Intermediate Events Research Articles

Direct Atomic-Scale Observation of Intermediate Pathways of Melting and Crystallization in Supported Bi Nanoparticles.

Uncovering the evolutional pathways of melting and crystallization atomically is critical to understanding complex microscopic mechanism of first-order phase transformation. We conduct in situ atomic-scale observations of melting and crystallization in supported Bi nanoparticles under heating and cooling within an aberration-corrected TEM. We provide direct evidence of the multiple intermediate state events in melting and crystallization. The melting of the supported nanocrystal involves the formation and migration of domain boundaries and dislocations due to the atomic rearrangement under heating, which occurs through a size-dependent multiple intermediate state. A critical size, which is key to inducing the transition pathway in melting from two to four barriers, is identified for the nanocrystal. In contrast, crystallization of a Bi droplet involves three stages. These findings demonstrate that the phase transformations cannot be viewed as a simple single barrier-crossing event but as a complex multiple intermediate state phenomenon, highlighting the importance of nonlocal behaviors.

Probabilistic analysis on the failure of reactivity control for the PWR

The fundamental safety function of the power reactor is to control reactivity, to remove heat from the reactor, and to confine radioactive material. The safety analysis is used to ensure that each parameter is fulfilled during the design and is done by deterministic and probabilistic method. The analysis of reactivity control is important to be done because it will affect the other of fundamental safety functions. The purpose of this research is to determine the failure probability of the reactivity control and its failure contribution on a PWR design. The analysis is carried out by determining intermediate events, which cause the failure of reactivity control. Furthermore, the basic event is determined by deductive method using the fault tree analysis. The AP1000 is used as the object of research. The probability data of component failure or human error, which is used in the analysis, is collected from IAEA, Westinghouse, NRC and other published documents. The results show that there are six intermediate events, which can cause the failure of the reactivity control. These intermediate events are uncontrolled rod bank withdrawal at low power or full power, malfunction of boron dilution, misalignment of control rod withdrawal, malfunction of improper position of fuel assembly and ejection of control rod. The failure probability of reactivity control is 1.49E-03 per year. The causes of failures which are affected by human factor are boron dilution, misalignment of control rod withdrawal and malfunction of improper position for fuel assembly. Based on the assessment, it is concluded that the failure probability of reactivity control on the PWR is still within the IAEA criteria.

Suspended sediment dynamics by event typology and its siltation effects in a semi-arid snowmelt-driven basin

Soil loss and transport processes are key issues to understand erosive and sedimentary dynamics in semi-arid environments. The aim of this work was to characterize the erosive patterns of different types of events and to analyse their effect downstream in a mountainous semi-arid watershed. With that purpose, different events have been typified according to atmospheric and hydrological descriptors from information of 1)historical meteorological data, 2) results of simulations from physically-based and distributed hydrological modeling, which includes the snowmelt dynamics, and 3) available MODIS satellite images. For each event, water samples were taken by an automatic measuring device and analysed to determine the suspended sediment loads. The results allowed to identify three types of events. Among them, the maximum values of the measured suspended solids during rainfall-dominated events, with little snow influence, were an order of magnitude higher than the snowfall-dominated events, with values of 25000 mg/l versus 2500 mg/l respectively. The response of intermediate events, despite of low flow, showed a significant gradient. The results highlight the great dynamic variability of the sediment yield along the basin and the importance of the snow in the lamination of the erosive processes and their consequences on reservoir siltation.

Northern Hemisphere Rossby Wave Initiation Events on the Extratropical Jet—A Climatological Analysis

A climatology of Rossby wave initiation (RWI) events on the Northern Hemisphere midlatitude jet is compiled by applying an objective RWI identification algorithm to the ERA-Interim dataset. In winter, RWI events occur most frequently over the northwestern Pacific and less often over the North Atlantic. In summer, the total number of RWI events is lower than in winter and the North Pacific RWI region shifts toward the Tibetan Plateau. Composite analysis of the large-scale flow prior to, during, and after winter North Pacific RWI events shows an upstream wave train propagating across Asia on the Arctic waveguide prior to RWI. The composite wave forms on a relatively weak zonal jet streak, exhibits a baroclinic structure, and is strongly amplified by latent heat release in the warm conveyor belt of a deepening surface cyclone. Moreover, the wave forms in a region of large-scale upper-level deformation, upstream of a preexisting ridge. Further, active tropical convection affects the longitude where RWI occurs and thus acts as a geographical anchor for RWI. Individual RWI events are characterized by preferred combinations of these composite features: a strong surface cyclone tends to occur in concert with strong latent heating and a pronounced positive PV anomaly aloft. A second group of co-occurring features contains active tropical convection, a strengthened subtropical anticyclone, and the downstream ridge. These feature groups might be regarded as idealized archetypal RWI scenarios, although numerous intermediate events exist where features from both groups occur together.

