thrust fault growth and segment linkage in the active ostler fault zone new zealand abstract thrust faulting is a fundamental mode of crustal deformation yet many of the key geometrical attributes of thrust faults and the controls on fault rupture growth and linkage remain poorly resolved numerous surface rupturing thrust faults cut through upper quaternary glacial outwash terraces within the ostler fault zone an active thrust system in the southern alps new zealand we use these deformed marker surfaces to define the three dimensional deformation field associated with their surface expression and to map displacement and length on 40 fault segments displacement transfer across two fault segment arrays occurs in distinctly different styles in one displacement is transferred between en echelon fault segments to produce a smooth linear displacement gradient in the other large scale folding and a population of small faults transfer displacement between two non overlapping fault segments with a residual displacement minimum within the transfer zone size distribution of fault segment length and maximum displacement follow a power law scaling relationship maximum displacement d max scales linearly with and represents 1 of segment trace length l d max l data from the segments of the ostler fault zone display similar scaling to a global fault dataset this similarity is surprising given that the observed displacements along the ostler fault represent only 20 ky of slip on fault segments that are likely to be many times older

underwater observations of active lava flows from kilauea volcano hawaii underwater observation of active submarine lava flows from kilauea volcano hawaii in march june 1989 revealed both pillow lava and highly channelized lava streams flowing down a steep and unconsolidated lava delta the channelized streams were 0 7 1 5 m across and moved at rates of 1 3 m s the estimated flux of a stream was 0 7 m 3 s jets of hydrothermal water and gas bubbles were associated with the volcanic activity the rapidly moving channelized lava streams represent a previously undescribed aspect of submarine volcanism

a geomorphological reconnaissance of the submarine part of the east rift zone of kilauea volcano hawaii more than half of the intensely active east rift zone of kilauea volcano crops out underwater along the crest of the submarine puna ridge i present multibeam bathmetry of the entire ridge near bottom photographic and sonar observations of the plunging crest of its deeper distal half and seismic profiles across the ridge tip and the adjacent structural moat analysis of large scale relief small scale topography and superficial rock types indicates that the rift zone is actively propagating across the moat but is probably a superficial structure that does not penetrate the underlying oceanic crust that its tip is covered with large lava flows erupted at high rates and is surrounded with extensive debris flow deposits and that the axial topography at depths of 2 4 km is dominated by gaping fissures and collapse pits showing a preponderance of intrusive rather than extrusive events some aspects of this central volcano rift zone such as its geometry at small lateral offsets resemble those at interplate rift zones along fast spreading mid ocean rises but the great contrast in lithosphere thickness results in fundamental structural differences

volcanic spreading at kilauea 1976 1996 the rift system traversing about 80 km of the subaerial surface of kilauea volcano has extended continuously since the m 7 2 flank earthquake of november 1975 widening across the summit has amounted to more than 250 cm decelerating after 1975 from about 25 to 4 cm yr 1 since 1983 concurrently the summit has subsided more than 200 cm even as the adjacent south flank has risen more than 50 cm the axes of the upper zones about 10 km from the summit subsided before 1983 at average rates of 9 and 4 cm yr 1 respectively and at rates of 4 and 3 cm yr 1 since the middle southwest rift zone is also subsiding and at the other end of kilauea s subaerial rift system subsidence along the lower east rift zone has averaged 1 2 cm yr 1 deformation of kilauea s south flank has been continuous although subject as well to displacements caused by major rift zone seismic swarms whereas horizontal strains across the subaerial south flank seem to have been generally compressive after 1975 they have been extensional since about 1980 or 1981 interrupted only by the east rift zone dike intrusion of 1983 because the magnitudes of these contractions and extensions are much less than the extension across the rift system the subaerial south flank is apparently sliding seaward on its basal decollement more than it is accumulating horizontal strains within the overlying volcanic pile kilauea suffers from gravitational spreading made even more unstable by accumulation of magma along the rift system at depths in excess of about 4 5 km in the presence hot rock incapable of withstanding deviatoric stresses this seismicly quiescent zone decouples the south flank from the rest of hawaii s volcanic edifice the rift zones at lesser depths exhibit a more brittle and therefore sporadic extensional behavior judging from the modern extension record of the summit which both predates the m 7 2 earthquake of 1975 and has outlived its 10 year period of aftershocks kilauea will continue to spread along its rift system as its south flank slips seaward to accommodate the accretion of magma and its relatively dense olivine rich differentiate

early growth of kohala volcano and formation of long hawaiian rift zones transitional composition pillow basalts from the toe of the hilo ridge collected from outcrop by submersible have yielded the oldest ages known from the island of hawaii 1138 34 to 1159 33 ka hilo ridge has long been interpreted as a submarine rift zone of mauna kea but the new ages validate proposals that it is the distal east rift zone of kohala the oldest subaerial volcano on the island these ages constrain the inception of tholeiitic volcanism at kohala provide the first measured duration of tholeiitic shield building 870 k y for any hawaiian volcano and show that this 125 km long rift zone developed to near total length during early growth of kohala long eastern trending rift zones of hawaiian volcanoes may follow fractures in oceanic crust activated by arching of the hawaiian swell in front of the propagating hotspot

scaling properties of normal fault populations in the western corinth graben greece implications for fault growth in large strain settings abstract a variety of one dimensional and two dimensional map techniques of fractal analysis have been employed to investigate the scaling properties of the dominant wnw trending normal fault population of the western corinth graben in central greece to assess possible constraints on fault geometry during fault growth the data have been compiled separately from the northern and southern domains of the graben which have experienced differing amounts of finite strain based on power law distributions of the fault throw the applied extension is estimated at 30 and 22 for the northern and southern domains respectively however the fault spacing and fault length populations in both domains obey similar power law relationships these conclusions are also supported by maximum throw vs trace length data which demonstrate that the faults in the northern domain have systematically higher values for the slip to length ratios than those in the southern domain it is proposed that the corinth graben has reached fracture saturation that is the fault spacing stops evolving and displacement increases rather than faults lengthening to accommodate the increasing extension this growth process consistent with throw distributions along individual faults may be explained either in terms of a stress feedback mechanism or by the mechanical interaction between the wnw trending normal faults with a set of nne trending transverse faults

what makes hydromagmatic eruptions violent some insights from the keanakāko i ash kilauea volcano hawai i abstract volcanic eruptions at the summit of kilauea volcano hawai i are of two dramatically contrasting types 1 benign lava flows and lava fountains and 2 violent mostly prehistoric eruptions that dispersed tephra over hundreds of square kilometers the violence of the latter eruptions has been attributed to mixing of water and magma within a wet summit caldera however magma injection into water at other volcanoes does not consistently produce widespread tephras to identify other factors that may have contributed to the violence of these eruptions we sampled tephra from the keanak ko i ash the most recent large hydromagmatic deposit and measured vesicularity bubble number density and dissolved volatile content of juvenile matrix glass to constrain magma ascent rate and degree of degassing at the time of quenching bubble number densities 9 10 4 1 10 7 cm 3 of tephra fragments exceed those of most historically erupted kilauean tephras 3 10 3 1 8 10 5 cm 3 and suggest exceptionally high magma effusion rates dissolved sulfur average 330 ppm and water 0 15 0 45 wt concentrations exceed equilibrium saturation values at 1 atm pressure 100 150 ppm and 0 09 respectively suggesting that clasts quenched before equilibrating to atmospheric pressure we interpret these results to suggest rapid magma injection into a wet crater perhaps similar to continuous uprush jets at surtsey estimates of reynolds number suggest that the erupting magma was turbulent and would have mixed with surrounding water in vortices ranging downward in size to centimeters such fine scale mixing would have ensured rapid heat exchange and extensive magma fragmentation maximizing the violence of these eruptions

