Japan Agency For Marine-Earth Science And Technology Research Articles

Arctic Science and Technology Advice with Ministries

This seventh Synthesis with the Science Diplomacy Action serial emerged from the panel session on Arctic Science and Technology Advice with Ministries, which was convened during the Arctic Circle Japan Forum in Tokyo on 5 March 2023. This session built on transdisciplinary dialogues with the February-March 2022 webinar series on Enhancing International Scientific Cooperation: Arctic Science and Technology Advice with Ministries, which was funded by the Ministry of Foreign Affairs of Japan with coordination and logistics provided by the United Nations Institute for Training and Research (UNITAR), as represented in Synthesis 6. Dialogues in both venues were strongly influence by Russia’s invasion of Ukraine and the ongoing war with consequences for international Arctic scientific cooperation, as reflected by the 3 March 2022 “pausing” of the Arctic Council. With this background, the Arctic Circle Japan Forum session addressed three questions: 1. How can nations maintain as well as enhance international Arctic scientific cooperation, especially in the context of Open Science? 2. How can individual scientists work with ministries to build Open Science inclusively during times of geopolitical strain? 3. How can ministries facilitate continuity with the Arctic Council inclusively beyond the Arctic Council chairship rotation from Russia to Norway in May 2023? The panel involved leaders from the Alfred Wegener Institute for Polar and Marine Research, International Arctic Science Committee (IASC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), National Institute for Polar Research (NIPR), Sasakawa Peace Foundation, Science Diplomacy Center™ and the University of the Arctic (UArctic). Panelists’ international perspectives from Finland, Germany, Japan, United Kingdom and the United States are represented in the transcript of their panel dialogue, which is reproduced herein to provide insights about continuity with international scientific cooperation and Open Science inclusively to achieve progress with Pan-Arctic sustainable development.

Underwater Image Enhancement Using Customized CLAHE and Adaptive Color Correction

Underwater images degraded due to low contrast and visibility issues. Therefore, it is important to enhance the images and videos taken in the underwater environment before processing. Enhancement is a way to improve or increase image quality and to improve the contrast of degraded images. The original image or video which is captured through image processing devices needs to improve as there are various issues such as less light available, low resolution, and blurriness in underwater images caused by the normal camera. Various researchers have proposed different solutions to overcome these problems. Dark channel prior (DCP) is one of the most used techniques which produced a better Peak Signal to Noise Ratio (PSNR) value. However, DCP has some issues such as it tends to darken images, reduce contrast, and produce halo effects. The proposed method solves these issues with the help of contrast-limited adaptive histogram equalization (CLAHE) and the Adaptive Color Correction Method. The proposed method was assessed using Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and some images were collected from the internet. The measure of entropy (MOE), Measure of Enhancement (EME), Mean Square Error (MSE), and PSNR opted as performance measures during experiments. The values of MSE and PSNR achieved by the proposed framework are 0.26 and 32 respectively which shows better results.

A New 1′ × 1′ Global Seafloor Topography Model Predicted from Satellite Altimetric Vertical Gravity Gradient Anomaly and Ship Soundings BAT_VGG2021

In this paper, we construct a new 1′ × 1′ global seafloor topography model, BAT_VGG2021, using the satellite altimetric vertical gravity gradient anomaly model (VGG), SIO curv_30.1.nc, and ship soundings. Approximately 74.66 million single-beam depths and more than 180 GB of multibeam grids were downloaded and adopted from the National Centers for Environmental Information (NCEI), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and Geosciences Australia (GA). The SIO curv_30.1.nc model was used to predict seafloor topography at 15~160 km wavelengths, and ship soundings were used to calibrate topography to VGG ratios. The accuracy of the new BAT_VGG2021 model was assessed by comparing it with ship soundings and existing models. The results indicate that the standard deviation of differences between the predicted model and ship soundings is about 40~80 m, and ~93% of the differences are within 100 m, similar to that of the SIO topo_20.1.nc model. The new BAT_VGG2021 model shows better accuracy than the DTU18BAT, ETOPO1, and GEBCO_08 models, and has been improved significantly from our last model, BAT_VGG2014.

