MERMAID

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MERMAID is a marine scientific instrument platform, short for Mobile Earthquake Recorder for Marine Areas by Independent Divers.

Contents

MERMAID evolved from a first prototype, [1] [2] developed and built by the Scripps Institution of Oceanography in partnership with Princeton University, to a second, [3] [4] built by Teledyne Webb Research in collaboration with the University of Nice Sophia Antipolis, and now third-generation model, [5] [6] [7] operational today, commercialized by OSEAN SAS in Le Pradet, France. Fourth-generation models add hydrographic monitoring capability to complement the acoustic sensor suite, and are designed to carry out measurement profiles to depths exceeding 4,000 m.

Technical diagram of a third-generation MERMAID instrument Mermaid technical diagram3.jpg
Technical diagram of a third-generation MERMAID instrument

MERMAID is a freely-drifting float equipped with a hydrophone to collect hydroacoustic data for the study of earthquakes worldwide. [8] Typically floating at a parking depth of 1500 m, the instrument uses a buoyancy engine (a hydraulic oil bladder system) to return to the surface for triggered data transmission (on average every 6–7 days) via the Iridium satellite constellation, to respond to on-demand data requests, and to receive mission parameter updates. MERMAID carries lithium-ion batteries, sufficient to power about 250 descend/ascend cycles, which translates to an instrument autonomy of about 5 years. A pressure sensor monitors descent depth, and a GPS receiver provides location and time corrections during the brief intervals that MERMAID surfaces (on average less than one hour).

Fourth-generation models are multidisciplinary and carry a conductivity-temperature-depth sensor to collect hydrographic profiles of ocean temperature and salinity (similar to those from the Argo program) during their voyages. They can be additionally equipped with high-frequency hydrophones for the study of, e.g. cetacean (whale) vocalizations, [9] and other sensors.

Scientific objectives and capabilities

Imaging Earth's interior via the technique of seismic tomography is reliant on dense source-receiver distribution, or data coverage, but two thirds of the Earth's surface are covered by water. Increasing station density in the oceanic domain is an objective widely shared in the global seismological research community. [10] [11] [12] After the first detections of teleseismic events by first-generation MERMAID, [13] relatively small-scale deployments of second-generation MERMAID instruments in the Mediterranean, the Indian Ocean, and in the Pacific around the Galápagos, demonstrated MERMAID's potential for closing the oceanic seismic coverage gap, both for global and regional seismic events, [14] [15] and for seismic tomography of the Earth's mantle. [16] [17]

The ongoing multinational experiment SPPIM (South Pacific Plume Imaging and Modeling), coordinated by Ifremer with JAMSTEC, deployed an array of fifty-one third-generation instruments to image, in detail, the massive mantle plume in the lower mantle beneath the South Pacific. The instruments are owned by Southern University of Science and Technology, Princeton University, JAMSTEC and Géoazur, and the data management and distribution is handled by EarthScope-Oceans.

The standard third-generation model reports pressure time-series, waveforms triggered by earthquakes, whereas the third-generation model deployed in the Mediterranean was configured to report time-resolved hydroacoustic spectral densities.

Deployments and network configuration

MERMAIDs first-generation model (2003-2005) retired after gathering about 120 hours of acoustic pressure data from a depth of around 700 m offshore from La Jolla, California. [1]

Of the second-generation MERMAIDs (2012-2016), the first were deployed in the Mediterranean and recovered after 10, respectively 18 months of autonomous operations. [14] Other deployments followed in the Indian Ocean, [14] and in the Pacific around Galápagos, where an array of nine MERMAIDs remained operational for about two years. [16]

Sixty-seven third-generation MERMAIDs (2018-now) were launched in the Pacific Ocean, the South China Sea, and the Mediterranean, from a variety of international (French, Japanese, Chinese) research vessels.

EarthScope-Oceans MERMAID array configuration as of January 15th, 2022 Whereismermaid 01152022.png
EarthScope-Oceans MERMAID array configuration as of January 15th, 2022

Data collection and distribution

Every MERMAID instrumental sensor has a unique identifier. In contrast to conventional (land-based) seismometers or ocean-bottom seismometers (OBS), MERMAID instruments are passively adrift with the ocean currents: they do not remain at any fixed geographic location. Data from particular units are location-tagged hydroacoustic time-series as recorded at depth in the oceans. Data segments triggering transmission mostly contain pressure-wave signals from particular earthquakes worldwide, [18] but also noise generated by a variety of sources (e.g. microseisms or volcanic eruptions [19] [20] ). Since GPS signals do not penetrate under water, the actual location of recording specific events is derived from interpolation in post-processing. [21]

Seismic data from the US and French MERMAIDs are being deposited with the IRIS Consortium. [22] Primary seismoacoustic arrivals from distant teleseismic earthquakes are prioritized for automatic reporting, [23] although the complete records (and the year-long buffer, which can be queried remotely) contain multiple other types of seismic arrivals. [24] Seismic waveforms are released to the public through the IRIS Data Management Center, after a rolling embargo period of typically two years.

