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

360 PATA Days 2024 Fig. 8: UAS image of the Finca Los Limones paleoseismic site in April 2022 showing the location of the trenches, ERT lines, and the offset canal. Tester Model 6472 configured in a Wenner array. Electrode positions were placed at 5 m, 10 m, and 20 m and elevation data of the electrodes surveyed with a RTK GNSS system for topographic correction. Our ERT lines (Fig. 9) across the site show a 20-m-wide structurally dropped fault zone with a thin wedge of low resistivity recent sediment along the 1976 earthquake fault rupture (Dollens et al., 2024). We excavated three trenches across the fault scarp at the Finca Los Limones site (Fig. 8). Trench 1 (T1) was at the edge of a dried sag pond and both Trench 2 (T2) and Trench 3 (T3) were across the base of a south- facing fault scarp developed in the Qft1 fluvial terrace surface. The fault in T1 shows a distinct offset of a lower fluvial terrace (Qft2) and boundary with organic-rich mud. Pulses of coarser clastic sediment into the sag suggest scarp-derived colluvial events. T2 and T3 (Fig. 9), separated by only 21 m, both show the development of multiple inset large fissures filled with dark brown soil. Dating of the paleoseismic record at this site has been difficult due to a lack of radiocarbon samples but downwarping and folding of buried soil surfaces suggest a minimum of four pre-1976 earthquakes. Fig. 9: Log of the east wall of Trench 3 rotated so that north is toward the right and in the same orientation as the ERT line shown. The Motagua fault has two parallel strands that bound a linear depression. Repeated faulting is found at the base of the north strand and is seen as multiple v-shaped fissures.