incremental growth of normal faults insights from a laser equipped analog experiment we conducted a laser equipped analog experiment aimed at quasi continuously monitoring the growth of a dense population of normal faults in homogeneous conditions to further understand the way geological faults progressively gain in slip and length as they accumulate more strain we measured with great precision the incremental slip and length changes that the analog faults sustain as they grow these measurements show that the analog faults share common features with the natural ones in particular during their growth the faults develop and maintain cumulative slip profiles that are generally triangular and asymmetric the growth takes place through two distinct phases an initial short period of rapid lateral lengthening followed by a longer phase of slip accumulation with little or no lengthening the incremental slip is found to be highly variable in both space along the faults and time resulting in variable slip rates in particular short and long term slip rates are markedly different we also find that slip measurements at local points on fault traces do not contain clear information on the slip increment repeat mode finally while the fault growth process is highly heterogeneous when considered at the scale of a few slip events it appears homogeneous and self similar at longer time scales which integrate many slip increments this is likely to be the result of a feedback between stress heterogeneities and slip development the long term scale homogeneity also implies that the long term faulting process is primarily insensitive to the short term heterogeneities that are rapidly smoothed or redistributed we propose a new conceptual scenario of fault growth that integrates the above observations and we suggest that faults grow in a bimodal way as a result of a self driven and self sustaining process

experiments on shortening of a 4 layer model of the continental lithosphere davy ph and cobbold p r 1991 experiments on shortening of a 4layer model of the continental lithosphere in p r cobbold editor experimental and numerical modelling of continental deformation tecronophysics 188 l 25 we present an experimental method for modelhng lithospheric deformation the method is based on a simplified profile of lithosphere rheology where only four layers are considered brittle crust ductile crust brittle mantle and ductile mantle the strengths of the four layers calculated from laboratory determined flow laws depend strongly on geothenns and slightly on strain rates and deformation regimes the rheological profiles of the lithosphere have been recreated in experimental models built with analog materials sand silicone putty and golden syrup which flow under their own weight during lithospheric shortening the style of deformation depends on the relative strengths of the four layers especially those in the mantle of special importance is the existence or non existence of a brittle mantle the initial stages of compression often produce flexures or buckles without local isostatic compensation buckling exerts a strong control on the localisation of thrust faults in later stages the thrusts tend to form at the inflexion points of buckles the style of crustal thickening depends on the relative thicknesses and resistances of the lithospheric layers in 2 layer lithospheric models without resistant mantle shortening was concentrated upon a small number of thrusts widely spaced in 3 layer models shortening was concentrated into a large number of reverse faults more closely spaced and more steeply dipping than before in clayer models a single thrust formed in the brittle mantle motion on this thrust dragged the crustal layers down forming an asymmetric crustal root with steep imbricate slices

subsidence of puna hawaii inferred from sulfur content of drilled lava flows abstract sulfur was analyzed in more than 200 lava samples from five drill holes located on the east rift zone of kilauea volcano on the island of hawaii the sulfur content is a gage of whether lava was erupted subaerially low sulfur or erupted subaqueously high sulfur despite considerable variation sulfur is generally low less than 0 025 in the upper part of the holes begins to increase at a depth of 250 320 m below sea level and generally reaches a high level greater than 0 1 indicative of steady submarine eruption at 330 450 m below sea level assuming that the island is subsiding at 2 4 mm yr an analysis of these data indicates that part of the variation in sulfur concentration results from past eustatic oscillation of sea level and that the volcano at the drill hole site finally emerged for the last time about 98 ka the long term average rate of lava accumulation is roughly 4 4 mm yr and upward growth of the volcano at the drill hole area is about 2 mm yr in excess of subsidence

lateral propagation of the surface trace of the south alkyonides normal fault segment central greece its impact on models of fault growth and displacement length relationships abstract the evolution of deformed marine terraces and drainage systems have been examined in order to investigate the growth and lateral propagation of an active normal fault geological mapping has revealed three distinct raised marine terraces in the immediate footwall of the western end of the active south alkyonides fault segment safs gulf of corinth central greece we correlate these terraces with sea level highstands at 125 240 and 330 ka using elevation estimates of the inner edges of the terraces we show that uplift rates decrease towards the perachora fault segment boundary at the western end of the safs analysis of terraces and drainage wind gaps in the footwall of the fault shows that the surface trace of the safs propagated westwards at a rate of 12 1 16 7 mm y over at least the last 330 ka whilst the surface trace length has increased analysis of the geometry and kinematics of fault slip suggests that fault length at depth has remained fixed implying progressive increase in the values for the displacement length ratio if this is correct growth is not self similar and fault length has been established early in the evolution of the system i e before 330 ka

rapid deformation of kilauea volcano global positioning system measurements between 1990 and 1996 campaign global positioning system gps measurements from 1990 to 1996 are used to calculate surface displacement rates on kilauea volcano hawaii the gps data show that the south flank of the volcano which has generated several large earthquakes in the past 3 decades is displacing at up to 8 cm yr to the south southeast the summit and rift zones are subsiding with maximum subsidence rates of 8 cm yr observed a few kilometers south of the summit caldera elastic dislocation modeling of the gps data suggests that the active sources of deformation include deep rift opening along the upper east and east rift zone fault slip along a subhorizontal fault near the base of the volcano and deflation near the summit caldera a nonlinear optimization algorithm was used to explore the parameter space and to find the best fitting source geometry there is a broad range of model geometries that fit the data reasonably well however certain models can be ruled out including those that have shallow rift opening or shallow fault slip some offshore aseismic slip on a fault plane that dips between 258 north northwest and 88 south southeast is required best fitting slip and rift opening rates are 23 28 cm yr although rates as low as 10 cm yr are permitted by the data

submarine growth and internal structure of ocean island volcanoes based on submarine observations of mauna loa volcano hawaii a recent model for the submarine growth of hawaiian volcanoes indicates that these volcanoes are composed mainly of fragmental lava debris formed as lavas enter the ocean this model has major implications for locating earthquake hypocenters and for the landslide hazard potential of these and other ocean island volcanoes observations from submersible dives and analyses of volcanic glasses collected from the western submarine flank of mauna loa indicate that subaerially erupted pillow lavas are abundant at depths of 950 to 1900 m below sea level fragmental lava is an important component of ocean island volcanoes as witnessed during the most recent eruption of kilauea volcano but probably is the dominant lithology only in the upper 1 km of the submarine section a submarine dike complex was discovered 17 km west of the assumed axis of mauna loa9s southwest rift which indicates that its intrusive complex is much broader than previously suspected 20 km vs 8 km the great width of this dike complex may be a consequence of crustal unloading following the south kona landslide or a normal feature of hawaiian rift zones that was previously unrecognized

slope failure and volcanic spreading along the submarine south flank of kilauea volcano hawaii 1 new multichannel reflection data and high resolution bathymetry over the submarine slopes of kilauea volcano provide evidence for current and prior landsliding suggesting a dynamic interplay among slope failure regrowth and volcanic spreading disrupted strata along the upper reaches of kilauea s flank denote a coherent slump correlated with the active hilina slump the slump comprises mostly slope sediments underlain by a detachment 3 5 km deep extension and subsidence along the upper flank is compensated by uplift and folding of the slump toe which surfaces about midway down the submarine flank uplift of strata forming papa u seamount and offset of surface features along the western boundary of kilauea indicate that the slump has been displaced 3 km in a south southeast direction this trajectory matches coseismic and continuous ground displacements for the hilina slump block on land and contrasts with the southeast vergence of the rest of the creeping south flank to the northeast slope sediments are thinned and disrupted within a recessed region of the central flank demonstrating catastrophic slope failure in the recent past debris from the collapsed flank was shed into the moat in front of kilauea building an extensive apron seaward sliding of kilauea s flank offscraped these deposits to build an extensive frontal bench a broad basin formed behind the bench and above the embayed flank uplift and back tilting of young basin fill indicate recent and possibly ongoing bench growth the hilina slump now impinges upon the frontal bench this buttress may tend to reduce the likelihood of future catastrophic detachment

