boron lithium relationships in rhyolites and associated thermal waters of young silicic calderas with comments on incompatible element behaviour abstract this study had three goals 1 1 to study b distribution in a rhyolitic volcanic sequence already extensively investigated for other elements 2 2 to interpret the joint behaviour of b and li during the interaction of such rocks with subsurface waters 3 3 to assess the manner in which water affects the behaviour of incompatible elements such as b and gd new b gd and sm analyses have been made on a suite of yellowstone rhyolites including fresh and partially devitrified glassy obsidian from surface exposures of several flows drill core of increasing degrees of alteration in the biscuit basin flow and two drill cores from other flows within the biscuit basin flow the sm and gd concentrations remain rather constant 9 12 and 8 10 ppm respectively and behave conservatively independent of alteration boron decreases from about 10 to 3 ppm with progressive alteration and li increases from about 40 ppm by a factor of 2 3 in the most altered rocks thermal waters reflect leaching from the fresh rocks but contain much less li than b b li 3 compared with 0 8 in fresh obsidian retention of li was favoured by abundant illitic alteration obsidians from the valles and long valley calderas show greater li loss during alteration all the rhyolitic rocks lose b during aqueous alteration the waters acquire both b and li but proportionately much more b natural waters of all kinds including those from the three calderas show six orders of magnitude range in aqueous b and li with a high degree of linear correlation and an average ratio b li essentially constant at 4 0 the linearity mainly expresses processes of dilution and concentration reactions specific to b or li engender waters with deviating b li the patterns of sm gd b li variation in rocks exemplify two kinds of behaviour in petrological processes with no hydrous phase lunar rocks mantle fresh seafloor basalt the lower continental crust these elements are incompatible and behave similarly when an aqueous phase is present b and li behave independently of sm and gd

strain partitioning in the transition area between oblique subduction and continental collision hikurangi margin new zealand spatial differences in late quaternary structural style and deformation rates indicate a complex pattern of strain partitioning within the transition area from oblique subduction beneath southern north island to oblique continental collision in northern south island new zealand the late quaternary structure of the offshore southern hikurangi margin is determined here using seismic reflection profiles mr1 side scan sonar swath images em12dual multibeam swath bathymetry and backscatter images and sediment core and dredge samples where oblique 50 subduction of the oceanic hikurangi plateau is occurring beneath southern wairarapa region the steep dissected upper margin consists of a wedge of rocks that are being deformed by strike slip and reverse faults beneath the lower margin an accretionary wedge of quaternary age has developed rapidly by frontal accretion of a thick succession of turbidites on the pacific plate estimates of late quaternary geological strain rates have been made on two margin perpendicular transects across southern north island and the offshore margin to budget the predicted nuvel 1a plate motion more than 33 55 of the total plate motion is expressed in the offshore part of the upper plate above the subduction detachment in the central hikurangi margin between 40 s and 41 s this offshore deformation could potentially include margin parallel fault slip of up to 14 15 mm yr across the upper plate strain is partitioned into zones of folding and thrust faulting and possibly more than one zone of strike slip faulting but the partitioning may be incomplete with oblique slip thrusting an important component of the deformation the wide distribution of deformation within the upper plate partially reflects strong coupling between the subducting oceanic plateau and the leading edge of the overriding plate this coupling increases toward the southwest where the continental part of the subduction zone beneath marlborough may now be inactive or very strongly coupled toward the southwest the transpressive deformation style of the upper wairarapa margin continues into the upper marlborough margin and onshore into the strike slip marlborough fault system of northern south island in contrast the accretionary wedge narrows to the southwest and terminates in southeastern cook strait approximately above the transition from subducted oceanic crust to subducted continental crust of the pacific plate farther southwest beneath the lower marlborough margin low strain folding and thrust faulting is occurring but the style of deformation is not typical of the accretionary wedge this shortening results either from a small amount of subduction slip beneath marlborough and or from contractional strain partitioned to the southeast of the continental transpression zone whereas the initial onset of continental collision occurs in marlborough the surface expression of deformation of the pacific plate occurs south of 42 30 s normal faulting of the northwestern margin of the continental chatham rise possibly reflects flexural extension of the pacific plate crust at the southern end of the subduction zone whereas folding and thrust faulting of the north canterbury coastal region results from nw se contraction of the delaminated upper crust entering the southern alps collision zone

evidence for an earthquake and tsunami about 3100 3400 yr ago and other catastrophic saltwater inundations recorded in a coastal lagoon new zealand abstract okupe lagoon is 2 02 masl brackish and ponded behind two boulder banks at the northern end of kapiti island new zealand the sediments of the lagoon provide a record of late holocene environmental changes such as tectonic uplift catastrophic saltwater inundation and vegetation change five main events were identified over a 5300 yr record with a sixth representing a re evaluation of previous work an uplift event of 1 5 3 0 m and an associated tsunami are recorded and are inferred to have been caused by a local fault rupture possibly the northern extension of the wairau fault about 3360 40 yr bp two additional tsunami generated by ruptures of either the ohariu or wellington faults 1290 and 1220 ad respectively and either the wellington or alpine faults 1450 ad have been tentatively proposed two catastrophic saltwater inundations csis have also been identified one possibly a tsunami generated by either the wairarapa fault 500 ad or taupo eruption 190 ad the other about 4780 150 yr bp may relate to a local fault rupture however further work is needed to determine whether these are tsunami or storm surge related and they are therefore designated csis the sixth event is the 1855 tsunami recorded from a raised shore platform to the west of okupe lagoon

sahke seismic scatter imaging of subduction beneath wellington north island new zealand scattering reflectivity analysis of onshore seismic data seismic array hikurangi experiment images slab geometry and crustal structure at a geodetically locked subduction boundary a broad seismic scattering zone bsz up to 10 km thick above the subduction interface at depths of 16 30 km has seismic properties vp vp vs and q that imply high fluid pressures probably associated with underplated sediments the listric strike slip wairarapa fault and other splay faults that sole into the bsz imply long term weakness high rates of intraslab seismicity with low rates above the slab imply stress decoupling across the bsz association of high fluid pressures and long term weakness with geodetic locking is in contrast to similar observations at zones of slow slip at the northern hikurangi margin and suggest that either 1 pore fluid pressure or locking behavior may cycle over times longer than two decades or 2 local material properties play a significant role in determining if slow slip or locking occurs

infrared stimulated luminescence dating of late quaternary aggradation surfaces and their deformation along an active fault southern north island of new zealand abstract loess and silt that overlies and forms the matrix of late quaternary fluvial aggradation surfaces from the central wairarapa valley southern north island new zealand have been dated using infrared stimulated luminescence irsl of k feldspar in fine grained 4 11 m diameter mineral fractions three irsl protocols were used involving both the additive dose with thermal transfer correction and regeneration methods and from four samples using both the additive dose method and the single aliquot regeneration method eight luminescence ages of between and 16 1 1 6 and 10 0 0 9 kyr date the most extensive and youngest fluvial aggradation surface that has been deformed by wairarapa fault the most active fault of the north island dextral shear zone the ages provide absolute rates of dextral and vertical slip on the fault over the last 30 kyr that deforms two aggradation surfaces an average horizontal slip rate of 11 5 0 5 mm yr and variable vertical slip rates of between 0 09 and 1 7 mm yr that correlate with compressional bulges developed on the upthrown side of the fault caused by left lateral sidesteps and reversals of the upthrown side of the fault the horizontal slip rate indicates that one third of the 33 mm yr strike slip motion of oblique convergence between the australian and pacific plates is taken up by the wairarapa fault three younger luminescence ages of

molybdenum and tungsten in volcanic rocks and in surface and 100 c ground waters in iceland abstract the concentrations of mo and w in tholeiite series basaltic to silicic volcanics in iceland increase with the concentrations of incompatible magmatic elements in normal mid ocean ridge basalt morb mo and w levels are as low as 0 03 and 0 01 ppm but in rhyolites they are up to 4 and 1 3 ppm respectively in the slightly evolved tertiary tholeiites of the main study area of skagafjordur northern iceland mo and w concentrations are 1 01 and 0 32 ppm respectively on average surface waters in this area typically contain 10 000 years waters in river and ground waters the average mo w ratio is the same as that of the basalt host rock on the other hand in peat soil waters the average mo w ratio is higher due to adsorption processes involving w in river and ground waters both mo and w display conservative behavior progressive water rock interaction leads to successively lower aquatic b mo and b w ratios however the b mo and b w ratios of the most reacted waters are considerably higher than those of the basalt due to non stoichiometric rock dissolution b is dissolved preferentially to both mo and w because b is largely present in a soluble form but mo and w are concentrated in the fe ti oxides these minerals are stable under both surface and sub surface conditions i e the waters are over saturated with respect to these minerals the main supply of mo and w to surface waters is from dissolution of plagioclase and pyroxene as well as volcanic glass olivine is not an important source due to its scarcity in the basalts in

five thousand years of surface ruptures on the wellington fault new zealand implications for recurrence and fault segmentation new paleoseismic studies have been undertaken on the wellington hutt valley w hv segment of the wellington fault to characterize its late holocene record of surface rupturing earthquakes trenches and radiocarbon dates from te kopahou and te marua have provided evidence and improved timing for the four most recent earthquake ruptures these events have been recognized on the basis of upward terminating faults coseismic deposition progressive displacement and faulting of colluviums at te kopahou colluvial and scree deposition resulting from surface rupture and strong earthquake shaking buries old ground surfaces associated with peat and or soil development at te marua the timing of the two youngest events has been refined by bracketing the ages of the youngest faulted and unfaulted alluvial terraces of the hutt river assuming that the w hv segment acts as a rupture segment along its length the approximate timings of these faulting events is as follows the most recent faulting event event i occurred between 110 and 310 cal yr b p a d 1640 1840 the penultimate faulting event event ii between 790 and 930 cal yr b p event iii occurred between 1835 and 2340 cal yr b p and event iv between 2460 and 4900 yr b p the minimum and maximum earthquake recurrence intervals derived from the four youngest events are 715 and 1575 yr respectively with a median value of 1145 yr revisions of the earthquake timing recurrence interval data and recently the single event displacement and slip rate collectively reduce the seismic hazard for the w hv segment of the wellington fault a four event paleoearthquake record from the pahiatua section of the wellington fault is statistically similar to that from the w hv segment this has significant implications with respect to the rupture length and magnitude or clustering of future surface rupturing earthquakes on the wellington fault

