Near real-time satellite monitoring during the 1997-2000 activity of Volcan de Colima (Mexico) and its relationship with seismic monitoring

The 1997-2000 activity of Volcan de Colima provided a unique opportunity for the joint analysis of satellite and seismic monitoring techniques. Three stages of volcanic activity were observed: pre-lava stage, stage of lava eruption, stage of explosive eruptions. Advanced Very High Resolution Radiometer satellite data provided observations of both summit thermal anomalies and ash emission. Daily monitoring of Volcan de Colima was performed using early morning or late night NOAA 12 and 14 satellite passes gathered in real time at our satellite ground receiving station. Seismic observations were carried out by the Red Sismica del Estado de Colima. Good correlations are observed between seismic activity and parameters monitored by satellite during the three stages. Five seismic swarms were recorded during the reactivation period. Four of the seismic swarms coincided with periods of increase in summit temperature and strong ash emissions. It is important to note that the ash emissions were observed a few days before the beginning of seismic swarms. The thermal saturation at the summit was reached a few hours after the beginning of lava effusion on November 20, 1998, and remained at this level until May 1999 even after the lava flow stopped in early February 1999. The lava front was also clearly identified as a source of thermal anomalies and ash plumes. Study of the summit temperature-ash emission relationship allowed us to classify the strong explosions of 1999-2000. The strongest explosion, on February 10, 1999, produced the largest, ash-rich plumes that were detected over a wide area (similar to150 km(2)) and near-saturation temperature anomalies (47.2, 48.4degreesC). The main limitation of volcano satellite monitoring occurs during overcast conditions. Clouds prevented us from monitoring the seismic swarm of July 1998 and the explosion of July 1999. This study shows that satellite monitoring on a near real-time basis is a powerful tool not only for research in volcanology but also as an aid for scientific committees to define probable eruption scenarios during volcanic crisis and for Civil Protection Authorities for risk mitigation due to ash emission and sudden heating of the crater without seismicity. (C) 2002 Elsevier Science B.V. All rights reserved.