piggyback tectonics long term growth of kilauea on the south flank of mauna loa abstract compositional and age data from offshore pillow lavas and volcaniclastic sediments along with on land geologic seismic and deformation data provide broad perspectives on the early growth of kilauea volcano and the long term geometric evolution of its rift zones sulfur rich glass rinds on pillow lavas and volcaniclastic sediments derived from them document early underwater growth of a large compositionally diverse alkalic edifice the alkalic rocks yield 40ar 39ar ages as old as about 275 ka transitional composition lavas which mark beginning of the shield stage while most or all the edifice remained below sea level probably first erupted after about 150 ka and tholeiitic lavas of present day type are probably younger than 100 ka breccia clasts from papau seamount and along the lower southwest corner of the hilina bench are derived from subaerial mauna loa requiring that mauna loa s flank underlies western parts of kilauea at shallow depth the volume of the kilauea edifice is therefore smaller 10 000 km3 than previous estimates 15 40 000 km3 lava thickness accumulation rates appear to have remained nearly constant during edifice growth as effusion rates increased from 25 106 m3 yr at end of the alkalic stage to the present day tholeiite rate of 100 106 m3 yr seismic and gravity data show that the deep plumbing system for kilauea s magma supply extends nearly vertically through the oceanic crust at least to mantle depths of 30 35 km directly below its present day caldera proximity of kilauea s caldera to the surface boundary with mauna loa and the presence of mauna loa rocks at shallow depth beneath the south flank are difficult to reconcile with a submarine origin for early kilauea alkalic lavas unless geometric relations between the two volcanoes have changed substantially during growth of the kilauea shield seismic and ground deformation data suggest seaward spreading of the entire south flank of hawaii island independently of the boundary between kilauea and mauna loa along a landward dipping detachment fault system near the basal contact of the composite volcanic edifices with underlying oceanic crust current steady state horizontal displacements increase seaward at rates of 1 5 cm yr on the lower flank of mauna loa and reaching 5 8 cm yr at the kilauea coastline infrequent 100 yr large earthquakes generate similar geometries but 102 larger displacements per event present day kilauea is the more dynamic edifice but prior to inception of kilauea and during its early growth mauna loa is inferred to have undergone intense volcano spreading involving the kaoiki honuapo fault system considered a geometric analog of the hilina system on kilauea cumulative deformation of mauna loa s south flank during growth of kilauea since 200 300 ka is estimated to have involved 10 km of seaward spreading displacing the rift zones of k lauea while its deep plumbing system and summit magma reservoir remained nearly fixed in space kilauea s rift zones rather than migrating southward with time solely due to dike emplacement preferentially on the mobile seaward side alternatively are interpreted to have been transported passively southward piggyback style during shield stage growth of kilauea as a blister on the still mobile south flank of mauna loa such an evolution of kilauea accounts for the arcuate geometry of the present day rift zones proximity of the summit magma supply to the exposed flank of mauna loa initial submarine growth of the ancestral edifice and present day location of mauna loa rocks at shallow depth beneath the south flank of kilauea

re and os concentrations in arc basalts the roles of volatility and source region fo2 variations olivine and spinel compositions major elements including ferric and ferrous iron s re and os contents have been measured for a suite of primitive most 6 wt mgo basalts from the trans mexican volcanic belt tmvb including the western mexican volcanic belt the michoacan guanajuato volcanic field sierra chichinautzin pico de orizaba region palma sola san martin tuxtlas and the eastern alkaline province eap sulfur contents at sulfide saturation were calculated to determine whether the measured s contents are representative of sulfide saturated liquids most of the samples have s contents much lower than expected for sulfide saturation a few have higher contents than calculated perhaps due to the presence of sulfate in the measured total sulfur i e more oxidized samples comparison of the tmvb samples along with previously analyzed morb oib babb and arc samples reveals a continuum of re and os contents that is best explained by variation in oxygen fugacity and thus sulfide stability in the source region high re and os magmatic suites are best explained by derivation by melting of oxidized mantle where sulfide is no longer stable and re and os behave incompatibly whereas low re and os magmatic suites are derived from melting of relatively reduced mantle where sulfide is stable and re and os behave compatibly intermediate examples abound and arc magmas span a wide range of re and os concentrations due to variation of fo2 in the source during genesis of arc magmas low re magmatic suites are furthermore potentially affected by volatility which can lower re by a factor of 3 5

vesiculation of basaltic magma during eruption vesicle size distributions in vent lavas from the pu9u9o9o kupaianaha eruption of kilauea volcano are used to estimate nucleation and growth rates of h 2 o rich gas bubbles in basaltic magma nearing the earth9s surface 120 m depth by using well constrained estimates for the depth of volatile exsolution and magma ascent rate nucleation rates of 35 9 events cm 3 s 1 and growth rates of 3 2 x 10 4 cm s are determined directly from size distribution data the results are consistent with diffusion controlled growth as predicted by a parabolic growth law this empirical approach is not subject to the limitations inherent in classical nucleation and growth theory and provides the first direct measurement of vesiculation kinetics in natural settings in addition perturbations in the measured size distributions are used to examine bubble escape accumulation and coalescence prior to the eruption of magma

normal fault growth and linkage in the whakatane graben new zealand during the last 1 3 myr determination of fault growth rates and fault network evolution at time scales from 104 106 years has been hampered by a lack of a well constrained stratigraphic succession that provides a high fidelity record of fault development over these time periods here we show how seismic reflection data of different spatial resolutions can be used to constrain the linkage history and displacement rate variations of a single major fault we present data collected in the offshore whakatane graben bay of plenty new zealand where intense normal faulting occurs as a result of active back extension the focus of our study is the rangitaiki fault a linked segmented normal fault which is the dominant active structure in the graben the total linked fault length is c 20 km long and has a displacement of up to 830 130 m in the top 1 5 km of sediments the fault has been actively growing for the last 1 34 0 51 ma and has developed from isolated fault segments to a fully linked fault system initially the dominant process of fault growth was tip propagation with an average and maximum displacement rates of 0 52 0 18 mm yr 1 and 0 72 0 23 mm yr 1 respectively interaction and linkage became more significant as the fault segments grew towards each other resulting in the fault network becoming fully linked between 300 and 18 ka following fault segment linkages the average displacement rate of the fault network increased by almost three fold to 1 41 0 31 mm yr 1 while the maximum displacement rate increased to 2 72 0 61 mm yr 1 this is the first time that the growth rate of unlinked fault segments has been resolved and has been shown to be slower than in the subsequent linked fault system

growth history of kilauea inferred from volatile concentrations in submarine collected basalts abstract major element and volatile h2o co2 s compositions of glasses from the submarine flanks of kilauea volcano record its growth from pre shield into tholeiite shield stage pillow lavas of mildly alkalic basalt at 2600 1900 mbsl on the upper slope of the south flank are an intermediate link between deeper alkalic volcaniclastics and the modern tholeiite shield lava clast glasses from the west flank of papau seamount are subaerial mauna loa like tholeiite and mark the contact between the two volcanoes h2o and co2 in sandstone and breccia glasses from the hilina bench and in alkalic to tholeiitic pillow glasses above and to the east were measured by ftir volatile saturation pressures equal sampling depths 10 mpa 1000 m water for south flank and puna ridge pillow lavas suggesting recovery near eruption depths and or vapor re equilibration during down slope flow south flank glasses are divisible into low pressure co2 0 5 wt s 1000 1700 ppm and high pressure groups co2 40 ppm s 1000 ppm corresponding to eruption sea level at moderate water depths 300 1000 m or shallower but in disequilibrium and in deep water 1000 m saturation pressures range widely in early alkalic to strongly alkalic breccia clast and sandstone glasses establishing that early k lauea s vents spanned much of mauna loa s submarine flank with some vents exceeding sea level later south flank alkalic pillow lavas expose a sizeable submarine edifice that grew concurrent with nearby subaerial alkalic eruptions the onset of the tholeiitic shield stage is marked by extension of eruptions eastward and into deeper water to 5500 m during growth of the puna ridge subaerial and shallow water eruptions from earliest kilauea show that it is underlain shallowly by mauna loa implying that mauna loa is larger and kilauea smaller than previously recognized

