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

420 PATA Days 2024 We have compared our findings with historical records and instrumental data, corroborating our interpretations and underscoring the importance of long-term evidence in assessing earthquake and tsunami hazards. C O N C L U S I O N S Our findings reveal both geological and historical evidence of significant earthquakes paired with tsunamis over the past 2000 years. Notably, a potential large tsunamigenic earthquake with a Mw exceeding 8 in approximately 1300AD surpasses any recorded events in the past century. The ages of the four identified sand units indicative of tsunamis predate the mid-Holocene sea-level highstand, with sea-level records indicating minimal changes until the late mid- 19th century (Ramirez-Herrera et al., 2024). Earlier research on this segment of the Mexican subduction zone (MSZ) has suggested evidence of older earthquakes, including three probable tsunami events in the last 4600 years. Additionally, evidence of a large earthquake around 3400 years BP, resulting in land subsidence and marine inundation (Ramirez- Herrera et al, 2007), further supports our findings along the Guerrero coast. The adjacent Oaxaca segment also presents historical and geological evidence of a magnitude 8.6 earthquake and tsunami in 1787, with flooding extending over 500 kilometres alongshore and up to 6 kilometres inland (Ramírez- Herrera et al., 2020). Our recent geological findings provide valuable insights into the occurrence of extraordinary catastrophic events within the Mexican subduction zone. These events may have occurred over centuries, indicating the variable rupture modes of subduction zones. It is imperative to combine long-termgeological records with instrumental observations to mitigate potential catastrophes in regions such as the Guerrero seismic gap (GSG) and other segments of the MSZ. By integrating our findings, communities can better prepare for the seismic and tsunami hazards posed by these subduction zones. A C K N O W L E D G E M E N T S We thankTinaDura for her feedback and valuable discussions.We are indebted toAlejandroRodriguezR. for assistingwithmicrofossil analysis and to Oswaldo Coca for uploading data into the Zenodo Database. AMS analysis were performed at Laboratorio Interinstitucional de Magnetismo Natural – UNAM. This research project was funded by CONACYT-284365 and PAPIIT- IN107721 and IN105524 awarded toM.T.R-H. R E F E R E N C E S Suarez, G., Montfret, T., Wittlinger, G. & David, C. (1990). Geometry of subduction and depth of the seismogenic zone in the Guerrero Gap, Mexico. Nature 345, 336–38. Husker, A., Ferrari, L., Arango- Galván, C., Corbo-Camargo, F. & Arzate-Flores, J. (2018). A geologic recipe for transient slip within the seismogenic zone: Insight from the Guerrero seismic gap, Mexico. Geology 46 (1), 35–38. 10.1130/G39202.1x. Ramírez-Herrera, M.T., Cundy, A., Kostoglodov, V., Carranza- Edwards, A., Morales, E. et al. (2007). Sedimentary record of late Holocene relative sea- level change and tectonic deformation from the Guerrero Seismic Gap, Mexican Pacific Coast. Holocene. 17(8),1211-1220; 10.1177/0959683607085127. Ramı́ rez-Herrera, M.-T., Corona, N., Cerny, J., Castillo-Aja, R., Melgar, D., et al. (2020). Sand deposits reveal great earthquakes and tsunamis at Mexican Pacific Coast. Sci. Rep. 10, 11452; 10.1038/ s41598-020-68237-2. Ramírez-Herrera, M.T., Corona, N., Černý, J. et al. Tsunami deposits highlight high-magnitude earthquake potential in the Guerrero seismic gap Mexico. Commun Earth Environ 5, 198 (2024). https: //doi- org. pbidi.unam.mx:2443/10.1038/ s43247-024-01364-0