the gutenberg richter or characteristic earthquake distribution which is it abstract paleoearthquake and fault slip rate data are combined with the cit usgs catalog for the period 1944 to 1992 to examine the shape of the magnitude frequency distribution along the major strike slip faults of southern california the resulting distributions for the newport inglewood elsinore garlock and san andreas faults are in accord with the characteristic earthquake model of fault behavior the distribution observed along the san jacinto fault satisfies the gutenberg richter relationship if attention is limited to segments of the san jacinto that are marked by the rupture zones of large historical earthquakes or distinct steps in fault trace the observed distribution along each segment is consistent with the characteristic earthquake model the gutenberg richter distribution observed for the entirety of the san jacinto may reflect the sum of seismicity along a number of distinct fault segments each of which displays a characteristic earthquake distribution the limited period of instrumental recording is insufficient to disprove the hypothesis that all faults will display a gutenberg richter distribution when averaged over the course of a complete earthquake cycle but given that 1 the last 5 decades of seismicity are the best indicators of the expected level of small to moderate size earthquakes in the next 50 years and 2 it is generally about this period of time that is of interest in seismic hazard and engineering analysis the answer to the question posed in the title of the article at least when concerned with practical implementation of seismic hazard analysis at sites along these major faults appears to be the characteristic earthquake distribution

structure and paleoearthquake records of active submarine faults cook strait new zealand implications for fault interactions stress loading and seismic hazard 1 a new interpretation of active faulting in central cook strait new zealand reveals tectonic structures associated with the spatial transition from subduction to continental transform faulting marine seismic reflection profiles and multibeam bathymetric data indicate that there are no throughgoing crustal faults connecting the north island dextral fault belt and the marlborough fault system in south island the major faults terminate offshore associated with 5 20 km wide step overs and a change in regional fault strike this structure implies that propagation of strike slip earthquake ruptures across the strait is not probable faulted sedimentary sequences in the wairau basin marlborough shelf correlated to glacioeustatic sea level cycles provide a stratigraphic framework for fault analysis a high resolution study of the postglacial 20 ka vertical displacement history of the cloudy and vernon faults reveals up to six and five paleoearthquakes since 18 ka respectively these long timescale records indicate variable recurrence intervals and possibly variable stress drop thus conforming to the variable slip model of earthquake behavior integration of these data with other submarine and terrestrial paleoearthquake records indicates the presence of clustered earthquake sequences involving multiple faults different sequences do not always involve the same faults it appears that earthquake clustering is driven by fault interactions that lead to specific loading conditions favoring the triggering of earthquakes on major faults in relatively short time intervals present day regional coulomb stress distribution has been calculated in two scenarios considered to represent minimum and maximum loading conditions the models incorporating secular tectonic loading and stress changes associated with major crustal earthquakes indicate high stress loading in a large part of central cook strait these conditions may favor the triggering of future damaging earthquakes in this region

coseismic strike slip at a point during the last four earthquakes on the wellington fault near wellington new zealand 1 we analyze progressively displaced late quaternary 12 ka fluvial terraces along the wellington fault near wellington new zealand optically stimulated luminescence dating indicates that degradational terraces were produced at a rate of about one terrace per 1000 years similar to the rate of earthquake surface rupturing along the hutt river near te marua we measured the strike slip of 15 terrace risers and paleochannels on the lowest 8 of these terraces of holocene age the river after earthquakes was generally capable of smoothing its faulted riverbanks the dextral offsets appear to fall into several groupings that record slip accumulation during the last four earthquakes we calculate a mean single event slip of 5 0 0 24 m 95 confidence with an rms scatter 1 of slips about the mean of 1 5 m the coefficient of variation cv of single event slip is thus 0 30 this cv is slightly less than a recently compiled global average for point measurements on strike slip faults suggesting that the southernmost wellington fault has behaved in a more nearly characteristic way we speculate that recent large earthquake ruptures have been bounded on their southern end by the wellington fault s offshore fault termination and perhaps on their northern end by a 2 km wide releasing step over such persistent sources of rupture arrest might have led to a relative uniformity of rupture dimensions and slip amounts we infer a late holocene dextral slip rate of 4 5 0 4 mm yr 1 and 8 2 mm yr and a mean earthquake recurrence interval of 610 1100 years

platinum enrichment at low temperatures and related microstructures with examples of hongshiite ptcu and empirical pt2hgse3 from itabira minas gerais brazil low temperature pt enrichment is illustrated with reference to two hypogene platiniferous minerals i a pd cu bearing pt2hgse3 an unnamed phase and ii hongshiite ptcu with up to 0 7 wt hg the former has patches oxidized to a pt o species with curvilinear microcracks originated by desiccation the latter displays parallel sets of cu depleted pt hg enriched patches along which microfractures occur such microstructures are interpreted to arise from two processes i oxidation and formation of a hydrated pt o compound which tends to succumb to a pt rich alloy by deoxygenation and dehydration leaving behind curvilinear desiccation cracks ii metal leaching conducive to native pt by removal of cu from hongshiite via micropores that coalesce along crystallographic planes to result in reticulated microcracks platinum enrichment either by oxidation or metal leaching ideally produces characteristic microcracks which may be indicative of the origin i e detrital vs supergene of alluvial and eluvial pt rich alloys

microstructures textures and deformation mechanisms in hematite abstract deformation and recrystallization of hematite in iron formations and high grade ore bodies of the caue formation from the quadrilatero ferrifero district minas gerais brazil resulted in several types of fabrics depending on the tectonic and metamorphic imprint the fabrics vary from randomly oriented granoblastic to strongly oriented lepidoblastic mylonitic with local development of cataclastic features complete pole figures of the crystallographic planes 003 basal plane 110 prism and 104 rhombohedron were measured on several samples from different areas by means of neutron diffraction revealing a typical crystallographic preferred orientation for the different fabric types the configuration and intensity of the maxima are directly related to the magnitude of the deformation and the type of response of the ore the analysis of the textures and microstructures of the iron ores and comparison with experimental deformation data lead us to the conclusion that three main mechanisms are active basal slip diffusion processes and anisotropic grain growth post tectonic recrystallization and secondary grain growth did not affect the textures developed during deformation

slip rate on the wellington fault new zealand during the late quaternary evidence for variable slip during the holocene we investigate fault offset fluvial terraces at two sites along the hutt river near wellington new zealand to determine horizontal slip rates for the southern part of the wellington fault for the last 100 ka using photogrammetric analysis of historic aerial photos we measured the original displacements of terrace risers at emerald hill which have been modified by urban development fourteen sediment samples from this site and from another location dry creek were analyzed using optically stimulated luminescence osl methods yielding ages of between 10 ka and 100 ka from our displacement age relations we estimate an average slip rate of graphic 1 2 during the last 100 ka however slip on the wellington fault has not been steady throughout this time during the holocene there was a phase of heightened ground rupture activity between 10 and 8 ka when an incremental dextral displacement of 32 m accrued this was followed by a period of relative quiescence between 8 and 4 5 ka with 5 m of displacement during this time another period of heightened activity followed resulting in a further 20 m of slip during the last 4 5 ka our inference of variable slip during the holocene accords with independent evidence from paleoseismological studies at other sites along the wellington fault slip on the wellington fault and its variability through time may be influenced by activity on neighboring faults online material part i optically stimulated luminescence osl dating technical report and results part 2 stratigraphic logs 1 embed inline graphic 1 gif

a record of lateglacial and early holocene environmental and ecological change from southwestern connecticut usa analyses of a sediment core from highstead swamp in southwestern connecticut usa reveal lateglacial and early holocene ecological and hydrological changes lateglacial pollen assemblages are dominated by picea and pinus subg pinus and the onset of the younger dryas yd cold interval is evidenced by higher abundance of abies and alnus viridis subsp crispa a s climate warmed at the end of the yd picea and abies declined and pinus strobus became the dominant upland tree species a shift from lacustrine sediment to organic peat at the yd holocene boundary suggests that the lake that existed in the basin during the lateglacial interval developed into a swamp in response to reduced effective moisture a change in wetland vegetation from myrica gale to alnus incana subsp rugosa and sphagnum is consistent with this interpretation of environmental changes at the beginning of the holocene copyright 2009 john wiley sons ltd

preliminary slip rate estimates for the duzce segment of the north anatolian fault zone from offset geomorphic markers abstract new estimates on the quaternary slip rate of the active transform margin of north anatolia are provided we investigated the area struck by a mw 7 1 earthquake on the 12th of november 1999 that ruptured the duzce fault segment of the north anatolian fault in order to analyze the spectacular tectonically driven cumulative landforms and the drainage pattern settings we carried out a 1 25 000 scale geological and geomorphological mapping along the fault trace we reconstruct and describe as offset geomorphic markers right hand stream deflections and fluvial terraces inset into alluvial fan deposits radiocarbon dating indicates that 100 m stream deflections were built up by the last 7000 yrs of fault activity conversely two documented and correlated late pleistocene fluvial terraces are horizontally offset by 300 and 900 m respectively these were dated by means of optically stimulated luminescence osl to 21 ka bp and 60 ka bp assuming a constant rate of deformation for the duzce fault ages and related offsets translate to consistent slip rates that yield an average slip rate of 15 0 3 2 mm yr for the last 60 ka thus the duzce fault importantly contributes to the north anatolian margin deformation suggesting a present day partitioning of displacement rates with the mudurnu fault to the south and confirming its important role in the seismic hazard of the area

a revised local magnitude ml scale for new zealand earthquakes in this study a new local magnitude m l scale is developed for new zealand and adjacent offshore regions seiscomp3 sc3 has been in use for earthquake analysis in new zealand since september 2012 with the original richter 1935 log a attenuation relationship for calculating m l the attenuation characteristics of new zealand differ significantly from southern california where m l was originally defined and therefore result in m l that is consistently high when compared with moment magnitude m w using m w from 528 regional moment tensor solutions along with peak observed amplitudes a new log a curve is derived along with station correction factors that define a revised m l scale for new zealand earthquakes that is more consistent with m w the new log a curve is similar to the original richter 1935 definition at hypocentral distances of 100 200 km but differs significantly at closer and farther distances the new m l is more consistent with m w across new zealand including crustal earthquakes and earthquakes below the crust the california institute of technology caltech u s geological survey seismic processer cusp system was used for earthquake analysis prior to sc3 and previous studies have derived regression relationships relating cusp m l with m w after applying the regression relationships to cusp m l we found very good agreement between cusp m l and the new sc3 m l which is important for developing a consistent m l between different catalogs online material table of station corrections for the new zealand seismograph network

the basin edge effect from weak ground motions across the fault bounded edge of the lower hutt valley new zealand basin edge effects are investigated in the lower hutt valley wellington new zealand using recordings of weak motion earthquakes twelve seismographs were deployed in a closely spaced array along the fault bounded edge of the valley peak ground motions appear to be locally amplified at 2 0 2 5 hz in the edge parallel component at around 116 172 m from the fault and in the edge normal component more than 295 m from the fault group velocity observations made of edge generated love waves show the fundamental mode airy phase frequency at 2 0 2 5 hz this frequency corresponds to the fundamental resonance mode of the holocene sediments as well as the third mode resonance of the whole basin large differential particle motions are observed at neighboring stations less than 50 m apart the most plausible explanation to account for these observations is constructive interference between edge generated surface waves and the delayed direct arrival commonly referred to as the basin edge effect manuscript received 23 october 2001

earthquake frequency distribution and the mechanics of faulting the level of intraplate seismicity in japan generally shows a positive correlation with the density of quaternary faulting in southwest japan where intraplate seismicity is concentrated on land rates of seismic moment release m 0 are similar when calculated from either the 400 year historical record of seismicity or geologically determined slip rates of quaternary faults a data set of 18 earthquakes with seismic moments m0 ranging from 0 01 to 3 1027 dyn cm shows a relationship between rupture lengthl and m0 log m0 23 5 1 94 log l when seismic moment on each quaternary fault is assumed to occur in discrete events every t m0 m 0g years where m0 is estimated for a rupture extended over the entire fault length and m 0g is proportional to the slip rate of each quaternary fault the moment frequency distribution of earthquakes log n a b log m0 predicted from the geologic record is virtually identical to that seen with the 400 year record of seismicity in contrast if it is assumed that earthquakes on each fault occur according to the gutenberg richter relation we obtain poor agreement with the observed seismicity thus while regional seismicity satisfies the relation log n a b log m0 or equivalently log n a b log m where m is magnitude it appears that seismicity on individual faults does not this further implies that the primary factor that leads to the magnitude frequency distribution in regional seismicity studies is the relative distribution of the slip rates and lengths of preexisting faults

