Original paper

Source region of volcanism and seismicity pattern beneath Central American volcanoes

Špičák, Aleš; Hanuš, Václav; Vaněk, Jiří

Abstract

The analysis of seismicity pattern, based on global data from the period 1964-99, is used as a tool for finding the source region of primary magma for active calc-alkaline volcanoes in Central America. The detailed analysis of the geometry of distribution of earthquake foci allowed to establish an aseismic gap in the subducting oceanic lithosphere in the depth between 100-200 km and a seismically active column in the continental wedge. Both phenomena are spatially and probably also genetically related to active volcanism and favour the concept of generation of calc-alkaline magma inside the subduction zone. We interpret the aseismic region in the Wadati-Benioff zone, found beneath all Central American volcanic domains, as a partially melted part of the slab that serves as main source region of magma for active volcanoes in the region. On the other hand, the relatively strong seismicity in the continental wedge beneath several volcanic domains points to brittle character of the mantle and excludes the generation of larger amounts of magma in the wedge overlying the subduction zone.

Keywords

Central Americasubductionvolcanismconvergent plate marginsWadati-Benioff zone