strength of hydrate bearing sediments decreases with increasing specific surface of soil minerals the lower the effective confining stress the greater the impact of hydrate formation on normalized strength

paleomagnetism of the pennington mountain terrane a near laurentian back arc basin in the maine appalachians paleomagnetic studies of volcanic terranes in the appalachians provide quantitative data on the ordovician paleogeography of the iapetus ocean new paleomagnetic results from submarine volcanics of the middle to late ordovician winterville formation of maine further constrain the evolution of iapetus ten sites yield a tilt corrected direction of d i 327 21 95 9 3 k 27 9 the corresponding paleomagnetic pole calculated for the average site location 46 8 n 291 3 e is located at 26 n 148 e d p 5 d m 10 a 95 7 7 a silurian conglomerate frenchville formation test is inconclusive due to a strong present day field overprint which obscures any primary remanence the presence of a positive tilt test however supports the conclusion that the characteristic magnetization of the winterville formation is a prefolding primary magnetization an ordovician paleolatitude of 111 5 for the pennington mountain terrane of northern maine is indistinguishable from that of the laurentian margin 15 20 during the middle to late ordovician the paleolatitude of the pennington mountain terrane is also similar to but slightly more equatorial than that of the previously studied bluffer pond formation of the nearby munsungun terrane 18 9 we conclude that the ordovician pennington mountain and munsungun volcanic terranes of maine were formed and acquired their characteristic magnetization near the laurentian margin the paleolatitudes of these terranes are also similar to that obtained from the stacyville volcanics of the more outboard lunksoos terrane 20 8 but they contrast strongly with the ordovician miramichi terrane of northern new brunswick that yielded a paleolatitude of 51 21 16 these results from maine support the presence of one or more backarc basins adjacent to the laurentian margin during the middle to late ordovician

stratigraphie framework for the cambrian ordovician rift and passive margin successions from southern quebec to western newfoundland the taconian humber zone stretches from western newfoundland to southern quebec the early cambrian slope succession in newfoundland is found in the curling group whereas in quebec various units were deposited during that first time slice biostratigraphic data allow correlation of the curling group with the labrador group in newfoundland and with the newly time constrained slope succession in quebec the end of the rift drift transition is marked by a sea level lowstand at the end of the early cambrian the middle cambrian to latest early ordovician passive margin history recorded five cyclic sea level fluctuations three of these cycles are recorded in the shallow marine middle to late cambrian platform port au port group and slope sediments preserved in the cow head and northern head groups in newfoundland the biostratigraphic information assists correlation with cambrian passive margin units in quebec major sea level lowstands are recognized along the continental margin in early middle late camb

fault geometry and slip distribution of the 2008 mw 7 9 wenchuan china earthquake inferred from gps and insar measurements author s wan y shen zk burgmann r sun j wang m abstract the authors 2016 published by oxford university press on behalf of the royal astronomical society we revisit the problem of coseismic rupture of the 2008 mw 7 9 wenchuan earthquake precise determination of the fault structure and slip distribution provides critical information about the mechanical behaviour of the fault system and earthquake rupture we use all the geodetic data available craft a more realistic earth structure and fault model compared to previous studies and employ a nonlinear inversion scheme to optimally solve for the fault geometry and slip distribution compared to a homogeneous elastic half space model and laterally uniform layered models adopting separate layered elastic structure models on both sides of the beichuan fault significantly improved data fitting our results reveal that 1 the beichuan fault is listric in shape with near surface fault dip angles increasing from 36 at the southwest end to 83 at the northeast end of the rupture 2 the fault rupture style changes from predominantly thrust at the southwest end to dextral at the northeast end of the fault rupture 3 fault slip peaks near the surface for most parts of the fault with 8 4mthrust and 5 m dextral slip near hongkou and 6 m thrust and 8 4 m dextral slip near beichuan respectively 4 the peak slips are located around fault geometric complexities suggesting that earthquake style and rupture propagation were determined by fault zone geometric barriers such barriers exist primarily along restraining left stepping discontinuities of the dextralcompressional fault system 5 the seismic moment released on the fault above 20 km depth is 8 2 1021 n m corresponding to an mw 7 9 event the seismic moments released on the local slip concentrations are equivalent to events of mw 7 5 at yingxiu hongkou mw 7 3 at beichuan pingtong mw 7 2 near qingping mw 7 1 near qingchuan and mw 6 7 near nanba respectively 6 the fault geometry and kinematics are consistent with a model in which crustal deformation at the eastern margin of the tibetan plateau is decoupled by differential motion across a decollement in the mid crust above which deformation is dominated by brittle reverse faulting and below which deformation occurs by viscous horizontal shortening and vertical thickening

paleogeography and tectono sedimentary history at the margin of laurentia during silurian to earliest devonian time the gaspe belt quebec the silurian lower devonian sequence of the gaspe belt at the laurentia margin south of the quebec reentrant and st lawrence promontory was deposited during the period between the two main orogenies that created the northern appalachians the late ordovician taconian and the middle devonian acadian orogenies although this sequence is traditionally considered to have been deposited during a period of quiescence between both orogenies significant tectonic activity attributed to the salinic disturbance began during late llandoverian telychian time and persisted until the acadian orogeny this tectonic activity has profoundly influenced the composition and distribution of the silurian earliest devonian sedimentary facies the shelf and shelf edge history at the laurentia margin along the quebec reentrant st lawrence promontory is summarized according to four broad phases phase 1 is a llandoverian wenlockian regressive phase r1 related to post taconian successor basin filling that culminated with extensive carbonate platform development phase 2 is a late wenlockian ludlovian transgressive phase t1 phase 3 corresponds to a later ludlovian pridolian second regressive phase r2 phases 2 and 3 were accompanied by extensional tectonics that produced shelf faulting and block tilting on top of which block reefs and reef complexes settled and built a reef tract all the way along the gaspe temiscouata shelf phase 4 is an early devonian phase of accelerated subsidence transgression t2 affecting the northwestern part of the segment quebec reentrant area while the southeastern part st lawrence promontory area was already uplifted due to the ongoing collision between laurentia and the western margin of gondwana related terranes to the south composition and distribution of sedimentary facies were controlled by the interaction of tectonics sediment influx and sea level fluctuations construction of a post taconian pre acadian palinspastic map to plot facies has proven to be basic to obtaining a realistic picture of the paleogeography of the shelf and shelf edge of the gaspe temiscouata segment at the margin of the laurentia craton during the silurian earliest devonian time interval

tectonic setting of the tetagouche group in northern new brunswick implications for plate tectonic models of the northern appalachians a regional compilation and reinterpretation of geochemical analyses of mafic igneous rocks from the ordovician tetagouche group in northern new brunswick indicates the presence of at least three mafic assemblages two groups of basalts and gabbros and one group of gabbros only the three groups can be separated on the basis of tio2 and trace element content group a basalts generally have mid ocean ridge basalt morb like compositions whereas group b basalts indicate a within plate setting wpb group c gabbros intrude into silicic volcanics that underlie the basalts but are rare or absent in the areas underlain by group a and b basalts the group c gabbros probably represent the earliest stages of mafic igneous activity and have morb like compositions or represent a transition between morb and arc basalts the association of group a and b basalts with abundant marine sediments such as thinly bedded turbidites and black and red shales and the fact that they erupted locally on top of continental crus

back projection imaging of earthquakes back projection analysis of earthquakes is a type of array processing that images the source of seismic waves coherently recorded at stations throughout the seismic network the method was developed following the magnitude 9 2 sumatra andaman earthquake in 2004 although properties of earthquakes have been investigated using array data prior to the introduction of the back projection method this technique differs from other approaches because it makes limited assumptions and allows detailed and complex rupture propagation to be examined these advantages have led several researchers to apply the method to many of the largest earthquakes to occur this century the method has also been effective for the detection of smaller events a critical component of the success of back projection has been the development of large scale dense seismic arrays further improvements and future applications of the method will depend greatly on the continued maintenance and development of these networks

degradation of stiffness of cemented calcareous soil in cyclic triaxial tests the deformation characteristics of artificially cemented calcareous soil subjected to undrained cyclic triaxial loading are investigated at different confining pressure and cyclic stress levels the influence of cementation on the shear stiffness is investigated by comparing the behavior of cemented and uncemented soils with similar initial conditions it is observed that the deviator stress and the deviatoric strain at yield reduced with increasing number of cycles for cemented sand due to progressive degradation of bond which results in significant decrease in stiffness on the other hand a strain hardening effect is observed in uncemented sand and this results in increasing yield stress and strain with progressive number of cycles a linear relationship between degradation index and number of cycles is observed for cemented sand this relationship has been synthesized in the form of an empirical equation by modifying a previously proposed equation for cohesive soils this empirical equation was further used to evaluate the fatigue life of soils by adopting a failure criterion

