Estimation of eruption source parameters based on field data and numerical modeling: application to the 1993 eruption of Lascar volcano, Chile

Estimating eruption source parameters is critical for volcanic hazard assessments and understanding eruptive dynamics. This study reconstructs the April 1993 sub-Plinian eruption of Lascar volcano (Chile) by integrating field-based analyses of tephra-fall deposits and numerical modeling. Data from 34 sampling sites along the main dispersal axis were statistically integrated, yielding a fallout volume of \( ~ 0.053 \, km³\) and, through independent isomass integration, a total erupted mass of \( ~ 6.1 × 10¹⁰ \, kg\) . By incorporating the volume of pyroclastic density currents ( \(0.09\ {km³}\) ), the total bulk erupted volume is estimated at \( ~ 0.14 \, km³\) , revealing a fallout-to-PDC volume partitioning ratio of \(1{:}1.7 \) that highlights the dominance of column-collapse dynamics during the climactic phase of the eruption. The maximum eruption column height reached \(22.6 \, km\) above the vent, supported by independent particle-settling calculations. NCEP/NCAR atmospheric reanalysis revealed that southeasterly winds at \(10-15 \, km\) altitude, reaching velocities of \(30-40 \, m/s\) , drove tephra dispersal \(1800 \, km\) toward the Atlantic coast. Both probabilistic and deterministic numerical models reproduced the main observed deposit features, supporting the derived parameters. This methodological integration establishes a robust framework for reconstructing historical Andean eruptions, thereby improving hazard assessments for northern Chile and adjacent regions.