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

shallow morphology of the subducted pacific plate along the hikurangi margin new zealand abstract along the east coast of the north island new zealand the pacific plate is subducted beneath the australian plate the seismicity associated with this subduction has been determined using the results from a number of temporary and permanent microearthquake networks a synthesis of the microearthquake seismicity the depths of thrust events the depth of s to p conversions and deep reflection seismic studies leads to a coherent picture of the subducting slab both in terms of its mechanical structure and in terms of the general morphology the slab is initially subducted at a low angle of a few degrees is bent through a circular arc of few hundred kilometre radius and then becomes planar again below 120 km depth the radius of curvature varies along strike from about 280 km just north of wellington to 240 km north of hawke bay the slab shape between depths of 15 45 km is thus approximately conical it also approximates within the errors of hypocentre location a surface of constant gaussian curvature as would be geometrically expected from the simple bending of a thin spherical lithospheric shell observed seismicity is primarily concentrated within what is interpreted as the subducted crust of the pacific plate with a lower level of activity within the subducted mantle normal fault mechanisms at the top of the plate probably reflect tensional stress associated with the plate bending whereas thrust events observed at the lower bound of the observed seismicity probably reflect compression below the neutral plane

using synthetic seismicity to evaluate seismic hazard in the wellington region new zealand summary a computer synthetic seismicity program for the wellington region has been implemented and used to infer the effect of the 1848 awatere and 1855 wairarapa mega earthquakes on the timing of the next characteristic magnitude 7 35 or more earthquake on the wellington hutt valley section of the wellington fault we find that on average over several hundred cases a wellington fault event is delayed by 259 years the synthetic catalogue of 500 000 events magnitude 5 5 or more also gives the average recurrence time of characteristic wellington fault events 960 yr and their coefficient of variation 0 40 there is also a strong retarding effect on moderate magnitude wellington fault events magnitude 6 5 7 3 sensitivity tests indicate that these results are robust the synthetic model contains 58 known major faults and 3000 randomly placed small faults to reproduce the rate and spatial distribution of background seismicity observed recently from the synthetic catalogue it is possible to determine the average recurrence rate for all major faults also there is strong evidence of the short term 10 yr temporal clustering of large events throughout the region a factor that contributes to a highly variable moment release rate over time spans of a few hundred years

quaternary temporal stability of a regional strike slip and rift fault intersection abstract intersecting strike slip and normal fault systems form either two or three plate configurations in circumstances where they intersect to form a triple junction internal block deformation produces a quasi stable 3 d configuration permitting maintenance of both the regional geometry and kinematics of the intersection this paper examines the temporal stability of such a triple junction in new zealand over a range of timescales from individual earthquakes to millions of years and discusses the factors that impact its stability using seismic reflection gravity drill hole and outcrop data the accumulation of vertical displacements is examined both on individual faults and across the intersection zone between the strike slip north island fault system nifs and the taupo rift fault throws and throw rates for the nifs and taupo rift suggest that despite a three fold increase in throw rates in both fault systems at about 0 3 ma which may have modified the orientation of the slip vectors and therefore the contemporary kinematics of the triple junction the intersection of the two fault systems has functioned coherently for the last 0 6 1 5 myr accumulating vertical displacements interdependently since the early stages of rifting the apparent arrest of a large magnitude earthquake on the rift bounding fault adjacent to the intersection suggests that the short term dynamic behaviour of the system is relatively complex compared to the more coherent long term kinematics

abrupt strike slip fault to subduction transition the alpine fault puysegur trench connection new zealand swath bathymetry and other geophysical data collected over the fiordland margin southwest of new zealand are used to investigate the mechanism of transform subduction transition between the alpine fault and the puysegur trench two segments of the pacific australian plate boundary in this region the cenozoic southeast tasman basin which obliquely underthrusts fiordland at the puysegur trench is separated from the cretaceous tasman basin by the resolution ridge system a major lithospheric discontinuity of the downgoing plate interpretation of seafloor morphology shows that the alpine fault extends offshore along the fiordland coast and splits into west and east branches the west branch cuts obliquely across the margin and connects sharply to the puysegur subduction front at the northeastern tip of the resolution ridge system earthquake and seismic reflection data indicate that the west branch is genetically controlled by downgoing plate structures associated with the resolution ridge system hence the west branch is interpreted as the surface trace of the plate boundary segment extending between the alpine fault and the puysegur trench we conclude that the development of the strike slip segment of the plate boundary and its sharp transition to the puysegur subduction are controlled by inherited structures of the australian plate furthermore according to geophysical data presented here a tearing of the downgoing plate can be interpreted beneath the west branch a review of geophysical data along the region of the alpine fault hikurangi trough northeast new zealand shows a progressive transform subduction transition that is accommodated by motion partitioning between the subduction interface and strike slip faults this transition is accounted for by an interplate coupling that progressively increases toward the alpine fault in relation with a gradual thickening of the downgoing crust the comparison between the fiordland and the hikurangi strike slip subduction transitions show that presence of inherited downgoing plate crustal faults properly oriented with respect to the plate motion facilitates a sharp strike slip subduction transition

shore platform morphology on a rapidly uplifting coast wellington new zealand the coast of wellington new zealand is tectonically active and contains a series of uplifted and contemporary shore platforms that are developed in triassic greywacke the platform profiles are rugged with relief of metre scale common the surveyed platforms were formed at and at two distinct levels 1 1 5 and 2 2 5 m above mean sea level they range in width up to 70 m and are highly fractured with fracture densities in excess of 20 sol m2 common the rate of development of these platforms is rapid with lateral erosion rates of up to 0 15 m sol yr calculated allowing platform development to occur over centennial scales even given this rapid development continued instantaneous uplift of the coast has meant they are unable to reach an equilibrium state whereby the effectiveness of wave processes in removing material is reduced by platform extension the co seismic uplift means that the rear of the platforms is raised beyond the limits of marine process and has become an area of deposition although no direct process measurements were made the highly fractured nature of the bedrock appears to play a major role in platform evolution with wave processes being easily able to pluck blocks as evidenced by fresh erosion scars and active gravel beaches at the rear of many platforms this coast therefore represents an extremely dynamic youthful shore platform environment where the processes of marine abrasion can be observed over historical timescales copyright 2005 john wiley sons ltd

the kinematics of a transition from subduction to strike slip an example from the central new zealand plate boundary 1 we develop a kinematic model for the transition from subduction beneath the north island new zealand to strike slip in the south island constrained by gps velocities and active fault slip data to interpret these data we use an approach that inverts the kinematic data for poles of rotation of tectonic blocks and the degree of interseismic coupling on faults in the region convergence related to the hikurangi subduction margin becomes very low offshore of the northern south island indicating that in this region the majority of the relative plate motion has been transferred onto faults within the upper plate as suggested by previous studies this result has implications for understanding the likely extent of subduction interface earthquake rupture in central new zealand easterly trending strike slip faults such as the boo boo fault are the key features that facilitate the transfer of strike slip motion from the northern south island faults further north into the southern north island and onto the hikurangi subduction thrust our results also indicate that the transition from rapid forearc rotation adjacent to the hikurangi subduction margin to a strike slip dominated plate boundary with negligible vertical axis rotation in the south island occurs via a crustal scale hinge or kink in the upper plate compatible with paleomagnetic and structural geological data despite the ongoing tectonic evolution of the central new zealand region our study highlights a remarkable consistency between data sets spanning decades gps thousands of years active faulting data and millions of years paleomagnetic data and bedrock structure

characterizing earthquake recurrence parameters for offshore faults in the low strain compressional kapiti manawatu fault system new zealand 1 seafloor fault scarps and near surface deformation of late quaternary seismic reflectors occur along the eastern margin of the wanganui basin 200 km behind the active hikurangi subduction front southern north island new zealand the offshore scarps are associated with the low strain compressional kapiti manawatu fault system kmfs which comprises high angle 60 reactivated reverse and normal faults oriented ne sw highly oblique to the coast seafloor scarps range from 10 m high and moderate to long fault seafloor rupture lengths and those in central parts of the fault system are characterized by low scarps 10 000 a suggest that the seismic hazard of the kapiti manawatu region is relatively low incorporation of these new geological data however is likely to increase slightly the expected seismic hazard in southern north island the method of determining the earthquake recurrence parameters of offshore faults has potentially wider applications elsewhere

structure of a growing accretionary prism hikurangi margin new zealand the hikurangi margin of eastern north island new zealand represents the feather edge of the indian plate at its convergent boundary with the subducting pacific plate a migrated seismic reflection profile across this margin clearly displays the structural evolution of an accretionary prism a 25 km wide band of protothrusts is delineated between the toe of the slope and a converging seamount this illustrates an early stage in the seaward propagation of a deformation front landward tilted trench slope basins are separated by ridges that have clearly defined thrusts which appear to sole out at a decollement the decollement continues at an angle of only 3 beneath the 150 km wide margin to a depth of 14 km near the coast where it coincides with an onshore zone of high seismicity

contemporary horizontal velocity and strain rate fields of the pacific australian plate boundary zone through new zealand we have inverted velocity solutions from nine geodetic networks distributed across new zealand to derive present day continuous horizontal velocity and strain rate fields at the earth s surface throughout the country the nine networks contain a total of 362 global positioning system gps stations that have been observed at least twice and at least a year apart between 1991 and 1998 the model velocity field is expanded as bicubic spline interpolation functions defined within a curvilinear grid that covers the country and extends into the assumed rigid australian and pacific plates to west and east the inversion jointly minimizes the magnitudes of fitted strain rates and the misfit to the observed velocity data the spline technique allows high spatial resolution of strain rate variations especially in regions with spatially dense gps data expansion of the model velocity field on the surface of a sphere allows arbitrarily large areas to be studied previously known aspects of new zealand plate boundary deformation are highlighted with improved resolution including back arc extension in the taupo volcanic zone rotation of the hikurangi forearc away from this zone in the north island and a band of high shear strain rate under the southern alps to the southeast of the alpine fault our results reveal several new features including a region of enhanced shear straining apparently associated with strike slip faults in the southern north island and a band of contractional straining subparallel and well east of the alpine fault that is similar to features found in numerical and sandbox models of continental collision