The correlation between three teleconnections and leptospirosis incidence in the Kandy District, Sri Lanka, 2004\u20132019

BackgroundLeptospirosis is a bacterial zoonosis. Leptospirosis incidence (LI) in Sri Lanka is high. Infected animals excrete leptospires into the environment via their urine. Survival of leptospires in the environment until they enter into a person and several other factors that influence leptospirosis transmission are dependent upon local weather. Past studies show that rainfall and other weather parameters are correlated with the LI in the Kandy district, Sri Lanka. El Niño Southern Oscillation (ENSO), ENSO Modoki, and the Indian Ocean Dipole (IOD) are teleconnections known to be modulating rainfall in Sri Lanka. There is a severe dearth of published studies on the correlations between indices of these teleconnections and LI.MethodsWe acquired the counts of leptospirosis cases notified and midyear estimated population data of the Kandy district from 2004 to 2019, respectively, from weekly epidemiology reports of the Ministry of Health and Department of Census and Statistics of Sri Lanka. We estimated weekly and monthly LI of Kandy. We obtained weekly and monthly teleconnection indices data for the same period from the National Oceanic and Atmospheric Administration (NOAA) of the USA and Japan Agency for Marine-Earth Science and Technology (JAMSTEC). We performed wavelet time series analysis to determine correlations with lag periods between teleconnection indices and LI time series. Then, we did time-lagged detrended cross-correlation analysis (DCCA) to verify wavelet analysis results and to find the magnitudes of the correlations detected.ResultsWavelet analysis displayed indices of ENSO, IOD, and ENSO Modoki were correlated with the LI of Kandy with 1.9–11.5-month lags. Indices of ENSO showed two correlation patterns with Kandy LI. Time-lagged DCCA results show all indices of the three teleconnections studied were significantly correlated with the LI of Kandy with 2–5-month lag periods.ConclusionsResults of the two analysis methods generally agree indicating that ENSO and IOD modulate LI in Kandy by modulating local rainfall and probably other weather parameters. We recommend further studies about the ENSO Modoki and LI correlation in Sri Lanka. Monitoring for extreme teleconnection events and enhancing preventive measures during lag periods can blunt LI peaks that may follow.

Estimation of stress state and detailed structure at shallow plate boundary based on 3D seismic data

The Earth's crust is a dynamic place, consisting of the large tectonic plates that sit atop the mantle, the extremely hot, high pressure zone of material between the crust and the core. The first several tens kilometres of the Earth's shell, the crust and uppermost mantle, is moving and shifting, causing the oceanic and continental plates to bang and crash with one another, resulting in the earthquakes and tsunamis that dramatically impact the countries at the boundaries of the plates. While the world takes notice when one of these disasters happen, we don't realise that there is constant activity in these zones causing measurable seismic waves to regularly ripple through the crust. Using artificially-generated seismic waves can help researchers to understand more about how the crust and upper mantle behave. Depending on the positioning of the plates and the nature of the crust, i.e., thickness, direction of movement and composition, the behaviour will differ. By using 'controlled sources' in marine seismic experiments, such as air-gun shooting, scientists are able to gather as much data as possible regarding the factors influencing the behaviours of the plates to help provide a better understanding of the processes leading to earthquakes.One organisation that builds and operates via international collaboration is the Japan Agency For Marine-Earth Science and Technology (JAMSTEC). Dr Ryuta Arai joined the Structural Seismology Group of JAMSTEC in 2014 and is now a scientist at the Research Institute for Marine Geodynamics of JAMSTEC. Arai is part of a team of researchers from Japan, New Zealand, the United States and the United Kingdom who are investigating the physical properties of the seismogenic area in the Hikurangi subduction zone.

Three-dimensional thermohaline anomaly structures of rings in the Kuroshio Extension region

Using AVISO satellite altimeter observations during 1993–2015 and a manual eddy detection method, a total of 276 anticyclonic rings and 242 cyclonic rings shed from the Kuroshio Extension (KE) were identified, and their three-dimensional (3D) anomaly structures were further reconstructd based on the Argo float data and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) cruise and buoy data through an interpolation method. It is found that the cyclonic (anticyclonic) rings presented consistent negative (positive) anomalies of potential temperature; meanwhile the relevant maximum anomaly center became increasingly shallow for the cyclonic rings whereas it went deeper for the anticyclonic rings as the potential temperature anomaly decreased from the west to the east. The above deepening or shoaling trend is associated with the zonal change of the depth of the main thermocline. Moreover, the composite cold ring between 140° and 150°E was found to exhibit a double-core vertical structure due to the existence of mode water with low potential vorticity. Specifically, a relatively large negative (positive) salinity anomaly and a small positive (negative) one appeared for the composite cyclonic (anticyclonic) ring at the depth above and below 600 m, respectively. The underlying driving force for the temperature and salinity anomaly of the composite rings was also attempted, which varies depending on the intensity of the background current and the temperature and salinity fields in different areas of the KE region, and the rings’ influences on the temperature and salinity could reach deeper than 1 000 m on average.