unspiked k ar dating of pleistocene tholeiitic basalts from the deep core soh 4 kilauea hawaii abstract tholeiitic subaerial lava flows from kilauea soh 4 deep core were successfully dated by unspiked k ar with 40ar contents as low as 0 1 ages between 436 and 42 ka were found on lavas between the depths of 1650 and 468 m all subaerial ages are consistent with their stratigraphic position and allow us to derive a lava accumulation rate of 3 07 0 44 mm a which is within the range of rates determined in high 40ar oibs age determinations on dike samples yield ages that are younger than those of the enclosing lavas the validity of the ages was cross checked with u series ages of coral terraces on the northwest flank of hawaii as determined by ludwig et al 1991 dating problems seem to be restricted to a submarine pillow lava sample from level 1808 m which gives an apparent age of 1 ma which is an overestimate with respect both to rate of construction of kilauea and the hawaiian plume history

submarine geology of the hilina slump and morpho structural evolution of kilauea volcano hawaii abstract marine geophysical data including sea beam bathymetry hawaii mr1 sidescan and seismic reflection profiles along with recent robot submersible observations and samples were acquired over the offshore continuation of the mobile kilauea volcano south flank this slope comprises the three active hot spot volcanoes mauna loa kilauea and loihi seamount and is the locus of the hawaiian hot spot the south flank is the site of frequent low intensity seismicity as well as episodic large magnitude earthquakes its sub aerial portion creeps seaward at a rate of approximately 10 cm year the hilina slump is the only large submarine landslide in the hawaiian archipelago thought to be active and this study is one of the first to more highly resolve submarine slide features there the slump is classified into four distinct zones from nearshore to the island s base estimates of size based on these data indicate a slumped area of 2100 km 2 and a volume of 10 000 12 000 km 3 equivalent to about 10 of the entire island edifice the overall picture gained from these data sets is one of mass wasting of the neovolcanic terrain as it builds upward and seaward though reinforcement by young and pre hawaii seamounts adjacent to the pedestal is apparent extensive lava delta deposits are formed by hyaloclastites and detritus from recent lava flows into the sea these deposits dominate the upper submarine slope offshore of kilauea with pillow breccia revealed at mid depths along the lower flanks massive outcrops of volcanically derived sedimentary rocks were found underlying kilauea thus necessitating a rethinking of previous models of volcanic island development the morphologic and structural evolutionary model for kilauea volcano and the hilina slump proposed here attempts to incorporate this revelation a hazard assessment for the hilina slump is presented where it is suggested that displacement of the south flank to date has been restrained by a still developing northeast lateral submarine boundary when it does fully mature the south flank may be more subject to land slips triggered by large long duration earthquakes and thus kilauea may undergo more frequent episodes of failure with increased displacements

hyaloclastites and the slope stability of hawaiian volcanoes insights from the hawaiian scientific drilling project s 3 km drill core abstract core samples recovered during the hawaiian scientific drilling project hsdp drilling project reveal that the upper 1 km of the submarine flank of mauna kea is comprised mainly of hyaloclastites progressive very low temperature alteration of these hyaloclastites has been accompanied by systematic transformations in physical properties of these deposits hyaloclastite deposits which directly underlie ca 1 km of subaerially emplaced lavas are very poorly consolidated but over a depth interval of ca 500 m compaction and especially precipitation of zeolitic pore filling cements associated with palagonitization of sideromelane have eliminated porosity as well as promoted the consolidation of these hyaloclastites the latter is reflected in unconfined compressive strengths which increase from mean values respectively of 2 5 and 4 6 mpa in weakly consolidated smectite rich hyaloclastites from the incipient 1080 to 1335 mbsl and smectitic 1405 1573 mbsl alteration zones to a mean value of 10 0 mpa in the more highly consolidated hyaloclastites of the palagonitic zone of alteration from 1573 mbsl to the bottom of the drill hole conversely overlying intercalated and underlying lava flows are generally much less altered and have mean compressive strengths which are 1 to 2 orders of magnitude greater then hyaloclastites at equivalent depths the shear strengths of the hyaloclastites also increase with depth and grade of alteration but are uniformly and substantially lower in the lavas those hyaloclastites exhibiting the highest grade of alteration i e palagonitic also exhibit the highest measured strengths and thus the alteration of hyaloclastites appears to strengthen as opposed to weaken the flanks of the edifice however the contrast in strength between hyaloclastites and lavas may be a primary factor in localizing destabilization and the zones of weak and poorly consolidated hyaloclastites may facilitate slumping by servings as hosts for shallow detachment surfaces on the unsupported flanks of these volcanoes

the structure of basaltic scoria and reticulite and inferences for vesiculation foam formation and fragmentation in lava fountains in this investigation pyroclast structures are used to constrain degassing in basaltic lava fountains vesicle size shape number density interconnectedness and packing character are quantified and related to 1 the kinetics of bubble nucleation and growth 2 the structural evolution of magmatic foams and 3 the influence of vesiculation rate on magma fragmentation measurements made on a diverse suite of pyroclasts from kilauea volcano indicate that basaltic foams evolve through an initially disordered closed celled spherical state to a well ordered open celled polyhedral state as the vesicularity rises from 75 to 98 the structural changes occur rapidly 10 s in the conduit and fountain in response to an intense vesiculation burst vesicle size distribution systematics indicate bubble nucleation rates 2 104 events cm 3s 1 that are approximately three orders of magnitude greater than those found for effusive eruptive activity bubble growth rates 9 10 4 cm s exceed effusive estimates by a factor of 3 the observed runaway rate of bubble production indicates strong supersaturations at the onset of nucleation we speculate that the rise speed of the magma as it reaches the level where significant volatile exsolution begins determines the intensity of the vesiculation burst and hence the vigor of the eruption rapid expansion and acceleration of the magma under these conditions may provide the impetus for fragmentation

crustal earthquake instability in relation to the depth variation of frictional slip properties recent stability studies using constitutive relations of the type found by dieterich ruina and others to describe frictional slip of rocks in the laboratory have provided a new explanation of the depth cutoff of shallow crustal earthquakes the class of friction laws discussed has the property that the sliding stress depends on normal stress temperature slip rate and slip history for sliding at a fixed slip rate v and fixed environment e g normal stress temperature etc the shear strength evolves toward a steady state value ss v stability analysis show that for d ss v dv 0 velocity strengthening implies stable steady state sliding at least for a broad class of constitutive laws more fully described in the paper experiments by dieterich and by tullis and weeks on westerly granite with mature sliding surfaces indicate that d ss v dv is negative at room temperature whereas higher temperature experiments by stesky show that d ss v dv becomes positive above approximately 300 c therefore in the case of the earth where temperature increases with depth the above observations seem to suggest that the depth cutoff of crustal earthquake activity can be understood in terms of the variation of the frictional response with depth from a regime with d ss v dv 0 this is not inconsistent with but rather refines the suggestion by sibson and others that the depth cutoff is due to a transition from brittle friction to ductile flow further our results show definitively that the shallow depth confinement of seismicity is compatible with a model in which deformation is localized to a fault zone extending well below the seismogenic depth the depth confinement does not require a model showing transition to a zone of broadly distributed creep flow beneath the seismogenic zone following mavko a two dimensional quasi static strike slip fault model is analyzed but using different numerical procedures and a depth variation of frictional properties based on the laboratory data mentioned above and the lachenbruch sass depth variation of temperature for the san andreas fault the resulting predictions of such features as the confinement of crustal earthquakes to shallow depths the development of locked patches the recurrence time for the seismic cycle the seismic stress drop and displacement etc are generally in agreement with the observed characteristics of large scale strike slip earthquakes along the san andreas fault calculations based on the laboratory data predict for example that stick slip nucleates around 5 7 km that large seismic motion occurs around the nucleation depth and above but diminishes gradually to zero at 13 15 km depths that rapid postseismic creep occurs over another 3 4 km depth and that at greater depths steady slip consistent with the average plate velocity is only modestly perturbed by the earthquakes occurring above the most uncertain parameter is the slip weakening distance l for evolution of fault surface state we illustrate how features of the predicted earthquake cycles vary with l over the range for which calculations are feasible