crustal deformation and stress transfer during a propagating earthquake sequence the 2013 cook strait sequence central new zealand the 2013 cook strait earthquake sequence began on 18 july 2013 with two foreshocks of mw 5 7 and mw 5 8 and culminated in the mw 6 6 cook strait and lake grassmere events on 21 july and 16 august respectively located 50 km south of new zealand s capital wellington the earthquakes generated the most significant ground shaking in the wellington and marlborough regions in recent decades during the first event located under cook strait continuously recording gps instruments across central new zealand recorded up to 5 cm of horizontal displacement modeling suggests that the rupture was 25 km long with up to 90 cm of dextral strike slip the second event located 20 km to the southwest caused displacements of up to 25 cm at gps sites located around the clifford bay area in addition two interferograms from radarsat 2 and terrasar x showed up to 30 cm of line of sight displacement in the vicinity of lake grassmere modeling indicates predominantly dextral strike slip of up to 2 1 m coulomb stress changes induced by the earlier foreshocks suggest that the cook strait event was triggered by the preceding events and that the lake grassmere event was subsequently triggered by the cook strait earthquake

synthetic seismicity models for the wellington region new zealand implications for the temporal distribution of large events our previous synthetic seismicity model for multiple interacting faults in a three dimensional half space has been extended and applied to the wellington region new zealand generating long catalogs of earthquakes for studying the effects of elastic interactions on the temporal distribution of large events the region is one of oblique plate convergence with the interface between the subducting and overlying plates at an average depth of 22 km faults included besides the subduction thrust are segments of the four major arc parallel strike slip faults overlying the plate interface we have used 40 different models with geometric and mechanical parameters chosen at random within reasonable ranges to generate catalogs of 200 000 years duration each for comparison each model was rerun with the elastic interactions suppressed considering events of magnitude 7 2 or more characteristic events in the sense that they rupture most of a fault plane the number of short 250 years the relative numbers are again mostly higher experiments with simple models indicate that this pattern requires both interfault enhancement and inhibition of large events mutual enhancement occurs most often between the subduction thrust and the overlying strike slip faults and between the two segments of the wellington fault that almost join end to end mutual inhibition mostly occurs between the subparallel strike slip faults

a new geomagnetic polarity time scale for the late cretaceous and cenozoic we have constructed a magnetic polarity time scale for the late cretaceous and cenozoic based on an analysis of marine magnetic profiles from the world s ocean basins this is the first time since heirtzler et al 1968 published their time scale that the relative widths of the magnetic polarity intervals for the entire late cretaceous and cenozoic have been systematically determined from magnetic profiles a composite geomagnetic polarity sequence was derived based primarily on data from the south atlantic anomaly spacings in the south atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles fine scale information was derived from magnetic profiles on faster spreading ridges in the pacific and indian oceans and inserted into the south ariantic sequence based on the assumption that spreading rates in the south atlantic were smoothly varying but not necessarily constant a time scale was generated by using a spline function to fit a set of nine age calibration points

experimental modelling of tectonics erosion sedimentation interactions in compressional extensional and strike slip settings tectonically controlled landforms develop morphologic features that provide useful markers to investigate crustal deformation and relief growth dynamics in this paper we present results of morphotectonic experiments obtained with an innovative approach combining tectonic and surface processes erosion transport and sedimentation coupled with accurate model monitoring techniques this approach allows for a qualitative and quantitative analysis of landscape evolution in response to active deformation in the three end member geological settings compression extension and strike slip experimental results outline first that experimental morphologies evolve significantly at a short time scale numerous morphologic markers form continuously but their lifetime is generally short because erosion and sedimentation processes tend to destroy or bury them for the compressional setting the formation of terraces above an active thrust appears mainly controlled by narrowing and incision of the main channel through the uplifting hanging wall and by avulsion of deposits on fan like bodies terrace formation is irregular even under steady tectonic rates and erosional conditions terrace deformation analysis allows retrieving the growth history of the structure and the fault slip rate evolution for the extensional setting the dynamics of hanging wall sedimentary filling appears to control the position of the base level which in turn controls footwall erosion two phases of relief evolution can be evidenced the first is a phase of relief growth and the second is a phase of upstream propagation of topographic equilibrium that is reached first in the sedimentary basin during the phase of relief growth the formation of triangular facets occurs by degradation of the fault scarp and their geometry height becomes stationary during the phase of upstream propagation of the topographic equilibrium for the strike slip setting the complex morphology of the wrench zone composed of several interacting fault segments enhances the interactions with the drainage network because of the widening of the main fault zone toward the surface a significant amount of distributed deformation is observed along the wrench zone locally where two terminations of fault segments interact less than a quarter of the far field displacement can remain measurable using fault offsets leading to a systematic underestimation of the real fault slip rate these different experimental examples illustrate the great potential of the approach coupling deformation mechanisms and erosion transport sedimentation processes to investigate qualitatively and quantitatively the morphotectonic evolution of tectonically controlled landscapes

a sr isotope study on fluorite and siderite from post orogenic mineral veins in the eastern harz mountains germany rb sr isotope data for siderite and fluorite from sediment hosted epithermal mineral veins in the eastern harz mountains germany are presented several fluorite and siderite bearing paragenetic stages have been proposed for these veins with the most important mineralization being related to a quartz sulfide and a subsequent calcite fluorite quartz stage which occurred at 226 1 and 209 2 ma respectively our rb sr data do not permit the identification of distinct generations of siderite and fluorite but rather reveal straight internal mixing relations reflecting mixing of fluids or differential fluid rock interaction processes this indicates merely two significant phases of mineral deposition related to the quartz sulfide and calcite fluorite quartz stages it is shown that the paleozoic sedimentary host rocks of the veins are the most likely source for the siderite sr whereas fluorite displays a two component mixture between sedimentary sr and radiogenic sr derived from locally occurring permian metavolcanic rocks

strain partitioning between structural domains in the forearc of the hikurangi subduction zone new zealand the pacific plate obliquely converges with the australian plate at latitude 39 50 s along the hikurangi margin off the east coast of the north island of new zealand an extensive and youthful subaerially exposed forearc on the east coast of the north island in the hawke s bay area provides the opportunity to document contemporaneous forearc deformation in this obliquely convergent margin setting geologic mapping and analysis of strain at both mesoscale and megascale indicates that strain is partitioning into domains of extension contraction and strike slip the domains are elongate and trend parallel to the margin measurements of net shortening and transcurrent slip in the forearc show that the obliquely convergent motion is transferred across the plate interface deformation rates calculated for the past 1 2 m y for structures in all six forearc domains account for 50 70 of the margin parallel motion required by pacific australian plate convergence and about 6 of the plate motion perpendicular to the plate boundary at the surface in the forearc this obliquely convergent motion is manifest not by transpressional faults but rather by paired structural domains that consist of a strike slip fault zone and an accompanying contractional fault and fold zone on the trenchward side there are two such transcurrent faulting and contraction couplets one where the backstop daylights at the arcward edge of the forearc and another couplet trenchward of a relatively undisturbed forearc basin the small amount of shortening relative to strike slip in the onshore part of the forearc suggests that shortening perpendicular to the plate boundary may be concentrated offshore and that most of the component of plate motion perpendicular to the plate boundary may be accommodated by slip along the subduction zone megathrust

seismicity structure and tectonics of the wellington region new zealand summary the wellington region lies on the border between the pacific and australian plates the former being subducted the plate interface lies at shallow depth under the region 10 60 km so that detailed and long term monitoring of the seismicity of the zone where large thrust earthquakes are expected to occur is possible hypocentres for events recorded by a 12 station seismic network for the period 1978 1982 7231 events have been refined by the use of a threedimensional velocity model derived from a simultaneous inversion of arrival time data from 129 local events for both hypocentres and velocity the hypocentres show that the subducting pacific plate is defined by a nw dipping zone of relatively intense activity the plate interface as given by the upper envelope of this activity is offset vertically by 7 km on average along a nw se line through cook strait parallel to the direction of absolute motion of the pacific plate rather than to the direction of convergence the strike of the interface at deeper levels also changes across this line this distortion may partly reflect effects of the transition to continent continent type convergence further south within the subducting pacific plate the seismic activity defines two parallel zones separated by about 20 km the lower zone being much less active and perhaps merging with the upper zone at a depth of 80 90 km composite focal mechanisms of events in the upper zone imply predominantly down dip tension with a compression axis perpendicular to the plate interface the mechanism in the lower zone also implies down dip tension but the compression axis has rotated to be horizontal and along strike indicating a component of lateral shearing within the plate these two types of mechanism correlate well with those found previously for events at depths of 150 km or more thus it seems that the large negative buoyancy of the subducted lithosphere dominates the internal stress field throughout the length of the seismically active region the lithosphere acting as a stress guide there is no evidence for a significant number of events with mechanisms indicating thrusting along the plate interface the seismic velocity in the region corresponding to the upper seismic band is close to that typical for oceanic crust which here is probably considerably thicker than normal there is no evidence for a substantial increase in velocity down

geochemistry of metal rich brines from central mississippi salt dome basin u s a abstract oil field brines are the most favored ore forming solutions for the sediment hosted mississippi valley type ore deposits detailed inorganic and organic chemical and isotope analyses of water and gas samples from six oil fields in central mississippi one of the very few areas with high metal brines were conducted to study the inorganic and organic complexes responsible for the high concentrations of these metals the samples were obtained from production zones consisting of sandstone and limestone that range in depth from 1900 to 4000 m 70 120 c and in age from late cretaceous to late jurassic results show that the waters are dominantly bittern brines related to the louann salt the brines have extremely high salinities that range from 160 000 to 320 000 mg l total dissolved solids and are na ca cl type waters with very high concentrations of ca up to 48 000 mg l and other alkaline earth metals but with low concentrations of aliphatic acid anions the concentrations of metals in many water samples are very high reaching values of 70 mg l for pb 245 mg l for zn 465 mg l for fe and 210 mg l for mn the samples with high metal contents have extremely low concentrations 2 s samples obtained from the smackover formation limestone have low metal contents that are more typical of oil field waters but have very high concentrations up to 85 mg l of h 2 s computations with the geochemical code solmineq 87 give the following results 1 both pb and zn are present predominantly as aqueous chloride complexes mainly as pbcl 4 2 and zncl 4 2 respectively 2 the concentrations of metals complexed with short chained aliphatic acid anions and reduced s species are minor 3 organic acid anions are important in controlling the concentrations of metals because they affect the ph and buffer capacity of the waters at subsurface conditions and 4 galena and sphalerite solubilities control the concentrations of pb and zn in these waters