Nutritional sources of meio- and macrofauna at hydrothermal vents and adjacent areas: natural-abundance radiocarbon and stable isotope analyses

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 622:49-65 (2019) - DOI: https://doi.org/10.3354/meps13053 Nutritional sources of meio- and macrofauna at hydrothermal vents and adjacent areas: natural-abundance radiocarbon and stable isotope analyses Hidetaka Nomaki1,*, Yuki Uejima2, Nanako O. Ogawa3, Masako Yamane4,7, Hiromi K. Watanabe1, Reina Senokuchi2, Joan M. Bernhard5, Tomo Kitahashi6, Yosuke Miyairi4, Yusuke Yokoyama3,4, Naohiko Ohkouchi3, Motohiro Shimanaga2 1Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan 2Aitsu Marine Station, Kumamoto University, Kumamoto 861-6102, Japan 3Research Institute for Marine Resources Utilization (MRU), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan 4Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba 277-8564, Japan 5Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA 6Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka 237-0061, Japan 7Present address: Institute for Space-Earth Environmental Research, Nagoya University, Nagoya 464-8601, Japan *Corresponding author: nomakih@jamstec.go.jp ABSTRACT: Deep-sea hydrothermal vents host unique marine ecosystems that rely on organic matter produced by chemoautotrophic microbes together with phytodetritus. Although meiofauna can be abundant at such vents, the small size of meiofauna limits studies on nutritional sources. Here we investigated dietary sources of meio- and macrofauna at hydrothermal vent fields in the western North Pacific using stable carbon and nitrogen isotope ratios (δ13C, δ15N) and natural-abundance radiocarbon (Δ14C). Bacterial mats and Paralvinella spp. (polychaetes) collected from hydrothermal vent chimneys were enriched in 13C (up to -10‰) and depleted in 14C (-700 to -580‰). The δ13C and Δ14C values of dirivultid copepods, endemic to hydrothermal vent chimneys, were -11‰ and -661‰, respectively, and were similar to the values in the bacterial mats and Paralvinella spp. but distinct from those of nearby non-vent sediments (δ13C: ~-24‰) and water-column plankton (Δ14C: ~40‰). In contrast, δ13C values of nematodes from vent chimneys were similar to those of non-vent sites (ca. -25‰). Results suggest that dirivultids relied on vent chimney bacterial mats as their nutritional source, whereas vent nematodes did not obtain significant nutrient amounts from the chemolithoautotrophic microbes. The Δ14C values of Neoverruca intermedia (vent barnacle) suggest they gain nutrition from chemoautotrophic microbes, but the source of inorganic carbon was diluted with bottom water much more than those of the Paralvinella habitat, reflecting Neoverruca’s more distant distribution from active venting. The combination of stable and radioisotope analyses on hydrothermal vent organisms provides valuable information on their nutritional sources and, hence, their adaptive ecology to chemosynthesis-based ecosystems. KEY WORDS: Meiofauna · Dirivultid copepods · Nematodes · Paralvinella · Neoverruca · Nutrition · Natural-abundance radiocarbon · Stable carbon and nitrogen isotope ratios Full text in pdf format Supplementary material PreviousNextCite this article as: Nomaki H, Uejima Y, Ogawa NO, Yamane M and others (2019) Nutritional sources of meio- and macrofauna at hydrothermal vents and adjacent areas: natural-abundance radiocarbon and stable isotope analyses. Mar Ecol Prog Ser 622:49-65. https://doi.org/10.3354/meps13053 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 622. Online publication date: July 18, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Crustal-scale depth imaging via joint full-waveform inversion of ocean-bottom seismometer data and pre-stack depth migration of multichannel seismic data: a case study from the eastern Nankai Trough

