Real-time geophysical measurements on the deep seafloor usingsubmarine cable in the southern Kurile subduction zone

A permanent real-time geophysical observatory using a submarine cable was developed and deployed to monitor seismicity, tsunamis, and other geophysical phenomena in the southern Kurile subduction zone. The geophysical observatory comprises six bottom sensor units, two branching units, a main electro-optical cable with a length of 240 km and two land stations. The bottom sensor units are: 1) three ocean bottom broadband seismometers with hydrophone; 2) two pressure gauges (PGs); 3) a cable end station with environmental measurement sensors. Real-time data from all the undersea sensors are transmitted through the main electro-optical cable to the land station. The geophysical observatory was installed on the continental slope of the southern Kurile trench, southeast Hokkaido, Japan in July 1999. Examples of observed data are presented. Sensor noises and resolution are mentioned for the ocean bottom broadband seismometers and the PGs, respectively. An adaptable observation system including very broadband seismometers is scheduled to be connected to the branching unit in late 2001. The real-time geophysical observatory is expected to greatly advance the understanding of geophysical phenomena in the southern Kurile subduction zone     

Study on 10 kVDC powered junction box for a cabled ocean observatory system

A cabled ocean observatory system that can provide abundant power and broad bandwidth communication for undersea instruments is developed. A 10 kV direct current (kVDC) with up to 10 kW power, along with 1 Gigabit/sec Ethernet communication, can be transmitted from the shore to the seafloor through an umbilical armored cable. A subsea junction box is fixed at a cable terminal, enabling the extension of up to nine connections. The box consists of three main pressure vessels that perform power conversion, power distribution, and real-time communication functions. A method of stacking modules is used to design the power conversion system in order to reduce the 10 kV voltage to levels that can power the attached instruments. A power distribution system and an Ethernet communication system are introduced to control the power supply and transmit data or commands between the terminals and the shore station, respectively. Specific validations of all sections were qualified in a laboratory environment prior to the sea trial. The ocean observatory system was then deployed at the coast of the East China Sea along with three in situ instruments for a 14-day test. The results show that this high voltage-powered observatory system is effective for subsea long-term and real-time observations.     

Improvement of earthquake locations with the Marine Cable Hosted Observatory (MACHO) offshore NE Taiwan

In order to improve the locating capability for offshore earthquakes and tsunamis monitored off northeastern Taiwan, a cable-based ocean bottom seismographic observatory named “Marine Cable Hosted Observatory” (MACHO) was constructed and began operation at the end of 2011. The installed instruments of the observatory include a broadband seismometer, a strong-motion seismometer and a pressure gauge. In addition, various scientific instruments could be deployed for other purposes as well. At present, the seismic data are transmitted in real-time via a fiber cable, and integrated into the current inland seismographic network in Taiwan. The ocean bottom station has contributed to provide high quality seismic data already. According to observations from January 2012 to June 2013, there were a total of 15,168 earthquakes recorded by the system. By using the data from the ocean bottom station, the number of relocated earthquakes with an azimuth gap less than 180 degrees substantially increase about 34 %. Meanwhile, the root–mean–square of the time residual, the error in epicenter, and the error in depth of the earthquake locations decrease. Therefore, the implementation of MACHO has the advantage of extending the coverage of existing the Taiwan seismic network to the offshore, providing more accurate and real-time seismic data for offshore earthquakes monitoring. The results show that MACHO is crucial and necessary for monitoring seismic activities in northeastern Taiwan.     

New Scientific Underwater Cable System Tokai-SCANNER for Underwater Geophysical Monitoring Utilizing a Decommissioned Optical Underwater Telecommunication Cable

We have developed a new cost-effective scientific underwater cable system named Tokai Submarine Cabled Network Observatory for Nowcast of Earthquake Recurrences (Tokai-SCANNER) using a decommissioned optical underwater telecommunication cable. We have used this cable in two ways simultaneously: 1) to construct an ocean-bottom observatory at the end of the cable, and 2) to use the cable as a long emitting antenna to sense electromagnetic properties of the Earth's crust. We have also developed a new time-synchronization system that sends a one-pulse-per-second (1PPS) signal and NMEA data to underwater sensors. To vary the supply voltage and current to the observatory and to emit a low-frequency electromagnetic field around the underwater cable, we have also developed an underwater power unit that has a wide input voltage and current range. Tokai-SCANNER has been functioning since April 2007.      

