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Marine multichannel and wide‐angle seismic data constrain the distribution of seamounts, sediment cover sequence and crustal structure along a 460 km margin‐parallel transect of the Hikurangi Plateau. Seismic reflection data reveals five seamount up‐to 4.5 km high and 35–75 km wide, with heterogeneous internal velocity structure. Sediment cover decreases south‐to‐north from ∼4.5 km to ∼1–2 km. The Hikurangi Plateau crust (VP 5.5–7.5 km/s) is 11 ± 1 km thick in the south, but thins by 3–4 km further north (∼7–8 km). Gravity models constructed along two seismic lines show the reduction in crustal thickness persists further east, coinciding with a bathymetric scarp. Gravity data suggest the transition in crustal thickness may reflect spatial variability in deformation and lithospheric extension associated with plateau breakup. Variability in the thickness of subducting crust may contribute to differences in megathrust geometry, upper‐plate stress state and high‐rates of contraction and uplift along the southern Hikurangi margin. Plain Language Summary: The thickness of crust arriving at subduction zones exerts a major influence on the configuration, structure, and distribution of stresses at plate boundaries. A region of thickened oceanic crust, the Hikurangi Plateau, is subducting beneath the North Island of New Zealand. To understand the structure of this Plateau, we analyze seismic data along a 460 km long transect, which reveals five large seamounts, and a 3–4 km reduction crustal thickness between the southern and northern areas of the Plateau. Gravity data show this difference is persistent across the plateau and reveal structures suggesting the crust may have thinned when the Hikurangi plateau separated from a second plateau (Manihiki), which is thought to have formed at the same time. We propose that the subduction of thicker crustal along the southern Hikurangi margin may contribute to the shallow angle of the subducting plate, and high rates of uplift and deformation in the overthrusting plate. Key Points: Crustal thickness of the Hikurangi Plateau reduces by ∼30% between the southern (10–11 km) and northern (7–8 km) PlateauCoincident contrasts in plateau fabric may attribute the thickness contrast to rifting from the Manihiki PlateauThickness contrasts may impact the geometry of the subducting plate and rates of upper‐plate compression and uplift along the Hikurangi margin [ABSTRACT FROM AUTHOR]

Devastating megathrust earthquakes and slow earthquakes both occur along subducting plate interfaces. These interplate seismic activities are strongly dependent on the nature of the plate interface, such as the shape of the plate interface and the materials and physical conditions along the plate interface. The oceanic plate, which is the input to the subduction zone, is the first order control on the nature of the plate interface. To reveal the nature of the subduction inputs to the northeastern Japan arc, we have conducted large-scale controlled-source seismic surveys of the northwestern part of the oceanic Pacific plate. The obtained seismic data have revealed (1) oceanic plate structural evolution caused by plate bending prior to subduction, suggesting the promotion of the oceanic plate hydration; (2) spatial variation of the oceanic plate structure, such as variations in the thickness of sediment and crust; (3) that the spatial variations are caused by both ancient plate formation processes and more recent volcanic activities; and (4) that spatial variations of the nature of the subduction inputs show good correlation with the along-strike variations in the seismic structure and seismic activities after subduction, including the coseismic slip distribution of the 2011 Tohoku earthquakes and the structural differences between the northern and the southern Japan Trench. These observations indicate that the incoming oceanic plate structure is much more spatially variable than previously thought and also imply that the spatial variation of the subduction inputs is a key controlling factor of the spatial variation of various processes in subduction zones, including interplate seismic activities and evolution of the forearc structure. [ABSTRACT FROM AUTHOR]