Abstract. Imaging via pre-stack depth migration (PSDM) of reflection towed-streamer multichannel seismic (MCS) data at the scale of the whole crust is inherently difficult. This is because the depth penetration of the seismic wavefield is controlled, firstly, by the acquisition design, such as streamer length and air-gun source configuration, and secondly by the complexity of the crustal structure. Indeed, the limited length of the streamer makes the estimation of velocities from deep targets challenging due to the velocity–depth ambiguity. This problem is even more pronounced when processing 2-D seismic data due to the lack of multi-azimuthal coverage. Therefore, in order to broaden our knowledge about the deep crust using seismic methods, we present the development of specific imaging workflows that integrate different seismic data. Here we propose the combination of velocity model building using (i) first-arrival tomography (FAT) and full-waveform inversion (FWI) of wide-angle, long-offset data collected by stationary ocean-bottom seismometers (OBSs) and (ii) PSDM of short-spread towed-streamer MCS data for reflectivity imaging, with the former velocity model as a background model. We present an application of such a workflow to seismic data collected by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and the Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER) in the eastern Nankai Trough (Tokai area) during the 2000–2001 Seize France Japan (SFJ) experiment. We show that the FWI model, although derived from OBS data, provides an acceptable background velocity field for the PSDM of the MCS data. From the initial PSDM, we refine the FWI background velocity model by minimizing the residual move-outs (RMOs) picked in the pre-stack-migrated volume through slope tomography (ST), from which we generate a better-focused migrated image. Such integration of different seismic datasets and leading-edge imaging techniques led to greatly improved imaging at different scales. That is, large to intermediate crustal units identified in the high-resolution FWI velocity model extensively complement the short-wavelength reflectivity inferred from the MCS data to better constrain the structural factors controlling the geodynamics of the Nankai Trough.

LINEARIZATION OF RELATIVE HUMIDITY OVER THE PACIFIC OCEAN ON THE EQUATORIAL LINE

The atmosphere system is ruled by the interaction of many meteorological parameters, causing a dependency between them, i.e., moisture and temperature, both suitable in front of any anomaly, such as storms, hurricanes, El Niño-Southern Oscillation (ENSO) events. So, understanding perturbations of the variation of moistness along the time may provide an indicator of any oceanographic phenomenon. Annual relative humidity data around the Equatorial line of the Pacific Ocean were processed and analyzed to comprehend the time evolution of each dataset, appreciate anomalies, trends, histograms, and propose a way to predict anomalous episodes such ENSO events, observing abnormality of lag correlation coefficients between every pair of buoys. Datasets were taken from the Tropical Atmosphere Ocean / Triangle Trans-Ocean Network (TAO/TRITON) project, array directed by Pacific Environmental Laboratory (PMEL) of the National Oceanic and Atmospheric Administration (NOAA), and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). All the datasets were processed, and the code was elaborated by the author or adapted from Mathworks Inc. Even occurrences of relative humidity in the east side of the Pacific Ocean seem to oscillate harmonically, while occurrences in the west side, do not, because of the size of their amplitudes of oscillations. This fact can be seen in the histograms that show Peak shapes in the east side of the ocean, and Gaussians in the west; lag correlation functions show that no one pair of buoys synchronize fluctuations, but western buoys are affected in front of ENSO events, especially between 1997-98. Definitely, lag correlations in western buoys are determined to detect ENSO events.

Motion simulation of sensor cable towed by X rudder AUV “YUMEIRUKA"

“YUMEIRUKA" is an AUV that Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has developed and is operating. A seabed resource exploration is carried out by two-set simultaneous operation with AUV “JINBEI" developed by JAMSTEC. “YUMEIRUKA" towing a sensor cable, and the cable is oscillated by the AUV. The up-and-down oscillation of the sensor has a bad influence on the exploration result. Therefore, in order to perform accurate seabed resource exploration, it is necessary to comprehend the motion of the sensor cable and to optimize it. In this paper, motion simulations of a sensor cable towed by X rudder AUV “YUMEIRUKA" are shown.

Human footprint in the abyss: 30 year records of deep-sea plastic debris

This study reports plastic debris pollution in the deep-sea based on the information from a recently developed database. The Global Oceanographic Data Center (GODAC) of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) launched the Deep-sea Debris Database for public use in March 2017. The database archives photographs and videos of debris that have been collected since 1983 by deep-sea submersibles and remotely operated vehicles. From the 5010 dives in the database, 3425 man-made debris items were counted. More than 33% of the debris was macro-plastic, of which 89% was single-use products, and these ratios increased to 52% and 92%, respectively, in areas deeper than 6000 m. The deepest record was a plastic bag at 10898 m in the Mariana Trench. Deep-sea organisms were observed in the 17% of plastic debris images, which include entanglement of plastic bags on chemosynthetic cold seep communities. Quantitative density analysis for the subset data in the western North Pacific showed plastic density ranging from 17 to 335 items km−2 at depths of 1092–5977 m. The data show that, in addition to resource exploitation and industrial development, the influence of land-based human activities has reached the deepest parts of the ocean in areas more than 1000 km from the mainland. Establishment of international frameworks on monitoring of deep-sea plastic pollution as an Essential Ocean Variable and a data sharing protocol are the keys to delivering scientific outcomes that are useful for the effective management of plastic pollution and the conservation of deep-sea ecosystems.

