89-8 Five Major Earthquakes from the Late Classic Maya Period to the 20th Century on the North America-Caribbean Plate Boundary in Guatemala

Session: Advancing Earthquake Geology and Surficial Deformation from Geologic Provinces to Political Entities through Multidisciplinary High-Resolution Data

Presenting Author:

Tina Niemi

Authors:

Niemi, Tina M.¹, Grützner, Christoph², Flores Beltetón, Omar³, Alberto Romero, Luis⁴, Gomez, Francisco⁵, Mauer, Jeremy⁶, McEnaney, Trenton⁷, Daniels, Robyn⁸, Dollens, Aleigha⁹, Ebell, Hannes¹⁰, Pérez Arias, Carlos¹¹, Graettinger, Alison¹², Obrist Farner, Jonathan¹³

(1) Earth and Environmental Sciences, University of Missouri-Kansas City, Kansas City, MO, USA, (2) Institute of Geosciences, Friedrich Schiller University Jena, Burgweg, Germany, (3) Universidad de San Carlos de Guatemala Guatemala, Guatemala City, Guatemala, (4) Universidad de San Carlos de Guatemala, Guatemala City, Guatemala, (5) Department of Geological Sciences, University of Missouri, Columbia, MO, USA, (6) Geology and Geophysics, Missouri University of Science and Technology, Rolla, MO, USA, (7) Geology and Geophysics, Missouri University of Science and Technology, Rolla, MO, USA, (8) Missouri Geological Survey, Rolla, MO, USA, (9) Earth and Environmental Sciences, University of Missouri-Kansas City, Kansas City, MO, USA, (10) Institute of Geosciences, Friedrich Schiller University Jena, Jena, Germany, (11) Ingeotecnia, Guatemala City, Guatemala, (12) Earth and Environmental Sciences, University of Missouri-Kansas City, Kansas City, MO, USA, (13) Geology and Geophysics, Missouri University of Science and Technology, Rolla, MO, USA,

Abstract:

The Motagua fault is an ENE-WSW striking, left-lateral fault at the western end of the transform plate boundary between the Caribbean and North American plates in Guatemala. The 1976 magnitude 7.5 Guatemala earthquake ruptured the Motagua fault in one of the most devastating earthquakes in the 20^th Century that resulted in over 23,000 fatalities. Despite its considerable scientific importance, and its potential for catastrophic societal impact, very little is known about the seismicity of this major fault. In January 2025, we concentrated paleoseismic field research at the La Laguna site—the location of the maximum coseismic surface rupture (3.4 m) of the Motagua fault in the 1976 earthquake. The geomorphology of the site was mapped from UAS LiDAR and orthophotomosaic images. A hand-dug trench across the active fault scarp revealed five colluvial wedge forming earthquakes over the past 1300 years. Because of the unique geometry of the active fault trace with a left bend across an agricultural field that was cultivated by Maya in antiquity, the La Laguna site was rich in charcoal and potsherds. The earthquake recurrence provided by the age modelling of the radiocarbon dates indicates that the interval between the 1976 earthquake and the penultimate event (likely 1751, 1765, or 1773) is 203-225 years, which falls within the average range of 295 ±45 years for the past five earthquakes. However, the interval between earthquakes is not regular. Three earthquakes occurred between the 8^th and 12^th centuries, followed by a ~550-year period of seismic quiescence that ended with earthquakes in the 18^th and 20^th centuries. These data suggest that we might be within a period of higher earthquake frequency. A stone wall at the site is offset 4.8 m, suggesting that the penultimate event had only 1.4 m of slip. Both the slip history and recurrence of seismic events show high variability.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10437

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