volcanotectonic interactions between mauna loa and kilauea insights from 2 d discrete element simulations abstract numerical simulations using the discrete element method dem are carried out to examine the dynamics and internal deformation of overlapping volcanoes constructed upon a weak decollement horizon as analogs to the kilauea mauna loa system of volcanoes in hawaii employing a frictional rheology the dem simulations capture much of the complex deformation behavior of mauna loa and kilauea volcanoes here referred to as the primary and secondary edifices respectively the models demonstrate incremental displacements of the outer flanks of the volcanoes and concurrent summit subsidence leading to characteristic low slopes and inward dipping strata slip discontinuities that develop within the piles define steeply dipping normal faults along the upper flanks and beneath the edifice summits that accommodate subsidence and flank spreading edifice overlap influences dynamic behavior significantly even small topographic perturbations restrict the internal deformation and spreading of the confined flanks the degree of buttressing depends on the relative positions of the two edifices if the secondary edifice grows high upon the flanks of the primary edifice outward spreading of the underlying flank is enhanced if the secondary edifice is built low upon the primary flanks spreading of the underlying flank is effectively prevented or possibly reversed furthermore as the second edifice grows it subsides into the underlying flank partitioning it into a mobile downslope region entrained by spreading of the second edifice and a comparatively stable upper flank region these results suggest that much of the mass of kilauea volcano may lie deeply buried within the underlying flank of mauna loa while older mauna loa rocks may lie far from their source beneath the mobile flank of the younger volcano

internal structure of puna ridge evolution of the submarine east rift zone of kilauea volcano hawai i abstract multichannel seismic reflection sonobuoy gravity and magnetics data collected over the submarine length of the 75 km long puna ridge hawai i resolve the internal structure of the active rift zone laterally continuous reflections are imaged deep beneath the axis of the east rift zone erz of kilauea volcano we interpret these reflections as a layer of abyssal sediments lying beneath the volcanic edifice of kilauea early arrival times or pull up of sediment reflections on time sections imply a region of high p wave velocity vp along the submarine erz refraction measurements along the axis of the ridge yield vp values of 2 7 4 85 km s within the upper 1 km of the volcanic pile and 6 5 7 km s deeper within the edifice few coherent reflections are observed on seismic reflection sections within the high velocity area suggesting steeply dipping dikes and or chaotic and fractured volcanic materials southeastward dipping reflections beneath the nw flank of puna ridge are interpreted as the buried flank of the older hilo ridge indicating that these two ridges overlap at depth gravity measurements define a high density anomaly coincident with the high velocity region and support the existence of a complex of intrusive dikes associated with the erz gravity modeling shows that the intrusive core of the erz is offset to the southeast of the topographic axis of the rift zone and that the surface of the core dips more steeply to the northwest than to the southeast suggesting that the dike complex has been progressively displaced to the southeast by subsequent intrusions the gravity signature of the dike complex decreases in width down rift and is absent in the distal portion of the rift zone based on these observations and analysis of puna ridge bathymetry we define three morphological and structural regimes of the submarine erz that correlate to down rift changes in rift zone dynamics and partitioning of intrusive materials we propose that these correspond to evolutionary stages of developing rift zones which may partially control volcano growth mobility and stability and may be observable at many other oceanic volcanoes

north kona slump submarine flank failure during the early tholeiitic shield stage of hualalai volcano abstract the north kona slump is an elliptical region about 20 by 60 km 1000 km 2 area of multiple geometrically intricate benches and scarps mostly at water depths of 2000 4500 m on the west flank of hualalai volcano two dives up steep scarps in the slump area were made in september 2001 using the rov kaiko of the japan marine science and technology center jamstec as part of a collaborative japan usa project to improve understanding of the submarine flanks of hawaiian volcanoes both dives at water depths of 2700 4000 m encountered pillow lavas draping the scarp and bench slopes intact to only slightly broken pillow lobes and cylinders that are downward elongate dominate on the steepest mid sections of scarps while more equant and spherical pillow shapes are common near the tops and bases of scarps and locally protrude through cover of muddy sediment on bench flats notably absent are subaerially erupted hualalai lava flows interbedded hyaloclastite pillow breccia and or coastal sandy sediment that might have accumulated downslope from an active coastline the general structure of the north kona flank is interpreted as an intricate assemblage of downdropped lenticular blocks bounded by steeply dipping normal faults the undisturbed pillow lava drape indicates that slumping occurred during shield stage tholeiitic volcanism all analyzed samples of the pillow lava drape are tholeiite similar to published analyses from the submarine northwest rift zone of hual lai relatively low sulfur 330 600 ppm and water 0 18 0 47 wt contents of glass rinds suggest that the eruptive sources were in shallow water perhaps 500 1000 m depth in contrast saturation pressures calculated from carbon dioxide concentrations 100 190 ppm indicate deeper equilibration at or near sample sites at water depths of 3900 to 2800 m either vents close to the sample sites erupted mixtures of undegassed and degassed magmas or volatiles were resorbed from vesicles during flowage downslope after eruption in shallow water the glass volatile compositions suggest that the tholeiitic lavas that drape the slump blocks were erupted either 1 early during shield stage tholeiitic volcanism prior to emergence of a large subaerial edifice or alternatively 2 from submarine radial vents during subaerial shield building because no radial vents have been documented on land or underwater for the unbuttressed flanks of any hawaii volcano alternative 1 is favored in comparison to other well documented hawaiian slumps and landslides north kona structures suggest a more incipient slump event with smaller down slope motions and lateral displacements

magmatic history of the east rift zone of kilauea volcano hawaii based on drill core from soh 1 abstract deep drilling has allowed for the first time an examination of most of the shield stage of a hawaiian volcano when it is centered over the hotspot and most of its volume is produced we determined the lithologies ages geochemical characteristics and accumulation rates of rocks from the continuously cored 1 7 km deep scientific observation hole soh 1 which was drilled into kilauea s east rift zone the uppermost 750 m of this hole contain relatively unaltered subaerially quenched lavas the lower portion is a mixture of weakly to moderately altered hyaloclastites and massive basalts intruded by dikes unspiked k ar dating was attempted on 14 lavas but only four yielded geologically reasonable ages the oldest age is 351 12 ka for a sample from 1541 m eighty xrf major and trace element analyses of lavas from throughout the section demonstrate that these lavas have the same compositional range as historical kilauea lavas and that there was no systematic geochemical variation for the volcano over the last 350 ka kilauea s average yearly magma supply during this period was probably 0 05 01 km 3 which is identical to its average historical magma supply rate thus kilauea s overall source and melting conditions have remained remarkably constant for the last 350 ka despite its having drifted 42 km over the hawaiian plume these results require that the portion of the plume being melted to produce kilauea magmas be relatively large and well mixed which is inconsistent with models that place this source on the margin of a radially zoned plume

earthquake scaling fault segmentation and structural maturity abstract slip and length measurements on earthquakes suggest large stress drop variability we analyze an extended set of slip length measurements for large earthquakes m 6 to seek for the possible origin s of this apparent variability we propose that such variability arises from earthquakes breaking a variable number of major fault segments that number depends on the strength of the inter segment zones which itself depends on the structural maturity of the faults we propose new d max l parameterizations based on that idea of multiple segment ruptures in such parameterizations each broken segment roughly scales as a crack while the total multi segment rupture does not stress drop on individual segments is roughly constant only varying between 3 5 to 9 mpa the slight variation that is still observed depends on fault structural maturity more mature faults have lower stress drops than immature ones the new d max l functions that we propose reduce uncertainties with respect to available relationships they thus provide a more solid basis to estimate seismic hazard by integrating fault properties revealed by geological studies