the undrained cyclic behaviour of a carbonate sand a series of undrained cyclic triaxial tests was carried out on a carbonate sand that had previously been the subject of extensive research for monotonic loading it was found that the generation of

source inversion of w phase speeding up seismic tsunami warning w phase is a long period phase arriving before s wave it can be interpreted as superposition of the fundamental first second and third overtones of spheroidal modes or rayleigh waves and has a group velocity from 4 5 to 9 km s 1 over a period range of 100 1000 s the amplitude of long period waves better represents the tsunami potential of an earthquake because of the fast group velocity of w phase most of w phase energy is contained within a short time window after the arrival of the p wave at a distance of 50 w phase energy is contained within 23 min after the origin time which is the distinct advantage of using w phase for rapid tsunami warning purposes we use a time domain deconvolution method to extract w phases from the broad band records of global seismic networks the bandwidth of w phase is approximately from 0 001 to 0 01 hz and we bandpass filter the data from 0 001 to 0 005 hz in most cases having extracted w phase from the vertical component records we perform a linear inversion using a point source to determine mw and the source mechanism for several large earthquakes including the 2004 sumatra andaman earthquake the 2005 nias earthquake the 2006 kuril is earthquake and the 2007 sumatra earthquake w phase inversion yields reliable solutions and holds promise of the use of w phase for rapid assessment of tsunami potential

late ordovician chatfieldian catastrophic volcanism and abrupt carbonate platform interior subsidence a tectonic link across a taconian foreland basin quebec embayment due to inherited crustal weakness the late ordovician trenton group of new york state and equivalent strata in south central canada peripheral to the quebec embayment form a regional carbonate platform succession within the taconian foreland basin the upper and lower group boundaries record geodynamically controlled changes in regional subsidence whereas a higher order allocyclic stratigraphy traced south along the foreland interior of the eastern united states may identify shorter term eustatic controls a tectonomagmatic event extending across the foreland basin is recorded a few million years prior to the regional collapse of the foreland platform in the quebec embayment within the lower c spiniferus graptolite zone platform margin retreat 50 km in southern quebec is contemporaneous with a shale rich limestone succession that thins 30 10 m westward over 300 km into the ottawa embayment eastern ontario west of the appalachian structural front this stratigraphic record coincides with catastrophic volcanism within the once distant volcanic arc terranes as recorded by a bentonite traced geophysically from the platform margin to the michigan basin core from the ottawa embayment demonstrates western directed transport of lithic bearing ash the lithic material representing reworked deep water sedimentary and or volcaniclastic sediment was entrained by eruption of calc alkaline felsic to basaltic andesitic and trachyandesitic magmatic sources the above geological history documents a short period of diminishing influence of subsidence moving into the platform interior an event that enhanced briefly cross platform oceanographic circulation as recorded by elevated shale abundance and change in macrofaunal assemblages short lived differential subsidence of the continental crust in this region in response to distal tectonism may have been predicated by inherited weakness of a shallowly buried intracratonic 400km precambrian fault system manifest today by the ottawa bonnechere graben the resulting thin 10 to 30 m stratigraphic record of the tectonomagmatic event is of similar thickness to high order allostratigraphic patterns within the taconic foreland interior of the eastern united states because there is a heterogeneous distribution of precambrian fault systems underlying the taconian foreland interior of eastern laurentia differential structural response of the foreland interior can be anticipated the apparent regional allostratigraphy may contain subtle facies differences along the strike of the foreland basin that reflect this tectonic component

late neoproterozoic to permian tectonic evolution of the quebec appalachians canada abstract due to the unique location of the quebec appalachians in a re entrant of the paleo north american margin and to the fact that the area largely escaped late paleozoic deformation this segment of the orogen preserves evidence of the early orogenic stages that are partly obscured elsewhere despite diachronicity both along and across strike of the orogen five tectonic events of regional significance are recognized 1 the earliest event is mainly recorded by neoproterozoic to early ordovician normal faults associated with extension of the laurentian craton and the establishment of a passive continental margin 2 the second event the ordovician taconian orogeny is marked by foreland directed deformation and corresponds to the principal deformational and metamorphic events recorded by the laurentian margin 3 the third event early salinic is early silurian it is restricted to the southern part of the quebec appalachians and consists of hinterland se directed thrusts folds and retrograde metamorphism 4 the fourth event late salinic is recorded by regional scale late silurian to early devonian normal or transtensional faults and is associated with the formation of the connecticut valley gaspe trough and 5 the last event the devonian acadian orogeny affects with variable intensity all the pre carboniferous lithologies this tectonic synthesis implies that the subdivision of the peri laurentian oceanic tracts proposed in other segments of the appalachians should be applied with caution in quebec and that the structural style the number of oceanic domains and possibly the vergence of subduction change along the strike of the orogen in particular the similarities of the thetford mines and boil mountain ophiolitic complexes and sedimentary covers and the lack of evidence for a major intervening suture are consistent with the maximum allochtony hypothesis i e the assumption that the southern quebec ophiolites are rooted east of the chain lake massif a geodynamic model involving the taconian obduction of a large ophiolitic nappe s the docking of a peri gondwanan gander medial new england terrane in early salinic the formation of large sedimentary basins connecticut valley gaspe and merrimack troughs due to trench rollback and or delamination during the late salinic event and collision at the outer margin of composite laurentia during the acadian orogeny can account for the protracted structural and metamorphic history of the quebec appalachians

slip heterogeneity and directivity of the ml 6 0 2016 amatrice earthquake estimated with rapid finite fault inversion on 24 august 2016 a magnitude ml 6 0 occurred in the central apennines italy between amatrice and norcia causing nearly 300 fatalities the main shock ruptured a nnw sse striking wsw dipping normal fault we invert waveforms from 26 three component strong motion accelerometers filtered between 0 02 and 0 5 hz within 45 km from the fault the inferred slip distribution is heterogeneous and characterized by two shallow slip patches updip and nw from the hypocenter respectively the rupture history shows bilateral propagation and a relatively high rupture velocity 3 1 km s the imaged rupture history produced evident directivity effects both n nw and se of the hypocenter explaining near source peak ground motions fault dimensions and peak slip values are large for a moderate magnitude earthquake the retrieved rupture model fits the recorded ground velocities up to 1 hz corroborating the effects of rupture directivity and slip heterogeneity on ground shaking and damage pattern

crustal movement from satellite observations in the australian region abstract the paper outlines the crustal structure in the australian and papua new guinea regions and explains the need for data on crustal motion and deformation two other papers at the same meeting describe operations to investigate crustal strain on the australian continent stolz and masters 1982 wellman 1981 this paper describes a third project designed to determine the motion of plates in the papua new guinea region here the structure and motions are complex with several minor plates between the major indo australian and pacific plates fifteen observing stations were selected so that there were at least two on each plate and in april may 1981 observations were taken to fix their position using five doppler satellite receivers in a multi station configuration the observations are currently being processed and analysed it is hoped to repeat the measurements at regular intervals

motion of the south bismarck plate papua new guinea the absolute motion of the south bismarck plate was first estimated by tregoning et al 1998 from three site velocities estimated from global positioning system gps observations we report an improved estimate of the euler vector for this plate using site velocities derived from new gps data which include the velocity of a site located 25 km from the pole of rotation the gps velocities of madang witu jacquinot bay and finschafen can be modelled to within 3 mm yr using a single pole of rotation located at 6 75 s 147 98 e with a clockwise rotation rate of 8 11 my the known tectonic features and available geophysical data surrounding the south bismarck plate can also be explained by a rotation of the south bismarck plate about this pole

geochemical variations in middle ordovician volcanic rocks of the northern miramichi highlands and their tectonic significance a detailed geochemical study of middle ordovician volcanic rocks undertaken in the northern miramichi highlands of new brunswick shows that 10 basaltic suites can be distinguished these suites are assigned to the tetagouche and fournier groups the contact between these two groups is a major thrust zone marked for over 70 km by a prominent blueschist zone all the tetagouche group volcanic rocks have chemistries consistent with extrusion in a continental rift but most fournier group basalts in the miramichi highlands have chemistries suggestive of an oceanic back arc setting the chemical signatures stratigraphic variations and structural data indicate that the northern miramichi highlands preserve a section across a telescoped middle ordovician back arc basin that initially opened as a result of asthenospheric injection near the rear part of a lower ordovician ensialic arc