Off Cape Muroto area, along the Nankai Trough in southwest Japan, is a typical area with adjacent occurrences of slow and megathrust earthquakes. High‐resolution monitoring of slow earthquakes is necessary to understand tectonic conditions. In the off Muroto area, distributed acoustic sensing (DAS) measurement, which provides high‐density strain data, has been conducted using offshore fiber‐optic cable. We observed shallow tremors, a type of slow earthquakes, using DAS measurement for the first time. The characteristics of the tremor signals recorded by DAS were longer durations than those recorded in seismographs and composed of several phases with apparent velocities of several hundreds of m/s to several km/s that are coherent only in tens of meters. By combining DAS and seismograph data, we located these tremors around a subducted seamount peak. Therefore, spatial relationship between slow earthquakes and structural characteristics is suggested. This is a pioneering study of slow earthquake observation using DAS. Plain Language Summary: Distributed acoustic sensing (DAS) measurement is a recent technology that uses a fiber‐optic cable as a strain sensor array. As DAS provides high‐density observation data, it has often been used for the observation of regular earthquakes in recent years. However, few studies have used DAS measurement to observe slow earthquakes, which have longer characteristic durations compared to regular earthquakes. We observed shallow tremors, a type of slow earthquake, using DAS for the first time off Cape Muroto, where slow and huge regular earthquakes occur in the neighboring areas. The characteristics of tremor signals in DAS data are long durations and composition of several phases with variable apparent velocities that are coherent only in tens of meters. We located tremors by picking the arrival of signals by visually checking the waveforms of DAS and an offshore seismograph network and locating them at the point where the difference between synthetic and observed arrival times was the smallest. Most tremors occurred around 134.7°E, 32.8°N, which corresponds to a subducted seamount peak; therefore, a spatial relationship between slow earthquakes and a subducted seamount is suggested in this region. Key Points: We first observed shallow tremors by distributed acoustic sensing (DAS) using offshore fiber‐optic cable in the Nankai TroughTremor signals of DAS are composed of several phases of variable apparent velocities that are coherent only in tens of metersSpatial relationship between shallow tremors and subducted seamount is suggested along the dip direction [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) are chemically stable and serve as excellent labels because their characteristic red coloration based on the localized surface plasmon resonance (LSPR) does not fade. However, it is necessary to control the structure of AuNPs to use them as labels for various analyses, because their optical properties depend strongly on their size, shape, and state of aggregation. In this study, we developed gold nanostructures (AuNSs) by encapsulating many small AuNPs within a polymer for scattering light-based bacterial detection. The AuNSs consisting of many small nanoparticles provided stronger scattered light intensity than a single AuNP of the same particle size. We found that the aggregation of the AuNSs enhanced the scattering light intensity, depending strongly on their aggregation states, and did not affect the wavelength of the scattering light observed under a dark-field microscope. By specifically binding the antibody-introduced AuNSs to the antigen on the bacterial surface, it was possible to label the target bacteria and detect them based on their light scattering characteristics. In addition, to improve the accuracy of the selective identification of the cells of interest, labels based on scattered light should ideally have a fixed wavelength of scattered light with high intensity. From these perspectives, we developed a method of constructing an optical antenna on the surface of target bacterial cells using antibody-introduced NSs. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) show unique size‐ and shape‐dependent photosensitive properties resulting from localized surface plasmon resonance, which can be exploited in colorimetric sensors. Polyamidoamine (PAMAM) dendrimers are suitable nanotemplates of AuNPs and nanoplatforms of some stimuli‐responsive materials. In this study, AuNP was loaded in phenylalanine (Phe)‐modified PAMAM dendrimers with dual pH‐ and temperature‐sensitive properties to produce a naked‐eye colorimetric sensor with responsivity to both pH and temperature. The ultraviolet‐visible (UV‐Vis) spectra of AuNP‐loaded PAMAM‐Phe‐Suc were changed by heating at pH 4 and 5, but unchanged at pH above 5.5. The UV‐Vis spectra of AuNP‐loaded PAMAM‐Phe and PAMAM‐Suc were only slightly changed by heating at pH above 5.5 and at pH 4 and 5, respectively. In solution, AuNP‐loaded PAMAM‐Phe‐Suc changed color (from brown to gray) under high temperature (≥50 °C) and acidic (pH≤5) conditions, suggesting its functionality as a naked‐eye colorimetric dual pH and temperature sensor. [ABSTRACT FROM AUTHOR]

