An analysis of the seismic activity of Popocatepetl volcano, Mexico, associated with the eruptive period of December 2002 to February 2003: looking for precursors

Since it reactivated in 1994, Popocatépetl Volcano has undergone cycles of formation and destruction of several lava domes. This surface activity is generally associated with increasing seismic activity before the explosions that destroy the domes. We carried out a comprehensive analysis of seismic records from November 2002 to February 2003 in order to identify precursors of a series of explosive events. We obtained daily numbers of volcano-tectonic earthquakes and long-period events, as well as daily tremor duration. Spectral features of the long-period events and tremors were calculated, and high-frequency precursory signals of the long-period events were studied. No clear variations of these characteristics of the seismicity could be detected before the eruptions. Real-time Seismic Amplitude Measurements (RSAM) calculations show that, besides small fl uctuations related to the explosions, the rate of seismic energy released was quite stable during the studied period. Minor short-lived variations of RSAM levels were observed before only fi ve of eighteen eruptions, with no accelerating release of energy. It is thus quite diffi cult to identify reliable seismic precursors during the eruptive sequence. This situation is probably related to the open state of the system and has important implications for future risk assessment regarding this volcano