This article reviews the American literature in social science for the period 1975–1992 on the determinants of volunteer participation in programs and associations. It finds that most studies are t...

Determinants of Voluntary Association Participation and Volunteering: A Literature Review:

Optical fiber sensors have attracted considerable attention for marine environment and marine structural health monitoring, owing to advantages including resistance to electromagnetic interference, durability under extreme temperature and pressures, light weight, high transmission rate, small size and flexibility. In this paper, the optical fiber sensors employed for marine environment and marine structural health monitoring are summarized for the understanding of their basic sensing principles, and their various sensing applications such as physical parameters, chemical parameters and structural health monitoring. This review paper shows the feasibility of using optical fiber sensing technology for marine application and, due to the aforementioned advantages, it is possible to envisage a widespread use in this research field in the next few years.

Optical fiber sensing for marine environment and marine structural health monitoring: A review

Two thirds of the surface of our planet are covered by water and are still poorly instrumented, which has prevented the earth science community from addressing numerous key scientific questions. The potential to leverage the existing fiber optic seafloor telecom cables that criss-cross the oceans, by using them as dense arrays of seismo-acoustic sensors, remains to be evaluated. Here, we report Distributed Acoustic Sensing measurements on a 41.5 km-long telecom cable that is deployed offshore Toulon, France. Our observations demonstrate the capability to monitor with unprecedented details the ocean-solid earth interactions from the coast to the abyssal plain, in addition to regional seismicity (e.g., a magnitude 1.9 micro-earthquake located 100 km away) with signal characteristics comparable to those of a coastal seismic station. Existing fibers beneath the world’s oceans can in principle be used as seismic sensors, but the full potential of this possibility has yet to be explored. Here, the authors demonstrate the feasibility of distributed acoustic sensing in a coastal fiber as a sensor for earthquakes and wave phenomena.

https://eartharxiv.org/repository/object/848/download/1880/

Distributed sensing of earthquakes and ocean-solid Earth interactions on seafloor telecom cables.

Distributed acoustic sensing (DAS) is a new, relatively inexpensive technology that is rapidly demonstrating its promise for recording earthquake waves and other seismic signals in a wide range of research and public safety arenas. It should significantly augment present seismic networks. For several important applications, it should be superior. It employs ordinary fiber‐optic cables, but not as channels for data among separate sophisticated instruments. With DAS, the hair‐thin glass fibers themselves are the sensors. Internal natural flaws serve as seismic strainmeters, kinds of seismic detector. Unused or dark fibers are common in fiber cables widespread around the globe, or in dedicated cables designed for special application, are appropriate for DAS. They can sample passing seismic waves at locations every few meters or closer along paths stretching for tens of kilometers. DAS arrays should enrich the three major areas of local and regional seismology: earthquake monitoring, imaging of faults and many other geologic formations, and hazard assessment. Recent laboratory and field results from DAS tests underscore its broad bandwidth and high‐waveform fidelity. Thus, while still in its infancy, DAS already has shown itself as the working heart—or perhaps ear drums—of a valuable new seismic listening tool. My colleagues and I expect rapid growth of applications. We further expect it to spread into such frontiers as ocean‐bottom seismology, glacial and related cryoseismology, and seismology on other solar system bodies.

https://par.nsf.gov/servlets/purl/10144022

Distributed Acoustic Sensing Turns Fiber‐Optic Cables into Sensitive Seismic Antennas

Distributed acoustic sensing (DAS) is an emerging technology that repurposes a fiber-optic cable as a dense array of strain sensors. This technology repeatedly pings a fiber with laser pulses, meas...

Fiber-Optic Seismology

The MEUST (Mediterranean Eurocentre for Underwater Sciences and Technologies) is a
permanent deep sea cabled infrastructure currently being deployed off shore of Toulon, France.
MEUST is shared between the neutrino physics and astro-physics communities in the context
of the European KM3NeT project, and the Environmental Science communities as the West-
Ligurian site of the EMSO European network of submarine observatories. The MEUST
submarine network has a modular and extendable topology which will allow hosting up to
120 neutrino detection units and to instrument a seafloor area with sea science sensors. The
MEUST terrestrial base is located in La Seyne sur Mer near Toulon, where a new building
is planned to host the technical activities, including a control room of the infrastructure.
The MEUST submarine site has been selected after intensive characterization campaigns
conducted in the past years leading to the choice of the site located ˜40km offshore of Toulon
at a depth of 2500m and 15km west of the Antares site. The full MEUST submarine network
has up to 6 nodes connected to the shore by two Main Electro Optical Cables (MEOC). The
MEOCs are standard telecommunication cables with optical fibres for data transfer and one
electrical conductor for power transfer. The nodes are equipped each with 8 wet mate-able
connectors allowing to connect at least 20 neutrino detection units (daisy chained by 4) and a
set of environmental instruments, with some redundancy. The power transfer is performed
in HV AC with sea return, as for Antares, and provides a usable power of ˜10kW on each
node (˜1kW/connector). A dedicated control/command system controls the power and optical
systems. The data transfer uses Dense Wavelength Division Multiplexing (DWDM). The
proposed talk will focus on the design and the status of the infrastructure with the first lessons
learnt from the ongoing deployments.

The MEUST deep sea infrastructure in the Toulon site

The novel technique of distributed acoustic sensing (DAS) holds great potential for underwater seismology by transforming standard telecommunication cables, such as those currently traversing most ...

On the Detection Capabilities of Underwater DAS

The novel technique of distributed acoustic sensing (DAS) holds great potential for underwater seismology by transforming standard telecommunication cables, such as those currently traversing various regions of the world’s oceans, into dense arrays of seismo‐acoustic sensors. To harness these measurements for seismic monitoring, the ability to record transient ground deformations is investigated by analyzing ambient noise, earthquakes, and their associated phase velocities, on DAS records from three dark fibers in the Mediterranean Sea. Recording quality varies dramatically along the fibers and is strongly correlated with the bathymetry and the apparent phase velocities of recorded waves. Apparent velocities are determined for several well‐recorded earthquakes and used to convert DAS S‐wave strain spectra to ground motion spectra. Excellent agreement is found between the spectra of nearby underwater and on‐land seismometers and DAS converted spectra, when the latter are corrected for site effects. Apparent velocities greatly affect the ability to detect seismic deformations: for the same ground motions, slower waves induce higher strains and thus are more favorably detected than fast waves. The effect of apparent velocity on the ability to detect seismic phases, quantified by expected signal‐to‐noise ratios, is investigated by comparing signal amplitudes predicted by an earthquake model to recorded noise levels. DAS detection capabilities on underwater fibers are found to be similar to those of nearby broadband sensors, and superior to those of on‐land fiber segments, owing to lower velocities at the ocean‐bottom. The results demonstrate the great potential of underwater DAS for seismic monitoring and earthquake early warning

On the Detection Capabilities of Underwater Distributed Acoustic Sensing

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Distributed sensing of earthquakes and ocean-solid Earth interactions on seafloor telecom cables.

The MEUST deep sea infrastructure in the Toulon site

On the Detection Capabilities of Underwater DAS

On the Detection Capabilities of Underwater Distributed Acoustic Sensing