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Surveillance in times of crisis

Two scientific publications have just appeared in Seismological Research Letters, confirming the ability of IPGP's observatories to deal with the major crises of recent years, whether climatic, with the devastating passage of hurricanes Irma and Maria in the West Indies, or health-related, with the management of an eruption at Piton de la Fournaise on Reunion Island during a period of confinement.

Surveillance in times of crisis

The Institut de Physique du Globe de Paris is responsible for accredited observation services in volcanology through its permanent observatories on the islands of Réunion (OVPF), Guadeloupe (OVSG) and Martinique (OVSM), as well as through REVOSIMA for Mayotte. Since their creation, these observatories have developed a large and dense monitoring network, as well as numerous solid national and international partnerships. These assets have enabled them to meet many challenges in recent years, particularly following hurricanes Irma and Maria in the West Indies in 2017 and, more recently, following the eruption of Piton de la Fournaise on Réunion in April 2020, in the middle of a period of containment as part of the health crisis. These two extreme situations highlight the resilience and professionalism of the teams working at these observatories.

The WI seismological network withstands the successive passage of two major cyclones

Deployed between 2008 and 2014 by the IPGP and the Seismic Research Center of the University of the West Indies in Trinidad and Tobago, the WI broadband seismological network extends from the north to the south of the Lesser Antilles. In order to avoid the natural hazards that can affect each of the islands (cyclones, earthquakes, tsunamis, volcanic eruptions), the stations have been designed using cutting-edge technologies to increase their resilience in the face of these potentially destructive phenomena. For example, Nanometrics’ VSAT technology enables the observatories in Guadeloupe (OVSG), Martinique (OVSM) and the SRC (Trinidad) to receive their data directly via satellite. In addition, a network core consisting of four stations and a reception hub is equipped with protective radomes to withstand hurricane winds.

On September 5th 2017, Hurricane Irma passed to the north of the Lesser Antilles and winds of more than 350 km/h destroyed the surface installations of the SBLM station in Saint-Barthélémy, located in the path of the eye of the hurricane. Three weeks later, Hurricane Maria crossed the centre of the Antilles, passing close to or directly over the islands of Martinique, Dominica and Guadeloupe. No operational stations were destroyed by this second hurricane.

The heavy rainfall first impacted the OVSM, forcing teams to redirect data collection from the OVSG. During the night, the cyclone caused damage to the buildings and the receiving antenna at the Guadeloupe observatory, rendering it inoperable for three days. On the morning of September 19th 2017, the IPGP data centre re-established the collection of all the data from the WI network via the OVSM. A few hours later, the network was able to record the Puebla earthquake (Mexico, Mw 7.1) at 12 of the network’s 15 stations.

The experience and expertise of the IPGP observatories in the design and maintenance in operational conditions of measurement networks in tropical environments enabled the interruption in data transmission to SATCAR to be limited to less than 12 hours.

Map of the WI broadband seismological network, showing the path of hurricanes Irma and Maria. Stations circled in black are equipped with a protective radome. The size of the cyclone symbols is proportional to the average wind speed estimated by NOAA (US meteorological administration in charge of hurricanes in the Caribbean basin).
Photos of the Saint-Barthélémy seismological station before and after the eye of category 5 hurricane Irma.

Real-time monitoring of a “confined” outbreak

In mainland France and the French overseas departments, the authorities have decided to impose a general lockdown of the population from March 17th to May 11th 2020 to restrict travel and social interaction, in a global effort to combat the COVID-19 pandemic. At the same time, from April 2nd to 6th, the Piton de la Fournaise on Réunion Island was erupting.

Short-term precursors to the eruption from April 2 to 6, 2020. (a) Seismic signals recorded on the vertical component of 19 OVPF network stations between 03:00 UTC and 11:59 UTC April 2 for each hour (time increases to the right). Each red vertical bar represents an earthquake. (b) Tremor map calculated for the period 08:45-09:00. (c) Maps of east-west (left), north-south (middle) and vertical (right) displacements associated with the April 2-6, 2020 eruption, calculated from Sentinel-1, PAZ and ALOS2 interferometric data. Solid circles represent displacements recorded on OVPF permanent GNSS stations. Displacement intensity is given by the colored bar.

As soon as the government announcement was made, a business continuity plan was implemented by the IPGP, which manages the Piton de la Fournaise Volcanological Observatory (OVPF), in order to maintain remote monitoring operations while allowing interventions in the field in the event of critical situations, such as serious breakdowns in real-time stations or transmission relays.

This eruption was an opportunity for the observatory to validate its ability to manage a volcanic crisis with 100% telemetered monitoring networks, without any additional field measurements at the eruption site. The short- and long-term precursors to the eruption enabled OVPF staff to provide the various parties involved (the prefecture and the Indian Ocean Zone and Civil Protection Staff) with real-time monitoring information on the volcano’s activity. The density and reliability of the OVPF’s networks, with field stations recording and transmitting continuously, combined with satellite observations, have enabled reliable instrumental monitoring of the eruption and continuity of the observatory’s missions.

This success is based on existing protocols that are operational 24 hours a day, 7 days a week, and on remote access to data in real time. Similar networks and protocols exist at the IPGP’s other volcanological observatories.

View of the eruption site on April 5, 2020 (© SAG / PGHM)

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