海底有缆在线观测系统研究与应用综述

获取高质量海洋观测数据是维护国家安全和权益、保障人类生存与可持续发展、应对全球气候变化、开发利用海洋资源、防灾减灾等的重要基础。随着海底观测技术的发展,海底有缆观测已成为地球观测的第三个平台。通过借鉴国内外海底观测网的成熟技术,设计研发单节点海底有缆在线观测系统,主要包含海底观测、电力信息传输和陆上人机交互信息管理等三个子系统,具有高度可扩展性,可根据监测需求集成安装常用的各类海洋观测仪器和水下高清摄像头,从而实现海洋环境和水下生物资源的原位、长期、连续、稳定的在线观测。研发的海底有缆在线观测系统构造简单、扩展性强、经济成本低,已广泛应用于山东省海洋牧场观测网的海洋生态环境和渔业资源、辽东湾的冬季海冰、海洋牧场与海上风电的融合效应、河流入海口水质、海上溢油等不同领域的业务化监测中,为我国海洋生态环境保护与修复、海洋资源开发利用、海洋防灾减灾等提供了高质量的科学数据支撑。海底有缆在线观测系统是业务化海洋在线观测技术领域里的创新研究,具有重要科学意义和广泛应用前景。     

A new approach for mobile and expandable real-time deep seafloorobservation - adaptable observation system

Although submarine cable in-line seafloor observation systems are very effective tools for real-time/long-term geo-scientific measurements,, there are technological difficulties for deploying as many sensors as on land. To solve this problem, JAM-STEC developed an expandable and replaceable satellite measurement station called the adaptable observation system (AOS). The AOS is a battery operated mobile observatory connected to the backbone cable system by a 10 km long thin fiber cable to ensure real-time data recovery. The system consists of a branching system, a junction box, a fiber cable, and a battery system for a six-month operation. Installation and construction of the AOS will be conducted by a towed vehicle and an ROV. A thin fiber cable-laying system was developed and tested for practical operation. This observation system provides a chance to extend existing seafloor networks from an in-line area to a wider area     

Powering cabled ocean-bottom observatories

A critical and potentially difficult problem for ocean-bottom observatories is the electrical power sub-system. While huge effort and expense has gone into development of land power grids and ocean communication cable power, the characteristics of ocean-bottom observatories require different strategies. Ocean-bottom observatories terminate on the ocean floor where large variable loads are installed, whereas commercial ocean-bottom cables terminate on land and normally have relatively fixed loads. Design considerations such as whether to use a constant current or constant voltage source, choice of voltage and current levels and cable capacitance and impedance are considered. Ocean-bottom observatory science requirements in the future will demand multiple loads along the cable, cable branches, fault protection and redundancy. The realities of high cable capacitance and the negative dynamic impedance of switching power supplies require that rapid load changes either be anticipated or prevented. Without proper control, rapid changes in load can result in instability and collapse of the power system. The strategy suggested in this paper requires that each load point (or junction box where science experiments will be attached to the system) be "smart" enough to keep load variations within tolerance bounds     

The Hawaii-2 Observatory

A permanent deep ocean scientific research facility-the Hawaii-2 Observatory (H2O)-was installed on the retired HAW-2 commercial submarine telephone cable in September 1998. H2O consists of a seafloor submarine cable termination and junction box in 5000 m of water located halfway between Hawaii and California. The H2O infrastructure was installed from a large research vessel using the Jason ROV and standard over-the-side gear. The junction box provides two-way digital communication at variable data rates of up to 80 kbit/s using the RS-422 protocol and a total of 400 W of power for both junction box systems and user equipment. Instruments may be connected by an ROV to the junction box at 8 wet-mateable connectors. The H2O junction box is a "smart" design, which incorporates redundancy to protect against failure and allows full control of instrument functionality from shore. Initial instrumentation at the H2O site includes broad-band seismometer and hydrophone packages     

A network-based telemetry architecture developed for the Martha'sVineyard Coastal Observatory

Underwater observatories with real-time data and virtually unlimited power transmission capabilities compared to traditional oceanographic moorings are beginning to provide scientists with continuous access to the coastal and open ocean. However, for any coastal observatory to serve as a cost-effective system for the collection of long-term scientific and environmental data, it must have a simple, upgradeable power and telemetry system and an instrument interface that is compatible with existing standards. It must be designed for extended environmental exposure and ease of service to avoid high maintenance costs. Most importantly, the observatory must be accessible to all potential users, including students, scientists, engineers, and policy makers. This strategy was applied to the design of the Martha's Vineyard Coastal Observatory on the south shore of the island of Martha's Vineyard. The new facility, and in particular its system architecture, as developed by the Woods Hole Oceanographic Institution with support from the National Science Foundation, are described     