Marine multichannel and wide‐angle seismic data constrain crustal structure along a 530 km margin‐parallel transect of the Hikurangi subduction zone. The subducting Hikurangi Plateau crust (VP 5.0–7.4 km/s) is ∼1 km thicker (11 ± 1 km) and mantle velocities are ∼0.2 km/s higher (VP 8.3–8.5 km/s) beneath south/central Hikurangi relative to north Hikurangi. In the overthrusting plate, an abrupt 0.5 km/s south‐to‐north reduction in forearc wavespeeds occurs in concert with a change in seismic reflection character. We analyze legacy seismic data to show that the forearc transition likely reflects lateral variability in the updip extent of the Torlesse Backstop. Furthermore, we map this unit along‐strike and note a broad correlation between the backstop and down‐dip extent of shallow slow‐slip. We propose that the geological architecture of the overthrusting plate contributes to spatial variability in the location of shallow frictional transitions along the Hikurangi margin, impacting both seismic and tsunami hazard. Plain Language Summary: Some subduction zones produce the largest earthquakes and tsunami on Earth, while others slip freely. To understand what factors impact subduction zone slip behavior, we analyze seismic data along a 530 km long transect spanning a transition from strong (south Hikurangi) to weak (central/north Hikurangi) interseismic locking. From south‐to‐north, we find that seismic wavespeeds in the overthrusting plate undergo an abrupt (∼10%) reduction, which coincides with a reduction in seismic reflectivity. We show that these changes likely reflect differences in the offshore (updip) extent of basement rocks within the forearc crust, which we map using seismic data. These maps also show that the offshore extent of basement rocks is broadly correlated with the maximum depth of shallow slow‐slip events. We propose that geological architecture of the overthrusting plate may contribute to spatial variability in megathrust slip‐behavior, impacting both seismic and tsunami hazard along the Hikurangi margin. Key Points: Coincident reductions in seismic wavespeeds and lower‐crustal reflectivity occur from south‐to‐north along the Hikurangi forearcLegacy seismic reflection data attribute the forearc transition to along‐strike differences in the updip extent of the Torlesse BackstopShallow slow‐slip is focused updip of the backstop, suggesting it may impact the location of shallow frictional transitions at Hikurangi [ABSTRACT FROM AUTHOR]

The offshore part of the North Anatolian Fault (NAF) beneath the Marmara Sea is a well-known seismic gap for future M > 7 earthquakes in the sense that more than 250 yr have passed since the last major earthquake in the Central Marmara region. Although many studies discussed the seismic potential for the future large earthquake in this region on the basis of historical record, geodetic and geological observations, it is difficult to evaluate the actual situation on the seismic activity and structure along the NAF beneath the Marmara Sea due to the lack of ocean bottom seismic observations. Using ocean bottom seismometer observations, an assessment of the location of possible asperities that could host an expected large earthquake is undertaken based on heterogeneities in the microseismicity distribution and seismic velocity structure. Specifically, seismic tomography and precise hypocentre estimations are conducted using offshore seismic data whose recording period is 11 months. About five times more microearthquakes are detected with respect to events recorded in a land-based catalogue. A comparison with previously published results from offshore observation data suggests that the seismicity pattern had not changed from 2014 September to 2017 May. The location accuracy of microearthquakes is greatly improved from only the land-based earthquake catalogue, particularly for depth direction. There are several aseismic and inactive zones of microearthquake, and the largest one is detected using land-based seismic observation, whereas other zones are newly detected via offshore observations. The obtained velocity model shows a strong lateral contrast, with two changing points. The western changing point corresponds to a segmentation boundary, where the dip angle of the NAF segments changed. High-velocity zones from tomographic images are characterized by low seismicity eastward of the segment boundary. To the east of 28.50°E, the high-velocity zone becomes thicker in the depth direction and is characterized by low seismicity. Although the low seismic activity alone could be interpreted as both strong coupling and fully creeping, the high-velocity features at the same can be concluded that these zones are consist of brittle material and strong coupling. From comparison with other geodetic and seismic studies, we interpret these zones as locked zones that had been ruptured by the past large earthquakes and could be ruptured by future ones. These zones might accumulate strain since the main shock rupture associated with the 1766 May M s 7.3 earthquake, the latest major earthquake in this region. [ABSTRACT FROM AUTHOR]