Trajectory metadata are released by EarthScope-Oceans in near real-time. Float trajectories allow for the reconstruction of ocean currents, and are used in educational and outreach programs, [25] e.g. using the free iOS app Adopt-A-Float.

The EarthScope-Oceans Consortium

EarthScope-Oceans is an international academic consortium that collects seismic data using robotic mobile—drifting—diving platforms (profiling floats) in the world's oceans, and distributes them to scientific user communities, with the objective to plug the oceanic data coverage gap in earthquake detection. [26] [27] [28] MERMAID is EarthScope-Oceans' chief instrument platform.

EarthScope-Oceans
FoundedDecember 2015;8 years ago (2015-12)
Services Research, Education
Website www.earthscopeoceans.org

Funded in part by the US National Science Foundation (NSF), EarthScope-Oceans is not affiliated with NSF's EarthScope program. EarthScope is a trademark of the IRIS Consortium.

EarthScope-Oceans is one of 361 Decade Actions endorsed by the Intergovernmental Oceanographic Commission of UNESCO, part of the Ocean Observing Co-Design program, falling under the umbrella of the United Nations Decade of Ocean Science for Sustainable Development (2021-2030).

The expansion of the EarthScope-Oceans fleet to include new multidisciplinary MERMAID models adds oceanography, meteorology, climate science, and bioacoustics to the seismological domain of interest of the EarthScope-Oceans Consortium.

EarthScope-Oceans is a member organization of the International Federation of Digital Seismograph Networks. Its network code is MH, and its doi 10.7914/SN/MH. EarthScope-Oceans is a member of the Marine Technology Society.

Related Research Articles

<span class="mw-page-title-main">Seismology</span> Scientific study of earthquakes and propagation of elastic waves through a planet

Seismology is the scientific study of earthquakes and the generation and propagation of elastic waves through the Earth or other planetary bodies. It also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, glacial, fluvial, oceanic microseism, atmospheric, and artificial processes such as explosions and human activities. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of Earth motion as a function of time, created by a seismograph is called a seismogram. A seismologist is a scientist working in basic or applied seismology.

<span class="mw-page-title-main">Seismometer</span> Instrument that records seismic waves by measuring ground motions

A seismometer is an instrument that responds to ground noises and shaking such as caused by quakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The output of such a device—formerly recorded on paper or film, now recorded and processed digitally—is a seismogram. Such data is used to locate and characterize earthquakes, and to study the Earth's internal structure.

Seismic tomography is a technique for imaging the subsurface of the Earth with seismic waves produced by earthquakes or explosions. P-, S-, and surface waves can be used for tomographic models of different resolutions based on seismic wavelength, wave source distance, and the seismograph array coverage. The data received at seismometers are used to solve an inverse problem, wherein the locations of reflection and refraction of the wave paths are determined. This solution can be used to create 3D images of velocity anomalies which may be interpreted as structural, thermal, or compositional variations. Geoscientists use these images to better understand core, mantle, and plate tectonic processes.

<span class="mw-page-title-main">IRIS Consortium</span>

IRIS was a university research consortium dedicated to exploring the Earth's interior through the collection and distribution of seismographic data. IRIS programs contributed to scholarly research, education, earthquake hazard mitigation, and the verification of a Comprehensive Nuclear-Test-Ban Treaty. Support for IRIS came from the National Science Foundation, other federal agencies, universities, and private foundations. IRIS supported five major components, the Data Management Center (DMC), the Portable Array Seismic Studies of the Continental Lithosphere (PASSCAL), the Global Seismographic Network (GSN), the Transportable Array (USARRAY), and the Education and Public Outreach Program (EPO). IRIS maintained a Corporate Office in Washington, DC.

<span class="mw-page-title-main">1970 Ancash earthquake</span> 1970 earthquake and resulting avalanche in Peru

The 1970 Ancash earthquake occurred on 31 May off the coast of Peru in the Pacific Ocean at 15:23:29 local time. Combined with a resultant landslide, it is the most catastrophic natural disaster in the history of Peru. Due to the large amounts of snow and ice included in the landslide that caused an estimated 66,000-70,000 casualties, it is also considered to be the world's deadliest avalanche.