behaviour of calcareous soils in undrained cyclic simple shear the behaviour of three calcareous sediments a muddy silt a silt and a sand from offshore areas on the north west shelf of australia is studied through undrained simple shear tests in monotonic tests the muddy silt shows contractive behaviour and the silt and sand show dilative behaviour in cyclic tests a cyclic mobility failure mode is observed for the three soils responses in non symmetrical cyclic tests were significantly different from those in symmetrical cyclic tests a cyclic phase transformation state which separates undrained cyclic stress paths into contractive and dilative phases was identified this was found to be different from the phase transformation line obtained from monotonic tests and it is unique for a particular soil the three soils show strain hardening behaviour in plots of stress ratio against shear strain which can be characterised by a backbone curve and hysteresis loops

geochemical constraints on the origin of the annieopsquotch ophiolite belt newfoundland appalachians the early ordovician annieopsquotch ophiolite belt occurs immediately west of the main iapetus suture zone and imposes important constraints on the tectonic processes associated with closure of the peri laurentian portion of iapetus the annieopsquotch ophiolite the most prominent ophiolite within the annieopsquotch ophiolite belt exposes a 5 5 km thick section of gabbros sheeted dikes and pillow basalts in which three magmatic episodes have been recognized based on field and geochemical data the first phase is composed of layered troctolites which are preserved as enclaves within the gabbro zone trace element modeling suggests the troctolites crystallized from boninitic melts the troctolite substrate was intruded by the dominant second tholeiitic magmatic phase which formed a gabbro sheeted dike basalt sequence all tholeiites have suprasubduction zone chemical characteristics but the suprasubduction zone signature decreases toward the top of the basalt sequence the third magmatic episode is composed of primitive dikes which are interpreted as off axis intrusions other ophiolites within the annieopsquotch ophiolite belt have comparable geochemical signatures suggesting they may have constituted a single piece of oceanic lithosphere based on geochemical and regional tectonic constraints the annieopsquotch ophiolite belt is interpreted to have formed during initiation of west directed subduction fast rollback of the subducting slab would have induced volatile fluxed decompression melting of previously depleted mantle yielding boninitic melts the suprasubduction zone tholeiite sequence would have formed from ascending fertile mantle fluxed with sub duction related fluids as rollback continued this suggests that the annieopsquotch ophiolite belt does not represent the remnants of normal oceanic crust or backarc basin crust as previously thought our model constrains the initiation and early evolution of a west dipping peri laurentian subduction zone that was responsible for formation of several arc backarc complexes currently preserved in the annieopsquotch accretionary tract

ordovician arc collision and foredeep evolution in the gaspe peninsula quebec the taconic orogeny in canada and its bearing on the grampian orogeny in scotland the middle to upper ordovician deslandes cloridorme and garin formations in the eastern gaspe peninsula quebec are some of the most extensively exposed foredeep successions along the northern appalachian portion of the taconic caledonian orogen their depositional and biostratigraphic frameworks n gracilis to c spiniferus zones approximate correlatives to the n gracilis to d clingani british zones indicate that foredeep evolution spanned c 10 ma and was essentially synchronous with the convergence and accretion of the popelogan arc to the laurentian margin during the caradoc c 458 449 ma these results when combined with metamorphic and radiometric age data synthesized from across the laurentian segments of the northern appalachian and northwestern ireland taconic caledonian orogen further substantiate that orogenesis consisted of several short lived c 10 20 ma deformational episodes confined to arenig through ashgill time c 485 440 ma this indicates that the total duration of orogeny as recorded by arc magmatism metamorphism and laurentian foredeep development spanned no more than c 45 ma in that the scottish caledonides are a consanguineous part of this orogen their tectonostratigraphic evolution i e grampian orogeny should be similar accordingly the results detailed above are geodynamically compatible with and thereby support tectonic models that define the grampian orogeny in scotland as a mostly early to mid ordovician c 480 460 ma tectonic episode of short rather than long duration

evaluation of cyclic shear strength of two cemented calcareous soils the mechanism controlling the cyclic shear strength of cemented calcareous soils was investigated based on the results obtained from monotonic and cyclic triaxial tests on two different types of calcareous soil undrained cyclic triaxial tests performed on artificially cemented calcareous soils with different loading combinations showed that the effective stress path moved towards or away from the origin due to the generation or dissipation of pore pressure with progressive cycles previous investigations have shown that the peak strength envelope or the state boundary surface or the critical state line forms a boundary beyond which effective stress paths during cyclic loading cannot exist however in this study it was observed that the maximum stress ratio h max obtained from monotonic tests defined the boundary for the cyclic tests based on the information obtained from this study an approach for evaluating the cyclic shear strength is proposed it was observed that the modified normalized cyclic shear strength had a strong linear relationship with the logarithm of the number of cyclic to failure irrespective of confining pressure type of consolidation and stress reversal

gps and seismological constraints on active tectonics and arc continent collision in papua new guinea implications for mechanics of microplate rotations in a plate boundary zone 1 the island of new guinea is located within the deforming zone between the pacific and australian plates that converge obliquely at 110 mm yr new guinea has been fragmented into a complex array of microplates some of which rotate rapidly about nearby vertical axes we present velocities from a network of 38 global positioning system gps sites spanning much of the nation of papua new guinea png the gps derived velocities are used to explain the kinematics of major tectonic blocks in the region and the nature of strain accumulation on major faults in png we simultaneously invert gps velocities earthquake slip vectors on faults and transform orientations in the woodlark basin for the poles of rotation of the tectonic blocks and the degree of elastic strain accumulation on faults in the region the data are best explained by six distinct tectonic blocks the australian pacific south bismarck north bismarck and woodlark plates and a previously unrecognized new guinea highlands block significant portions of the ramu markham fault appear to be locked which has implications for seismic hazard determination in the markham valley region we also propose that rapid clockwise rotation of the south bismarck plate is controlled by edge forces initiated by the collision between the finisterre arc and the new guinea highlands

the ordovician history of the iapetus ocean in britain new palaeomagnetic constraints new late tremadoc early arenig palaeomagnetic results from sw wales imply that s britain part of eastern avalonia occupied a southerly latitude of c 60 s in early ordovician times when combined with scottish ordoviaan palaneomagnetic data which indicate a 15 s latitude the results indicate that the british sector of the iapetus ocean reached n latitudinal width of c 5000 km in tremadoc arenig times which was reduced to c 3000 km by llanvirn llandeilo mid ordovician times the new data resolve two previous controversies in palaeozoic palaeogeography first the high southerly palaeolatitude links avdonia to gondwana marginal to w africa thus reconciling codlicting reconstructions based upon either palaeomagnetic or faunal facies evidence alone second reliable llanvim palaeomagnetic data imply that avlonia had rifted northwards by arenig time whereas armorica remained proximal to northern africa throughout the ordovician the combined data therefore establish that avdonia and armorica formed separate micro continents when rifting from gondwana

the ordovician volcanics of the elmtree belledune inlier and their relationship to volcanics of the northern miramichi highlands new brunswick an investigation of the geology and chemistry of the basic igneous rocks in the elmtree and belledune inliers in northern new brunswick shows that the bulk of the middle ordovician rocks of the ophiolitic fournier group are best interpreted as the products of volcanism and sedimentation in an extensive ensimatic back arc basin southeast of a volcanic arc the oceanic back arc basin igneous rocks form the basement to renewed arc related basaltic volcanism in late middle to late ordovician time the fournier group is separated from the structurally underlying shale dominated elmtree formation of the tetagouche group by an extensive tectonic melange which incorporates lenses of serpentinite mafic volcanic rocks and sedimentary rocks of both the tetagouche and fournier groups the mafic volcanic rocks in the elmtree formation correlate best with those intercalated with the lithologically similar sediments of the llandeilian caradocian boucher brook formation in the northern miramichi highlands the melang

stratigraphy and tectono sedimentary evolution of the late ordovician to middle devonian gaspe belt in northern new brunswick evidence from the restigouche area the gaspe belt in the restigouche area comprises three successions separated by a late silurian salinic disconformity and an early devonian angular unconformity the lower upper ordovician to lower silurian sequence consists of siliciclastic turbidites of the boland brook and whites brook formations grog brook group overlain by calcareous turbidites of the pabos and white head formations matapedia group and slope and shelf deposits of the upsalquitch and limestone point formations lower chaleurs group above the salinic disconformity the upper chaleurs group and the dalhousie group record a transgressive regressive cycle the former comprises pridolian carbonate rocks of the west point formation and overlying pridolian to lochkovian sedimentary rocks of the indian point formation the chaleurs group is conformably overlain by lochkovian to early emsian subaerial volcanic rocks of the dalhousie group val d amour formation which is unconformably overlain by alluvial lacustrine deposits of the late emsian campbellton formation acadian orogenesis began during the emsian and is characterized by open to closed folding heterogenous cleavage development and reverse and strike slip faults the salinic orogeny is manifested in extensional block faulting within plate volcanism and uplift and deep erosion of early silurian strata early devonian high level intrusion of the matapedia group white head clasts in indian point conglomerate and thermal maturation data all indicate an extended period of late silurian early devonian uplift in parts of the restigouche area thermal maturities of west point and indian point strata are within the oil and condensate windows and suggest potential for hydrocarbons in the study area

