Guatemala

Guatemala experiences frequent and often devastating earthquakes generated by one of the most tectonically active corridors in Central America, where the North American Plate, Caribbean Plate, and Cocos Plate converge within its borders. The Motagua Fault Zone and the Polochic Fault Zone are the dominant seismic structures onshore, together accommodating the left-lateral motion of the Caribbean Plate relative to the North American Plate at roughly 2 centimetres per year. The Motagua Fault runs the length of the Motagua Valley — the structural boundary between the two plates — passing through densely populated agricultural land before entering the Caribbean Sea. Offshore, the Middle America Trench marks the [[subduction-zone]] where the Cocos Plate dives beneath the Caribbean Plate, generating additional seismic hazard along the Pacific coast and beneath the volcanic arc. The Central American volcanic arc crosses Guatemala from west to east, with active volcanoes including Santiaguito, Acatenango, Fuego, Pacaya, and Agua all capable of generating volcano-tectonic earthquake swarms.

The 4 February 1976 Guatemala earthquake stands among the most destructive disasters in twentieth-century Latin America. A magnitude 7.5 strike-slip rupture on the Motagua Fault killed 23,000 people, injured 76,000, and left over one million homeless — roughly a fifth of the country's population at the time. The [[epicenter]] was near the town of Los Amates in the Motagua Valley; surface rupture extended over 230 kilometres along the fault, and towns directly overlying the fault trace were essentially destroyed. Differential displacement of more than one metre was measured across the fault scarp. The earthquake was particularly devastating because most of the rural housing stock consisted of unreinforced adobe and block masonry that collapsed completely in strong shaking. Poorer communities, whose construction was weakest, suffered disproportionately. The event prompted what journalists called an "earthquake of class" because the differential survival rates mapped almost perfectly onto socioeconomic class lines. Guatemala has also experienced significant offshore subduction events: a 1902 magnitude 7.5 earthquake near Quezaltenango killed thousands, and the region continues to experience M6+ subduction events roughly every 5 to 10 years. More recently, a 2014 magnitude 6.9 earthquake in Huehuetenango killed two people and caused significant structural damage.

The geological complexity of Guatemala reflects the junction of three major tectonic plates, an unusual configuration that generates multiple styles of [[fault]]ing and seismicity at different depths and mechanisms. At the surface, the Motagua and Polochic faults are classic transform boundaries where plates slide horizontally past one another, capable of hosting very large shallow earthquakes with long surface ruptures. Below the volcanic arc, the subducting Cocos Plate generates intermediate-depth intraslab earthquakes as the cold, brittle oceanic crust is stressed by bending and dehydration. Beneath the volcanic arc, the [[subduction-zone]] coupling produces additional locked-zone hazard. Guatemala City sits in a highland valley on thick volcanic ash deposits that can amplify shaking significantly and are susceptible to [[liquefaction]] during strong ground motion. [[aftershock]] sequences following major Guatemalan earthquakes typically last for months. Guatemala's Instituto Nacional de Sismología, Vulcanología, Meteorología e Hidrología (INSIVUMEH) maintains the national seismological network.