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 \( \sim 0.053 \, \text {km}^{3}\) and, through independent isomass integration, a total erupted mass of \( \sim 6.1 \times 10^{10} \, \text {kg}\) . By incorporating the volume of pyroclastic density currents ( \(0.09\ \mathrm {km^{3}}\) ), the total bulk erupted volume is estimated at \( \sim 0.14 \, \text {km}^{3}\) , 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 \(22.6 \, \text {km}\) above the vent, supported by independent particle-settling calculations. NCEP/NCAR atmospheric reanalysis revealed that southeasterly winds at \(10\text {-}15 \, \text {km}\) altitude, reaching velocities of \(30\text {-}40 \, \text {m/s}\) , drove tephra dispersal \(1800 \, \text {km}\) 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.