ABSTRACT The Seafloor Observation Network for Earthquakes and Tsunamis along the Japan Trench (S‐net) is a novel cabled ocean‐bottom station network covering broad offshore region east of northeastern Japan. To best use S‐net data, we estimated sensor orientations all 150 stations, because without this information measurements in geodetical coordinates cannot be specified. We determined three parameters orientation at each station: tilt angle long axis cable, rotation around axis, azimuth...

Abstract Long-period ground motions in plain and basin areas on land can cause large-scale, severe damage to structures buildings have been widely investigated for disaster prevention mitigation. However, such ocean-bottom are poorly studied because of their relative insignificance uninhabited the lack strong-motion data. Here, we report evidence development long-period (10–20 s) using deep The waveforms spectrograms demonstrate prolonged amplified that inconsistent with attenuation patterns...

A low-velocity zone (LVZ) has been detected by seismic exploration surveys within the Nankai accretionary prism toe off Kii Peninsula, southwestern Japan, and is considered to be a mechanically weak volume at depth. Such mechanical heterogeneities potentially influence tsunamigenic slips on megathrust earthquakes in subduction zone. However, spatial distribution of LVZ along trough-parallel direction still elusive. Here we show sporadic LVZs from one-dimensional shear wave velocity (Vs)...

Megathrust earthquakes anticipated in the Nankai trough will likely cause severe damage central and western Japan. The Dense Oceanfloor Network System for Earthquakes Tsunamis (DONET), a network of permanent ocean-bottom seismic stations early detection tsunamis developed by Japan Agency Marine-Earth Science Technology (JAMSTEC), is place above expected source region such earthquakes. Data from DONET sensors are transmitted real time to our laboratory at JAMSTEC. Intensive ongoing activity...

Research Article| April 16, 2019 Ground‐Motion Characteristics and Nonlinear Soil Response Observed by DONET1 Seafloor Observation Network during the 2016 Southeast Off‐Mie, Japan, Earthquake Hisahiko Kubo; Kubo Corresponding Author aNational Institute for Earth Science Disaster Resilience, 3‐1, Tennodai, Tsukuba, Ibaraki 305‐0006, hkubo@bosai.go.jp Search other works this author on: GSW Google Scholar Takeshi Nakamura; Nakamura Wataru Suzuki; Suzuki Yadab P. Dhakal; Dhakal Kimura; Kimura...

Abstract Feasibility studies on simulating seismic‐wave propagation in media for a suboceanic earthquake, including both land and ocean‐bottom topographies seawater layer, are scarce. Some of the conventional staggered‐grid finite‐difference method (FDM) simulations use simplified structure model without layer with flat topography. In this study, we apply our heterogeneity, oceanic topography scheme (HOT)‐FDM 3D topographies, fluid–solid boundary condition to an aftershock ( M w  5.8) 2009...

Research Article| March 27, 2018 Site Amplification Characteristics at Nankai Seafloor Observation Network, DONET1, Japan, Evaluated Using Spectral Inversion Hisahiko Kubo; Kubo aNational Institute for Earth Science and Disaster Resilience, 3‐1, Tennodai, Tsukuba, Ibaraki 305‐0006, hkubo@bosai.go.jp Search other works by this author on: GSW Google Scholar Takeshi Nakamura; Nakamura Wataru Suzuki; Suzuki Kimura; Kimura Takashi Kunugi; Kunugi Narumi Takahashi; Takahashi Shin Aoi Author Article...

We adopted the GPU (graphics processing unit) to accelerate large-scale finite-difference simulation of seismic wave propagation. The can benefit from high-memory bandwidth because it is a "memory intensive" problem. In single-GPU case we achieved performance about 56 GFlops, which was 45-fold faster than that by single core host central unit (CPU). confirmed optimized use fast shared memory and registers were essential for performance. multi-GPU with three-dimensional domain decomposition,...

Offshore ocean bottom pressure gauges (OBPs) are often used to estimate the spatial distribution of initial sea-surface height associated with offshore earthquakes (the tsunami source model). However, sensors sometimes record changes that neither related tsunamis nor seafloor coseismic displacements non-tsunami components) due sensor rotation or tilt ground shaking long-term mechanical drift. These components can be a error when accurately estimating model and thus need removed provide...