long term slip rates and fault interactions under low contractional strain wanganui basin new zealand the newly mapped kapiti manawatu fault system kmfs in southern north island new zealand accommodated 3 5 km of basement throw over the last 3 myr along strike throw profiles are generated using seven stratigraphic markers interpreted from seismic reflection profiles acquired 3 km apart the profiles are symmetrical about their point of maximum displacement and cumulative profiles suggest that the reverse fault system behaves coherently the kmfs originates from the reactivation of extensional structures with fault lengths remaining constant over time contractional deformation started at circa 1750 400 ka maximum dip slip rates along individual faults are 1 77 0 53 and 0 74 0 22 mm yr 1 for the 0 120 and 120 1350 ka periods respectively the maximum cumulative throw rates across the kmfs are 4 9 1 5 and 1 5 0 5 mm yr 1 for the same periods long term strain rates across the kmfs are 2 5 times smaller than strain rates in the forearc basin of the hikurangi subduction margin located less than 100 km to the east the faults of the kmfs may extend to depth and link with the subducted pacific plate

seismic imaging of the alpine fault near inchbonnie new zealand 1 the transpressive alpine fault is the boundary between the pacific and australian plates across the south island of new zealand earthquakes on the alpine fault and related structures pose a serious risk to many urban centers including the city of christchurch although it is a major feature on satellite images the alpine fault is a difficult target for surface studies along much of its length it mostly traverses densely forested and mountainous terrain and where it occurs in the lowlands it is usually covered by recent sediments to investigate the alpine fault at a rare accessible location inchbonnie we have acquired high resolution seismic reflection data along five 380 1200 m long lines images produced from these data reveal a glacially overdeepened valley containing a thick sequence of diverse glacigenic sediments that have been disrupted by three en echelon strands of the principal alpine fault and several secondary fault strands based on their seismic facies the sedimentary sequence is interpreted to comprise basal lacustrine beds overlain successively by alluvial colluvial deposits that possibly include the remnants of large landslides deltaic fan units and braided river gravels whereas the principal alpine fault strands disrupt the entire post glacial sedimentary section and likely offset basement at depths up to 400 m most of the secondary faults either merge with the principal fault strands at shallow depths or are surficial features limited to the sedimentary section

possible source models for the 1855 wairarapa earthquake new zealand the magnitude 8 wairarapa new zealand earthquake of 1855 was associated with surface rupture along the wairarapa fault and regional uplift of the southwest of the north island forward elastic dislocation modelling shows that movement on a steeply dipping wairarapa fault alone cannot account for the recorded deformation data modelling of movement on the subduction interface that underlies the wellington region as well as the wairarapa fault also fails to produce a satisfactory ill to the data although a complex wairarapa fault model may be able to explain the deformation pattern if its location subsurface geometry and slip distribution could be independently constrained the best effort supported by available data a flexed model incorporating a left side step of 8 km at the surface incorrectly locates the deformation the best fit to the data is obtained from a listric wairarapa fault model involving rupture on 0 to 50 km width of the deeper part of the subduction interface the shallower pan of the subduction interface east of the wairarapa fault apparently did not rupture in 1855 and the uplift mechanism for the overlying aorangi range remains unexplained partitioning of strike slip and dip slip components of the relative plate motions may involve separate earthquakes seismological verification of listric fault rupture mechanisms is required to determine the plausibility of the listric model presented here because its implications arc that the 1855 earthquake did not completely account for the relative plate motion in the region

early cretaceous mineralizing activity in the st andreasberg ore district southwest harz federal republic of germany in the st andreasberg ore district southwest harz at some time between the main and subsequent stages of mineralization sensu wilke 1952 potassium feldspar adularia was formed hydrothermally based on isotopic dating rb sr 40ar 39ar the formation of this mineral is ascribed to the early cretaceous thus part of the st andreasberg mineralization is proved to have been formed in the late mesozoic the mineralization process forming feldspar does not coincide with magmatic phases of the area

seismic gap hypothesis ten years after the seismic gap hypothesis states that earthquake hazard increases with time since the last large earthquake on certain faults or plate boundaries one of the earliest and clearest applications of the seismic gap theory to earthquake forecasting was by mccann et al 1979 who postulated zones of high medium and low seismic potential around the pacific rim in the 10 years since there have been over 40 large m 7 0 earthquakes enough to test statistically the earlier forecast we also analyze another forecast of long term earthquake risk that by kelleher et al 1973 the hypothesis of increased earthquake potential after a long quiet period can be rejected with a large confidence the data suggest that contrary to these forecasts places of recent earthquake activity have larger than usual seismic hazard whereas the segments of the circum pacific belt with no large earthquakes in recent decades have remained relatively quiet the clustering of earthquake times does not contradict the plate tectonic model which constrains only the long term average slip rate not the regularity of earthquakes

factors affecting seismic moment release rates in subduction zones the amount of shallow seismic activity in subduction zones varies greatly from region to region we quantify this seismicity by calculating seismic moment release rates and seismic slip rates for 24 subduction zones to calculate the moment release we sum the seismic moment for all interplate thrust type events with surface wave magnitude ms 7 0 occurring from 1904 to 1980 we present a time history plot of the seismic moment release for each subduction zone these exhibit the differences in the seismic release patterns for subduction zones where the time window of our study is not representative the total moment release is corrected using information on repeat times the moment release rates are compared with various subduction parameters in order to determine which factors influence the degree of coupling these parameters include the age of the subducting lithosphere absolute velocities of the upper and subducting plates convergence velocity and length maximum depth and dip of the wadati benioff zone the moment release rate decreases as the age of the subducting lithosphere increases when the zones belonging to a single subducting plate are considered this age versus moment release relation is consistent for the zones in which the pacific cocos philippine sea and indian plates are subducting the moment release rates for the subduction zones in which the pacific plate is subducting are much higher than for zones of other plates with similar age the age versus moment release relation holds among the zones which belong to one subducting plate however zones with similar ages but belonging to different plates do not have the same moment release rates this suggests that within a single plate the age is the dominating factor affecting the strength of seismic coupling but that each plate as a whole has a characteristic moment release budget zones with retreating upper plates tend to have lower moment release rates the moment release rate does not increase with convergence velocity no simple relationship was found between these two parameters the moment release rate depends most clearly on the age of the subducting lithosphere and the absolute velocity of the upper plate these are the two independent subduction zone parameters among the variables considered the other variables depend on these two parameters

surface rupture earthquakes over the last 1000 years in the wellington region new zealand and implications for ground shaking hazard the wellington region is cut by five active right lateral strike slip faults wairarapa wellington ohariu shepherds gully pukerua and wairau faults that have average recurrence intervals of meter scale surface rupture that range from 500 years to 5000 years and lateral slip rates that range from 1 to 10 mm yr only the wairarapa fault has ruptured since european settlement since circa a d 1840 paleoseismological studies on these faults have allowed the compilation of a complete record of surface rupture events over the past 1000 years in the wellington region within this time period there does not appear to be any temporal clustering of surface rupture events on adjacent faults the m 8 a d 1855 wairarapa earthquake did not trigger rupture on any other fault in the region the most recent surface faulting event on the wellington fault 290 440 cal years b p cal years are calendar years before a d 1950 does not coincide with rupture of any other onland fault and over 300 years separate the timing of the second most recent rupture on the wellington fault 660 720 cal years b p and the most recent rupture of the ohariu fault 1060 1140 cal years b p the most recent rupture of the shepherds gully pukerua fault is probably older than that of the ohariu fault the apparent nonclustering of surface rupture earthquakes in the wellington region has been documented only for the on land strike slip faults there are other possible seismogenic sources in the region and thus important issues remain to be addressed regarding the history of large earthquakes in the wellington region 1 the seismogenic potential and earthquake recurrence interval of the subduction thrust beneath wellington is not known 2 the timing of rupture events on the offshore portion of the wairau fault is not known and 3 paleoseismic data are not available for the section of the wellington fault north of the wellington hutt valley segment estimates of earthquake hazard in the wellington region for all return times greater than 50 years that incorporate paleoseismicity data are between one and two modified mercalli mm intensity units higher than the hazard based solely on the historical seismicity catalog and the hazard is spatially more variable using a deterministic attenuation model the level of shaking hazard approaches near maximum values within a return time of 500 years largely reflecting the recurrence interval 500 770 years of surface rupture earthquakes on the wellington fault inclusion of a plausible model for magnitude 8 subduction zone earthquakes does not affect the level of mm intensity in wellington region at return times greater than 500 years but does make a small contribution to the hazard at return times between 50 and 500 years

sahke geophysical transect reveals crustal and subduction zone structure at the southern hikurangi margin new zealand 1 the seismic array hikurangi experiment sahke investigated the structure of the forearc and subduction plate boundary beneath the southern north island along a 350 km transect tomographic inversion of first arrival travel times was used to derive a well resolved 15 20 km deep p wave image of the crust the refracted phases and migrated reflection events image subducting slab geometry and crustal structure in the west australian plate moho depth decreases westward across the taranaki fault system from 35 to 28 30 km in the east subducted pacific plate oceanic crust is recognized to have a positive velocity gradient but becomes less distinct beneath the tararua ranges where the interface increases in dip at about 15 km depth from 15 this bend in the subducted plate is associated with vertical clusters in seismicity splay fault branching and low velocity high attenuation material that we interpret to be an underplated subduction sedimentary channel we infer that a step down in the decollement transfers slip on the plate interface at the top of a subduction channel to the oceanic crust and drives local uplift of the tararua ranges reflections from the wairarapa fault show that it is listric and soles into the top of underplated sediments which in turn abut the moho of the overriding plate at 32 km depth near the downdip end of the strongly locked zone the change in dip of the hikurangi subduction interface is spatially correlated with the transition from geodetically determined locked to unlocked areas of the plate interface

on the handling of uncertainties in estimating the hazard of rupture on a fault segment uncertainties in data and parameter values have often been ignored in hazard estimates based on historic and prehistoric records of rupture on fault segments a mixture of distributions approach is appropriate to handle uncertainties in parameters of recurrence time distributions estimated from the geological and historical earthquake record of a fault segment and a mixture of hazards approach is appropriate for data uncertainties and for uncertainties in parameters estimated from a set of similar faults the former approach admits updating of the distributions for uncertainty as time passes the aim is to present the hazard as a single value which takes account of both data and parameter uncertainties conditional only on modeling assumptions the proposed methods are described in detail for the exponential and lognormal recurrence time models for fault rupturing earthquakes and applied by way of illustration to selected fault segments namely the mojave segment of the san andreas fault california and the wellington hutt valley segment of the wellington fault new zealand