Mining non-redundant closed flexible periodic patterns

Mining periodic patterns from time series databases is needed to predict any future situation. Flexible pattern mining is a special kind of periodic pattern mining where intermediate events can be overlooked purposely. Mining such patterns from time series data is advantageous due to its capability of modeling various real life scenarios. The goal of mining closed flexible patterns is to avoid unnecessary flexible patterns but preserving the same information of a complete set of patterns. Though it has wide range of application domains, existing algorithms failed to mine closed flexible patterns without generating any false positive, i.e. non-closed and ∕or redundant patterns. In this paper, a new algorithm NRCFP (Non-Redundant Closed Flexible Pattern) has been proposed that generates complete set of non-redundant closed flexible patterns in time series databases. Three pruning techniques- BackScan (existing), RangeScan (proposed) and Column-pruning (proposed) have been applied to avoid generation of non-closed patterns, redundant flexible patterns and fictitious patterns. Proposed NRCFP efficiently mines non-redundant closed flexible periodic patterns. The performance of our algorithm has been extensively analyzed using several real-life databases based on runtime and memory consumption and compared with existing state-of-the-arts approach to prove effectiveness of the algorithm with respect to required processing time and memory consumption. Some applications of our proposed algorithm in various real life domains are discussed.

Fuzzy fault tree analysis of oil and gas leakage in subsea production systems

This paper presents a probabilistic failure analysis of leakage of the oil and gas in a subsea production system using fault tree analysis (FTA). A fault tree was constructed by considering four major areas where the leakages can be initiated. These are: gas and oil wells, pipelines, key facilities and third party damage. Conventional FTA requires precise values for the probability of failure of the basic events. However, since the failure data are uncertain, a fuzzy approach to these data is taken which leads to the so-called fuzzy fault tree analysis (FFTA), a method that employs expert elicitation and fuzzy set theories to calculate the failure probabilities of the intermediate events and the top event through identification of the minimal cut sets of the fault tree. A number of importance measures for minimal cut sets and the basic events have been obtained which helps to identify the nature of dependence of the top event on the basic events and thereby can identify the weakest links that may cause leakage in the subsea production system.

Modeling Postconvective Submesoscale Coherent Vortices in the Northwestern Mediterranean Sea

AbstractFor the first time, the formation of submesoscale coherent vortices (SCVs) during intermediate and deep convection events is documented in a realistic high‐resolution (1 km) numerical simulation of the oceanic circulation in the northwestern Mediterranean Sea. Winter intermediate and deep convection leads to the formation of anticyclonic and cyclonic eddies with lifetimes exceeding 1 year. By focusing on three typical eddies, the main characteristics of such vortices are discussed. The anticyclonic eddies are typical of SCVs observed in deep convection areas so far. They are characterized by a small radius (∼6.5 km) and orbital peak velocities of about 7 cm/s located at great depth (∼1500 m) or intermediate depth (∼500 m). The cyclonic vortices show very similar characteristics, such as a high Rossby number (∼0.4), but with surface‐intensified structures. The long lifetimes of both anticyclonic and cyclonic eddies reflect very slow diffusive processes between their core and their surroundings and a strong resistance to external perturbations. These long‐lived eddies are found to participate in the spreading of a significant portion (from 15 to 35%) of the convected waters in the Gulf of Lions and contribute to the ventilation of the deep basin.

Interactions of Estuarine Shoreline Infrastructure With Multiscale Sea Level Variability

AbstractSea level rise increases the risk of storms and other short‐term water‐rise events, because it sets a higher water level such that coastal surges become more likely to overtop protections and cause floods. To protect coastal communities, it is necessary to understand the interaction among multiday and tidal sea level variabilities, coastal infrastructure, and sea level rise. We performed a series of numerical simulations for San Francisco Bay to examine two shoreline scenarios and a series of short‐term and long‐term sea level variations. The two shoreline configurations include the existing topography and a coherent full‐bay containment that follows the existing land boundary with an impermeable wall. The sea level variability consists of a half‐meter perturbation, with duration ranging from 2 days to permanent (i.e., sea level rise). The extent of coastal flooding was found to increase with the duration of the high‐water‐level event. The nonlinear interaction between these intermediate scale events and astronomical tidal forcing only contributes ∼1% of the tidal heights; at the same time, the tides are found to be a dominant factor in establishing the evolution and diffusion of multiday high water events. Establishing containment at existing shorelines can change the tidal height spectrum up to 5%, and the impact of this shoreline structure appears stronger in the low‐frequency range. To interpret the spatial and temporal variability at a wide range of frequencies, Optimal Dynamic Mode Decomposition is introduced to analyze the coastal processes and an inverse method is applied to determine the coefficients of a 1‐D diffusion wave model that quantify the impact of bottom roughness, tidal basin geometry, and shoreline configuration on the high water events.

