Rare M5.5 earthquake hits Gabon – the strongest since 1974

A rare earthquake, registered by the USGS as M5.5, hit Gabon at 09:53 UTC on December 4, 2022. The agency is reporting a depth of 3.6 km (2.2 miles). EMSC is reporting M5.5 at a depth of 10 km (6.2 miles).

The epicenter was located 37.5 km (23.3 miles) S of Lambaréné (population 20 714), 163.7 km (101.7 miles) ESE of Port-Gentil (population 109 163), and 180.4 km (112.1 miles) SSE of Libreville (population 578 156), Gabon.

1 000 people are estimated to have felt very strong shaking, 2 000 strong, 66 000 moderate and 1 547 000 light.

The USGS issued a Green alert for shaking-related fatalities and a Yellow alert for economic losses. Some damage is possible and the impact should be relatively localized. Estimated economic losses are less than 1% of GDP of Gabon. Past events with this alert level have required a local or regional level response.

Overall, the population in this region resides in structures that are vulnerable to earthquake shaking, though resistant structures exist. The predominant vulnerable building types are mud wall and informal (metal, timber, GI etc.) construction.

This is the strongest earthquake to hit Gabon since M6.2 at 19:28 UTC on September 23, 1974.

Several moderate to strong earthquakes were registered near yesterday’s M5.5 quake over the past 2 years. The magnitudes ranged from 4.4 to 5.2.

Estimated population exposure to earthquake shaking

Selected cities exposed

Regional seismicity

Featured image credit: TW/SAM, Google