Between March 20th and 21st a series of earthquakes struck along the Pacific Ring of Fire. On March 20, 2012 (12:02 at the epicenter) a 7.4 magnitude earthquake struck in the Mexican state of Oaxaca. On March 20, 2012 (09:07 at the epicenter) a 5.2 magnitude earthquake struck in the Tonga Region. On March 20,2012 (02:56 at the epicenter) a 6.2 magnitude earthquake struck in Papua, Indonesia. On March 20,2012 (02:06 at the epicenter) a 5.0 magnitude earthquake struck in Vanuatu.
Mexico lies on the eastern rim of the Ring of Fire. Its state of Oaxaca lies along the Middle American Trench. Oaxaca encompasses 36,375 sq mi (94,211 sq km). The state is dominated Sierra Madre de Oaxaca mountain range with deep narrow valleys. It has semiarid valleys and plateaus; the periphery of the state is tropical. Also, on March 21, 2012 (05:36 at the epicenter) a 5.0 magnitude earthquake struck in the Mexican state of Guerrero. The natural hazards facing Mexico include: tsunamis along the Pacific coast, volcanoes and destructive earthquakes in the center and south, and hurricanes on the Pacific, Gulf of Mexico, and Caribbean coasts.
Tonga is an archipelago directly south of Western Samoa. Its 171 islands, 48 of them inhabited, are divided into three main groups -- Vava'u, Ha'apai, and Tongatapu -- and cover an 800-kilometer (500 mi.) long north-south line. The largest island, Tongatapu, on which the capital city of Nuku'alofa is located, covers 257 square kilometers (99 sq. mi.). Geologically the Tongan islands are of two types: most have a limestone base formed from uplifted coral formations; others consist of limestone overlaying a volcanic base. The natural hazards facing Tonga include: cyclones (October to April), earthquakes and volcanic activity on Fonuafo'ou.
Papua, Indonesia shares the island with Papua New Guinea in the Pacific Ocean. The earthquake struck south of the port city of Jayapura. This regional trade center lies on Yos Sudarso Bay (formerly Humboldt Bay). Shortly after hostilities with the Dutch ended in 1949, Indonesia adopted a new constitution, but the province of Papua saw continued struggles concerning Dutch control. The island is dominated by a central mountain region, where the earthquake struck. The natural hazards of Indonesia include: occasional floods, severe droughts, tsunamis, earthquakes, volcanoes, and forest fires.
Vanuatu is a 'Y' shaped archipelago of 83 islands within Oceania, a group of islands in the South Pacific Ocean, about three-quarters of the way from Hawaii to Australia. Vanuatu's economy is based primarily on small-scale agriculture, but fishing, offshore financial services, and tourism are other mainstays of the economy. The natural hazards facing Vanuatu include: tropical cyclones or typhoons (January to April), volcanic eruption (also causing minor earthquakes), and tsunamis.
For more information on this earthquake and others, please see the USGS Earthquake Hazards Program site.
CIA World Factbook; U.S. State Department Background Notes; The Columbia Gazetteer, 2/2012; 1/2012 ; 3/2012