Nitrifying bio-cord reactor: performance optimization and effects of substratum and air scouring

ABSTRACT Ammonia removal kinetics and solids’ production performance of the bio-cord technology are studied in this research. Three nitrifying reactors housing different bio-cord substratum were operated at five different ammonia loading rates. All of the bio-cord substrata demonstrated stable and high ammonia-nitrogen removal efficiencies of 96.8 ± 0.9%, 97.0 ± 0.6% and 92.0 ± 0.4% at loading rates of 0.8, 1.6 and 1.8 g -N/m2 d, respectively. At these same loading rates, the bio-cord reactors housing the three substrata also showed low solids’ production rates of 0.19 ± 0.03, 0.23 ± 0.02, 0.25 ± 0.03 g total suspended solids/d. A reduction of system stability, identified via fluctuating ammonia removal rates, was however observed for all substrata at loading rates of 2.1 and 2.4 g -N/m2 d. Further, the solids’ production rates at these higher loading conditions were also observed to fluctuate for all substrata, likely indicating intermediate sloughing events. The effects of enhancing the air scouring of the bio-cord on the ammonia removal rate was shown to be dependent upon the substratum, while enhanced air scouring of the bio-cord was shown to stabilize the production of solids for all substrata. This study represents the first performance and optimization study of the bio-cord technology for low-carbon nitrification and shows that air scouring of the substratum reduces sloughing events at elevated loading and that the bio-cord technology achieves stable kinetics above conventional rates of 1 g -N/m2 d to values of 1.8 g -N/m2 d.

Volcanic stratospheric sulfur injections and aerosol optical depth from 500 BCE to 1900 CE

Abstract. The injection of sulfur into the stratosphere by explosive volcanic eruptions is the cause of significant climate variability. Based on sulfate records from a suite of ice cores from Greenland and Antarctica, the eVolv2k database includes estimates of the magnitudes and approximate source latitudes of major volcanic stratospheric sulfur injection (VSSI) events from 500 BCE to 1900 CE, constituting an update of prior reconstructions and an extension of the record by 1000 years. The database incorporates improvements to the ice core records (in terms of synchronisation and dating) and refinements to the methods used to estimate VSSI from ice core records, and it includes first estimates of the random uncertainties in VSSI values. VSSI estimates for many of the largest eruptions, including Samalas (1257), Tambora (1815), and Laki (1783), are within 10 % of prior estimates. A number of strong events are included in eVolv2k which are largely underestimated or not included in earlier VSSI reconstructions, including events in 540, 574, 682, and 1108 CE. The long-term annual mean VSSI from major volcanic eruptions is estimated to be ∼ 0.5 Tg [S] yr−1, ∼ 50 % greater than a prior reconstruction due to the identification of more events and an increase in the magnitude of many intermediate events. A long-term latitudinally and monthly resolved stratospheric aerosol optical depth (SAOD) time series is reconstructed from the eVolv2k VSSI estimates, and the resulting global mean SAOD is found to be similar (within 33 %) to a prior reconstruction for most of the largest eruptions. The long-term (500 BCE–1900 CE) average global mean SAOD estimated from the eVolv2k VSSI estimates including a constant background injection of stratospheric sulfur is ∼ 0.014, 30 % greater than a prior reconstruction. These new long-term reconstructions of past VSSI and SAOD variability give context to recent volcanic forcing, suggesting that the 20th century was a period of somewhat weaker than average volcanic forcing, with current best estimates of 20th century mean VSSI and SAOD values being 25 and 14 % less, respectively, than the mean of the 500 BCE to 1900 CE period. The reconstructed VSSI and SAOD data are available at https://doi.org/10.1594/WDCC/eVolv2k_v2.

