Borehole data to model caldera unrest: the example of Campi Flegrei Deep Drilling Project

To understand the genesis and the physics governing the volcanic area of Campi Flegrei (Southern Italy) a drilling project started on July 2012, in the framework of the International Continental Scientific Drilling Program (ICDP). The Campi Flegrei Deep Drilling Project (CFDDP) schedules two phases: a pilot well, 500 m deep (I phase), and a 3.5 km deeper well (II planned phase), both located within the active resurgent caldera of Campi Flegrei, west to the city of Naples. In this framework new filed data from pilot borehole have been recorded by using a novel procedure of Leak Off Test (LOT). The test has been performed in order to obtain, before the onset of rock failure (which furnishes indication of the minimum principal stress value), a reliable value of in situ permeability. These new data, particularly the actual permeability, are fundamental to calibrate the caldera unrest model at Campi Flegrei and to advance in the quantitative analysis of volcanoes behavior for the assessment of possible future eruptive scenarios. Calderas worldwide are, in fact, characterized by frequent episodes of unrest which, only in few cases, culminate with eruption. This behavior is generally explained in terms of magma intrusion and/or disturbance of geothermal fluids in the shallow crust, which are both source of ground deformations and seismicity. A major goal is, thus, to determine the relative contribution of each process, because the potential for eruptions significantly enhanced if magma movements emerges as the primary component. Here we report the new results of the LOT and its implication in the modeling of Campi Flegrei caldera unrest.