Seismicity and seismically active faulting of Guatemala: A review

Abstract

We present a review of the main sources of seismicity of Guatemala. The largest seismically active faults are related to the transform, left-lateral, North America-Caribbean plate boundary zone, the most prominent of which are the Motagua and Polochic faults, both exceeding 350 km in length. Additionally, the Ixcán fault, a 150-200-km-long left-lateral structure, is located north of the Polochic and Motagua faults. Other seismically active faults associated to the Polochic-Motagua system and smaller in length are the Seleguá, Nentón and Las Conchas.The Jocotán and Chamelecón faults are located south of and parallel to, the Polochic-Motagua, with a combined length of about 300 km. These faults are not active at present but probably were part of the plate boundary zone in the geologic past. A system of North-South-trending grabens is located immediately south of the Jocotán-Chamelecón fault system, and cutting through it. These grabens are seismically active. South-southwest of the grabens, there is a system of conjugate faults, called the Arco Volcánico fault system, whose main structure is the Jalpatagua fault, a right-lateral strike-slip structure parallel to the volcanic arc. There are other minor faults along this system striking perpendicular to the Jalpatagua with left-lateral displacement. These faults are partially covered by volcanic deposits and have only been identified by their seismic activity. Finally, the Middle America trench offshore southern Guatemala is the plate boundary between the overriding Caribbean and the subducting Cocos plates.All these structures have produced large earthquakes. Historical data show that epicenters of great earthquakes have indeed been located along one of these faults, such as the July 22, 1816 (Magnitude 7.6) along the Polochic fault. More recently, on February 4, 1976, a Magnitude 7.5 earthquake took place, with epicenter on the Motagua fault. This event caused severe damages to the infrastructure of the country, and about 23,000 deaths. The rest of the faults and grabens have also been the site of destructive earthquakes, such as the seismic sequence of December 1917–January 1918, which caused severe damages in Guatemala City. The Cocos-Caribbean convergent boundary is also seismically active, producing events of magnitude 7.0 or larger, the latest of which took place on November 2012, damaging towns and cities along the coastal plain of southern Guatemala.