estimated seismic source parameters for 2019 magnitude 7 6 papua new guinea earthquake on 14 may 2019 a major mw 7 6 earthquake struck eastern papua new guinea causing a tsunami warning that was later canceled the last major rupture in the region was a 2000 mw 8 0 event which resulted in massive horizontal land movements of up to several meters and a series of aftershocks with primarily thrust mechanisms and caused a damaging tsunami seismic methods for characterizing the source process were applied vertical components of the long period p waves from 35 stations of the global seismic network with even azimuthal coverage were adopted in the inversions first the focal mechanism solution was retrieved after the earthquake from the inverted results as well as aftershock distribution the causative fault of the great png earthquake was confirmed to be a fault of strike 316 dip 84 and rake 0 indicating that the earthquake was a left lateral strike slip event then to clearly understand the spatiotemporal evolutionary process of the source rupture of the earthquake far field body wave data were collected and the source rupture process of this earthquake was studied using the finite fault inversion method a finite fault model was estabished with length and width of 152 and 32 km respectively and we set the initial seismic source parameters referring to the center of the focal mechanism solution this was estimated by the focal mechanism solutions of defferent studies referring to different focal mechanism solutions we found that the focal mechanism solution determined by global centroid moment tensor catalog was not appropriate inversion results indicated that the seismic moment was 3 63 1020 nm mw 7 6 and the source duration was 40 s the rupture propagated mainly toward the northwest in an asymmetrical bilateral mode with a maximum slip of 13 2 m and a large scale slip patch strongly ruptured to the surface the study of coulomb stress changes suggested that the png earthquake may trigger a thrust type rupture in the new britain trench which has the potential to trigger a tsunami

assembly of the annieopsquotch accretionary tract newfoundland appalachians age and geodynamic constraints from syn kinematic intrusions abstract the annieopsquotch accretionary tract aat comprises several ophiolites and arc back arc igneous complexes that were accreted to the dashwoods microcontinent during the ordovician taconic orogeny the lloyds river fault zone which separates the aat from the dashwoods microcontinent yielded 40ar 39ar hornblende ages of ca 470 ma the fault zone was intruded syn kinematically by the shoshonitic portage lake monzogabbro and the pierre s pond suite which gave u pb zircon ages of documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document lan

paleogeography of the matapedia basin in the gaspe appalachians initiation of the gaspe belt successor basin the matapedia basin consists of the uppermost ordovician lowermost silurian deep water fine grained carbonate siliciclastic rocks of the honorat garin formation and matapedia groups pabos and white head formations the lower rock assemblage of the gaspe belt in the gaspe appalachians paleogeographic maps of eight time slices from the caradocian to the llandoverian are presented to better understand the tectonosedimentary evolution of the matapedia basin deposition evolved from siliciclastic garin fm to argillaceous limestones pabos fm to limestones white head fm the overall change from terrigenous garin fm to limestone facies white head fm reflects a change in the source area paleocurrent directions and composition of sandstones indicate an orogenic source area to the south for the garin formation which is believed to be the inliers of the humber and dunnage zones in the southern gaspe and new brunswick appalachians lime muds deposited by turbidity currents coming from the nor

w phase inversion and tsunami inundation modeling for tsunami early warning case study for the 2011 tohoku event centroid moment tensor solutions for the 2011 tohoku earthquake are determined by w phase inversions using 5 and 10 min data recorded by the full range seismograph network of japan f net by a scaling relation of moment magnitude to rupture area and an assumption of rigidity of 4 1010 n m 2 simple rectangular earthquake fault models are estimated from the solutions tsunami inundations in the sendai plain minamisanriku rikuzentakata and taro are simulated using the estimated fault models then the simulated tsunami inundation area and heights are compared with the observations even the simulated tsunami heights and inundations from the w phase solution that used only 5 min data are considerably similar to the observations the results are improved when using 10 min of w phase data these show that the w phase solutions are reliable to be used for tsunami inundation modeling furthermore the technique that combines w phase inversion and tsunami inundation modeling can produce results that have sufficient accuracy for tsunami early warning purposes

the dog bay liberty line and its significance for silurian tectonics of the northern appalachian orogen1this article is one of a series of papers published in this cjes special issue in honour of ward neale on the theme of appalachian and grenvillian geology 2geological survey of canada contribution 20100257 the dog bay line a silurian suture key to deciphering appalachian accretionary history was first recognized in newfoundland it marks where the ordovician tetagouch exploits ensimatic back arc basin teb which had opened within the leading peri gondwanan gander terrane finally closed here we extrapolate this suture into new england placing it between the liberty orrington miramichi inliers lom and the merrimack fredericton trough mft southeastward marine strata of the mft overlie the teb passive margin exposed in the ganderian st croix block and display southeast vergent structures transected by acadian cleavage they structurally underlie southeast vergent thrusts at the base of the lom northwestward the lom central maine matapedia trough cmmt and lower silurian igneous rocks record elements of the upper plate trench arc system respectively a subduction complex forearc basin and arc the cmmt forearc received detritus both from the northwesterly arc region and also from the

effect of cementation on the small strain parameters of sands natural cementation affects the properties of soils the interpretation of in situ and laboratory test results and the selection of criteria for geotechnical design in this paper published exper

slip model of the 2015 mw 7 8 gorkha nepal earthquake from inversions of alos 2 and gps data we use surface deformation measurements including interferometric synthetic aperture radar data acquired by the alos 2 mission of the japanese aerospace exploration agency and global positioning system gps data to invert for the fault geometry and coseismic slip distribution of the 2015 mw 7 8 gorkha earthquake in nepal assuming that the ruptured fault connects to the surface trace of the main frontal thrust mft fault between 84 34 e and 86 19 e the best fitting model suggests a dip angle of 7 the moment calculated from the slip model is 6 08 1020 nm corresponding to the moment magnitude of 7 79 the rupture of the 2015 gorkha earthquake was dominated by thrust motion that was primarily concentrated in a 150 km long zone 50 to 100 km northward from the surface trace of the main frontal thrust mft with maximum slip of 5 8 m at a depth of 8 km data thus indicate that the 2015 gorkha earthquake ruptured a deep part of the seismogenic zone in contrast to the 1934 bihar nepal earthquake which had ruptured a shallow part of the adjacent fault segment to the east

lower ordovician iron ooids and associated oolitic clays in russia and estonia a clue to the origin of iron oolites abstract on the baltic platform a lower llanvirn ordovician iron oolite can be traced for a distance of 1200 km from norway to the east of lake ladoga in russia this oolite is usually thin seldom exceeding 0 5 m and is dominated by goethite limonite type ooids the easternmost part of the oolite from tallinn to ladoga is examined here the oolitic limestone is intercalated with oolitic clay beds the mineralogical chemical and isotopic composition and other indicators point to volcanic ash being the source for the clay similarities in ree distribution patterns and immobile element contents between ooids and the oolitic clay suggest that the ooids were also formed from volcanic ash

stratigraphic context geochemical and isotopic properties of magmatism in the siluro devonian inliers of northern maine implications for the acadian orogeny this paper reports detailed stratigraphic analysis whole rock geochemistry and nd isotopic ratios of basalts from the northern maine inliers these data place constraints on first order controversies about the tectonic conditions leading up to and during the early stages of the acadian orogeny in northern maine late silurian and early devonian stratigraphic sequences indicate a progressive change from shallow water and subaerial exposure ripogenus and the forks formations east branch group to a rapidly subsiding basin prior to the onset of acadian deformation subsidence was accompanied by mafic to intermediate volcanism of the west branch spider lake and fish pond volcanics and that continued with intrusion of the syn deformational greenville plutonic belt including the flagstaff lake igneous complex whose properties we report in this paper trace element geochemistry indicates that magmatism is transdiscriminant showing aspects of within plate volcanic arc and back arc affinities and nd isotopic ratios are moderately positive 2 3 to 3 8 indicating either an uncontaminated and moderately enriched mantle source or a depleted mantle source contaminated by continental crust four possible tectonic models of the acadian orogeny and the siluro devonian sedimentary volcanic sequences of northern maine are evaluated in the context of a subsiding basin associated with this magmatism developed on the amalgamated laurentian plate these include 1 slab detachment during southeast directed subduction of the laurentian continental margin 2 laramide style thrust basins above a shallow northwest dipping subduction zone 3 back arc extension followed by thin skinned shortening above a northwest dipping subduction zone and 4 moluccan style dual dipping subduction zones

