Calderas are among the most spectacular, dangerous and active volcanoes on Earth. Seismicity, surface deformation, and anomalous degassing are commonly ...
Understanding recent caldera unrest from monitoring data Di Lorenzo R.1, Acocella V.1, Scandone R.2, Geshi N.3
1. Dipartimento di Scienze - Università Roma Tre, 2. Dipartimento di Matematica e Fisica - Università Roma Tre, 3. Geological Survey of Japan, AIST
Calderas are among the most spectacular, dangerous and active volcanoes on Earth. Seismicity, surface deformation, and anomalous degassing are commonly observed at many calderas, denoting unrest. The unrest can be intermittent, lasting for months to years, or persistent, over decades to centuries. Although most caldera unrest episodes do not lead to an eruption, the possibility of an impending eruption warrants detailed monitoring and study. The restless Campi Flegrei Caldera (CFC), which includes a part of the city of Naples, represents a serious risk. From November 2004, a new unrest episode has been occurring, characterized by a continuous rate of uplift: since early 2012, the caldera center has been rising of 70 mm. At the same time, the temperatures of the fumaroles have increased 10-15°C since 2003 and the composition of the released gases has shown a prevailing “magmatic” component since 2000. To better understand the dynamics of CFC, and also to try to forecast an impending eruption, we carried a critical review of the available data on the recent calderas unrest in the world. We focused our analysis on the unrest episodes which have occurred in the last 25 years, complementary to that of Newhall and Dzurisin (1988). In this frame, we analyzed the monitoring data of more than 40 unresting calderas, some of which characterized by eruptions. Attention has been given to seismicity, deformation and gas variations, along with their possible interaction. The preliminary results confirms that all eruptions are preceded by an unrest episode, but not all unrest episodes culminate in an eruption; this suggests that these indicators are a necessary condition to establish the state of unrest, which may anticipate an impending eruption, but they are not always adequate to determine the occurrence of any eruption. Seismicity seems the most widespread/reliable indicator for the state of unrest.. However, there is not any expectable of predictable behaviour in any unrest indicator before the occurrence of an eruption and very different trends have been observed to occur before an eruption. In this context, silicic calderas tend to have the least linear or predictable behaviour. This qualitative analysis will be followed by a more quantitative statistical analysis of the measured parameters during unrest-episodes, in order to better constrain caldera unrest and its possible culmination in eruptions.