The 2011 M w 9.0 Tohoku-oki earthquake ruptured the subduction megathrust fault in the central Japan Trench. We investigated the aftershock activity in the southern Japan Trench to the south of the main rupture area using ocean bottom seismographs deployed both landward and seaward of the trench. In the trench-outer rise region seaward of the trench axis, we identified several ∼100-km-long linear earthquake trends both parallel and oblique to the southern Japan Trench. The earthquake trend oblique to the southern Japan Trench is a southward extension of the trench-parallel linear earthquake trend in the central to northern Japan Trench. The trench-parallel normal-faults in the trench-outer rise region could extend linearly, despite the change of the trench strike from N–S to NNE–SSW to the south of the main rupture area. Normal-faults oblique to the trench should be considered as substantial parts of large intraplate normal-faulting earthquakes. In addition, intraplate seismicity coinciding with the lower velocity oceanic mantle suggest that the structure heterogeneity would be indicative of normal-faults extending into the mantle. In the trench landward area, earthquake activity showed along-trench variations. Earthquakes along the shallow megathrust interface near the trench were observed south of 37°N. These shallow near-trench regular earthquakes, which are located close to the episodic tremors and temporally correlated with the tremor activities, suggest that the afterslip on the plate interface likely extended to the shallow plate interface close to the trench axis. Smaller spatial scale structure heterogeneity, such as the thickness variation in the channel-like low-velocity sedimentary unit, likely relate to the proximity of the regular earthquakes and slow slip which results in the formation of diverse slip behaviours in the shallow subduction zone of the southern Japan Trench. [ABSTRACT FROM AUTHOR]

Exploring the structure of convergent margins is key to understanding megathrust slip behavior and tsunami generation. We present new wide‐angle and marine multichannel seismic data that constrain the crustal structure and accretion dynamics of the northern Hikurangi margin. The top of the basement of the Hikurangi Plateau is overlain by a rough, 2–3 km thick layer of volcanic cover with P‐wave velocities (VP) between 3 and 5 km/s. This volcanic cover contributes significantly to seismic reflectivity beneath the shallow subduction plate boundary. The frontal prism structure varies along‐strike from ∼25 km wide with imbricate thrust faults where accretion of trench sediments is undisrupted, to narrower (∼14 km) with slumps and branching, irregular thrust fault geometries, which may reflect lower sediment supply or past seamount collisions. A large thrust fault network in the inner prism with a seismically fast hanging wall indicates a mechanical boundary between a seismically faster deforming backstop and the seismically slower frontal prism. Near the coastline, VP increases between 2.8 and 4 km/s at 2–8 km depth and is 0.5–1.7 km/s slower than the southern Hikurangi margin. Low seismic wavespeeds and low vertical velocity gradients in the inner prism support the hypothesis that a weak overthrusting plate contributes to historic tsunami‐earthquakes and long duration seismic ground motion. Plain Language Summary: The northern Hikurangi margin is a subduction zone that generates hazardous earthquakes and tsunami, as well as months‐long slow slip events. Here, we use a controlled seismic energy source to image and map the seismic wavespeed of the overthrusting plate, downgoing plate—which is called the Hikurangi Plateau—and the megathrust fault that generates earthquakes. Thick layers of volcanic sediments and lavas on the Hikurangi Plateau produce bright reflections beneath the megathrust fault. Volcanic mountains on the subducting plate, called seamounts, are shown to influence the volume of sediment that scrapes off the downgoing plate and complicate the way that thrust faults form in the overthrusting plate. An increase in seismic velocity and change in fault geometry in the overthrusting plate indicates that the upper plate can be divided into a weak outer prism of young off‐scraped sediments and a stronger inner prism of older, deformed sediments. However, the strength of the interior of the overthrusting plate is still relatively weak. A weak overthrusting plate with slow seismic wavespeeds is believed to promote larger than predicted tsunami and excessive shaking during earthquakes. Key Points: Sharp along‐strike contrasts in frontal accretion indicate variable sediment supply and past subduction of topographyWe identify a deformed inner prism with elevated seismic velocity and an accreted frontal prism divided by a network of thrust faultsLow P‐wave velocities in the overthrusting plate near Gisborne may contribute to tsunamigenesis and enhanced ground motion duration [ABSTRACT FROM AUTHOR]