a reevaluation of the position of the baie verte brompton line in the quebec appalachians the influence of middle devonian strike slip faulting in gaspe peninsula the baie verte brompton line bbl the surface expression of the taconian suture in the canadian appalachian orogen extends from southern quebec to the northeast end of newfoundland in the que

cyclic response of calcareous soil from the north west shelf of australia this paper reports the results from 23 cyclic ciu and cau triaxial tests on undisturbed samples of calcareous soil the samples which include both uncemented and cemented material have heen subjected to a range of mean and cyclic shear stresses results from the tests on the uncemented soil display many of the characteristics of the cyclic response of other cohesionless soils the more cemented soils sustained higher cyclic stresses and depending on the load level showed either elastic behaviour with no pore pressure build up eventual stabilization after some pore pressure build up or steady state pore pressure build up and eventual failure the effect of frequency on the response in the range 0 1 to 10 hz has heen studied since no dramatic differences in performance could he detected no firm conclusions could be drawn regarding the effect of testing rate l article preente les reultats obtenus a partir de 23 essais triaxiaux cycliques de type ciu et cau effectues sur des echantillons de sol calca

evidence for a ridge subduction event in the ordovician rocks of north central maine modern and past ridge subduction events are characterized by the intrusion of midocean ridge basalt morb magmas into an overlying accretionary prism the fi eld relationships and trace element geochemistry of ordovician mafi c igneous rocks of the weeksboro lunksoos and munsungun anticlinoria of north central maine indicate that they resulted from such an event the bean brook gabbro intrudes the hurricane mountain melange and other related sedimentary strata of continental derivation the gabbro and associated dry way volcanics have morb trace element chemistries while the bluffer pond and stacyville volcanics are more enriched e morb all of which indicate derivation from a mid ocean ridge on petrogenetic diagrams mafi c samples plot in morb fi elds or when th is used as a discriminator in arc fi elds along trends that originate from morb fi elds and extend toward the composition of upper continental crust these trends are consistent with the presence of silicic and metasedimentary xenoliths in the dry way volcanics and bean brook gabbro and indicate the magmas were not subduction products but were contaminated by th rich upper continental crust the nearby chain lakes massif likely represents the basement to the chain lakes microcontinent and the geographic relationship and ages of the massif hurricane mountain melange and dry way bean brook magmatic rocks indicate northwestdirected subduction modern coordinates on the southeastern margin of the chain lakes microcontinent within the early to middle ordovician taconic ocean subduction at this boundary probably terminated because of the ridge subduction analogous to neogene california

lower to middle ordovician evolution of peri laurentian arc and backarc complexes in iapetus constraints from the annieopsquotch accretionary tract central newfoundland the annieopsquotch accretionary tract in newfoundland is composed of a series of west dipping structural panels each containing remnants of ophiolitic and arc backarc complexes of laurentian affinity formed during the ordovician closure of iapetus panels were transferred from an upper plate to a lower plate setting during their middle to late ordovician accretion to the laurentian margin and become progressively younger eastward geochronological data indicate a complex and rapid history of generation and accretion of peri laurentian suprasubduction zone rocks the rapid changes in tectonic environments and the complexity of the relationships are analogous to the complex arc backarc relationships observed in the western pacific today the recognition of the peri laurentian provenance of these units based on stratigraphy geochronology isotopes and geochemistry defines the position of the red indian line the fundamental suture zone in the northern appalachians but more importantly enables the development of a realistic tectonic model for the annieopsquotch accretionary tract involving both thrust and sinistral transcurrent displacements the oldest and most inboard unit in the annieopsquotch accretionary tract is the annieopsquotch ophiolite belt ca 480 ma which marks the initiation of subduction outboard of the laurentian margin the lloyds river ophiolite complex ca 473 ma preserves a fragment of younger more mid ocean ridge like backarc oceanic crust than the adjacent structurally overlying annieopsquotch ophiolite belt the lloyds river ophiolite complex originated as a backarc to the buchans group ca 473 ma ensialic bimodal calc alkaline arc the panels containing the annieopsquotch ophiolite belt and lloyds river ophiolite complex were stitched and overlain by ensialic arc rocks of the otter pond complex ca 468 ma immediately after their accretion to composite laurentia together with the structurally underlying buchans group the youngest structurally lowest two panels comprise the elements of the red indian lake group 465 460 ma which record the opening of a backarc basin and the subsequent establishment of a bimodal ensialic calc alkaline arc sequence the observed relationships indicate that the annieopsquotch accretionary tract was generated above a single west dipping subduction zone outboard of the laurentian margin over 20 m y accretion mainly took place in two stages at ca 468 and 450 ma which correspond with the collision between laurentia and the dashwoods ribbon continent and the collision with the peri gondwanan victoria arc along the red indian line respectively both collisions form part of the taconic orogeny the latter late ordovician collision terminated the relatively rapid closure of the main iapetan tract the proposed model is similar to the correlative tracts in the british and irish caledonides and may encourage a new look at the new england appalachians

tectonic setting and regional correlation of ordovician metavolcanic rocks of the casco bay group maine evidence from trace element and isotope geochemistry ordovician metamorphic rocks of the casco bay group are exposed in an approximately 170 km long ne trending belt liberty orrington belt in southern and south central maine geochemical analysis of rocks within the spring point formation 469 3 ma of the casco bay group indicate that it is an assemblage of metamorphosed bimodal volcanic rocks the mafic rocks originally basalts have trace element and nd isotopic characteristics consistent with derivation from a mantle source enriched by a crustal and or subduction component the felsic rocks originally rhyolites and dacites were likely generated through partial melting of continental crust in response to intrusion of the mafic magma relatively low initial e nd values for both the mafic 1 3 to 0 6 and felsic 4 1 to 3 8 rocks suggest interactions with gander zone continental crust and support a correlation between the casco bay group and the bathurst supergroup in the miramichi belt of new brunswick this correlation suggests that elements of the early to middle ordovician tetagouche exploits back arc basin can be traced well into southern maine a possible tectonic model for the evolution of the casco bay group involves the initiation of arc volcanism in early ordovician time along the gander continental margin on the eastern side of the iapetus ocean basin slab rollback and trenchward migration of arc magmatism initiated crustal thinning and rifting of the volcanic arc around 470 ma and resulted in the eruption of the spring point volcanic rocks in a back arc tectonic setting

stratigraphy of the aroostook perce anticlinorium in the gaspe peninsula quebec in quebec the aroostook perce anticlinorium exposes two stratigraphic groups the honorat and the matapedia the terrigenous units of the honorat group form the core of the anticlinorium and are overlain by the carbonate sequence of the matapedia group each group comprises two formations the honorat is herein divided into two new formations the arsenault and the garin which are defined for the first time the matapedia group includes the pabos and white head formations the pabos formation a transitional unit between the noncalcareous strata of the honorat group and the carbonate facies of the white head formation is here redefined the white head formation comprises four members these two groups represent continuous sedimentation from the late ordovician caradocian to the early silurian llandoverian the lithostratigraphy of the type areas of the honorat group honorat township region and pabos formation chandler region are fully described whereas the lithostratigraphy of the type area of

llanvirnian ord iron ooids in baltoscandia element mobility ree distribution patterns and origin of the ree abstract the chemical and mineralogical compositions of llanvimian ordovician iron and associated phosphate ooids from sweden estonia and russia have been examined the oolites are generally thin and lean mud supported and dominated by fe oxyhydroxide goethite limonite ooids one swedish oolite contains a mixture of chamosite goethite and hematite ooids and it is suggested that the two latter types were derived from chamosite ooids by early diagenetic alteration the ree distribution patterns were unaffected by these reactions all ooids in the area show a typical negative eu anomaly inherited from the source material major and minor element contents in limonite and chamosite ooids are similar whereas their ree patterns are different limonite ooids have a lree hree ratio from 1 to 2 4 and chamosite ooids from 3 to 5 the amounts of ree in the ooids are strongly dependent on the amount of phosphate