We investigate the hypocenter distribution of aftershocks December 26, 2003 Bam earthquake M w 6.5 by using a temporal seismic network. The hypocenters distribute linearly over about 20 km in parallel with line 3.5 west geological fault and extend from south city to heavily damaged area eastern part including historical mud brick citadel “Arg‐e‐Bam”. Based on distribution, we propose schematic 3‐D structural model new that have named Arg‐e‐Bam fault. suggest occurred not but is located just...

Seismic wave amplifications were investigated using strong-motion data obtained from the ground’s surface (K-net) on Kii peninsula (southwestern Japan) and network of twenty seismic stations seafloor (DONET) located off near Nankai trough. Observed seismograms show that signals at DONET are significantly larger than those K-net stations, independent epicentral distances. In order to investigate cause such amplifications, wavefields for local events simulated finite-difference method, in...

Abstract Tsunamis with amplitudes of up to 40 cm, related the M w 7.1 normal‐faulting earthquake off Fukushima, Japan, on November 21, 2016, were clearly recorded by a new offshore wide and dense ocean‐bottom pressure gauge network, S‐net, high azimuthal coverage located closer focal area. We processed S‐net data found some stations included tsunami‐irrelevant drift step signals. analyzed infer tsunami source distribution. A subsidence region narrow spatial extent (∼40 km) large peak (∼200...

Deployment of cabled stations on the ocean bottom enhances effectiveness early warning systems for suboceanic earthquakes in terms signal detection and improved accuracy hypocentre analyses. We investigated strong-motion data at ocean-bottom deployed source area 2011 Tohoku earthquake (Mw 9.0) northeastern Japan. found a significantly large change direct current component accelerations due to roll pitch motions that are proportional strong motions. further angle is affected more by than...

Abstract We investigated the hypocenter distribution along Nankai trough off Kii Peninsula, Japan, by using data from both ocean‐bottom and land‐based seismic networks. Because velocity structures differ greatly below land ocean, we used a 3D model based on structural of Philippine Sea plate (PHS), which provides much more accurate estimations source locations than 1D models derived either onshore or alone, especially for sources between coast axis. identified intensive activity axis trough,...

Seismic wave propagation from shallow subduction-zone earthquakes can be strongly affected by 3D heterogeneous structures, such as oceanic water and sedimentary layers with irregular thicknesses. Synthetic waveforms must incorporate these effects so that they reproduce the characteristics of observed properly. In this paper, we evaluate accuracy synthetic for small in source area 2011 Tohoku–Oki earthquake (MJMA 9.0) at Japan Trench. We compute on basis a land–ocean unified structure model...

We conducted a detailed investigation of seismic activity from January 2011 to February 2013 along the Nankai trough off Kii Peninsula, central Japan, by using data obtained DONET ocean-bottom observation network. The hypocenters are mostly within subducting Philippine Sea (PHS) plate, although few plate boundary or in sedimentary wedge below Kumano forearc basin. can be separated into events above and 20 km depth, which corresponds approximately Moho. hypocenter distributions distinctly...

S-net is the online and real-time seafloor observation network of 150 observatories for earthquakes tsunamis along Japan Trench. It covers focal region 2011 off Pacific coast Tohoku earthquake its vicinity regions. was established to enhance reliability early warnings tsunami after occurrence earthquake. Full-scale operation has started since April 2017. The data from are being transferred center at NIED on a basis, then verification integrity carried out. Obtained reveal that can observe...

Abstract A series of purified polyglycerol monolaurates (PGML), such as di‐, tri‐, tetra‐, and pentaglycerol monolaurates, were synthesized, their surfactant properties in aqueous solutions examined. The PGML compared with those n ‐dodecyl polyoxyethylene monoethers (C 12 EO ) to examine the function hydrophilic part these compounds. critical micelle concentration (CMC) values surface tension at CMC C increased linearly an increase number glycerol oxyethylene units, respectively; slope was...