Hazard assessment of the ongoing lava dome eruption at Popocatépetl volcano from the statistical analysis of significant explosive events in the period of 1997 to 2016

Abstract

After 70 years of quiescence Popocatépetl volcano began a new episode of activity in 1994, which is still ongoing. The predominant activity has been a succession of dome emplacements followed by sequences of dome-destruction explosions producing prominent volcanic ash columns. Moreover, relatively large eruptive columns have also been produced during the dome growth stages. To assess the hazard of this activity we use the height of the columns as an indicator of the rate of energy release of the events and of their dispersive power and destructive potential. We hence built a database of the events producing columns exceeding heights of 4 km above the volcano summit for the period 1997 to 2016. Considering the occurrences of such columns as a random variable representing the hazard of such explosive activity, we studied the statistical features of the database, and found that the occurrence rate of significant explosions is a point process developing in at least two stages, with the significant changepoint in 2003. The first stage from 1997 to 2003 is non stationary, while the second one, from 2003 to 2016, shows a stationary behavior. While the former is well described by a Mixture of Exponentials distribution (MOED), the latter fits well an Exponential distribution. The probabilities of significant eruptive columns occurring in given time intervals result to be strongly dependent on the stationarity of the process. The assessment of hazard thus requires a continuous testing of the time dependence of the ongoing process, since there is no clear physical evidence of the factors controlling this behavior.