Relationships between extensional tectonics and magmatism are ubiquitous in continental rifts and oceanic spreading centers. Yet few studies document interactions between extensional faults and mantle melts in volcanic arcs. We constrain the crustal structure of the extensional offshore Taupo Volcanic Zone (TVZ) from a marine multichannel and wide‐angle seismic experiment. The TVZ crust thins from >26 km to ∼18–19 km across ∼50 km in the Bay of Plenty. Elevated P wave velocities in the lower crust indicate mafic additions. Magmatic sills between 4‐ and 15‐km depth lie beneath listric normal faults in a ∼40‐km‐wide active rift zone. P wave velocities in the middle and upper crust along the arc front are ∼0.3–0.5 km/s slower than in the adjacent crust, indicating a possible thermal anomaly imparted by heat from magmatic intrusions. We propose that rifting in the offshore TVZ is partially compensated by intrusions and assisted by thermal weakening of the lithosphere. Plain Language Summary: The offshore Taupo Volcanic Zone is a rifting volcanic arc located in the North Island of New Zealand. We use seismic waves from man‐made sources to map seismic wave speeds and image fault and magma‐related structures beneath the offshore Taupo Volcanic Zone. We find that rifting has stretched the crust from >26 km to ∼18–19 km. Fast seismic wave speeds in the lower crust suggest that magma has partially filled some of the stretched crust to reduce the amount of thinning. Using seismic reflections, we find that the zone with the largest faults coincides with an area of intruded magma located between 4‐ and 15‐km depth. We propose that a feedback relationship influences the locations of faults and magma. Extension helps magma to rise from deep in the Earth. In response, the intruded magma heats and weakens the rigid outer layer of the earth to assist more rifting. The hazard potential of the fault and magma systems in this region is not fully known, motivating the need for further investigations to map and monitor magma bodies and faults in the offshore Taupo Volcanic Zone. Key Points: Magmatic intrusions and thermal weakening may facilitate rifting in the offshore Taupo Volcanic ZoneBay of Plenty crust rifted from >26 km to ∼18–19 km across a 50‐km‐wide zone; magmatic additions compensate ∼20–30% of crustal extensionListric faulting overlies an ∼40‐km‐wide zone of sill complexes and heterogeneous P wave velocities in the upper and middle crust [ABSTRACT FROM AUTHOR]

Oceanic plates play an important role in transporting water from Earth's surface into the mantle. The trench–outer rise region is one of the places where hydration of the oceanic plate occurs. We investigated oceanic plate hydration in the trench–outer rise region of the Japan Trench on the basis of the seismic velocity structure as estimated by a tomographic analysis of data from ocean bottom seismograph arrays. This analysis demonstrates a reduction in P- wave and S- wave velocity (Vp and Vs) within the uppermost oceanic mantle of the incoming Pacific plate in the direction towards the trench axis. This seismic velocity reduction, which was observed in at least the uppermost 15 km of the mantle, is consistent with hydration of the uppermost mantle due to infiltration of water through the oceanic crust along bending-related normal faults. Under the assumption that the velocity reduction is caused solely by serpentinization of the mantle, the Vp changes suggest that water content increases by about 1.1 to 2.9 wt per cent at depths as great as 15 km below the oceanic Moho. An increase in water-filled fractures can also account for this velocity reduction with a smaller amount of water. Aside from the general trend of velocity reduction towards the trench axis, the Vp structure of the incoming plate shows spatial heterogeneity related to mantle seismicity, in that earthquakes within the uppermost mantle generally coincide with areas of low Vp. This spatial seismic heterogeneity is consistent with localized hydration or formation of water-filled fractures along bending-related normal faults. Hence, a low- Vp anomaly within the uppermost oceanic mantle could be an indicator of possible sites of large outer-rise normal-faulting earthquakes in which the rupture extends into the mantle. [ABSTRACT FROM AUTHOR]