Development of Underwater Shuttle Glider for Virtual Mooring

A prototype of a 3000m-class underwater glider for virtual mooring is being developed by JAMSTEC (Japan Agency for Marine-Earth Science and Technology) with RIAM (Research Institute for Applied Mechanics) of Kyushu University. The vehicle houses observation equipment and glides back and forth between the sea surface and the seabed collecting ocean data in a specific area (virtual mooring area). The motions of the vehicle are controlled by moving its center of gravity using mounted weight-shifters.

Investigation of Offshore Fault Modeling for a Source Region Related to the Shakotan-Oki Earthquake

The purpose of this study is to verify fault modeling in the source region of the 1940 Shakotan-Oki earthquake using active faults offshore of Japan. Tsunami heights simulated in previous studies are found to be lower than observed levels, which makes it difficult to explain historical tsunami records of this earthquake. However, the application of appropriate slip magnitudes in the fault models may explain these differences. In the “Project for the Comprehensive Analysis and Evaluation of Offshore Fault Informatics (the Project),” a new fault model is constructed using marine seismic data and geological and geophysical data compiled by the Offshore Fault Evaluation Group, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) as part of the Project for Fault Evaluation in the Seas around Japan (Ministry of Education, Culture, Sports, Science and Technology, MEXT). Single-channel and multichannel reflection seismic data were used that includes information from a new fault identified in previous surveys. We investigated fault geometries and their parameters using the above data. Here, we show that the geometric continuity of these faults is adjusted by increasing the magnitude of fault slip. Standard scaling laws are applied on the basis of strong ground motion of the fault parameters, and the validity of the fault model is examined by comparing tsunami heights along the Japanese coastline from historically observed records with tsunami height from simulation analysis. This verification quantitatively uses Aida’s K and κ scale and variance parameters. We determine that the simulated tsunami height determined using the new model approach the heights observed historically, which indicates that the model is valid and accurate for the source region.

Development of a 300 L Calibration Bath for Oceanographic Thermometers

The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been developing a 300 L calibration bath to calibrate 24 oceanographic thermometers (OT) simultaneously and thereby reduce the calibration work load necessary to service more than 180 OT every year. This study investigated characteristics of the developed 300 L calibration bath using a SBE 3plus thermometer produced by an OT manufacturer. We also used 11 thermistor thermometers that were calibrated to be traceable to the international temperature scale of 1990 (ITS-90) within 1 mK of standard uncertainty through collaboration of JAMSTEC and NMIJ/AIST. Results show that the time stability of temperature of the developed bath was within $$\pm 1 \,\hbox {mK}$$ . Furthermore, the temperature uniformity was $$\pm 1.3 \,\hbox {mK}$$ . The expanded uncertainty ( $$k=2$$ ) components for the characteristics of the developed 300 L calibration bath were estimated as 2.9 mK, which is much less than the value of 10 mK: the required specification for uncertainty of calibration for the OT. These results demonstrated the utility of this 300 L calibration bath as a device for use with a new calibration system.

Department of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)

Department of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC)

A basic study of acoustic communications between an autonomous surface vehicle and an autonomous underwater vehicle

Recently, there has been an increasing interest in submarine resources and demand to survey them. For that purpose, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has developed autonomous underwater vehicles (AUVs). Currently, only one AUV is operated by a research vessel because a mother ship must always follow an AUV. However, to make survey more efficient, the project of multiple AUVs operation, paired with autonomous surface vehicles (ASVs), is being progressed. In this plan, one ASV always monitor status and position of its paired AUV with acoustic communication and localization, and follow it autonomously. The size of an ASV is desired to be as small as possible in terms of operation. Thus, it causes two difficulties. First, such a small ASV rolls and pitches up to a large angle easily. Second, receivers are close to the noise sources, such as thrusters or sea surface. As a basic study, at-sea experiments were demonstrated with various types of modulation using a prototype of an ASV. The results show that OFDM signals are more sensitive to rolling and pitching movement than single carrier modulation (SCM) and that it is possible to achieve demodulation with SCM in spite of noise as mentioned above.