<span class="mw-page-title-main">Earthscope</span> Earth science program exploring the structure of the North American continent

The EarthScope project was an National Science Foundation (NSF) funded earth science program that, from 2003-2018, used geological and geophysical techniques to explore the structure and evolution of the North American continent and to understand the processes controlling earthquakes and volcanoes. The project had three components: USArray, the Plate Boundary Observatory, and the San Andreas Fault Observatory at Depth. Organizations associated with the project included UNAVCO, the Incorporated Research Institutions for Seismology (IRIS), Stanford University, the United States Geological Survey (USGS) and National Aeronautics and Space Administration (NASA). Several international organizations also contributed to the initiative. EarthScope data are publicly accessible.

<span class="mw-page-title-main">Marsquake</span> Seismic event occurring on Mars

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<span class="mw-page-title-main">Centro Sismológico Nacional</span>

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<span class="mw-page-title-main">Seismic Experiment for Interior Structure</span> Scientific instrument aboard the InSight Mars lander

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Frederik J. Simons is a Flemish Belgian geophysicist. He is a professor at Princeton University in the Department of Geosciences. From 2010 to 2013, Simons was the Dusenbury University Preceptor of Geological & Geophysical Sciences. From 2004 to 2006, he was a lecturer in the Department of Earth Sciences at University College London. Between 2002 and 2004 he was a Harry H. Hess Postdoctoral Fellow in the Department of Geosciences and a Beck Fellow with the Council on Science and Technology, also at Princeton University.

Galperin configuration are a particular configuration of sensing elements found in a class of seismic instruments measuring ground motion and are named after Soviet seisomologist Evsey Iosifovich Galperin, who introduced it in 1955 for petroleum exploration.

Anne Meltzer is a seismologist known for her research on earthquakes and the formation of mountain ranges. Her research primarily focused on the evolution of the Earth's lithosphere and the surface processes associated with faulting and deformation in the Earth's crust. Through her own personal research and collaboration with other colleagues, she strived to make advancements in the efficiency and effectiveness of monitoring earthquakes. In addition, her work aimed to effectively reduce earthquake destruction in countries that experience frequent seismic phenomena.

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<span class="mw-page-title-main">Wood–Anderson seismometer</span> Instrument fo measuring strength of earthquakes

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Subsurface mapping by ambient noise tomography is the mapping underground geological structures under the assistance of seismic signals. Ambient noise, which is not associated with the earthquake, is the background seismic signals. Given that the ambient noises have low frequencies in general, the further classification of ambient noise include secondary microseisms, primary microseisms, and seismic hum, based on different range of frequencies. We can utilize the ambient noise data collected by seismometers to create images for the subsurface under the following processes. The filtered ambient noise raw data Since the ambient noise is considered as diffuse wavefield, we can correlate the filtered ambient noise data from a pair of seismic stations to find the velocities of seismic wavefields. A 2-dimensional or 3-dimensional velocity map, showing the spatial velocity difference of the subsurface, can thus be created for observing the geological structures. Subsurface mapping by ambient noise tomography can be applied in different fields, such as detecting the underground void space, monitoring landslides, and mapping the crustal and upper mantle structure.

References

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  19. ↑ Tepp, Gabrielle; Dziak, Robert P. (2021). "The seismo‐acoustics of submarine volcanic eruptions". Journal of Geophysical Research. 126 (4): e2020JB020912. Bibcode:2021JGRB..12620912T. doi:10.1029/2020JB020912. S2CID   233677024.
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  21. ↑ Joubert, Cécile; Nolet, Guust; Bonnieux, Sébastien; Deschamps, Anne; Dessa, Jean-Xavier; Hello, Yann (2016). "P‐Delays from floating seismometers (MERMAID), Part I: Data processing". Seismological Research Letters. 87 (1): 73–80. doi:10.1785/0220150111.
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  24. ↑ Simon, Joel; Simons, Frederik J (2021). "A MERMAID miscellany: Seismoacoustic signals beyond the P wave". Seismological Research Letters. 92 (6): 3657–3667. doi:10.1785/0220210052. S2CID   235245049.
  25. ↑ Bigot‐Cormier, F.; Berenguer, J.‐L. (2017). "How students can experience science and become researchers: Tracking MERMAID floats in the oceans". Seismological Research Letters. 88 (2A): 416–420. doi:10.1785/0220160121.
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