A simple processing technology based on spontaneous arrangement of gold nanoparticles (AuNPs) on cellulose nanofibers (CNFs) makes it possible to form a gold leaf with superior mechanical, chemical and electrical characteristics with a small amount of gold (<15 vol.%). The electrical resistivity of the AuNP/CNF hybrid film reached 8.7×10−6 Ω cm at 13 vol.% corresponding to that of a gold plate (2.9×10−6 Ω cm) through a distribution of AuNP inside the film in the form of a band. The AuNPs work not only as linkers between various CNFs in the hybrid structure but also as scaffolds. Self‐assembly allows the formation of leaves on three‐dimensional micrometer‐sized substrates, on which it is impossible to form a uniform flexible metallic layer using conventional techniques such as sputtering, vapor deposition, and electroless plating. The hybrid film holds great promise as a novel gold leaf for a wide range of applications, including coatings, smart papers, electronic skins, and wearable devices owing to its unique combination of superior properties, as well as good productivity, processability, and renewability. [ABSTRACT FROM AUTHOR]

In this study, the creep rate across the North Anatolian Fault was directly measured in the western Sea of Marmara using the seafloor acoustic ranging technique; the data reveal coupling conditions on the fault interface and stress accumulation with implications for regional seismic risk evaluation. Continuous measurements over a period of 3.5 years at a site in the Western High clearly indicate right‐lateral displacement at a rate of 10.7 ± 4.7 mm/year (95% confidence level); approximately half of the regional block motion at this location is released by this steady motion. A simple model of three elastic layers—a partially creeping sedimentary layer (8 km) at the top with the observed rate, a locked (3 km) and fully creeping layer in the middle, and a bottom layer—assumed from seismicity, reasonably explains onshore Global Navigation Satellite System data for the surrounding region. Plain Language Summary: The North Anatolian Fault (NAF) cuts across the east and west of the Turkish mainland and has repeatedly generated destructive earthquakes (magnitude ~7‐class) to release accumulated strain originating from regional plate motion. The NAF beneath the Sea of Marmara has remained as a "seismic gap" for more than a century and the stress condition of the fault plane is thought to be nearly matured. An earthquake in this region is expected to cause severe damage in Istanbul, the most populous city in Turkey. However, the submarine environment prevents investigation of the fault movement using the traditional geodetic techniques applicable to onshore surveys. We applied a seafloor geodetic technique using continuous acoustic ranging for 3.5 years and found that the NAF in the western Sea of Marmara is creeping at nearly half of the regional plate motion. Despite the partial creep, strain accumulation on the fault has already reached the equivalent of a M7‐class earthquake. Key Points: First direct evidence of creep in the submarine part of the North Anatolian Fault based on a seafloor geodetic surveyEstimated creep rate for the western part of the Sea of Marmara amounts to nearly half of the regional block motionA fault model incorporating the observed creep rate and the coupling condition estimated from microseismicity well explains GNSS data [ABSTRACT FROM AUTHOR]

Bacterial detection has attracted substantial interest in recent years owing to its importance in biology, medical care, drug discovery, and public health. For such applications, bacterial cell-imprinting technologies are regarded as potential methods, as they can fabricate artificial tailor-made receptors for cellular recognition. In comparison to conventional methods, which generally require a few days for bacterial determination, cell-imprinted polymers can save a substantial amount of time. Here, we report a high-throughput bacterial detection method based on a cell-imprinted 96-well microplate. The fabrication of the bacterial cell-imprinted polypyrrole and nafion complex was accomplished on a gold nanoparticle-coated microplate. The cell-imprinted polymer complex on the microplate can spontaneously rebind and specifically detect target cells with high selectivity in a short time frame (within 30 min). Furthermore, the microplates could discriminate particular target Escherichia coli O157:H7 cells from bacterial mixtures. This simple method may be used for a variety of applications such as clinical testing, food safety, and continuous environmental monitoring. [ABSTRACT FROM AUTHOR]

Specific identification of enterohemorrhagic Escherichia coli was achieved using microspheres coated with overoxidized polypyrrole. The microspheres are well dispersed in aqueous media, and they specifically, spontaneously, and efficiently bind E. coli O157:H7 through surface area effects. In addition, we found that light-scattering by a single microsphere depended linearly on the number of bound cells. [ABSTRACT FROM AUTHOR]