国立研究開発法人海洋研究開発機構（JAMSTEC） 海洋生命理工学研究開発センター 深海バイオ応用研究開発グループ

国立研究開発法人海洋研究開発機構（JAMSTEC） 海洋生命理工学研究開発センター 深海バイオ応用研究開発グループ

Array Observations of the 2012 Haida Gwaii Tsunami Using Cascadia Initiative Absolute and Differential Seafloor Pressure Gauges

The purpose of this article is to test the ability of the seafloor pressure sensors utilized in the Cascadia Initiative (CI) experiment (Toomey et al. , 2014) to provide useful recordings of tsunamis, and to compare the performance of the different types of seafloor pressure sensors for long‐period recordings. These tests are performed through analysis of CI seafloor pressure recordings of the 2012 Haida Gwaii tsunami. Seafloor pressure measurements are a central part of tsunami warning systems. Deep‐ocean Assessment and Reporting of Tsunamis (DART) buoy systems, designed by National Oceanic and Atmospheric Administration (NOAA), are equipped with seafloor pressure sensors (also referred to as bottom pressure recorders [BPRs]), providing tsunami data in real time (Eble and Gonzalez, 1991; Gonzalez et al. , 1998; Bernard et al. , 2001; Meinig et al. , 2005; Titov et al. , 2005; Mofjeld, 2009; Rabinovich and Eble, 2015). The DART instruments are widely spaced in deep water (typically >2700 m) along coastal regions and near subduction zones. Cabled BPR arrays are becoming more common, such as the BPR array of NorthEast Pacific Time‐Series Undersea Networked Experiments (NEPTUNE)‐Canada ocean observatory (Thomson et al. , 2011), the Japan Agency for Marine‐Earth Science and Technology (JAMSTEC) BPR array (Baba et al. , 2004; Saito et al. , 2010), and the BPR array in the Cascadia basin (Rabinovich et al. , 2011). Observations of tsunamis have also been made serendipitously on pressure gauges accompanying a variety of nontsunami field programs (e.g., Drushka et al. , 2008; Lin et al. , 2015). In this study, we use seafloor pressure measurements from absolute pressure gauges (APGs), differential pressure gauges (DPGs), and DART BPRs to study the tsunami caused by the 2012 Haida Gwaii earthquake. The APG, used by the DART and increasingly in other oceanographic studies (Ito et al. , 2011; Chadwick et al. …

Bathymetry Change Investigation of the 2011 Tohoku Earthquake

Bathymetry change due to the 2011 Tohoku (M9.0) earthquake was investigated through satellite altimetryderived free-air gravity anomalies (SAFAGA) and shipborne measurements. The earthquake occurred at the plate boundaries near the northeastern coast of Japan, where the oceanic plate subducts beneath the continental plate along deep-sea trench. Data analyzed in this study include SAFAGA from Scripps Institution of Oceanography (SIO), shipborne bathymetry (SB) from the U.S. National Geophysical Data Center (NGDC) and the Japan Agency for Marine-Earth-Science And Technology (JAMSTEC). To estimate the bathymetry change, a reference bathymetry before the earthquake was predicted by gravity-geologic method (GGM) and Smith & Sandwell’s (SAS) method. In comparison with the bathymetry models before the earthquake, GGM bathymetry model generated by a tuning density contrast of 17.04 g/cm3 by downward continuation method was selected because it shows better bathymetry in the short wavelength below about 6 km. From the results, remarkable bathymetry change of about ±50 m was found on the west side of the Japan Trench caused by the earthquake.

Re–Os isotope geochemistry in the surface layers of ferromanganese crusts from the Takuyo Daigo Seamount, northwestern Pacific Ocean

1Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 2Institute for Research on Earth Evolution (IFREE), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan 3Submarine Resources Research Project (SRRP), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan 4Department of Systems Innovation, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan 5Geological Survey of Japan (GSJ), National Institute of Advanced Industrial Science and Technology (AIST), Central 7, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8567, Japan 6Frontier Research Center for Energy and Resources (FRCER), School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan 7Department of Geology, Natural Sciences Cluster, Kochi University, 2-5-1 Akebono, Kochi 780-8520, Japan