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

Fig. 3: ERT profile at La Laguna showing a high resistivity block along the Motagua fault zone, and a low resistivity wedge along the 1976 rupture below the red arrow. At the site 1.5 km east of Gualán, ERT data were collected along three lines (Fig. 4) parallel to two paleoseismic trenches (McEnaney et al., 2022, Niemi et al., 2024). These transects are oriented perpendicular to a fault scarp and at the edge of a sag pond. TheERTline1(Fig.5)is100mlongandtraversesanupperterrace,crosses the linear depression, and ends across the fault scarp on the northern terrace. ERT line 1 is parallel to paleoseismic trench 3. The ERT lines 2 (75mlong) andERTLine 3 (100mlong) are located approximately 200 mwest of ERT line 1 and are parallel to paleoseismic trench 1. These lines were oriented across a terrace and a sagdepressionand are in two segments because of a fence. The 20-m-wide wedge that is lower in resistivity in ERT1 (Fig. 5) suggests saturated soil and fine-grained sediment fill the sag along a structurally dropped block between the terrace sand and gravel. Themole track and fissure zone of the 1976 earthquake are shown by the low resistivity 2mwedgemarkedwith a red arrow. Fig. 4: Map of the ERT lines at the Gualán (Finca Limones) paleoseismic site. Fig. 5: ERT profile from Gualán showing a low resistivity block along the Motagua fault zone, and a low resistivity wedge along the 1976 rupture below the red arrow.