M. Madi¹

¹Centre National de Documentation et de Recherche Scientifique (CNDRS), National Data Centre of the Comoros, Comoros

Abstract:

The Comoro-Islands formed along the process of a mantle plume moving eastward within the Somali plate (e.g. Emmerick & Ducan, 1982). They are four volcanic Islands, Grand Comore (1148km2), hosting the active "Karthala volcano" (rising up to 2361 m .al), Moheli (211km2; 790m al.), Anjouan (424km2; 1595m al.), and Mayotte (374 km2; 660m al.), whose respective eruptions are estimated generally 10 million years ego westwards with time. They are composed of basalts and associated volcanic, plutonic rocks (e.g. Thompson & Flower, 1971; Ludden, 1977). In the past 3 years, Anjouan Island recorded moderate earthquakes, and in 2014, a motion from Magnitude 4.8 ML (IDC-REB record) of March 12 has been felt partly in the western side of the Island, with about 7- 8s tremor duration (villager testimony). Seventeen days separated the earthquake and a landslide whose displacement commenced on March 29 in the eastern side of the Island (determined through local oral interviews) after strong rainfall in the area and in many regions of the Islands. The objective of this study is to comprehend the triggering geological causes as well as to understand the possible seismic activity effects in such cases of future landslides within the Islands.