isotropic yielding in an artificially cemented soil cured under stress the work simulates in the laboratory the formation of a cemented sedimentary deposit in which cement bonding occurs after burial and under geostatic stresses isotropic compression tests were carried out on artificially cemented specimens made with variable cement contents after consolidating the samples to the uncemented normal compression line the specimens were allowed to cure for 48 h before testing the curing confining stresses ranged from 50 to 2000 kpa and were intended to represent soil elements at different depths in the fictitious sedimentary deposit when the cementing occurred the contribution of the cement bonds to soil compression and the changes in the isotropic yield stress as a function of void ratio and cement content were analysed the results showed the importance of the void ratio during the formation of cement bonds and also of the degree of cementation for the compressive behaviour of the cemented soil and demonstrated that the variation in yield stress with void ratio and ce

real time inversion of gps data for finite fault modeling and rapid hazard assessment 1 responses to recent great earthquakes and ensuing tsunamis in sumatra chile and japan with the resulting loss of life and damage to infrastructure demonstrate that our ability to ascertain the full extent of slip of catastrophic earthquakes and their tsunamigenic potential in the first minutes after the initiation of rupture is problematic regional gps networks such as those in western north america and japan are complementary to seismic networks by being able to directly measure displacements close to the source during large earthquakes in real time we report on rapid modeling of two large earthquakes the 2003 mw 8 3 tokachi oki earthquake 100 km offshore hokkaido island using 356 geonet stations and the 2010 mw 7 2 el mayor cucapah earthquake in northern baja california using 95 crtn stations in southern california about 75 km northwest of the epicenter working in a simulated real time mode we invert for finite fault slip in a homogeneous elastic half space using green s functions obtained from okada s formulation we compare two approaches the first starts with a catalog of pre defined faults while the second uses a rapid centroid moment tensor solution to provide an initial estimate of the ruptured fault plane in either case we are able to characterize both earthquakes in less than two minutes reducing the time necessary to obtain finite fault slip and moment magnitude for medium and greater earthquakes compared to traditional methods by an order of magnitude

rapidly estimated seismic source parameters for the 16 september 2015 illapel chile m w 8 3 earthquake on 16 september 2015 a great m w 8 3 interplate thrust earthquake ruptured offshore illapel chile producing a 4 7 m local tsunami the last major rupture in the region was a 1943m s 7 9 event seismic methods for rapidly characterizing the source process of value for tsunami warning were applied the source moment tensor could be obtained robustly by w phase inversion both within minutes chilean researchers had a good solution using regional data within 5 min and within an hour using broadband seismic data short period teleseismic p wave back projections indicate northward rupture expansion from the hypocenter at a modest rupture expansion velocity of 1 5 2 0 km s finite fault inversions of teleseismic p and sh waves using that range of rupture velocities and a range of dips from 16 consistent with the local slab geometry and some moment tensor solutions to 22 consistent with long period moment tensor inversions indicate a 180 to 240 km bilateral along strike rupture zone with larger slip northwest to north of the epicenter with peak slip of 7 10 m using a shallower fault model dip shifts slip seaward toward the trench while a steeper dip moves it closer to the coastline slip separates into two patches as assumed rupture velocity increases in all cases localized 5 m slip extends down dip below the coast north of the epicenter the seismic moment estimates for the range of faulting parameters considered vary from 3 7 1021nm dip 16 to 2 7 1021 nm dip 22 the static stress drop estimates range from 2 6 to 3 5 mpa and the radiated seismic energy up to 1 hz is about 2 2 3 15 1016 j

behavior of hydrocarbon reservoir sands and sandstones most new oil and gas reservoirs are discovered in sands and weak sandstones and the petroleum industry has therefore generated an extensive amount of data from laboratory tests on these materials some of these data are reexamined in this paper within the context of recent soil mechanics research of key importance to petroleum engineers is the compressibility of the sands and this is shown to be related both to the current density and stress level of the soil and to the location of its normal compression line when present the cement bonds between the particles appear to be weaker than the particles themselves so that the major yield point during compression is still associated with breakage of the particles rather than of the cement bonds the paper also examines the behavior of the sands and sandstones in shearing allowing a more general understanding of the mechanics of the materials to be developed

a method for intercalibration of u th pb and 40ar 39ar ages in the phanerozoic the increasing analytical precision of 40ar 39ar geochronological data and its use in studies that combine u pb and 40ar 39ar data has necessitated derivation of a means to intercalibrate ages between the two isotopic systems the primary determinants inhibiting accurate cross calibration are uncertainty in decay constant values and uncertainty in 40ar 40k usually presented as apparent age for 40ar 39ar standards notably those derived from the fish canyon tuff by utilizing a monazite and biotite bearing oligocene ash flow tuff mac 83 as the primary standard material precise u th pb and 40ar 39ar ages can be derived because both isotopic systems should reflect closure during the instantaneous eruption event the 24 21 0 10 ma 207pb 235u age should match the age resulting from 40ar 39ar biotite analysis this forced equivalence will partly offset the effects of decay constant uncertainty furthermore by co irradiating fish canyon tuff sanidine with mac 83 biotite the apparent age for fish canyon tuff sanidine is back calculated to 27 98 0 15 ma relative to the mac 83 207pb 235u age hence intercalibration between the two isotopic systems in a relative sense can be accomplished allowing for a direct and valid comparison of ages it is also shown that forcing equivalence of the two isotopic systems minimizes the effect of decay constant uncertainty for samples of phanerozoic age

suspect terranes and accretionary history of the appalachian orogen the north american connection or the grenvillian continental crust that separated from eastern north america during the initiation of the appalachian orogenic cycle is poorly defined within the present orogen a variety of terranes occur outboard of the north american miogeocline all structurally uncoupled and therefore suspect stratigraphic analysis indicates that appalachian accretion progressed from the miogeocline outward the boundaries of the earliest accreted western terranes are marked by melange and ophiolite complexes later boundaries between eastern terranes are steep mylonitic zones and brittle faults accretionary events defined by stratigraphic analysis correspond to times of major deformation plutonism and metamorphism in the history of the orogen

deformation characteristics of two cemented calcareous soils the effect of cementation on the deformation characteristics of two cemented calcareous soils was investigated through a series of undrained triaxial tests performed under both monotonic and cyclic

age and correlation of the honorat group southern gaspe peninsula the honorat group of southern gaspe consists of two formations the arsenault and the garin the arsenault formation heretofore considered barren has yielded a graptolite faunule indicative of a llanvirn llandeilo age early middle ordovician suggesting a correlation with the lower mictaw group of gaspe as revised by de broucker a hiatus of indeterminate magnitude corresponding to the taconic unconformity probably separates the arsenault formation from the overlying garin formation the garin has yielded graptolites ranging from the upper climacograptus spiniferus zone to the paraclimatograptus manitoulinensis zone late middle to early late ordovician the c spiniferus zone graptolites are identical to those of the upper sequence of the cloridorme formation of northern gaspe and the blind brook formation of the munsungun anticlinorium of maine but differ somewhat from those from the upper tetagouche group of new brunswick which are closer to those from the summerford and exploits groups of no

estimation of current plate motions in papua new guinea from global positioning system observations plate tectonic motions have been estimated in papua new guinea from a 20 station network of global positioning system sites that has been observed over five campaigns from 1990 to 1996 the present velocities of the sites are consistent with geological models in which the south bismarck woodlark and solomon sea plates form the principal tectonic elements between the pacific and australian plates in this region active spreading is observed on the woodlark basin spreading centre but at a rate that is about half the rate determined from magnetic reversals the other major motions observed are subduction on the new britain trench seafloor spreading across the bismarck sea seismic lineation convergence across the ramu markham fault and left lateral strike slip across the papuan peninsula these motions are consistent with a 8 2 myr 1 clockwise rotation of the south bismarck plate about a pole in the huon gulf and a rotation of the woodlark plate away from the australian plate second order deformation may also be occurring in particular manus island and northern new ireland may be moving northward relative to the pacific plate at 5 8 mm yr 1 significant at the 95 but not at the 99 confidence level which may suggest the existence of a north bismarck plate

