Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

S U M M A R Y Field notes, maps, and photographs from the U.S. Geological Survey archival materials of George Plakfer who led a team to investigate the fault in February 1976, April 1976, and October 1977 were invaluable in relocating the offset canal at the Finca Los Limones site east of Gualán. From high- resolution LiDAR imagery, the displacement on the canal has increased from 93 cm in 1976 to 165-180 cm in 2023. These data document aseismic slip. ERT data show a low velocity zone with two parallel faults flanking a linear depression. The paleoseismic trench also crossed two faults 20-m apart. The northern strand shows multiple fault ruptures that are not currently well constrained chronologically. A C K N O W L E D G E M E N T S This research was conducted as a part of the Guatemala GeoHazards International Research Experience for Students program directed by Tina M. Niemi and funded by the National Science Foundation (Award OISE-2153715). Grützner was funded by the German Research Foundation DFG, project 529303576. We thank Shane Detweiler from the U.S.G.S. in Menlo Park, California for finding and sending the archival materials of George Plafker to us. R E F E R E N C E S Brueckner, H.K., et al., (2009). Metamorphic reworking of a high pressure-low temperature mélange along the Motagua fault, Guatemala: A record of Neocomian and Maastrichtian. EPSL 284, 228-235. Bucknam, R.C., G. Plafker, & R.V. Sharp, (1978). Fault movement (afterslip) following the Guatemala earthquake of February 4, 1976. Geology 6, 170-173. Dollens, A., T.M. Niemi, I . Torres Ewert, J. Lee, C. Grützner, C. Pérez Arias, & O. Flores Beltetón, (2024). Electrical resistivity tomography imaging of the Moagua fault along the 1976 earthquake rupture in Guatemala: 12th International INQUA Meeting on Paleoseismology, Active Tectonics and Archaeoseismology (PATA), Oct. 6-11, 2024, Los Andes, Chile. Espinosa, A. F., Editor, (1976). The Guatemalan Earthquake of February 4, 1976, A Preliminary Report, U.S. Geological Survey Professional Paper 1002, 90 p. Johnson, K. R. (1984). Geology of the Gualán and southern Sierra de las Minas quadrangles, Guatemala. Dissertation, State University of New York at Binghamton. Plafker, G., (1976). Tectonic aspects of the Guatemala earthquake of 4 February 1976. Science 193 (4259), 1201-1208. Plafker, G., (1977). Color slides showing geologic effects and damage caused by the destructive Guatemala earthquake of February 4, 1976. U.S. Geological Survey Open- File Report 77-165. Plafker, G., (1978). A Guide to the Motagua Fault Field Trip: International Symposium on the February 4, 1976 Guatemala Earthquake and the Reconstruction Process, Guatemala City, May 15-19, 1978. McEnaney T.N. & T.M. Niemi, (2021). Building a georeferenced database for the 1976 Guatemalan Earthquake rupture of the Motagua fault system along the North American-Caribbean Plate Boundary: Geological Society of America Abstracts with Programs 53 (6), doi: 10.1130/ abs/2021AM-370687. McEnaney, T.N., T.M Niemi, J. Obrist Farner, & O. Flores, (2022). Paleoseismic trenching of the 1976 Guatemalan earthquake rupture of the Motagua Fault along the North American- Caribbean plate boundary at the Gualan site: Annual Meeting of the American Geophysical Union. Mendez, J., Alvarez, K., Lopez Leon, L., Flores, O., Gomez, F., and Niemi, T.M., (2023). Measuring offsets of the Motagua fault using LiDAR Drone Surveying near Rio El Tambor, Guatemala: Geological Society of America Abstract with Programs 55 (6), doi: 10.1130/ abs/2023AM-392274. Niemi, T., Gomez, F., Flores Beltetón, O., Alvarez, K., Lopez Leon, L., Mendez, J., McEnaney, T., and Obrist Farner, J., (2024). Relocation of 1976 earthquake rupture and reassessment of slip using Lidar Imagery on the Motagua fault near La Laguna and Gualán, Guatemala: Latin America-Caribbean Seismological Commission Assembly, Costa Rica, June 24-28, 2024. Niemi, T.M., T.N. McEnaney, J. Obrist Farner, O. Flores, & C. Pérez Arias, (2022). A new look at the ground rupture of the Motagua Fault in the 1976 Guatemalan earthquake along the Caribbean- North American plate boundary: International Workshop on the Paleoseismology, Active Tectonics and Archeoseismology, Aix- de- Provence, France, sciencesconf. org: patadays-2022:408864, 137-140. Schwartz, D.P., L.S., Cluff, & T.W. Donnelly, (1979). Quaternary faulting along the Caribbean- North American plate boundary in Central America. Tectonophysics 52(1-4), 431-445.