We conduct seismic tomography to model subsurface seismicity between 2010 and 2012 and structural heterogeneity off the Kii Peninsula, southwestern Japan, and to investigate their relationships with segmentation of the Nankai and Tonankai seismogenic zones of the Nankai Trough. In order to constrain both the shallow and deep structure of the offshore seismogenic segments, we use both active- and passive-source data recorded by both ocean-bottom seismometers and land seismic stations. The relocated microearthquakes indicate a lack of seismic activity in the Tonankai seismogenic segment off Kumano, whereas there was active intraslab seismicity in the Kii Channel area of the Nankai seismogenic segment. Based on comparisons among the distribution of seismicity, age, and spreading rate of the subducting Philippine Sea plate, and the slip-deficit distribution, we conclude that seismicity in the subducting slab under the Kii Channel region nucleated from structures in the Philippine Sea slab that pre-date subduction and that fluids released by dehydration are related to decreased interplate coupling of these intraslab earthquakes. Our velocity model clearly shows the areal extent of two key structures reported in previous 2-D active-source surveys: a high-velocity zone beneath Cape Shionomisaki and a subducted seamount off Cape Muroto, both of which are roughly circular and of 15–20 km radius. The epicenters of the 1944 Tonankai and 1946 Nankai earthquakes are near the edge of the high-velocity body beneath Cape Shionomisaki, suggesting that this anomalous structure is related to the nucleation of these two earthquakes. We identify several other high- and low-velocity zones immediately above the plate boundary in the Tonankai and Nankai seismogenic segments. In comparison with the slip-deficit model, some of the low-velocity zones appear to correspond to an area of strong coupling. Our observations suggest that, unlike the Japan Trench subduction zone, in our study area there is not a simple correspondence between areas of large coseismic slip or strong interplate coupling and areas of high velocity in the overriding plate. [ABSTRACT FROM AUTHOR]

Abstract: The Nankai and Hyuga-nada seismogenic segments, in the western part of the Nankai subduction zone off southwestern Japan, have sometimes ruptured separately and sometimes simultaneously. To investigate the relationships among heterogeneities of seismic structure, spatial variation of the incoming plate, and the seismogenic segments, we carried out seismic observations in the western Nankai subduction zone and modeled the area with 3D seismic tomography using both onshore and offshore seismic data. Our seismic observations suggested that the pattern of seismicity is related to heterogeneities within the subducted plate rather than the seismogenic segments. The up-dip depth limit of seismicity along the plate boundary and in the oceanic crust is typically around 15 km, corresponding to the depth of dehydration of the oceanic crust. In addition, the seaward-extended seismicity observed where the subducted plate was considered to have rough internal structures. In the resulting velocity model, the up-dip limit of the area where the P-wave velocity just above the plate boundary exceeds 6 km/s corresponds to the up-dip limit of coseismic slip in the 1968 Hyuga-nada and 1946 Nankai earthquakes. Between the two coseismic rupture zones is an area of lower P-wave velocity about 40 km wide that is evidence of lateral heterogeneities in the upper plate along the trough-parallel direction. Structural heterogeneities in the upper plate may explain the variety of coseismic slip patterns in this region. [Copyright &y& Elsevier]

We demonstrate a simple manipulation of gold nanoparticles that creates a structure-dependent nanometer-scale antenna on the surface of bacteria. Our studies illuminate the concept of the “effective use of light” based on the absorption and emission of light by antennas formed on bacteria. [ABSTRACT FROM AUTHOR]

A synthetic route for mass production of monodisperse gold nanoclusters and nanoparticles is presented. A nanometer-sized raspberry-like architecture, consisting of an aggregation of repeated sequences of a three dimensional gold nanoparticle (AuNP)- organic component-AuNP arrangement, has been prepared with a single-step procedure in a biphasic organic/water system. In the biphasic mixture, reduction of Au3+ by aniline monomers affords nanoclusters as well as a polyaniline colloid that controls the growth of the clusters into nanoparticles. The reaction parameters (ratio of reactants, time, and temperature) can be varied to control the size of the nanoclusters and nanoparticles from 0.73 nm to 5.5 nm in the polyaniline matrix. Finally, electrochemical degradation of the polyaniline matrix affords isolated monodisperse nanoclusters and nanoparticles. [ABSTRACT FROM AUTHOR]