极低频海洋噪声与风的相关性研究

风通过影响海洋表面从而产生200 Hz以上的深海环境噪声,但有研究指出,通过风生表面波之间的非线性相互作用产生的驻波,能够与海床共振构成海底微震,从而产生10 Hz以下的噪声。针对这一新型风生噪声机制,本研究对威克岛海域10 Hz以下的极低频噪声进行了分析。比较了不同频率下海洋环境噪声功率谱级与风速的相关性,并讨论了风速和风向对设立在威克岛南北部二组水听器三联体信号的影响,结果表明2 Hz处的海洋环境噪声级与风速相关性最好,而风速和风向变化越剧烈海洋环境极低频噪声与风速风向的相关性越好。     

Ocean bottom seismograph development at Hawaii Institute of Geophysics

Three distinct ocean bottom seismograph (OBS) systems have been developed at the Hawaii Institute of Geophysics to satisfy the different requirements for short-range refraction and anisotropy experiments, long-range refraction experiments, and short-term and semi-permanent monitoring for earthquakes. One system, originally designed for semi-permanent use in conjunction with a monster buoy of the IDOE North Pacific Experiment has been modified for emplacement off Oahu. It contains 3-component 1 Hz seismometers and a hydrophone and obtains power and transmits data via tow conductor cable. Two additional systems were designed for short-term use: a 2 Hz telemetering system (TOBS); and 4.5 Hz free-fall pop-up system (POBS). The TOBS contains 3-component seismometers and a hydrophone and transmits data to the ship via light-weight single-conductor electromechanical cable and an HF-VHF radio link from a surface buoy. The bottom package also includes a backup tape recorder. This system exhibits the advantages of real-time data acquisition (e.g. precise timing, rapid appraisal of data quality, optimum use of explosives, and common recording with other data) and the complexities and difficulties associated with a deep-sea mooring. However, use of cable with near neutral bouyancy permits the design of a deep-water system with low weights and stress levels. The POBS is a self-contained package containing a vertical and single horizontal seismometer, hydrophone, cassette tape recorder, and pre-set timed release. This system is relatively simple and inexpensive. Total weight of 150 kg in air (before launch) permits emplacement and retrieval from a ship with no special equipment by two (strong) persons. Experience to data suggests that the optimum deployment scheme for many studies is a combination of TOBS's and POBS's.Hawaii Institute of Geophysics Contribution 835.     

Submarine cables: a challenge for ocean management

The international submarine cable industry is a major component of the global telecommunications system, providing important services and requiring increased levels of protection for the maintenance of global economic and maritime security, broadly defined. An overview is given of the submarine cable industry, including its technological developments, legal aspects, security considerations, and implications for integrated ocean planning and management. In the context of multiple ocean use, submarine cables can cause spatial conflicts with other ocean users, particularly the fishing industry. Issues to be examined include compensation for lost or damaged gear, legal liability for cable damage, and regulation and licensing of cables on the seabed of the continental shelf and the high seas. Recent industry-to-industry agreements and programs for compensation to fishers in the USA and Canada are significant advancements in the implementation of integrated approaches to ocean management and planning. The development of transparent and stable interdepartmental processes for the coordinated planning, management and regulation of submarine cables is required for national EEZs. The regulation of international cable industry practices must be harmonized with national management approaches.     

基于LZW的海底声学探测数据压缩方法研究

针对海底声学探测仪器采集数据量大而存储容量有限、数据传输带宽不足的实际问题,基于Lempel-Ziv-Welch(LZW)无损压缩算法,研究海底声学探测数据的实时压缩方法,提高数据压缩效果、节省传输带宽。并在LZW无损压缩算法的基础上结合数据存储的特点对压缩结果进行内存重新分配,极大提高压缩比(压缩数据大小/原始数据大小)。利用海底地震仪(OBS)采集的原始声学探测数据进行测试验证,结果表明该方法对于OBS声学探测数据有很好的压缩比,可用于对OBS采集的声学探测数据进行压缩处理,对于海底探测仪器的研发有很好的指导意义。     

