Figure 6. Benioff strain release at Campi Flegrei.

(a) Virtually all the seismicity recorded between 1982 and 2016 occurred during the 1982–1984 uplift crisis. (b) The slow corrected uplift of c. 0.4 m since 2005 was accompanied by a seismic energy release of 3 × 10¹¹ J, which approximately corresponds to 0.2% of the energy supplied during the uplift (equivalent to a relative stress drop of c. 4%). The proportion of energy lost is an order-of-magnitude smaller than the 5% estimated for the main VT-deformation trend during the 1982–1984 episode of major uplift (see the section ‘Regimes of deformation in Campi Flegrei' in the main text). The slow uplift thus represents a low-seismicity return to the stress–strain condition that prevailed in 1984 (positions 6–8 in Fig. 5), which is consistent with a predominantly elastic restressing following the Kaiser effect³⁵.