phanerozoic ironstones an introduction and review s u m m a r y ironstones particularly ooidal ironstones have long fascinated sedimentary geologists and have generated an enormous variety of interpretations but have remained poorly understood a recent upsurge in interest in this group of rocks has generated much new information derived from many different disciplines within the earth sciences the first part of this introduction examines recent advances and attempts to produce a synthesis of them with particular reference to the genesis of marine ooidal ironstones current models for the formation of marine oolitic ironstone formations are discussed and a working model based on various lines of recent research is proposed this model invokes the intrasedimentary formation of berthierine ooids in marine environments during postoxic diagenesis the ooids may be mechanically modified and mineralogically transformed by reworking as well as by later diagenesis goethite ooids may be oxidized berthierine ooids reworked lateritic ooids or primary grains the formation of oolitic ironstoneformations is favoured by a break in clastic sediment supply continued supply of iron and physical reworking many sedimentary environments may supply these parameters but changes in sea level leading to the flooding of land masses and the reworking of suitable terrestrial soils may be both an important source for the iron and provide a break in clastic sediment supply in the second part of this introduction the terminology and classification are discussed and conventions proposed the term berthieroid is introduced as a non specific term for material of undetermined berthierine or chamosite composition the term ironstone is proposed as a petrological term and as an informal lithostratigraphic term a deposit composed of ironstones may be termed an ironstone formation it is recommended that a dunham style of classification is employed petrographically with ironstone replacing the stone of the original carbonate classification the nomenclature of allochems in ironstones is also discussed a glossary of ironstone terminology is provided

volcanic ash the source material for ordovician chamosite ooids in sweden abstract iron rich oolites from a middle ordovician llanvirn llandeilo sequence in south central sweden are associated with volcanic ash beds clear evidence that volcanic activity was coeval with a period of extensive iron ooid formation in baltoscandia relict texture of the ash is preserved as illitical rims on primary glass shards that underwent rapid calcitization in a marine environment xrd and mossbauer spectroscopy reveal that the ooids are composed mainly of chamosite with a fe2 fe3 ratio of 6 3 it is suggested that authigenic chamosite was formed from elements released into the sediment when the ash dissolved on the sea bottom chamosite precipitated on skeletal grains and repeated reworking of the sediment oxidized the outer surface of the grains to goet ite hematite thus creating the typical concentric ooid lamination the presence of fe2 in ooids is in contrast to the agitated environment in which they are formed fresh volcanic ash however usually contains more fe2 than fe3 which can explain the high fe2 fe3 ratio in the ooid chamosite if the iron is derived from the volcanic ash

w phase source inversion for moderate to large earthquakes 1990 2010 rapid characterization of the earthquake source and of its effects is a growing field of interest until recently it still took several hours to determine the first order attributes of a great earthquake e g m w 7 5 even in a well instrumented region the main limiting factors were data saturation the interference of different phases and the time duration and spatial extent of the source rupture to accelerate centroid moment tensor cmt determinations we have developed a source inversion algorithm based on modelling of the w phase a very long period phase 100 1000 s arriving at the same time as the p wave the purpose of this work is to finely tune and validate the algorithm for large to moderate sized earthquakes using three components of w phase ground motion at teleseismic distances to that end the point source parameters of all m w 6 5 earthquakes that occurred between 1990 and 2010 815 events are determined using federation of digital seismograph networks global seismographic network broad band stations and sts1 global virtual networks of the incorporated research institutions for seismology data management center for each event a preliminary magnitude obtained from w phase amplitudes is used to estimate the initial moment rate function half duration and to define the corner frequencies of the passband filter that will be applied to the waveforms starting from these initial parameters the seismic moment tensor is calculated using a preliminary location as a first approximation of the centroid a full cmt inversion is then conducted for centroid timing and location determination comparisons with harvard and global cmt solutions highlight the robustness of w phase cmt solutions at teleseismic distances the differences in m w rarely exceed 0 2 and the source mechanisms are very similar to one another difficulties arise when a target earthquake is shortly e g within 10 hr preceded by another large earthquake which disturbs the waveforms of the target event to deal with such difficult situations we remove the perturbation caused by earlier disturbing events by subtracting the corresponding synthetics from the data the cmt parameters for the disturbed event can then be retrieved using the residual seismograms we also explore the feasibility of obtaining source parameters of smaller earthquakes in the range 6 0 mw 6 5 results suggest that the w phase inversion can be implemented reliably for the majority of earthquakes of mw 6 or larger

diagenetic and low grade metamorphic terranes of gaspe peninsula related to the geological structure of the taconian and acadian orogenic belts quebec appalachians illite crystallinity ic measurements determination of the proportion of 2m mica polytypes and organic matter reflectance measurements establish regional diagenetic low grade metamorphic trends for the taconian and acadian belts of gaspe peninsula ic varies as a function of many factors besides maximum burial temperature and heating time correlation between ic and 2m illite polytypes for the fortin group and temiscouata formation suggests i that the amount of high grade detrital mica in the samples is low and ii that ic can be used with some confidence as an estimator of regional thermal maturation levels correlation of these parameters with available organic reflectance values further supports this assumption the illites of the temiscouata and western fortin groups are mostly phengitic in composition whereas in the eastern outcrop belt they are more mg and fe rich celadonitic but generally also of lower grade and lower 2m content the d 060 values for illites measured on the unorientated 2 m fraction of samples fall between 1 502 and 1 503 a range 1 500 1 504 a indicating relatively low octahedral occupancy by mg and fe between one fifth and one third of the available spaces pyrophyllite and paragonite were not detected chlorites are fe rich and ripidolitic the ic map for the acadian belt of the peninsula displays general congruence between ic contours 2200 sample points and structural trends for the 27 000 km2 area the highest grades anchimetamorphic are associated with the oldest rocks honorat and matapedia groups exposed in the cores of major anticlines anchimetamorphic grades associated with the western outcrop belt of the lower devonian fortin group require 7 8 km of subsidence to accommodate sufficient thickness of overlying younger rocks on top of 4 5 km of fortin group deep water clastics to explain the grades in terms of burial metamorphism assuming a geothermal gradient of 30 c km 1 the lowest grade diagenetic rocks occupy a large area in the northeastern part of the peninsula smaller areas in the northwestern part of the acadian belt in the centre of chaleurs bay synclinorium and in the ordovician mictaw group the contact between the taconian and acadian belt is marked by a distinct maturation discontinuity the grand pabos fault juxtaposes rocks of contrasting maturation levels matapedia group against fortin group in the west but shows no maturation offset further east in the honorat group the fault zone limiting the fortin group in the north is also associated with a major ic jump

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

evidence of supershear during the 2018 magnitude 7 5 palu earthquake from space geodesy a magnitude 7 5 earthquake hit the city of palu in sulawesi indonesia on 28 september 2018 at 10 02 43 coordinated universal time it was followed a few minutes later by a 4 7 m high tsunami palu is situated in a narrow pull apart basin surrounded by high mountains of up to 2 000 m altitude this morphology has been created by a releasing bend in the palu koro fault a rapidly moving left lateral strike slip fault here we present observations derived from optical and radar satellite imagery that constrain the ground surface displacements associated with the earthquake in great detail mapping of the main rupture and associated secondary structures shows that the slip initiated on a structurally complex and previously unknown fault to the north extended southwards over 180 km and passed through two major releasing bends the 30 km section of the rupture south of palu city is extremely linear and slightly offset from the mapped geological fault at the surface this part of the rupture accommodates a large and smooth surface slip of 4 7 m with no shallow slip deficit almost no aftershock seismicity was recorded from this section of the fault as these characteristics are similar to those from known supershear segments we conclude that the palu earthquake probably ruptured this segment at supershear velocities the devastating 2018 magnitude 7 5 earthquake in palu indonesia ruptured at supershear speeds according to evidence from space geodesy

chemical correlation of k bentonite beds in the middle ordovician decorah subgroup upper mississippi valley strata of the champlainian middle ordovician decorah subgroup in the upper mississippi valley region have been correlated on the basis of the chemical composition of k bentonite beds in widely distributed outcrops and cores the four principal k bentonite beds in the decorah the deicke millbrig elkport and dickeyville can be differentiated by their unique chemical fingerprints which were established using a linear discriminant function analysis the elements that served as the best discriminators of differences between beds were in order of atomic number na sc ti zr sm eu tb dy yb lu hf ta and th although no one element serves to delineate a k bentonite bed completely from others a combination of elements can do so the chemical signatures of the deicke and millbrig k bentonite beds the two thickest and most widespread k bentonites in the mississippi valley were recognized in outcrop and subsurface from southern minnesota to southeastern missouri a distance of about 900 km the elkport and the dickeyville k bentonites were chemically identified in a limited area in northern illinois southwestern wisconsin and northern iowa the decorah consists of widespread lithologic units that are approximately parallel to k bentonite beds in some areas but in other areas lateral gradation of lithologies as shown by k bentonite correlations indicates contemporaneity of decorah lithofacies