diverse basalt types from loihi seamount hawaii loihi seamount is the southeasternmost active volcano in the hawaiian emperor volcanic chain the seamount is considered representative of the early phase of hawaiian volcanism because of its youth small size and location near the melting anomaly seventeen dredge stations recovered transitional basalt alkalic basalt and basanite in addition to the expected tholeiitic basalt four flows of alkalic basalt contain common small dunite xenoliths the recovered samples have thin palagonite rinds and almost no manganese on the glassy surfaces we estimate that the lavas are less than about 4 000 yr old and many are less than 1 000 yr old loihi seamount is apparently in a transitional growth phase between the early eruption of alkalic lavas and the commonly observed subaerial tholeiitic eruptive phase previously thought to dominate hawaiian volcanism from inception until the postcaldera collapse alkalic stage

the origin of mauna loa s nīnole hills evidence of rift zone reorganization in order to identify the origin of mauna loa volcano s n nole hills bouguer gravity was used to delineate density contrasts within the edifice our survey identified two residual anomalies beneath the southwest rift zone swrz and the n nole hills the n nole hills anomaly is elongated striking northeast and in inversions both anomalies merge at approximately 7 km above sea level the positive anomaly modeled as a rock volume of 1200 km3 beneath the n nole hills is associated with old eruptive vents based on the geologic and geophysical data we propose that the gravity anomaly under the n nole hills records an early swrz orientation now abandoned due to geologically rapid rift zone reorganization catastrophic submarine landslides from mauna loa s western flank are the most likely cause for the concurrent abandonment of the n nole hills section of the swrz rift zone reorganization induced by mass wasting is likely more common than currently recognized

argon geochronology of kilauea s early submarine history submarine alkalic and transitional basalts collected by submersible along kilauea volcano s south flank represent early eruptive products from earth s most active volcano strongly alkalic basalt fragments sampled from volcaniclastic deposits below the mid slope hilina bench yield 40 ar 39 ar ages from 212 38 to 280 20 ka these ages are similar to high precision 234 9 and 239 10 ka phlogopite ages from nephelinite clasts in the same deposits above the mid slope bench two intact alkalic to transitional pillow lava sequences protrude through the younger sediment apron samples collected from a weakly alkalic basalt section yield 138 30 to 166 26 ka ages and others from a transitional basalt section yield 138 115 and 228 114 ka ages the ages are incompatible with previous unspiked k ar studies from samples in deep drill holes along the east rift of kilauea the submarine birth of kilauea volcano is estimated at 300 ka if the weakly alkalic sequence we dated is representative of the volcano as a whole the transition from alkalic to tholeiitic basalt compositions is dated at 150 ka

estimates of strain due to brittle faulting sampling of fault populations abstract the geometry of sampling domains is a first order consideration in the characterization of brittle fault populations in most cases descriptions of fault size distributions based on map cross section traverse or borehole data systematically underestimate the number of small faults present in a volume the geometry of sampling domains may be accounted for using an empirical proportionality between fault displacement and trace length estimates of strain in which the sampling geometry is considered suggest that small faults accommodate a significant portion of the total strain due to the brittle faulting process

overthrusting and sediment accretion along kilauea s mobile south flank hawaii evidence for volcanic spreading from marine seismic reflection data a large intermittently active submarine landslide known as the hilina slump has been interpreted along the south flank of kilauea volcano seaward dipping faults on land mark its headwall and an offshore bench may define its uplifted toe geodetic data show that the entire south flank is also moving seaward by a process referred to as volcanic spreading this provides an alternative explanation for the bench i e overthrusting along the edge of the sliding flank the latter interpretation is consistent with new seismic reflection data across the submarine flank a prominent reflection near the top of the oceanic plate suggests the decollement upon which the mobile flank slides landward dipping reflections rise from this horizon and bound packages of bedded strata faulted and imbricated within the bench the absence of correlative seaward dipping faults and rotated strata on the upper flank suggests that the bench is not coupled to a slump moreover kinematic reconstructions of the bench indicate that it has accommodated 15 24 km of displacement this value is consistent with estimates for rift zone extension but too high for shortening at the toe of a slump we interpret the bench to result from overthrusting and accretion of volcaniclastic sediments to the edge of the mobile flank and suggest that morphologic benches develop preferentially where landslide debris has accumulated near the base of the volcano and can be accreted to its sliding edifice

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

volatiles in glasses from mauna loa volcano hawai i implications for magma degassing and contamination and growth of hawaiian volcanoes glasses from mauna loa pillow basalts recent subaerial vents and inclusions in olivine were analyzed for s cl f and major elements by electron microprobe select submarine glasses were also analyzed for h2o and co2 by infrared spectroscopy the compositional variation of these tholeiitic glasses is dominantly controlled by crystal fractionation and they indicate quenching temperatures of 1 115 1 196 c submarine rift zone glasses have higher volatile abundances except f than nearly all other submarine and subaerial glasses with the maximum concentrations increasing with water depth the overwhelming dominance of degassed glasses on the submarine flanks of mauna loa implies that much of volcano s recent submarine growth involved subaerially erupted lava that reached great water depths up to 3 1 km via lava tubes anomalously high f and cl in some submarine glasses and glass inclusions indicate contamination possibly by fumarolic deposits in ephemeral rift zone magma chambers the relatively high co2 but variable h2o k2o and s k2o in some submarine rift zone glasses indicates pre eruptive mixing between degassed and undegassed magma within mauna loa s rift system volatile compositions for mauna loa magmas are similar to other active hawaiian volcanoes in s and f but are less cl rich than l ihi glasses however cl k2o ratios are similar mauna loa and l ihi magmas have comparable but lower h2o than those from kilauea thus kilauea s source may be more h2o rich the dissimilar volatile distribution in glasses from active hawaiian volcanoes is inconsistent with predictions for a simple concentrically zoned plume model

slip distributions on intersecting normal faults abstract slip distributions on normal faults often are asymmetric and display multiple local maxima numerically computed slip distributions from elastic models indicate that such irregular slip distributions can be caused by mechanical interaction between intersecting faults that produce local perturbations of the stress field resolved on the faults a three dimensional boundary element model based on the displacement discontinuity method has been used to analyze the mechanical interaction of faults that form y or t shaped intersections slip distributions are asymmetric with a steeper slip gradient toward the line of intersection multiple slip maxima occur depending on the angle between the faults but generally they are not located along the intersections nor at the fault centers examples of intersecting normal faults taken from oil reservoir seismic surveys and sandbox experiments have been used to confirm the application of the theoretical results despite considerable simplifications in terms of geometry and boundary conditions the computed slip distributions capture the characteristics of the observed slip distributions

localization and fault growth in layered brittle ductile systems implications for deformations of the continental lithosphere we present experiments and numerical simulations dealing with the growth of faults in thin brittle ductile systems to understand deformation modes in the continental lithosphere experiments were uniaxial shortening of layers of dry sand and silicone putties of various viscous resistances for large strength ratios between the brittle and ductile layers r 5 10 the deformation localizes into two shear bands the fault pattern is created before reaching 10 shortening and has fractal dimensions varying between 1 6 and 1 8 for small strength ratios r 5 10 deformation never localizes the fault pattern is homogeneous with a trivial dimension of 2 and grows continuously during deformation the transition between localized and homogeneous deformation occurs when the mechanical resistance of brittle layers is 5 10 times larger than the resistance of ductile layers this transition was also investigated by means of electrical analog simulations a fuse network which represents an elasto brittle layer is coupled with a capacitor layer which models strain rate dependent fluids an ac potential is applied and the fuses progressively burned out until they form a connected network the ac potential frequency is a tuning parameter similar to the applied strain rate in experiments a critical frequency is obtained marking a transition between a localization mode where the density of burned fuses decreases as the system size increases and a delocalization mode where the density of burned fuses remains constant with increasing system size the scaling dependency of the fracture process as well as the critical frequency are consistent with experimental results available information on the rheology of the continental lithosphere shows that this mechanical transition is bracketed by the possible range of brittle to ductile strength ratios