Insights on the seismotectonics of the western part of northern Calabria (southern Italy) by integrated geological and geophysical data: Coexistence of shallow extensional and deep strike-slip kinematics

We assess the seismotectonics of the western part of the border area between the Southern Apennines and Calabrian Arc, centered on the Mercure extensional basin, by integrating recent seismicity with a reconstruction of the structural frame from surface to deep crust. The analysis of low-magnitude (ML≤3.5) events occurred in the area during 2013–2017, when evaluated in the context of the structural model, has revealed an unexpected complexity of seismotectonics processes. Hypocentral distribution and kinematics allow separating these events into three groups. Focal mechanisms of the shallower (<9km) set of events show extensional kinematics. These results are consistent with the last kinematic event recorded on outcropping faults, and with the typical depth and kinematics of normal faulting earthquakes in the axial part of southern Italy. By contrast, intermediate (~9–17km) and deep (~17–23km) events have fault plane solutions characterized by strike- to reverse-oblique slip, but they differ from each other in the orientation of the principal axes. The intermediate events have P axes with a NE-SW trend, which is at odds with the NW-SE trend recorded by strike-slip earthquakes affecting the Apulia foreland plate in the eastern part of southern Italy. The intermediate events are interpreted to reflect reactivation of faults in the Apulia unit involved in thrust uplift, and appears aligned along an ~WNW-ESE trending deep crustal, possibly lithospheric boundary. Instead, deep events beneath the basin, which have P-axis with a NW-SE trend, hint to the activity of a deep overthrust of the Tyrrhenian back-arc basin crust over the continental crust of the Apulia margin, or alternatively, to a tear fault in the underthrust Apulia plate. Results of this work suggest that extensional faulting, as believed so far, does not solely characterizes the seismotectonics of the axial part of the Southern Apennines.

The Impact of Urbanization on Temporal Changes in Sediment Transport in a Gravel Bed Channel in Southern Ontario, Canada

AbstractA field investigation has been undertaken to characterize the event‐based bed load transport dynamics of a highly urbanized gravel bed stream. A combination of direct bed load and tracer particle measurements were taken over a 3 year period during which time approximately 30 sediment mobilizing events occurred. Sediment transport measurements were used to calibrate a fractional bed load transport model and combined with hydrometric data which represent four different land use conditions (ranging from rural to highly urbanized) to analyze the differences in discharge magnitude and frequency and its impact on sediment transport. Fractional transport analysis of the bed load measurements indicates that frequent intermediate discharge events can mobilize sand and fine gravel to an approximate equally mobile condition, however, the transport rates at these discharges exhibit greater variability than at discharges above the bankfull discharge. Path lengths of the coarse fraction, measured using tracer clasts, are insensitive to peak discharge, and instead transport at distances less than those reported in other gravel bed channels, which is attributed to the shorter duration discharge events common to urban streams. The magnitude‐frequency analysis reveals that the frequency, time, and volume of competent sediment mobilizing events are increasing with urbanization. Variability in effective discharges suggests that a range of discharges, spanning between frequent, low magnitude events to less frequent, high magnitude events are geomorphically significant. However, trends in the different land use scenarios suggest that urbanization is shifting the geomorphic significance toward more frequent, lower magnitude events.

Probabilistic Models For Earthquakes With Large Return Periods In Himalaya Region

Determination of the frequency of large earthquakes is of paramount importance for seismic risk assessment as large events contribute to significant fraction of the total deformation and these long return period events with low probability of occurrence are not easily captured by classical distributions. Generally, with a small catalogue these larger events follow different distribution function from the smaller and intermediate events. It is thus of special importance to use statistical methods that analyse as closely as possible the range of its extreme values or the tail of the distributions in addition to the main distributions. The generalised Pareto distribution family is widely used for modelling the events which are crossing a specified threshold value. The Pareto, Truncated Pareto, and Tapered Pareto are the special cases of the generalised Pareto family. In this work, the probability of earthquake occurrence has been estimated using the Pareto, Truncated Pareto, and Tapered Pareto distributions. As a case study, the Himalayas whose orogeny lies in generation of large earthquakes and which is one of the most active zones of the world, has been considered. The whole Himalayan region has been divided into five seismic source zones according to seismotectonic and clustering of events. Estimated probabilities of occurrence of earthquakes have also been compared with the modified Gutenberg–Richter distribution and the characteristics recurrence distribution. The statistical analysis reveals that the Tapered Pareto distribution better describes seismicity for the seismic source zones in comparison to other distributions considered in the present study.

A joint model of cancer incidence, metastasis, and mortality.

