Abstract
On 4 February 1976, a Mw 7.5 earthquake along the Motagua fault, Guatemala, ruptured ∼230 km of the North American and Caribbean plate boundary. Today, the plate boundary remains poorly monitored, and the 1976 earthquake is still not fully understood. Here, we present seismic reflection profiles and radiometrically dated sediment core data from six lakes around the Motagua fault, together with reports of destruction and a quasi-dynamic rupture model, which show that the 1976 earthquake experienced strong directivity that impacted the distribution of shaking. The earthquake left behind a detailed record of event deposits (EDs) in five of the six study lakes. Thicker EDs are present in Lake Atitlán, near the terminus of the earthquake rupture, whereas thinner EDs were found in lakes off axis of the rupture direction. We argue that EDs can be utilized to constrain asymmetrical distribution of shaking during earthquakes and that paleo seismic studies should consider directivity as a factor controlling the thickness of EDs.
Recommended Citation
J. Obrist-Farner and J. Maurer and D. Gibson and T. McEnaney and A. Eckert and W. F. Kenney and J. Beeson and N. Wattrus and Q. Stangeland and F. Reyes, "Paleoseismic Evidence of Directivity for the 1976 Mw 7.5 Motagua Earthquake, Guatemala," Geology, vol. 53, no. 11, pp. 971 - 976, Geological Society of America, Sep 2025.
The definitive version is available at https://doi.org/10.1130/G53449.1
Department(s)
Geosciences and Geological and Petroleum Engineering
Publication Status
Open Access
International Standard Serial Number (ISSN)
1943-2682; 0091-7613
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2026 Geological Society of America, All rights reserved.
Publication Date
10 Sep 2025
