Aeromagnetic survey over an active stratovolcano in central Mexico

Abstract

In this paper, we briefly summarize an aeromagnetic survey over a large stratovolcano (Popocatepetl) and surrounding volcanic terrain in central Mexico to show the potential that recent improvements in these methods have in studying active volcanoes. After a decades-long period of quiescence, the Popocatepetl volcano reawakened in 1994. Background seismicity showed a two-fold increase in October 1994. This was followed on 21 December by a swarm of volcano-tectonic events and tremors accompanying a large ash plume. Popocatepetl is an andesitic stratovolcano (Figure 1) in the central sector of the Plio-Quaternary Trans-Mexican volcanic belt (TMVB)—a continental arc associated with subduction of the Cocos and Rivera plates along the Middle Ainerican trench, and oriented almost E-W from the Pacific Ocean to the Gulf of Mexico. The TMVB volcanic-capped plateau is heavily populated. Mexico City is just 70 km away. Figure 1. Landsat thematic mapper image of the Iztaccihuatl-Popocatepetl volcanic range, eastern Mexico. The volcanic range is formed by several stratovolcanoes aligned north-south. Popocatepetl forms the southern end of a north-south trending range of large volcanic structures. The Popocatepetl stratovolcano has evolved through alternate periods of cone formation and destruction, with major cataclysmic events that destroyed ancient cones followed by formation of dome complexes and new summit cones. Recent activity at first was characterized by emission of ash rich in nonjuvenile material and volatiles, marked by intense seismicity with volcano-tectonic earthquakes (VT), long-period (LP) and tremor events. The ash and gas clouds from some events distributed ash over Mexico City and surrounding areas, with lapilli and small blocks falling over the volcano flanks. In March 1996, a dacitic dome built within the summit crater; magnetic activity to the present has been characterized by episodes of dome growth and destruction. Activity during December 2000 was particularly intense and, on 21 January 2001, a major explosive event …