The 2020 and 2021 Seismic Swarms in the Tancítaro-Paricutín Area (Uruapan- Michoacán, México) Evidence Magma Intrusion in an Area with High Density of Monogenetic Cones

Abstract

The Michoacán-Guanajuato Volcanic Field (MGVF) in central-western Mexico, with more than 1,000 monogenetic volcanoes, has been well known since 1943 when an eruption formed the Paricutín volcano, 11 km to the NW of the summit of Tancítaro stratovolcano. In the highly fractured zone around Tancítaro, referred to as the Paricutín-Tancítaro region (PTR), two major seismic swarms have been recorded, the first between January 5 and February 22, 2020, and the second between May 30 and July 22, 2021. The Mexican National Seismological Service (SSN) reported a total of 4,956 earthquakes with coda magnitudes between 2.6 and 4.2. With the aim to determine the causes of the swarms and the potential hazard they may pose on the region, we first analyze their spatial distributions by relocating all of the events using the Double Difference method and testing different 1-D velocity models to select the one with the lowest residual errors. Secondly, we analyze the temporal distributions finding that their temporal occurrence fits a Mogi’s type 3 volcanic seismic swarm. We conclude that each swarm is due to stresses induced by dike-fed intrusions of moderate volumes of magma in a pre-existing temporal magma reservoir, probably a sill.