The small Indian Ocean island of Mayotte has experienced an earthquake swarm since last week, according to BRGM Mayotte, the France-based geological agency serving the territory – and the swarm is consistent with seismic activity last seen in the 1980s.

In a statement Monday, the BRGM said Mahorans began feeling earthquakes on Thursday night with at least eight quakes at or higher than a 4.0-magnitude recorded. All told, there were more than 250 small events recorded at the Iloni station in a four-day period. The Iloni data-monitoring site is one of three used by the agency.

All of the quakes appear to be coming from the same general spot, which is circled on the map.

“A seismic swarm is a succession of earthquakes that occur in a given place over a period of days or weeks,” the agency said. “There is not, strictly speaking, a main earthquake which stands out from the others, but a succession of earthquakes … hardly distinguishable from each other,” they added.

There was no let up on Monday at the Mamoudzou recording station, and the BRGM said other earthquakes of similar magnitude will likely be felt in days to come. “These earthquakes do not produce damage and, although at sea, are too weak to generate tsunamis,” the agency said.

Mayotte, a troubled territory disputed by neighboring Comoros and the French, does not have a history of large or frequent quakes. A 5.2-magnitude event in 1993 was the strongest recorded in at least 60 years, and no destructive earthquake greater than a 6.0 is recorded at the island.

Mayotte is the oldest volcanic island in the Comoros Basin grouping, the BRGM said, and quakes likely are the result of seismic hot spot as well as the island’s position along the East African rift.

Image: BRGM