A preliminary seismic catalog for the Mozambique Channel

Andry Ramarolahy, Andriamiranto Raveloson, Rasheed Ajala, Folarin Kolawole

The Mozambique Channel is a 1,600-km long, 950 – 1,000-km wide deep-water arm of southwestern Indian Ocean, located between Mozambique and Madagascar Island. The channel hosts the offshore continuation of the East African Rift System, an active divergent plate boundary that has propagated from the African continent, across Mesozoic continental rifted margins, into Mesozoic oceanic lithosphere. The earthquake and tsunami hazards posed by the network of active plate boundaries in the Mozambique Channel necessitates a regional seismic database to aid scientific investigations, hazard analysis, and mitigation efforts. However, the Mozambique Channel lacks a systematic regional-scale analysis of event distribution, thus limiting advances in seismological investigations of the region. Here, we utilize 256 seismic stations onshore mainland Africa and in Madagascar to detect and locate earthquakes in the Mozambique Channel between 1990 and 2021, to produce its first regional earthquake catalog. The stations comprise two permanent (Africa Array and the Malagasy seismic networks) and six temporary seismic networks distributed across the two land masses. We detected and located 178 high-quality events with a magnitude of completeness of ML3.5, and b-value of 0.76. In the catalog, the events collocate with the known active plate boundaries and associated Quaternary submarine volcanic centers in the Mozambique Channel.