Many diseases, especially cancer, are not static, but rather can be summarized by a series of events or stages (e.g. diagnosis, remission, recurrence, metastasis, death). Most available methods to analyze multi-stage data ignore intermediate events and focus on the terminal event or consider (time to) multiple events as independent. Competing-risk or semi-competing-risk models are often deficient in describing the complex relationship between disease progression events which are driven by a shared progression stochastic process. A multi-stage model can only examine two stages at a time and thus fails to capture the effect of one stage on the time spent between other stages. Moreover, most models do not account for latent stages. We propose a semi-parametric joint model of diagnosis, latent metastasis, and cancer death and use nonparametric maximum likelihood to estimate covariate effects on the risks of intermediate events and death and the dependence between them. We illustrate the model with Monte Carlo simulations and analysis of real data on prostate cancer from the SEER database.

Building Predictive Adverse Outcome Pathway Models: Role of Molecular Initiating Events and Structure–Activity Relationships

Abstract The original contribution of the adverse outcome pathway (AOP) concept to predictive toxicology is that the use of a range of assays covering the main events of the whole toxicity pathway would improve the prediction of the apical endpoints with alternative tests. This would permit more solid, mechanistically based predictions. However, explicit and systematic quantitative analysis of the AOPs and their integration into larger schemes is at times lacking. This leaves room to subjective implementations. We have investigated the quantitative modeling aspects of AOPs related to important apical endpoints, that is, skin sensitization, endocrine disruptors, and carcinogenicity. A common trend is that the major contribution to the final predictivity is given by in vitro or in silico models of molecular initiating events (MIEs), which appear to be the rate-limiting steps of the toxicity pathways, whereas models for intermediate events have poor correlations with apical endpoints. Since MIEs are in gener...

결측되었거나 구간중도절단된 중간사건을 가진 준경쟁적위험 자료에 대한 가산위험모형

결측되었거나 구간중도절단된 중간사건을 가진 준경쟁적위험 자료에 대한 가산위험모형

A quantitative approach for risk assessment of a ship stuck in ice in Arctic waters

Arctic waters have historically been regarded as harsh environments owing to their extreme weather conditions and remoteness from land. The advantages of shorter sea routes and hydrocarbon energy exploitation have recently led to increased marine activities in such harsh environments. To ensure safe operation within the area, the potential risks of ship accidents, need to be systematically analyzed, assessed and managed along with the associated uncertainties. The treatment of epistemic uncertainty in the likelihoods of adverse events due to lack of knowledge and information should also be considered. This paper presents a Frank copula-based fuzzy event tree analysis approach to assess the risks of major ship accidents in Arctic waters, taking uncertainty into consideration. The quantitative approach includes four steps, namely, accident scenario modeling by an event tree model, probability and dependence analysis of the associated intermediate events, risk assessment with respect to the consequent outcome events. A major ship accident in Arctic waters - ships stuck in ice, is chosen as a case to interpret the modeling process of the approach proposed. Crews and ships owners can use such approach to defining risk control options that enable optimal risk mitigation. Maritime management may also benefit from better risk assessment.

Metabolic Disruption Early in Life is Associated With Latent Carcinogenic Activity of Dichloroacetic Acid in Mice.

Early-life environmental factors can influence later-life susceptibility to cancer. Recent evidence suggests that metabolic pathways may mediate this type of latency effect. Previously, we reported that short-term exposure to dichloroacetic acid (DCA) increased liver cancer in mice 84 weeks after exposure was stopped. Here, we evaluated time course dynamics for key events related to this effect. This study followed a stop-exposure design in which 28-day-old male B6C3F1 mice were given the following treatments in drinking water for up to 93 weeks: deionized water (dH2O, control); 3.5 g/l DCA continuously; or 3.5 g/l DCA for 4-52 weeks followed by dH2O. Effects were evaluated at eight interim time points. A short-term biomarker study was used to evaluate DCA effects at 6, 15, and 30days. Liver tumor incidence was higher in all DCA treatment groups, including carcinomas in 82% of mice previously treated with DCA for only 4 weeks. Direct effects of DCA in the short-term study included decreased liver cell proliferation and marked mRNA changes related to mitochondrial dysfunction and altered cell metabolism. However, all observed short-term effects of DCA were ultimately reversible, and prior DCA treatment did not affect liver cell proliferation, apoptosis, necrosis, or DNA sequence variants with age. Key intermediate events resulting from transient DCA exposure do not fit classical cytotoxic, mitogenic, or genotoxic modes of action for carcinogenesis, suggesting a distinct mechanism associated with early-life metabolic disruption.

