POST-ERUPTIVE VOLCANIC EARTHQUAKES WITH SPECTRAL PEAKS OF VOLCÁN DE COLIMA, MEXICO.
Volcán de Colima is an andesitic stratovolcano located in western Mexico. On July 10th-11th 2015, Volcán de Colima had its major eruption since the 1913 Plinian event. A partial collapse of the dome and of the crater’s wall generated several pyroclastic density currents, the largest of which reached 10.3 km to the south of the volcano. During the following months, hundreds of volcanic earthquakes with pronounced spectral peaks reaching up to 30 Hz were recorded. This type of seismic event had not been previously reported for Volcán de Colima. Employing broadband seismic data from August 2015 to February 2017, we characterize these earthquakes and study their temporal variation throughout the different phases of activity, which was dominated by intermittent Vulcanian eruptions along with several dome emplacements in February, September and November 2016. We find that, unlike the rest of common long-period and high-frequency events which can be present during all stages of the activity of Volcán de Colima, the post-eruptive July 2015 earthquakes are exclusively related to the stages of explosive or passive degassing of the volcano. We discuss the possible processes behind their generation as well as their role in the monitoring of Volcán de Colima.