formation of submarine flat topped volcanic cones in hawai i high resolution bathymetric mapping has shown that submarine flat topped volcanic cones morphologically similar to ones on the deep sea floor and near mid ocean ridges are common on or near submarine rift zones of kilauea kohala or mauna kea mahukona and haleakala volcanoes four flat topped cones on kohala were explored and sampled with the pisces v submersible in october 1998 samples show that flat topped cones on rift zones are constructed of tholeiitic basalt erupted during the shield stage similarly shaped flat topped cones on the northwest submarine flank of ni ihau are apparently formed of alkalic basalt erupted during the rejuvenated stage submarine postshield stage eruptions on hilo ridge mahukona hana ridge and offshore ni ihau form pointed cones of alkalic basalt and hawaiite the shield stage flat topped cones have steep 25 sides remarkably flat horizontal tops basal diameters of 1 3 km and heights 300 m the flat tops commonly have either a low mound or a deep crater in the center the rejuvenated stage flat topped cones have the same shape with steep sides and flat horizontal tops but are much larger with basal diameters up to 5 5 km and heights commonly greater than 200 m the flat tops have a central low mound shallow crater or levees that surrounded lava ponds as large as 1 km across most of the rejuvenated stage flat topped cones formed on slopes 10 and formed adjacent semicircular steps down the flank of ni ihau rather than circular structures all the flat topped cones appear to be monogenetic and formed during steady effusive eruptions lasting years to decades these and other submarine volcanic cones of similar size and shape apparently form as continuously overflowing submarine lava ponds a lava pond surrounded by a levee forms above a sea floor vent as lava continues to flow into the pond the lava flow surface rises and overflows the lowest point on the levee forming elongate pillow lava flows that simultaneously build the rim outward and upward but also dam and fill in the low point on the rim the process repeats at the new lowest point forming a circular structure with a flat horizontal top and steep pillowed margins there is a delicate balance between lava heat supply to the pond and cooling and thickening of the floating crust factors that facilitate construction of such landforms include effusive eruption of lava with low volatile contents moderate to high confining pressure at moderate to great ocean depth long lived steady eruption years to decades moderate effusion rates probably ca 0 1 km3 year and low but not necessarily flat slopes with higher effusion rates sheet flows flood the slope with lower effusion rates pillow mounds form hawaiian shield stage eruptions begin as fissure eruptions if the eruption is too brief it will not consolidate activity at a point and fissure fed flows will form a pond with irregular levees the pond will solidify between eruptive pulses if the eruption is not steady lava that is too volatile rich or that is erupted in too shallow water will produce fragmental and highly vesicular lava that will accumulate to form steep pointed cones as occurs during the post shield stage the steady effusion of lava on land constructs lava shields which are probably the subaerial analogs to submarine flat topped cones but formed under different cooling conditions

turbidites from giant hawaiian landslides results from ocean drilling program site 842 pliocene to pleistocene volcanic sand turbidites recovered 320 km west of the island of hawaii at ocean drilling program site 842 contain fragments off fresh weakly vesicular glass and tests of pleistocene and eocene radiolarians this sand is probably related to turbidity currents generated from debris avalanches produced by giant landslides on the flanks of the hawaiian islands on their way to site 842 the currents flowed over the m bigh ha waiian arch indicating that the turbidity currents were at least 325 m thick similar sand has been reported 930 km south of the islands thus hawaiian giant landslides play a significant role in central pacific deep sea sedimentary processes

ultra high chlorine in submarine kilauea glasses evidence for direct assimilation of brine by magma basaltic glass grains from the submarine south flank of kilauea hawai i have cl concentrations of 0 01 1 68 wt the latter being the highest cl content yet recorded for a hawaiian glass the high cl glass grains are products of brine assimilation by tholeiite magma the glasses are grains in a sandstone clast from bedded breccias draping the southwestern margin of kilauea s submarine midslope bench the clast contains two distinct suites of glass grains abundant degassed tholeiites perhaps derived from subaerial lavas of mauna loa that shattered upon ocean entry and a smaller population of kea type tholeiite n 17 analyzed that erupted subaqueously based on elevated s 780 1050 ppm h2o 0 42 1 27 wt and co2 1000 ppm six 5000 ppm and two grains have 10 000 ppm dissolved cl abundances of h2o na2o k2o and several trace elements increase regularly with cl concentration and we estimate that cl enrichment was due to up to 13 wt addition of a brine consisting of 78 h2o wt 13 cl 4 4 na 2 6 k 2 6 ca 620 ppm ba 360 ppm sr 65 ppm rb and 7 ppm pb the large amounts of brine addition argue against bulk assimilation of low porosity brine bearing rock the brine s composition is appropriate for a seawater derived hydrothermal fluid that reacted with basaltic wall rocks at t 100 c losing mg and s and gaining k ca rb ba sr and pb followed by phase separation near 500 c and 50 mpa 5 km below sea level at hydrostatic pressure brine was assimilated at or near the depth it formed as estimated on petrologic grounds but under lithostatic conditions the highest extents of assimilation either forced volatile saturation of the magma or enriched already coexisting magmatic vapor in h2o possible mechanisms for assimilation are 1 forcible injection of brine into magma during bursting of overpressured pockets heated by new dikes or 2 intrusion of magma into lenses or sills occupied by trapped brine

models of hawaiian volcano growth and plume structure implications of results from the hawaii scientific drilling project the shapes of typical hawaiian volcanoes are simply parameterized and a relationship is derived for the dependence of lava accumulation rates on volcano volume and volumetric growth rate the dependence of lava accumulation rate on time is derived by estimating the eruption rate of a volcano as it traverses the hawaiian plume with the eruption rate determined from a specified radial dependence of magma generation in the plume and assuming that a volcano captures melt from a circular area centered on the volcano summit the timescale of volcano growth is t 2 r plate where r is the radius of the melting zone of the circular plume and plate is the velocity of the pacific plate the growth progress of a volcano can be described by a dimensionless time t t plate 2r where t 0 is chosen to be the start of volcano growth and t 1 approximates the end of shield growth using a melt generation rate for the whole plume of 0 2 km 3 yr a plume diameter of 50 km and a plate velocity of 10 cm yr we calculate that the lifetime of a typical volcano is 1000 kyr for a volcano that traverses the axis of the plume the standard dimensions are a volume of 57 000 km 3 a summit thickness of 18 km a summit elevation of 3 6 km and a basal radius of 60 km the volcano first breaches the sea surface at t 0 22 when it has attained only 5 of its eventual volume 80 of the volume accumulates between t 0 3 and t 0 7 typical lava accumulation rates start out over 50 m kyr in the earliest stages of growth from the seafloor and level out at 35 m kyr from t 0 05 until t 0 4 from t 0 4 to t 0 9 the submarine lava accumulation rates decrease almost linearly from 35 m kyr to 0 subaerial accumulation rates are about 30 lower the lava accumulation rate is a good indicator of volcano age a volcano that passes over the plume at a distance 0 4r off to the side of the plume axis is predicted to have a volume of about 60 of the standard volcano a lifetime about 8 shorter and lava accumulation rates about 15 20 smaller the depth age data for mauna kea lavas cored by the hawaii scientific drilling project are a good fit to the model parameters used given that mauna kea appears to have crossed the plume about 15 20 km off axis the lifetime of mauna kea is estimated to be 920 kyr mauna loa is predicted to be at a stage corresponding to t 0 8 kilauea is at t 0 6 and loihi is at t 0 16 the model also allows the subsurface structure of the volcanoes the interfaces between lavas from different volcanoes to be modeled radial geochemical structure in the plume may be blurred in the lavas because the volcanoes capture magma from a sizeable cross sectional area of the plume this inference is qualitatively born out by available isotopic data the model predicts that new hawaiian volcanoes are typically initiated on the seafloor near the base of the next older volcano but generally off the older volcano s flank