holocene paleoseismicity in the fold and thrust belt of the hikurangi subduction zone eastern north island new zealand abstract along the 500 km long eastern coastline of the north island new zealand there are at most seven distinct holocene marine terraces aged 7 ka b p or less the highest of the terraces is 27 m above present day mean sea level the coastal region is subdivided into fourteen distinct subregions based on radiocarbon ages of marine deposits overlying wave cut shore platforms and geographic distribution of similarly aged terraces holocene marine terraces are the result of uplift associated with large earthquakes co seismic deformation this conclusion is based on characteristic stepped terrace morphology clustering of ages of terrace deposits within subrogions and the occurrence of co seismic uplift in historic time differential uplift across structures and distinct age variations at subregion boundaries are also characteristic recurrence intervals of uplift in any one terrace sequence vary from 0 4 ka to 2 0 ka and individual amounts of uplift vary from 1 0 m to 4 0 m in the past 2 5 ka ages from all terraces within subrogions indicate at least 21 paleoseismic events affecting coastal areas of eastern north island in that period these events cluster in time and in separate parts of eastern north island several earthquakes occurred 0 3 0 6 1 0 1 5 2 1 and 2 3 ka b p our data strongly support the concept of segmentation of deformation along the subduction margin the likely cause of coastal uplift is movement on steep reverse faults local structures rather than the subduction thrust that propagate from or near the subduction thrust some 20 25 km below the region earthquakes of moment magnitude 7 3 8 0 are estimated to be associated with these fault movements

stratigraphic architecture and fault offsets of alluvial terraces at te marua wellington fault new zealand revealed by pseudo 3d gpr investigation 1 past earthquake slips on faults are commonly determined by measuring morphological offsets at current ground surface because those offsets might not always be well preserved we examine whether the first 10 m below ground surface contains relevant information to complement them we focus on the te marua site new zealand where 11 alluvial terraces have been dextrally offset by the wellington fault we investigated the site using pseudo 3d ground penetrating radar and also produced a high resolution digital elevation model dem of the zone to constrain the surface slip record the gpr data reveal additional information 1 they image the 3d stratigraphic architecture of the seven youngest terraces and show that they are strath terraces carved into graywacke bedrock each strath surface is overlain by 3 5 m of horizontally bedded gravel sheets including two pronounced and traceable reflectors 2 thanks to the multilayer architecture terrace risers and channels are imaged at three depths and their lateral offsets can be measured three to four times constraining respective offsets and their uncertainties more reliably and 3 the offsets are better preserved in the subsurface than at the ground surface likely due to subsequent erosion deposition on the latter from surface and subsurface data we infer that te marua has recorded six cumulative offsets of 2 9 7 6 18 23 2 26 and 31 m 1 2 m large earthquakes on southern wellington fault might produce 3 5 m of slip slightly less than previously proposed pseudo 3d gpr thus provides a novel paleoseismological tool to complement and refine surface investigations

derivation of direct on fault submarine paleoearthquake records from high resolution seismic reflection profiles wairau fault new zealand direct on fault submarine paleoearthquake records can be derived from high resolution seismic reflection profiles of active fault growth sequences coseismic vertical increments of displacement are best preserved in the architecture of the growth sequence when the long term rate of sedimentation exceeds the rate of fault vertical displacement postseismic stratigraphic intervals can be recognized on vertical displacement history curves from which estimates of the earthquake timing and vertical displacements can be made the strike slip wairau fault is a major seismic hazard in central new zealand and is partially submarine analysis of 10 high resolution seismic profiles spanning a 20 km section of the offshore fault trace reveals two types of postseismic growth sequences and a composite paleoearthquake record with up to eight surface rupturing earthquakes since 18 ka the recurrence intervals range from 0 9 to 3 8 ka mean is 2 2 ka while the coseismic vertical displacements range from 0 5 to 5 3 m mean is 2 5 m these data conform to the variable slip model of earthquake behavior the vertical coseismic displacement is not always predictable from the recurrence interval preceding the event the data indicate that the seismic moment release has not been constant between earthquakes or that the ratio of horizontal to vertical coseismic displacement at a given site has varied over multiple earthquake cycles the offshore data are consistent with onshore paleoearthquake records long term dextral slip rate of 2 mm yr compared to 3 5 mm yr 40 km in land and paleoearthquakes of mw 7 5 the last earthquake occurred on the fault 2 0 0 3 kyr ago indicating that significant elastic strain has now accrued

detection of large holocene earthquakes using diatom analysis of coastal sedimentary sequences wellington new zealand abstract paleoenvironmental reconstructions of three coastal waterbodies in wellington new zealand reveal that sites were isolated from the sea within the last 7500 years through coseismic uplift and barrier growth evidence for coseismic uplift consists of distinct transitions in diatom assemblages representing large changes in relative sea level or water table level commonly in association with sedimentological evidence for catchment disturbance or marine influx transitions are abrupt laterally extensive and synchronous within each waterbody amount of change across transition horizons is assessed using quantitative estimates of paleosalinity and waterbody type as proxies for relative sea level change seven transitions involve large paleoenvironmental changes and provide evidence for earthquakes occurring at approximately 5100 3200 recorded at two sites 2300 recorded at two sites 1000 cal years bp and 1855 ad five other transitions involve smaller paleoenvironmental changes and are considered to be consistent with effects of earthquakes but do not provide independent evidence for earthquake occurrence these smaller transitions occur at approximately 6800 3600 2200 1000 coincident with a large transition and 500 cal years bp the data refine ages and provide information about the extent and effects of past large earthquakes in the region these are the first paleoecologically derived earthquake signatures for wellington and they contribute to the sparse collection worldwide of off fault sedimentary earthquake records for predominantly strike slip faults

long term earthquake clustering summary we analyse statistically the long term properties of several instrumental earthquake catalogues complete catalogues exhibit both short and long term clustering for earthquakes of all depth ranges after accounting for the effect of short term clustering we find that in residual declustered catalogues long term clustering not periodicity characterizes the occurrence of all earthquakes shallow intermediate and deep the degree of clustering in residual catalogues is the same for earthquakes in different depth ranges circumstantial evidence indicates that the long term v ariation of seismicity is governed by a power law temporal distribution as in short term clustering it is scale invariant the fractal dimension of an earthquake set on the time axis is of the order of 0 8 0 9 therefore mainshock occurrence is closer to a stationary poisson process than standard aftershock sequences of shallow earthquakes

dating the itabira iron formation quadrilatero ferrifero of minas gerais brazil at 2 65 ga depositional u pb age of zircon from a metavolcanic layer abstract uranium pb dating of zircon from a metavolcanic layer within the itabira iron formation or caue itabirite quadrilatero ferrifero of minas gerais brazil indicates that its deposition occurred at 2 65 ga i e considerably earlier than proposed by previous geochronological studies which suggested deposition between 2 58 ga detrital zircon age from the underlying moeda formation and 2 42 ga pb pb isochron age from dolomitic rocks of the immediately overlying gandarela formation the new age has major implications for the geology of the quadrilatero ferrifero and connects it with the neoarchaean iron formation of the carajas mineral province

tests of the precursory accelerating moment release model using a synthetic seismicity model for wellington new zealand 1 we have constructed a synthetic seismicity model of the wellington region new zealand including seven superfaults and 500 subfaults which are randomly positioned from this model a synthetic catalogue of 2000 years duration containing events of magnitude 5 0 or more has been generated the properties of the catalogue such as the long term slip rates b value average activity rate and hypocenter distribution are in accord with paleoseismic studies and the real seismicity over the last 40 years such a synthetic catalogue can replace the short incomplete and inhomogeneous historic and instrumental records in research which needs a long time duration and many strong shocks we have used our catalogue to examine tests for the existence of accelerating moment release amr before large events and compared the results with those from random poisson catalogues we find that 1 the apparent success rate is very dependent on the rules used to define the test window 2 when appropriately defined the amr pattern occurs before about 20 of the strong m 7 0 shocks with a typical precursor time of about 22 years 3 the amr pattern is found almost equally frequently before large events in random catalogues and 4 there are some false alarms amr pattern without a large event this extended study reinforces the conclusion in our preliminary report that in synthetic catalogues of the kind we have constructed the amr pattern is essentially an artefact of the method of sampling

a new 14 c age for the oruanui wairakei eruption new zealand the oruanui eruption was the largest known outburst of taupo volcano new zealand and is among the larger quaternary eruptions documented the eruption deposits are variously known as the oruanui wairakei kawakawa tephra or aokautere ash formations and represent a bulk volume probably exceeding 500 km 3 four new 14 c age determinations on carbonized vegetation in the non welded oruanui ignimbrite are combined to give a conventional age of 22590 230 yr b p compared with the previously accepted figure of 20000 yr b p this new age resolves the anomaly of apparently older 14 c ages being obtained from a demonstrably younger new zealand deposit and strengthens correlation of this eruption with an antarctic ice core acid anomaly the trace of this eruption has great potential as a time plane marker in the antarctic just prior to the last glacial maximum the close similarity in ages between the oruanui and a comparable sized eruption ito aira tn in japan suggests that this period of activity may represent the best chance of resolving any linkages between large scale explosive silicic volcanism and climate changes

a more precise chronology of earthquakes produced by the san andreas fault in southern california improved methods of radiocarbon analysis have enabled us to date more precisely the earthquake ruptures of the san andreas fault that are recorded in the sediments at pallett creek previous dates of these events had 95 confidence errors of 50 100 calendar years new error limits are less than 23 calendar years for all but two of the dated events this greater precision is due to larger sample size longer counting time lower background noise levels more precise conversion of radiocarbon ages to calendric dates and better stratigraphic constraints and statistical techniques the new date ranges with one exception fall within the broader ranges estimated previously but our estimate of the average interval between the latest 10 episodes of faulting is now about 132 years variability about the mean interval is much greater than was suspected previously five of the nine intervals are shorter than a century three of the remaining four intervals are about two to three centuries long despite the wide range of these intervals a pattern in the occurrence of large earthquakes at pallett creek is apparent in the new data the past 10 earthquakes occur in four clusters each of which consists of two or three events earthquakes within the clusters are separated by periods of several decades but the clusters are separated by dormant periods of two to three centuries this pattern may reflect important mechanical aspects of the fault s behavior if this pattern continues into the future the current period of dormancy will probably be greater than two centuries this would mean that the section of the fault represented by the pallett creek site is currently in the middle of one of its longer periods of repose between clusters and sections of the fault farther to the southeast are much more likely to produce the next great earthquake in california the greater precision of dates now available for large earthquakes recorded at the pallett creek site enables speculative correlation of events between paleoseismic sites along the southern half of the san andreas fault a history of great earthquakes with overlapping rupture zones along the mojave section of the fault remains one of the more attractive possibilities

temporal variations in latest quaternary slip across the australian pacific plate boundary northeastern south island new zealand rates of latest quaternary slip from stream terraces and moraines displaced by faults of the alpine shear system in ne south island new zealand vary in space and time detailed histories of fault slip are obtained from combining displacement data with estimates of the age of the surface from weathering characteristics precision in surface ages is 5 20 using rock weathering rinds and 15 50 using soil properties the oldest surfaces examined are 15 20 ka and have right lateral fault offsets up to 400 600 m the main faults of the in the ne south island the wairau awatere clarence hope kekerengu and porters pass faults have average latest quaternary right lateral slip rates of 3 10 5 10 7 10 25 40 5 7 and 3 4 mm yr respectively every fault has undergone a substantial decrease in lateral slip rate in the last 3 5 kyr summed across the plate boundary the average latest quaternary slip rates are comparable to long term rates of horizontal slip across the australian pacific plate boundary around 40 mm yr parallel to the boundary and rates of geodetic strain and seismic moment release over the last 50 100 years approximately the same however sums of lateral fault slip rates over the interval from 15 to 5 ka exceed the plate motions whereas late holocene lateral fault slip rates are less than half the long term average the best explanation of these variations is slip across the plate boundary is episodic varying over perhaps 5 kyr intervals this implies that 15 20 kyr is the time interval necessary to average out shorter 5 kyr episodic variations in plate boundary motions

