Wednesday, May 12 at 6 p.m., Mauritius – Earthquakes recorded in Reunion, Announced by the websiteGeological Survey of the United States (USGS). The epicenter was reported below the Pacific Ocean floor, however; no tsunami alert was issued. Earthquakes occur frequently in the region, the highest ever recorded.
What causes earthquakes in the region? “This earthquake is located in the foothills of central India. It is a region of seismic plateau that usually produces earthquakes.”, Explains Valerie Ferrassini, seismologist at the Pitton de la Fornes Volcano Laboratory, Institute de Physique to Globe de Paris.
The oceanographer, Wason Coop Payamuthu, talks about the accumulation of energy in the lithosphere. “Rodriguez is located a few hundred kilometers from the normal sea mountain and three junctions of the Indian Ocean, where three oceans collide. This backbone is very active and produces earthquake-causing energy accumulations and releases.”
Prem Sadul, geographer, agrees. Mauritius is located in the middle of the Somali plate, far from the Triple Junction, which connects the Indo-Australian, African and Antarctic plates, and the island of Rodrigues. These are different plates. “When the plates are different, there are magical ups and downs that create underwater mountain ranges. These climbs create the vibrations we feel in the region of Rodriguez.
“Because of the proximity of the Rodriguez Triple Junction to the east of the island, 12-14 tremors occur each year, measuring 3.5-5 on the Richter scale.”, Explains the geologist. According to him, the 6.7 level is very consistent, but still moderate.
Trembling with magma
Prem Sadul, who has studied volcanic and tectonic plate movements in our region, points out that tremors occur with magmatic rises, as magma is absorbed by shocks. The reason why Mauritius is not affected by earthquakes. “We are still at the level of vibrations. Different plates do not cause earthquakes, just as plates do in Indonesia. This is not a rare occurrence. ”
Add to that when he was president Mauritius Oceanographic Institute (ME), he set up a committee to coordinate the organization, the Ministry of Environment and the Meteorology to establish seismic maps in Agalega, Mauritius and Rodrigues to catch the waves of earthquakes in the region. “With Reunion Island, which already has seismic maps, we had a network with the islands of the Indian Ocean. ”
The geologist says that the Somali plate moves westward at a speed of 4 cm per year and that there is a hot spot beneath the active volcano of La Fornes. “If Reunion and Mauritius move west at a rate of 3 to 4 cm per year, the hot spot will be east of La Fornes. Suddenly, an island emerges. When it comes out, it’s trembling. “
The risk of a tsunami is very low
With a magnitude of 6.7, is Mauritius tsunami safe? Prem Sadul says tsunamis are caused by earthquakes near the edges of the submerged plates, beneath the submarine surface. “Tsunami is caused by the sudden destruction of the earth’s crust. Because there are cracks or fissures in the different plate, it emits only small shock waves that cannot create a tsunami. ”
Nevertheless, he believes the magnitude of 6.7 is still a concern, so a network should be set up to monitor any tectonic movement in the region.
Seismologist Valerie Ferrassini agrees. According to her, the trigger for a tsunami depends on a number of factors, including the magnitude of the earthquake and its magnitude. In the case of a ridge, he believes, it is much less likely to have a mechanism capable of creating a tsunami (ground displacement is mainly in the horizontal plane). “In addition, a magnitude 7 earthquake is estimated to trigger a tsunami. You should realize that a magnitude 7 earthquake is 30 times more powerful than a magnitude 6 earthquake, so the risk of a tsunami in Mauritius is very low. , And the size of the tsunami will be small. ”
But oceanographer Vasan Kuppayamuthu disagrees. He believes no island in the Indian Ocean will be affected by a tsunami caused by a regional or far-flung earthquake. “In fact, an earthquake of this magnitude could cause submarine landslides, which could cause a tsunami.”
Five earthquakes in the region of Mauritius between 1786 and 1925
According to historical documents from the Bureau of Geological and Mining Research (PRGM), five earthquakes were felt in the region of Mauritius between 1786 and 1925. Their location is unknown due to the lack of seismic measurements in the region.
According to the USGS, the seas of southwestern India showed moderate seismicity, mostly concentrated along the ridge of Mayotte, Madagascar and the central Indian Ocean west.
On February 27, 2018, a magnitude 4.1 earthquake was recorded about 100 km southwest of Le Morne. At 8:02 pm on November 12, 2019, an earthquake measuring 4.8, 216 km east of Boise-des-Amorettes struck.
According to Prem Sadul, the two quakes were located on the east coast of Mauritius near a fossil fault from northeast to southwest. “Fossil fault refers to the seismic locking system that began to release energy in the form of an earthquake”, Bringing out the geologist.
When Mauritius, Agalega and Rodriguez were fitted with seismic stations, Montanger et al. (2–8 April 2012), in a document entitled “Report of the Panel of Experts on Earthquake and Tsunami Risks in Mauritius and Rodrigues” It was submitted to the Prime Minister’s Office and recommended that an earthquake station be provided for St. Brandon to help identify the tectonic features and weak areas currently active in the quake.
On September 21, 2020, a magnitude 4.4 earthquake shook the region of La Reunion, 22 km northwest of Saint-Denis and about 200 km west. Southwest of Port Louis. What made the Mauritians tremble … The depth of the earthquake was about 27 km.