Madagascar

Madagascar separated from the African continent approximately 160 million years ago and from India about 88 million years ago, and today it occupies an isolated position as a large continental island in the western Indian Ocean. The island sits on the southward-propagating extension of the East African Rift System — specifically, the Davie Ridge and the Mozambique Channel fracture zones represent ancient rifting structures between Madagascar and mainland Africa. Though the main active rifting now occurs on the African continent rather than on Madagascar itself, the island's western margin remains seismically active.

The most seismically active region of Madagascar is the north and northwest, particularly around Diego Suarez (Antsiranana) and the Tsaratanana massif. A significant earthquake struck northern Madagascar on 15 March 1950 with an estimated magnitude of 6.0, causing structural damage in Diego Suarez. The central highlands, which form the backbone of the island, have also experienced moderate earthquakes. The southern and eastern coasts are generally quieter.

The eastern coast of Madagascar faces the Indian Ocean and has experienced occasional [[tsunami]] impacts from distant large subduction zone earthquakes — most notably from the 2004 Indian Ocean earthquake, though wave heights reaching Madagascar were much smaller than those in Southeast Asia or East Africa. A locally generated tsunami hazard could arise from submarine landslides on the steep eastern continental slope of Madagascar.

The tectonic setting of Madagascar involves the interaction between the African plate (to which Madagascar is attached) and the diffuse boundary zone of the Somali plate to the north. The Davie Fracture Zone, which runs along the western margin of Madagascar and northward through the Mozambique Channel, represents an ancient plate boundary that is no longer the locus of major plate separation but continues to experience occasional [[seismic-wave]] activity. [[fault]] structures within Madagascar itself include northwest-trending Precambrian ductile shear zones that can be reactivated as brittle faults under modern stress. Overall, Madagascar's seismic hazard is low to moderate, with the highest risk in the north.