seismic driving of nationwide changes in geomorphology and prehistoric settlement a 15th century new zealand example abstract we propose a model for the seismic driving of environmental changes and illustrate it using a case study from new zealand dated to the 15th century ad a seismic staircase shows a chronological progression of environmental outcomes that includes tsunami rock avalanches vegetation disturbance rapid coastal dune building river aggradation and abandonment of prehistoric coastal settlements the 15th century event appears to be unique in the past millenium and is most notable for its period of rapid coastal dune building the coincidence of a catastrophic el nino episode in the mid 15th century ad may have served to move sediments rapidly through the terrestrial system thus delimiting clearly separate geomorphological after effects we contend that seismic driving is a major factor in determining paleoenvironmental change in tectonically active areas during the holocene and provides the palaeoenvironmental context within which smaller scale events operate

consideration and propagation of epistemic uncertainties in new zealand probabilistic seismic hazard analysis this article presents results from the consideration of epistemic uncertainties in new zealand nz probabilistic seismic hazard analysis uncertainties in ground motion prediction are accounted for via multiple ground motion prediction equations within the logic tree framework uncertainties in the fault based seismicity of the earthquake rupture forecast due to uncertainties in fault geometry slip parameters and magnitude scaling relationships are considered in a monte carlo simulation framework because of the present lack of fault specific data quantifying uncertainties for many faults in nz representative values based on judgement and available data for nz and foreign faults were utilized uncertainties in the modelling of background seismicity were not considered the implications of the considered epistemic uncertainties in terms of earthquake magnitude frequency distributions and probabilistic seismic hazard analyses for two spectral acceleration ordinates two soil classes and two locations wellington and christchurch are examined the results illustrate that for the uncertainties considered the variation in seismic hazard due to the adopted ground motion prediction model is larger than that due to the uncertainties in the earthquake rupture forecast of the earthquake rupture forecast uncertainties considered the magnitude geometry scaling relationships was the most significant followed by fault rupture length hence the obtained results provide useful guidance on which modelling issues are the most critical in the reliability of seismic hazard analyses for locations in nz

seismic strain release in the mexican subduction thrust abstract in this paper the seismic strain release in the mexican subduction zone is discussed the paper is based on a revised catalog of large earthquakes in mexico new in this catalog are estimates of the seismic moment for many of the larger pre 1962 earthquakes of this century based on instrumental recordings from uppsala sweden a regression between moment and magnitude is established and used to estimate moments for the remaining events of this and the previous century the envelopes of the cumulative seismic moment curves can thus be developed consistent with the nineteenth century seismicity these indicate that the guerrero region is currently the most likely within the mexican subduction zone to experience one great event or several large events with a moment deficit approaching 20 10 27 dyn cm this is comparable with the moment released between 1899 and 1912 in the region in guerrero and also perhaps in michoacan the seismic strain release is consistent with plate tectonic expectations for a seismogenic zone 50 km in width in oaxaca either the seismogenic zone is much narrower and there is considerable aseismic slip or events to rupture the downdip extremes of the subduction zone have not occurred so far this century this last alternative arises because in guerrero the 1907 and 1957 earthquakes have relatively strong 40 s surface waves recorded at uppsala compared with all the other events such events which we infer are deeper present new problems for seismic hazard estimation in mexico since they are not represented in the available strong motion records

the chemical composition of specular hematite from tilkerode harz germany implications for the genesis of hydrothermal hematite and comparison with the quadrilatero ferrifero of minas gerais brazil the black shale hosted selenide vein type deposit at tilkerode eastern harz germany has specular hematite enclosed in clausthalite pbse the specular hematite has ti and v in amounts of up to 1 wt tio2 and 3 wt v2o5 and subordinate but important contents of mo 22 372 ppm and b up to 68 ppm the tilkerode hematite serves as a reference for hydrothermal hematite formed at relatively low temperatures 150 c the composition of the tilkerode hematite is compared with that of two generations of specular hematite from itabirite hosted iron ore deposits in the quadrilatero ferrifero of minas gerais brazil the first generation of specular hematite represents an early tectonic hematitisation of dolomitic itabirite at aguas claras and occurs as fine grained crystals reconnaissance data indicate that the aguas claras hematite is poorer in ti and v relative to the tilkerode hematite but has 5 10 ppm b and 7 11 ppm li the second generation of specular hematite defines the pervasive tectonic foliation of the gongo soco iron ore this hematite has ti contents of up to 2 wt tio2 and subordinate amounts of v 62 367 ppm its b and li concentrations are mostly below 2 ppm b and 1 ppm li the presence of ti and b in the tilkerode hematite can be explained by highly saline b bearing fluids that were capable of mobilising otherwise immobile ti the mo signature of the tilkerode hematite suggests that mo was derived from the host black shale in minas gerais b and li were incorporated into the early tectonic hematite from saline fluids at relatively low temperatures aguas claras and then released during metamorphic hematite growth at higher temperatures as suggested by the foliation defining hematite without b li signature gongo soco

evidence from gps measurements for contemporary interplate coupling on the southern hikurangi subduction thrust and for partitioning of strain in the upper plate the spatial extent and strength of contemporary coupling between the pacific and australian plates on the hikurangi subduction interface beneath the wellington region of new zealand are not well known consequently the potential for the plate interface to produce great thrust earthquakes or to load the major wellington and wairarapa faults in the overlying plate is also unknown to address these issues a gps network across the southern north island has been partially or wholly surveyed six times between 1992 and 1999 and yields well determined relative velocities between 82 points the relative velocity of the east coast with respect to the west coast across the 80 km width of the southern end of the north island is 14 mm yr 1 at an azimuth of 258 this is about one third of and closely parallel to the nuvel 1a relative velocity of the pacific with respect to the australian plate 39 4 mm yr 1 at 261 strain rate solutions indicate partitioning of contemporary strain with a 35 change in principal axis orientations across the network using elastic dislocation theory an inversion of the observed point velocities and their full variance covariance matrix determines the variation with depth of contemporary coupling at the subduction interface if uniform coupling is assumed then 100 coupling occurs from very shallow depths down to 29 1 km however if variable coupling is assumed it reaches 100 at depths between 16 and 24 km at greater depths there is a transition zone at least 20 km wide down to a depth of at least 40 km over which contemporary coupling diminishes to zero these depth ranges correlate moderately well with low angle thrust focal mechanisms recently obtained by other workers and indicate that the downdip width of the interface over which a great thrust earthquake could occur exceeds 100 km elastic dislocation models also explain the observed partitioning of strain with coulomb stress calculations indicating that the wairarapa fault is being loaded at seismogenic depths

location and geometry of the wellington fault new zealand defined by detailed three dimensional georadar data 1 earthquakes with surface wave magnitudes of 7 3 7 9 are estimated to be associated with the rupture of the wellington fault at relatively regular intervals of 500 770 years the last such earthquake probably happened between ad 1510 and 1660 along its southern segment the wellington fault passes through wellington new zealand s capital and the densely populated hutt valley it is considered to be a highly hazardous structure to map the shallow geometry of the wellington fault we have collected 3 d ground penetrating radar georadar data at two sites along the fault in the hutt valley at one site the first ever georadar fault plane reflections from an active strike slip fault are observed they coincide with conspicuous diffractions generated by abrupt truncations of structures against the fault plane these georadar data provide the most vivid shallow images of any active fault surveyed to date at the second site apparent offsets of lineaments in the sedimentary sections on either side of the fault are consistent with 20 m of dextral displacement estimated from the offset of a nearby terrace riser the dips and minimum depth extents of the primary zones of fault displacement at the two sites are 55 75 se and 20 m and 72 84 se and 12 m respectively although the georadar defined zones of faulting are a few meters wide prominent reflection fabrics suggest that shearing fracturing and crushing extend for several tens of meters on either side of the fault

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

geometry and scale of fault segmentation and deformational bulging along an active oblique slip fault wairarapa fault new zealand the active dextral reverse wairarapa fault in the north island new zealand cuts ca 12 ka post last glacial maximum post lgm fluvial gravels with a highly segmented fault trace this

active upper plate thrust faulting in regions of low plate interface coupling repeated slow slip events and coastal uplift example from the hikurangi margin new zealand 1 contractional fore arc faulting and deformation is a characteristic feature of many subduction systems definition of the three dimensional geometry and displacement rates of active upper plate out of sequence thrust faults along 250 km of the upper hikurangi margin enables us to examine the relationship between fore arc deformation and the subduction interface in light of interseismic coupling estimates and distribution of slow slip events both modeled from gps measurements these mid fore arc structures include the seaward vergent outer shelf lachlan and ariel faults with vertical separation rates up to 5 mm yr and several other major inner shelf faults with rates that are up to 3 8 mm yr and comparable with holocene coastal uplift rates seismic reflection imaging and geometric projection of these faults at depth indicate that they splay from the region of the plate interface where geodetic inversions for interseismic coupling and slow slip events suggest that the plate boundary undergoes aseismic slip this observation may indicate either 1 that frictional properties and interseismic coupling on the plate interface are independent and unrelated to the active splay fault deformation in the inner middle fore arc or 2 that the active splay faulting reflects long term mechanical coupling related to higher shear stress or the relative yield strength of the plate interface to the overriding plate and that the current pattern of interseismic coupling may not be persistent over geological time scales of 20 ka we compare structure and processes on the northern hikurangi and costa rican margins and find similarities and significant differences astride these subduction systems

late quaternary paleoseismic history and surface rupture characteristics of the eastern awatere strike slip fault new zealand the recurrence and magnitude of paleo earthquakes on the eastern section of the dextral strike slip awatere fault 105 km long are determined from stratigraphic evidence in a fault trench and measurement of fault displaced geomorphic features we identify at least six ground rupturing events younger than 8330 8610 yr the youngest being a historically recorded mw 7 5 event in a d 1848 that ruptured the entire eastern section the maximum mean recurrence interval is 1 4 k y although repeat intervals range from 605 235 to 2500 600 yr the smallest fault offsets on the easternmost 27 km of the onshore part of the fault indicate a mean strike slip displacement of 4 9 m during the 1848 event the second smallest offsets are approximately double the smallest displacements suggesting that the last two events were ruptures of comparable dimensions 105 km and magnitude because the awatere fault terminates 20 km northeast of the study area the penultimate rupture probably extended inland perhaps rupturing the entire eastern section further evidence of characteristic earthquake behavior is preserved in the fault trench where a regular event subsidence of 50 cm per event is indicated during the last two events a slip maximum of 7 1 m occurred on a 5 5 km long fault subsection consisting of adjacent restoring and releasing fault bends these bends define a 1 km wide side step in the fault that although of short wavelength apparently strongly influences the amount of coseismic slip and moment release new data on the age of late quaternary alluvial surfaces in the awatere valley when combined with observed horizontal displacements indicate that strike slip has accrued on the awatere fault at a constant rate of 6 mm yr for at least the past 20 k y