where is the iapetus suture in northern new england a study of the ammonoosuc volcanics bronson hill terrane new hampshire 1 the 470 ma ammonoosuc volcanics of the bronson hill terrane of new hampshire have back arc basin basalt compositions major and trace element compositions compare favorably to coeval volcanic rocks in the miramichi highlands of new brunswick and the munsangan and casco bay volcanics of maine back arc basin basalts of known peri gond wanan origins additionally the ammonoosuc volcanics have nd and pb isotopic compositions indicative of peri gond wanan provenance thus the ammonoosuc volcanics correlate with middle ordovician peri gondwanan tetagouche exploits back arc rocks of eastern new england and maritime canada this correlation indicates that the red indian line the principle iapetus suture lies along the western margin of the bronson hill terrane however the younger 450 ma oliverian plutonic suite rocks that intruded the ammonoosuc volcanics forming domes along the core of the bronson hill anticlinorium have laurentian isotopic signatures this suggests that the ammonoosuc volcanics were thrust westwardly over the laurentian margin and that laurentian basement rocks are present under the bronson hill terrane a plausible ex planation for these relationships is that an easterly dipping subduction zone formed the ammonoosuc volcanics in the tetagoughe exploits oceanic tract just east of the coeval popelogan arc with the closure of the iapetus ocean this terrane was thrust over the laurentian margin subsequent to obduction of the ammonoosuc volcanics subduction polarity flipped to the west with the oliverian arc resulting from a westerly dipping subduction zone that formed under the taconic orog eny modified laurentian margin resume les roches volcaniques ammonoosuc 470 ma du terrane de bronson hill au new hampshire ont des compo sitions de bassins basaltiques d arriere arc les compositions en elements majeurs et traces se comparent favorablement aux roches volcaniques contemporaines des terres hautes de miramichi au nouveau brunswick et les roches volcaniques de munsangan et de casco bay au maine des bassins basaltiques d arriere arc d origine peri gondwanienne connue de plus les roches volcaniques ammonoosuc ont des compositions d isotopes de nd et de pb qui indiquent leur provenance peri gondwanienne ainsi les roches volcaniques ammonoosuc sont correlees avec les roches d arriere arc tetagouche exploits ordovicien moyen peri gondwana de l est de la nouvelle angleterre et des provinces maritimes canadiennes cette correla tion signifie que la ligne red indian la principale suture iapetus se situe le long de la bordure ouest du terrane de bronson hill toutefois les roches de la suite plutonique olivierian plus jeune 450 ma formant des domes le long du c ur de l anticlinorium bronson hill ont des signatures isotopiques laurentiennes cela suggere que les roches volcaniques ammo noosuc aient ete chevauchees vers l ouest par dessus la bordure laurentienne et que les roches du socle laurentien se retrou vent sous le terrane de bronson hill une explication plausible pour ces relations est qu une zone de subduction a pendage vers l est a forme les roches volcaniques ammonoosuc dans l etendue oceanique tetagouche exploits tout juste a l est de l arc popelogan contemporain avec la fermeture de l ocean iapetus ce terrane a ete chevauche par dessus la bordure lau rentienne apres l obduction des roches volcaniques ammonoosuc la polarite de la subduction a bascule vers l ouest l arc oliverian proviendrait d une zone de subduction a faible pendage vers l ouest qui s est formee sous la bordure laurentienne modifiee par l orogenese taconienne traduit par la redaction

pre acadian magmatic suites of the southeastern gaspe peninsula there are two phases of post taconic pre acadian magmatism in the eastern gaspe peninsula of quebec a the middle to upper ordovician pabos suite and b widespread silurian devonian volcanics and hypabyssal intrusions the pabos suite forms two large intrusions composed of lree depleted n morb like gabbros and ferrogabbros evolution within this suite was controlled by fractional crystallization and the presence of the intrusions implies a tensional event between the taconic and acadian orogenies the silurian devonian volcanic and intrusive rocks are chemically variable tholeiitic to alkaline basaltic to rhyolitic and do not belong to a single fractionation series quartz xeno cryst bearing rocks are enriched in si k zr and lree9s providing evidence of disequilibrium contamination by a felsic melt similar to locally occurring rhyolites the lavas and dikes that do not carry felsic xenocrysts also show patterns of enrichment depletion of trace elements which suggest that felsic contamination hybridization was an important factor in their development but show little si enrichment this is interpreted to be due to maintenance of chemical equilibrium during contamination this would have forced the composition of the magma to remain on the plagioclase clinopyroxene olivine cotectic and would thus have inhibited si enrichment the xenocryst bearing rocks superficially resemble a calc alkaline series but most of the pre acadian silurian devonian volcanics of the gaspe peninsula do not appear to have been directly associated with subduction the preferred model is that of local tensional environments in an orogenic foreland

a lost arc back arc terrane of the dunnage oceanic tract recorded in clasts from the garin formation and mccrea melange in the gaspe appalachians of quebec upper ordovician garin conglomerates base of the gaspe belt quebec appalachians contain three igneous clast populations 1 calc alkaline intermediat felsic rocks resemble exploits new brunswick maine and notre dame quebec newfoundland subzone lavas clasts monzonite rhyodacite give u pb zircon ages between 465 and 466 ma precluding correlation with exploits rocks we suggest that the suite represents peri laurentian continental arc magmas coeval with the red indian lake group of newfoundland correlation of lavas from a gaspe well with the popelogan arc implies that the red indian line passes through southern gaspe 2 mafic tholeiitic to alkaline clasts resemble new brunswick and maine exploits subzone alkaline lavas we interpret them as magmas associated with initiation of a back arc basin possibly on the laurentian margin 3 mafic intermediate tholeiitic to calc alkaline clasts have an oceanic subduction component and correlate with notre dame subzone lavas quebec newfoundland they are interpreted as products of spreading and off axis magmatism of a peri laurentian back arc basin we correlate mccrea melange lavas to the calc alkaline intermediat felsic and mafic intermediate suites and interpret them as samples of a notre dame subzone terrane coeval with the red indian lake group of newfoundland during initiation of a successor arc back arc a terrane which is no longer preserved in new brunswick and maine but that provides some evidence for possible extensions of newfoundland9s geology into the gaspe appalachians of quebec a mid ocean ridge basalt like intrusion in the mccrea melange ar ar age 471 2 11 2 ma is coeval with peri laurentian ophiolites in newfoundland and may record a back arc opening event

triggering of tsunamigenic aftershocks from large strike slip earthquakes analysis of the november 2000 new ireland earthquake sequence 1 the november 2000 new ireland earthquake sequence started with a mw 8 0 left lateral main shock on 16 november and was followed by a series of aftershocks with primarily thrust mechanisms the earthquake sequence was associated with a locally damaging tsunami on the islands of new ireland and nearby new britain bougainville and buka results from numerical tsunami propagation models of the main shock and two of the largest thrust aftershocks mw 7 0 indicate that the largest tsunami was caused by an aftershock located near the southeastern termination of the main shock off the southern tip of new ireland aftershock 1 numerical modeling and tide gauge records at regional and far field distances indicate that the main shock also generated tsunami waves large horizontal displacements associated with the main shock in regions of steep bathymetry accentuated tsunami generation for this event most of the damage on bougainville and buka islands was caused by focusing and amplification of tsunami energy from a ridge wave between the source region and these islands modeling of changes in the coulomb failure stress field caused by the main shock indicate that aftershock 1 was likely triggered by static stress changes provided the fault was on or synthetic to the new britain interplate thrust as specified by the harvard cmt mechanism for other possible focal mechanisms of aftershock 1 and the regional occurrence of thrust aftershocks in general evidence for static stress change triggering is not as clear other triggering mechanisms such as changes in dynamic stress may also have been important the 2000 new ireland earthquake sequence provides evidence that tsunamis caused by thrust aftershocks can be triggered by large strike slip earthquakes similar tectonic regimes that include offshore accommodation structures near large strike slip faults are found in southern california the sea of marmara turkey along the queen charlotte fault in british columbia and near the alpine fault of new zealand results from this study and previous stress modeling studies suggest that the likelihood of local tsunamis in these regions may significantly increase after a great strike slip earthquake

modern iron ooids from a shallow marine volcanic setting mahengetang indonesia an unconsolidated submarine deposit of iron ooids and pisoids located offshore the volcanic island mahengetang indonesia is described herein the deposit occurs in a shallow marine setting in an area characterized by venting of hydrothermal fluids and expulsion of gas across the sediment water interface the ooid deposit is essentially pure to a minimum depth of 0 5 m and covers an area of at least 1000 m 2 ooids are composed of concentric accretionary layers of limonite admixed with amorphous silica precipitated around andesitic rock fragments the smallest layers forming the ooids are about 10 min thickness the iron rich precipitate is 50 iron by weight ooid formation is likely promoted by precipitation of iron and silica from exhalative fluids rising up through the substrate concentric layering is thought to result from constant agitation of ooids associated with currents and expulsion of gas from the sediment