SEISMIC ANALYSIS OF THE NORTHWEST OF SAN RAFAEL DEL SUR

The book provides a comprehensive geosciences and engineering evaluation of a 46 km² rectangular polygon located in the northwestern region of the San Rafael del Sur municipality, Nicaragua. Authored by geologist and researcher Tupak Ernesto Obando Rivera, the study establishes a technical baseline for territorial physical planning and structural risk mitigation to safeguard its 41,574 inhabitants.
Key Findings
* Blind Tectonic Faults: The primary source of local seismicity is a network of hidden or blind faults masked by modern soil layers and tropical erosion. These show transcurrent (strike-slip) displacement mechanics aligned along NE-SW and N-S axes.
* Seismic Catalogue: The investigation analyzed 24 recent low-magnitude shallow earthquakes ranging between 2.7 and 3.6 on the Richter scale, with focal depths spanning strictly from 0 to 8.9 km. Their extreme shallowness presents severe destruction hazards to unreinforced infrastructure.
* Geomechanical Site Effects: Using an exponential predictive model for Peak Ground Acceleration (PGA), the study proves that surface soil consistency dictates the damage levels:
* Fragile Soils: The communities of El Tamarindo and Los Jaras sit on loose, unconsolidated alluvial clay-silt matrices, experiencing critical seismic amplification with peak spectral intensities between 40%g and 50%g.
* Firm Soils: Conversely, the San Rafael del Sur urban core, Los Gutiérrez Norte, and Sánchez Norte rest on stable, high-rigidity sedimentary rocks of the Brito Formation, exerting a natural damping effect that drastically drops intensities to 0.9%g - 1.0%g. leer todo...