quaternary deformation along the wharekauhau fault system north island new zealand implications for an unstable linkage between active strike slip and thrust faults 1 the southern wairarapa region of the north island of new zealand preserves a variably deformed late quaternary stratigraphic sequence that provides insight into the temporal variability in the partitioning of contraction onto faults in the upper plate of an obliquely convergent margin detailed mapping stratigraphic data and new radiocarbon and optically stimulated luminescence ages from quaternary units reveal the interaction between tectonics and sedimentation from 125 ka to 9 ka along the wharekauhau thrust and related faults i e wharekauhau fault system at the southern end of the wairarapa fault zone a major oblique slip fault in the upper plate of the hikurangi margin the wharekauhau thrust accommodated a minimum of 280 60 m of horizontal shortening from 70 to 20 ka the inferred shortening rate 3 5 8 4 mm yr may have accounted for 11 30 of margin normal plate motion by 20 ka the thrust was abandoned subsequent deformation at shallow levels occurred on a segmented fault system that accommodated 1 mm yr shortening active deformation in the region is partitioned between slip on 1 the more western wairarapa mukamuka fault system dominantly dextral slip but also causing local uplift of the coast 2 a series of discontinuously expressed strike slip faults and linking blind oblique reverse thrusts near the trace of the inactive wharekauhau thrust and 3 a blind thrust fault farther to the east the spatial and temporal complexity of the wharekauhau fault system and the importance it has had in accommodating upper plate deformation argue for an unsteady linkage between upper plate faults and between these faults and the plate interface

terminations of large strike slip faults an alternative model from new zealand the 500 km long strike slip north island fault system nifs intersects and terminates against the taupo rift both fault systems are active with strike slip displacement transferred into the rift without displacing normal faults along the rift margin data from displaced landforms fault trenching gravity and seismic reflection profiles and aerial photograph analysis suggest that within 150 km of the northern termination of the nifs the main faults in the strikeslip fault system bend through 258 splay into five principal strands and decrease their mean dip these changes in fault geometry are accompanied by a gradual steepening of the pitch of the slip vectors and by an anticlockwise swing up to 508 in the azimuth of slip on the faults in the nifs as a consequence of the bending of the strike slip faults and the changes in their slip vectors near their intersection the slip vectors on the two component fault systems become subparallel to each other and to their mutual line of intersection this subparallelism facilitates the transfer of displacement from one fault system to the other accounting for a significant amount of the ne increase of extension along the rift whilst maintaining the overall coherence of the strike slip termination changes in the slip vectors of the strike slip faults arise from the superimposition of rift orthogonal differential extension outside the rift margin resulting in differential motion of the footwall and hanging wall blocks of each fault in the nifs the combination of rift orthogonal heterogeneous extension dip slip and strike slip results in a steepening of the pitch of the slip vectors on the terminating fault system slip vectors on each splay close to their terminations are therefore the sum of strike slip and dip slip components with the total angle through which the pitch of the slip vectors steepens being dependent on the relative values of both these two component vectors in circumstances where interaction of the velocity fields for the intersecting fault systems cannot resolve to a slip vector that is boundary coherent either rotation about vertical axes of the terminating fault relative to the through going fault system may take place to accommodate the termination of the strike slip fault system or the rift may be offset by the strike slip fault system rather than terminating into it at the termination of the nifs an earlier phase of such rotations may have produced the 258 anticlockwise bend in fault strike and contributed up to about one third of the anticlockwise deflection in slip azimuth on the terminating strike slip nifs therefore rotational and nonrotational termination mechanisms have both played a role but at different times in its evolution as the thermal structure the rheology and the thickness of the crust in the rift intersection region

temporal stability of deformation rates comparison of geological and geodetic observations hikurangi subduction margin new zealand abstract we examine how well contemporary horizontal velocity fields from global positioning system gps geodetic measurements describe long term deformation rates million year rates of extension shortening strike slip and vertical axis rotations are compared with modelling of gps velocities from the last 10 15 years in the hikurangi subduction margin new zealand within measurement uncertainties of mainly 50 the rates of deformation and vertical axis rotations for each time interval are usually indistinguishable the comparable deformation rates are consistent with the notion of near constant rates since 1 5 ma during this time oblique relative plate motion was partitioned with the majority 85 of margin normal motion accommodated on the plate interface and most 60 margin parallel motion by strike slip faulting and vertical axis rotations in the upper plate prior to 1 5 ma gps velocities cannot be reliably used to describe deformation and rotations of the hikurangi margin because at this time the taupo rift commenced opening the boundary between raukumara and wairoa rotational domains was abandoned and the rates of upper plate shortening increased the broad compatibility of gps and geological deformation and rotation rates since 1 5 ma suggests that the build up of contemporary elastic strains in the north island measured by gps is largely uniform for much of the duration of each seismic cycle the good agreement between the gps and geological deformation rates in the north island is consistent with the view that contemporary elastic strains will mainly be converted to permanent dip slip on the subduction thrust and to displacement on upper plate faults during future large magnitude earthquakes

balancing the plate motion budget in the south island new zealand using gps geological and seismological data summary the landmass of new zealand exists as a consequence of transpressional collision between the australian and pacific plates providing an excellent opportunity to quantify the kinematics of deformation at this type of tectonic boundary we interpret gps geological and seismological data describing the active deformation in the south island new zealand by using an elastic rotating block approach that automatically balances the pacific australia relative plate motion budget the data in new zealand are fit to within uncertainty when inverted simultaneously for angular velocities of rotating tectonic blocks and the degree of coupling on faults bounding the blocks we find that most of the plate motion budget has been accounted for in previous geological studies although we suggest that the porter s pass amberley fault zone in north canterbury and a zone of faults in the foothills of the southern alps may have slip rates about twice that of the geological estimates up to 5 mm yr 1 of active deformation on faults distributed within the southern alps 100 km to the east of the alpine fault is possible the role of tectonic block rotations in partitioning plate boundary deformation is less pronounced in the south island compared to the north island vertical axis rotation rates of tectonic blocks in the south island are similar to that of the pacific plate suggesting that edge forces dominate the block kinematics there the southward migrating chatham rise exerts a major influence on the evolution of the new zealand plate boundary we discuss a model for the development of the marlborough fault system and hikurangi subduction zone in the context of this migration

extremely high solubility of rutile in chloride and fluoride bearing metamorphic fluids an experimental investigation rutile tio 2 is an important high field strength element sequestering phase and thus understanding its solubility in metamorphic fluids is important if we are to understand terrestrial trace element cycling titanium is often assumed to be fluid immobile and previous experimental data suggest that rutile has very low solubility in h 2 o however fluids in high temperature metamorphic rocks are known to be more complex in composition the solubility of rutile in chloride and fluoride rich hydrous fluids was determined experimentally at 0 5 gpa and high temperatures the experimental results indicate much higher rutile solubility in brines compared to pure h 2 o in chloride brines solubility was 2 4 times higher than in h 2 o and in fluoride brines solubility was elevated 20 100 times the results imply that titanium may be much more mobile in metamorphic fluids than previously anticipated as solubility is critically dependent on fluid chemistry we also present a possible mechanism for rutile precipitation in metamorphic veins due to a change in fluid chemistry following the precipitation of halogen rich minerals such as apatite

changes in state of stress on the southern san andreas fault resulting from the california earthquake sequence of april to june 1992 the april to june 1992 landers earthquake sequence in southern california modified the state of stress along nearby segments of the san andreas fault causing a 50 kilometer segment of the fault to move significantly closer to failure where it passes through a compressional bend near san gorgonio pass the decrease in compressive normal stress may also have reduced fluid pressures along that fault segment as pressures are reequilibrated by diffusion that fault segment should move closer to failure with time that fault segment and another to the southeast probably have not ruptured in a great earthquake in about 300 years

national seismic hazard model for new zealand 2010 update a team of earthquake geologists seismologists and engineering seis mologists has collectively produced an update of the national probabilistic seismic hazard psh model for new zealand national seismic hazard model or nshm the new nshm supersedes the earlier nshm published in 2002 and used as the hazard basis for the new zealand loadings standard and numerous other end user applica tions the new nshm incorporates a fault source model that has been updated with over 200 new onshore and offshore fault sources and utilizes new new zealand based and international scaling relationships for the parameterization of the faults the dis tributed seismicity model has also been updated to include post 1997 seismicity data a new seismicity regionalization and improved methodology for calculation of the seismicity parameters probabilistic seismic hazard maps produced from the new nshm show a similar pattern of hazard to the earlier model at the national scale but there are some significant reductions and increases in hazard at the regional scale the national scale differences between the new and earlier nshm appear less than those seen between much earlier national models indicating that some degree of consis tency has been achieved in the national scale pattern of hazard estimates at least for return periods of 475 years and greater online material table of fault source parameters for the 2010 national seismic hazard model

metal enrichment in bitumens from carboniferous hosted ore deposits of the british isles abstract bitumens from hydrothermal ore deposits and from other mineral showings in the lower carboniferous of the british isles are enriched in metals the enrichments are evident as micrometre scale inclusions of metalliferous ore minerals within the bitumens the bitumens were derived from hydrocarbon source rocks within the carboniferous and the metals are assumed to be derived from hydrothermal fluids a regional survey showed that there is some correlation between the metals present as inclusions in the bitumens and the metals present in the related host ore deposits showings the results suggest that the metal geochemistry of bitumens may be of value in ore exploration

characterization of the shallow structures of active fault zones using 3 d ground penetrating radar data 1 where they can be correlated with geological exposures and trenches 3 d ground penetrating radar gpr data can contribute critical subsurface information to paleoseismic investigations because active faults are typically characterized by complicated near surface structures that vary with the styles of faulting and the types of rock that are ruptured gpr data can be difficult to interpret we have acquired 3 d gpr data sets across three active fault zones within new zealand that have different deformation styles the strike slip wellington fault zone reverse faults of the ostler fault zone and normal faults of the maleme fault zone to improve our interpretation of the processed gpr volumes we employed two suites of geometric attributes the first suite was computed using a coherence based algorithm it provided estimates of the coherency azimuth and dip of reflections the second suite quantified the volumetric textures of reflections which allowed different reflection facies to be defined objectively we have demonstrated how some attributes were more successful at visualizing certain structural or depositional characteristics than others for example the coherency attribute was an excellent tool for highlighting normal faults within volcanic deposits of the maleme fault zone whereas the texture based attributes were most useful for discriminating between the gravel and metasediment units juxtaposed by the wellington fault zone our gpr data sets and associated attribute volumes showed details of near surface fault geometry that were not obvious from surface mapping and they revealed evidence of off fault deformation gravitational collapse and topple structures