海底光缆工程发展20年

对全球第一条海底光缆问世后20年来海底光缆工程发展的历程作了简要回顾。随着光纤传输技术的不断进步,海底光缆的通信技术得到了飞速发展,近20年来,其商用系统已经历了四代。海底光缆工程发展的重要标志,还体现在海底光缆施工技术的日趋完善,水下定位、海底数字式高分辨率的地球物理探测、海底原位测试等高新技术在海缆路由调查与埋设评价调查中的广泛应用。此外,对海底光缆市场与行业结构所经历的深刻变化作了分析,并预测了国际海底光缆网络的发展和市场前景。     

Sedimentary processes and sediment dispersal in the southern Strait of Georgia,BC, Canada

This paper presents a review of sediment dispersal processes in the Strait of Georgia, based on marine geological studies. Sediment from the Fraser River is dispersed around the Strait through a variety of transport pathways. Most sand and coarser silt fractions settle out and are deposited within a few 100 m of the channel mouths. Both channelled and non-channelled gravity flows probably transport sediment downslope and onto the basin floor. Asymmetric tidal currents force a predominantly northward sediment drift, resulting in a reworked slope off Roberts Bank and a finer-grained depositional slope off Sturgeon Bank. Far-field sediment accumulation is controlled by local morphology and sediment dynamics. Multibeam mapping and seismic profiling reveal that some parts of the basin floor are characterized by bottom sediment reworking and erosion. Given the complexities of sediment dispersal and seafloor reworking, generalizations about sediment dispersal paths and sedimentation rates are difficult. Future understanding will be advanced by the cabled observatory, VENUS, which will enable near real-time monitoring of key processes.     

海缆安全影响因素评述

通过对国内外威胁海缆安全因素的研究资料和研究成果的分析，全面论述了影响海缆安全因素的种类及其对海缆的可能破坏方式和破坏的严重程度。简要说明了不同因素对海缆威胁的可能原因与相应的预防措施，为海缆安全运营提供科学的理论依据。     

Recent developments in ocean data telemetry at Woods HoleOceanographic Institution

The Woods Hole Oceanographic Institution is developing techniques for telemetering oceanographic data from the deep ocean to the laboratory in near real time. Three general approaches that provide a link between subsurface instruments and surface buoys equipped with satellite transmitters are being pursued. These approaches are: cabled systems that use electromechanical cables to connect subsurface instruments to a central controller; high data rate acoustic modems to transfer information between multiple remote units and a central controller; and inductive modems that use standard mechanical mooring lines as the transmission medium between instruments deployed on the mooring and a central controller. These telemetry systems are targeted for general use by the oceanographic community and are designed to be power efficient, low in cost, and capable of integration with most oceanographic data collection systems     

The Long-term Ecosystem Observatory: an integrated coastalobservatory

An integrated ocean observatory has been developed and operated in the coastal waters off the central coast of New Jersey, USA. One major goal for the Long-term Ecosystem Observatory (LEO) is to develop a real-time capability for rapid environmental assessment and physical/biological forecasting in coastal waters. To this end, observational data are collected from satellites, aircrafts, ships, fixed/relocatable moorings and autonomous underwater vehicles. The majority of the data are available in real-time allowing for adaptive sampling of episodic events and are assimilated into ocean forecast models. In this observationally rich environment, model forecast errors are dominated by uncertainties in the model physics or future boundary conditions rather than initial conditions. Therefore, ensemble forecasts with differing model parameterizations provide a unique opportunity for model refinement and validation. The system has been operated during three annual coastal predictive skill experiments from 1998 through 2000. To illustrate the capabilities of the system, case studies on coastal upwelling and small-scale biological slicks are discussed. This observatory is one part of the expanding network of ocean observatories that will form the basis of a national observation network     

Formation of submarine canyons on the flanks of the Canary Islands

Detailed morphological data collected from the submarine flanks of the Canary Islands have revealed numerous submarine canyons down to water depths of >3,000 m. These canyons are interpreted to have formed by submarine erosion. We postulate formation of proto-canyons by downslope-eroding mass flows which originate on land, enter the sea, and continue below sea level for several tens of kilometers. Once proto-canyons have been formed, they become deepened by further erosion and failures of the canyon walls and/or floor. Large amounts of sediments, funnelled through the canyons from the islands into the adjacent deep-ocean sedimentary basins, play an important role in the evolution of volcanic aprons surrounding ocean islands. Some major canyon systems appear to have persisted for at least 14 million years.