DEMATERIALIZZAZIONE DELLA FISICA

Quantum Mechanics has taught us a lesson that goes well beyond a set of new physical laws. It has provided us with genuine “theorems of epistemology”. We now know that there are situations when the observation of the world cannot be considered as the mere reading of a reality pre-existing the observation, whereas there are circumstances where the knowledge of the whole do not corresponds to the knowledge of the parts (holism). We know that there are incompatible properties that are complementary. We know that there exist properties of the whole that are incompatible with any property of each part. The notion of “object” defined in terms of its “properties ” is in contrast with its mereologic connotation according to which objects can be composed to form new objects. The particle ontology as localizable unity is in contrast with the Malament theorem in quantum field theory. To the above add the fact that the two more general fundamental theories in physics – the quantum theory of fields and the general relativity of Einstein – are logically incompatible. In order to reconcile the logical coherence of the observations with their theoretical explanation we need a radical change of paradigm. The solution here proposed is to abandon the vision of the world as a “mechanism” and to substitute it with that of “algorithm”. This is the paradigm of the “universe as a huge computer” that have been latent within the community since Richard Feynman, and nowadays is resurrecting in physics, showing its full theoretical power. In the new algorithmic vision the “mechanics” becomes an emergent phenomenology. Without the need of physical primitive, the new “informational” program allows us to found physics on solid axiomatic grounds. The quantum theory of abstract systems along with the free quantum field theory are derived from information-theoretic axioms. The axioms of quantum theory all have an epistemological connotation, and pertain the possibility of falsifying the propositions of the theory. They reconnect holism with reductionism, probabilism and falsifiability, substituting the notion of “object” with that of “system” and of “event”, and logically implying the theorem of quantum theory without the need of using the abstract Hilbert-spaces toolkit. The free quantum field theory (Weyl, Dirac e Maxwell) is obtained by adding axioms of minimization of algorithmic complexity. The informational framework well separates the notions of “experiment”and “theory”: the theory connects input with output, the experiment being identified with the collection of input, output, and objective intermediate events. The objective reality (experiment) is made of “icons” with which we interact: the theory is the underlying algorithm. The paradigm describes the tapestry of reality as pure software, “software”. “Software without hardware”: the dematerialization of physics. “Reality without realism” means pure logical coherentism.

Constraining the hydration of the subducting Nazca plate beneath Northern Chile using subduction zone guided waves

Guided wave dispersion is observed from earthquakes at 180–280 km depth recorded at stations in the fore-arc of Northern Chile, where the 44 Ma Nazca plate subducts beneath South America. Characteristic P-wave dispersion is observed at several stations in the Chilean fore-arc with high frequency energy (>5 Hz) arriving up to 3 s after low frequency (<2 Hz) arrivals. This dispersion has been attributed to low velocity structure within the subducting Nazca plate which acts as a waveguide, retaining and delaying high frequency energy. Full waveform modelling shows that the single LVL proposed by previous studies does not produce the first motion dispersion observed at multiple stations, or the extended P-wave coda observed in arrivals from intermediate depth events within the Nazca plate. These signals can however be accurately accounted for if dipping low velocity fault zones are included within the subducting lithospheric mantle. A grid search over possible LVL and faults zone parameters (width, velocity contrast and separation distance) was carried out to constrain the best fitting model parameters. Our results imply that fault zone structures of 0.5–1.0 km thickness, and 5–10 km spacing, consistent with observations at the outer rise are present within the subducted slab at intermediate depths. We propose that these low velocity fault zone structures represent the hydrated structure within the lithospheric mantle. They may be formed initially by normal faults at the outer rise, which act as a pathway for fluids to penetrate the deeper slab due to the bending and unbending stresses within the subducting plate. Our observations suggest that the lithospheric mantle is 5–15% serpentinised, and therefore may transport approximately 13–42 Tg/Myr of water per meter of arc. The guided wave observations also suggest that a thin LVL (∼1 km thick) interpreted as un-eclogitised subducted oceanic crust persists to depths of at least 220 km. Comparison of the inferred seismic velocities with those predicted for various MORB assemblages suggest that this thin LVL may be accounted for by low velocity lawsonite-bearing assemblages, suggesting that some mineral-bound water within the oceanic crust may be transported well beyond the volcanic arc. While older subducting slabs may carry more water per metre of arc, approximately one third of the oceanic material subducted globally is of a similar age to the Nazca plate. This suggests that subducting oceanic lithosphere of this age has a significant role to play in the global water cycle.