coastal lava flows from mauna loa and hualalai volcanoes kona hawaii a major carbonate reef which drowned 13 ka is now submerged 150 m below sea level on the west coast of the island of hawaii a 25 km span of this reef was investigated using the submersiblemakali i the reef occurs on the flanks of two active volcanoes mauna loa and hualalai and the lavas from both volcanoes both underlie and overlie the submerged reef most of the basaltic lava flows that crossed the reef did so when the water was much shallower and when they had to flow a shorter distance from shoreline to reef face lava flows on top of the reef have protected it from erosion and solution and now occur at seaward projecting salients on the reef face these relations suggest that the reef has retreated shoreward as much as 50 m since it formed a 7 km wide shadow zone occurs where no hualalai lava flows cross the reef south of kailua these lava flows were probably diverted around a large summit cone complex a similar shadow zone on the flank of mauna loa volcano in the kealakekua bay region is downslope from the present mauna loa caldera which ponds mauna loa lava and prevents it from reaching the coastline south of the mauna loa shadow zone the 150 m reef has been totally covered and obscured by mauna loa lava the boundary between hualalai and mauna loa lava on land occurs over a 6 km wide zone whereas flows crossing the 150 m reef show a sharper boundary offshore from the north side of the subaerial transition zone this indicates that since the formation of the reef hualalai lava has migrated south mantling mauna loa lava more recently mauna loa lava is again encroaching north on hualalai lava

geochemical sourcing of rock specimens and stone artifacts from nihoa and necker islands hawai i we report geochemical analysis of seven rock specimens and six stone artifacts from nihoa and necker islands hawai i the analyzed rock specimens exhibit chemistry consistent with published data sets and establish a major element distinction between nihoa and necker their trace element data indicate that the analyzed rocks and artifacts are local in origin and they reliably discriminate from sources on kaua i these preliminary results support emory s thesis that early archaic hawaiian colonists on nihoa and necker relied on their local basaltic stone to manufacture stone tools containers and other portable objects

in search of ancestral kilauea volcano submersible observations and samples show that the lower south flank of hawaii offshore from kilauea volcano and the active hilina slump system consists entirely of compositionally diverse volcaniclastic rocks pillow lavas are confined to shallow slopes submarine erupted basalt clasts have strongly variable alkalic and transitional basalt compositions to 41 sio 2 10 8 alkalies contrasting with present day kilauea tholeiites the volcaniclastic rocks provide a unique record of ancestral alkalic growth of an archetypal hotspot volcano including transition to its tholeiitic shield stage and associated slope failure events

native gold in a hawaiian alkalic magma native gold found in fresh basanite glass from the early submarine phase of kilauea volcano hawaii may be the first documented case of the transport of gold as a distinct precious metal phase in a mantle derived magma the gold bearing glass is a grain in bedded volcanic glass sandstone japan marine science and technology center jamstec sample s508 r3 collected by the submersible shinkai 6500 at 3879 m depth off kilauea south flank extensive outcrops there expose debris flow breccias and sandstones containing submarine erupted alkalic rock fragments and glasses from early kilauea precipitation of an immiscible gold liquid resulted from resorption of magmatic sulfides during crystallization differentiation with consequent liberation of sulfide hosted gold elevated whole rock gold concentrations to 36 ppb for fresh lavas and clasts from early kilauea further show that some magmas erupted at the beginning stages of hawaiian shield volcanoes were distinctly gold rich most likely owing to limited residual sulfide in their mantle source alkalic magmas at other ocean islands may also be gold rich and oceanic hot spot provinces may contain underappreciated gold resources

estuary plumes and fronts in shelf waters a layer model abstract a layer model that treats fronts as discontinuities is developed to study the steady state behavior of shallow estuary plumes on the continental shelf the complete range of earth rotation effect is evaluated from small scale or nonrotating plumes kelvin number equal zero to large scale rotating plumes kelvin number equal order one supercritical flow is assumed in the outlet channel and the method of characteristics is used to compute the flow downstream nonrotating plumes have strong boundary fronts and concentrate their greatest layer depth and mass transport offshore near the front but form no coastal current rotating plumes have boundary fronts that weaken soon after discharge form a turning region where coriolis action deflects the flow toward shore and subsequently set up a coastal current soon after its formation this coastal current is bounded offshore by a strong front called the coastal front across which the momentum balance changes from nearly inertial in the turning regi

high resolution locations of triggered earthquakes and tomographic imaging of kilauea volcano s south flank 1 the spatiotemporal patterns of seismicity beneath kilauea s south flank give insight to the structure and geometry of the decollement on which large tsunamigenic earthquakes have occurred and its relation to slow slip events sses which have been observed every 1 to 2 years since 1997 in order to record earthquakes triggered by a sse that was predicted to occur in march 2007 a temporary network of 20 seismometers was deployed on kilauea s south flank termed the seq network while the sse did not occur until 17 june 2007 theseq network recorded over 3000 earthquakes including those triggered by the sse we relocate hypocenters of volcano tectonic earthquakes and invert for p and s wave velocity structure using waveform cross correlation and double difference tomography using data from the seq network and the permanent hawaii volcano observatory network hvo data with additional data from other previous temporary arrays the best constrained hypocenters recorded by both the seq and hvo networks indicate the decollement as a subhorizontal layer of seismicity at 8 km depth less than 1 km thick in most areas with the western portion of the decollement dipping to the southeast the seismicity triggered by the june 2007 sse includes over 400 earthquakes overlapping with the southern edge of the decollement seismicity a shallower swarm of earthquakes also occurred between 2 and 7 km depth in april 2007 near apua point and may have been indirectly triggered by the mw 8 1 solomon islands earthquake at 6000 km distance which occurred 48 h prior to the beginning of the swarm

insar observations of low slip rates on the major faults of western tibet two contrasting views of the active deformation of asia dominate the debate about how continents deform i the deformation is primarily localized on major faults separating crustal blocks or ii deformation is distributed throughout the continental lithosphere in the first model western tibet is being extruded eastward between the major faults bounding the region surface displacement measurements across the western tibetan plateau using satellite radar interferometry insar indicate that slip rates on the karakoram and altyn tagh faults are lower than would be expected for the extrusion model and suggest a significant amount of internal deformation in tibet

low sulfur content in submarine lavas an unreliable indicator of subaerial eruption low s content 250 ppm has been used to identify subaerially erupted hawaiian and icelandic lavas large differences in s content of submarine erupted lavas from different tectonic settings indicate that the behavior of s is complex variations is s abundance in undegassed submarine erupted lavas can result from different source compositions different percentages of partial melting and crystal fractionation low s concentrations in highly vesicular submarine lavas suggest that partial degassing can occur despite great hydrostatic pressure these processes need to be evaluated before using s content as an indicator of eruption depth

formation of segmented normal faults a 3 d perspective the interpretation of fault kinematics from geometric data is an essential step in developing an understanding of the growth of fault systems constraints on fault geometry are however often restricted to 2 d maps or cross sections in this article we consider the extent to which kinematic interpretations of faulting benefit from a 3 d rather than 2 d geometrical perspective concentrating on relay zones and segmented normal fault arrays we suggest that very different interpretations of their evolution arise from the recognition that the propagation directions of faults and fault segments will rarely be contained within the inspection plane of 2 d data a 3 d perspective favours an interpretation in which the segments of a fault array are kinematically interrelated from their initiation individual segments in such systems may link into a single fault surface out of the plane of inspection or may be unconnected in 3 d we argue that this interpretation which conflicts with the often suggested model of incidental overlap of originally isolated faults should be the preferred model for the generation and growth of segmented normal fault arrays

sources of the large a d 1202 and 1759 near east earthquakes the sources of the may 1202 and november 1759 m 7 5 near east earthquakes remain controversial because their macroseismal areas coincide straddling subparallel active faults in the lebanese restraining bend paleoseismic trenching in the yammouneh basin yields unambiguous evidence both for slip on the yammou neh fault in the twelfth thirteenth centuries and for the lack of a posterior event this conclusion is supported by comparing the freshest visible fault scarps which imply more recent slip on the r chaiya serghaya system than on the yammouneh fault our results suggest that the recurrence of an a d 1202 type earthquake might be due this century as part of a sequence similar to that of a d 1033 1202 possibly heralded by the occurrence of the 1995 mw 7 3 aqaba earthquake the seismic behavior of the levant fault might thus be characterized by millennial periods of quiescence separated by clusters of large earthquakes