DONET
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| DONET | |
|---|---|
| Name | DONET |
| Type | Ocean-bottom seismograph network |
| Established | 2000s |
| Location | Nankai Trough, Pacific Ocean off Japan |
| Operators | Japan Agency for Marine-Earth Science and Technology |
DONET
DONET is a Japanese ocean-bottom seismograph and observatory network designed to monitor seismicity, tsunami generation, and crustal deformation along the Nankai Trough. It provides real-time seismic and geophysical data for earthquake early warning, tsunami assessment, and geoscientific research, interfacing with international observatories and research institutes. DONET's instruments are deployed offshore of Shikoku and the Kii Peninsula to study subduction processes related to major megathrust earthquakes and tsunamis.
Overview
DONET consists of arrays of ocean-bottom seismometers, pressure sensors, magnetotelluric units, and accelerometers connected by submarine cables and satellite links to shore stations at ports such as Kii, Kochi, and Muroto. The project integrates with networks and institutions including the Japan Meteorological Agency, National Research Institute for Earth Science and Disaster Resilience, University of Tokyo, Kyoto University, Tohoku University, and Hokkaido University to exchange data with global systems like the Global Seismographic Network, IRIS, USGS, NOAA, and ECMWF for hazard mitigation and science. DONET operations involve collaborations with engineering and industry partners such as Mitsubishi Heavy Industries, Japan Radio Co., NEC, Toshiba, Hitachi, and JGC Corporation for cable laying and platform manufacture, and with international partners including JAMSTEC, WHOI, Scripps Institution of Oceanography, GEOMAR, and the British Geological Survey for methodology and comparative studies.
History and Development
DONET grew from earlier marine geophysical initiatives including Japan’s seismic research following the 1946 Nankai earthquake, the 1995 Kobe (Great Hanshin) event studies, and post-2004 Indian Ocean tsunami initiatives involving IOC and UNESCO discussions. Initial planning involved funding and oversight from the Ministry of Education, Culture, Sports, Science and Technology, the Cabinet Office, and METI, with technical input from JAXA satellite communications programs and JOGMEC logistical support. Milestones include prototype trials alongside projects such as the Ocean Drilling Program, Integrated Ocean Drilling Program, and the IODP Expeditions, installation phases informed by work from the Japan Seismological Society, the Seismological Society of America, and NIED, and programmatic reviews by committees including the Science Council of Japan and advisory input from international panels like the Intergovernmental Oceanographic Commission.
Technical Specifications
DONET nodes feature broadband and short-period seismometers comparable to instruments used by IRIS and USGS, 24-bit digitizers, GPS-synchronized timing adapted from JAXA and GNSS standards, ocean-bottom pressure gauges with sensitivity similar to DART systems used by NOAA, and broadband magnetotelluric sensors used in marine MT surveys by institutions such as GFZ and EAGE. Communication uses fiber-optic cable technologies developed by NEC and Mitsubishi, with power supplies and telemetry designed following deep-sea engineering practices from companies like Furuno, Kongsberg, SubCom, and Schlumberger. Data acquisition systems follow protocols comparable to SEED and miniSEED formats endorsed by IASPEI and utilize software frameworks similar to Antelope and SeisComP for real-time streaming to command centers at JAMSTEC and partner universities.
Instrumentation and Deployment
Deployment leverages oceanographic vessels and equipment including the seismic survey vessels used by JAMSTEC, cable-laying ships used by Nippon Yusen Kabushiki Kaisha, remotely operated vehicles comparable to those developed by AIST and IFREMER, and deep-sea connectors modeled on technology from MacArtney and Teledyne. Instruments include broadband seismometers similar to Streckeisen and Nanometrics models, strong-motion accelerometers comparable to Kinemetrics units, and differential pressure gauges analogous to those in the Deep-ocean Assessment and Reporting of Tsunamis network. Arrays are sited using bathymetry and seismic reflection data from surveys by JOG, the Hydrographic and Oceanographic Department, and the Japan Coast Guard; installation campaigns have been coordinated with port authorities in Osaka, Tokushima, Wakayama, and Kochi.
Scientific Contributions and Findings
DONET data have improved understanding of megathrust rupture processes relevant to historical events such as the 1707 Hoei earthquake, the 1854 Ansei-Tokai earthquake, and relationships to the 1944 Tonankai and 1946 Nankai events. Analyses have been published in journals and conferences of the American Geophysical Union, the Japan Geoscience Union, and the European Geosciences Union, influencing models of slow slip events observed in Cascadia, Alaska, and Chile, and informing comparative studies with earthquake sequences like the 2011 Tohoku-Oki rupture, the 2004 Sumatra–Andaman event, and the 1960 Valdivia earthquake. DONET observations have contributed to improved tsunami modeling used by the Pacific Tsunami Warning Center, UNESCO IOC tsunami guidance, and numerical simulations employing the shallow-water equations and finite-element codes developed in collaborations with universities such as Stanford, MIT, Caltech, and ETH Zurich. The network has also supported studies of fluid migration, seismogenic zone locking similar to studies in the Hikurangi and Nicoya margins, and seafloor electromagnetic experiments tied to magnetotelluric campaigns in cooperation with GFZ, WHOI, and NIOZ.
Operational Management and Collaborations
Operation and maintenance are managed by a consortium led by JAMSTEC with scientific leadership from the University of Tokyo, Kyoto University, Tohoku University, and Kochi University, and logistical support from the Japan Coast Guard and port authorities. Data-sharing agreements align with policies from IRIS, ISC, and the Global Earthquake Model, while legal, safety, and environmental compliance involve the Ministry of Land, Infrastructure, Transport and Tourism, the Fisheries Agency, and coastal prefectural governments including Kagawa, Mie, and Ehime. International collaborations include joint workshops with NOAA, USGS, CSIRO, CNRS, and the European Commission’s Horizon programs, and capacity-building initiatives with APEC, ASEAN, and the Pacific Islands Forum for regional resilience and hazard preparedness.