GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 1.1 47 Quotidiani citati Corriere della Sera , 17.08.1932. Corriere della Sera , 25 marzo 1938. La Stampa , 25 marzo 1938. Neues Wiener Tagblatt , 25.03.1938. Salzburger Volksblatt , 22.08.1932. SLIP BEHAVIOR OF THE CAMPOTOSTO NORMAL FAULT (CENTRAL ITALY) IMAGED BY GEODETIC AND SEISMOLOGICAL DATA: INSIGHTS FROM THE 18 JANUARY 2017, M>5 EVENTS D. Cheloni 1 , N. D’Agostino 1 , L. Scognamiglio 1 , E. Tinti 1 , C. Bignami 1 , A. Avallone 1 , R. Giuliani 2 , S. Calcaterra 3 , P. Gambino 3 , M. Mattone 3 1 Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy 2 Dipartimento della Protezione Civile, Roma, Italy 3 Istituto Superiore per la Protezione e la Ricerca Ambientale, Rome, Italy On 18 January 2017, the 2016-2017Amatrice-Visso-Norcia earthquakes sequence in Central Italy reached the Campotosto area with four M>5 events occurring in three hours. This fault remained as the last, 2009-2016 unruptured part of the central Apennines fault system from L’Aquila to Visso. On-going debate is focused on the vertical continuity of the surface trace of the Campotosto fault with the seismogenic structure beneath, and its relevance for the dam sustaining the Campotosto lake. In this work, we use geodetic and seismological observations to document the coseismic and aseismic deformation associated with these multiple moderate seismic events (main event Mw 5.5). In particular, to study the slip behavior of the causative fault we followed two different approaches: 1) we use InSAR and GPS static displacements to retrieve the fault geometry and the ~1-month cumulative slip distribution; 2) we invert strong- motion, high-rate GPS waveforms and high-rate GPS-derived static offsets to constrain the kinematic source models of the two major events (Mw 5.5 and 5.4) of the 18 January 2017. The geodetic inversion shows that the deformation due to the four M>5 earthquakes is due to the ~50° SW-dipping and ~150° striking Campotosto normal fault, with an average slip of about 40 cm, mainly concentrated in the shallower part of the fault. This fault is well known by geological and paleoseismological studies (e.g. Galadini and Galli, 2003; Boncio et al. , 2004; Galli et al. , 2008), being the fault plane well exposed in the central-southern portion of the structure where the fault scarps are evident at the base of the western flank of the Laga Mts. Rupture histories of the two largest events of the sequence show that the two shocks ruptured two distinct and adjacent portions of the Campotosto fault, with significant slip up-dip from the hypocenters. Both geodetic and seismological observations required significant slip extending at shallow depths (< 1-2 km), challenging the hypothesis supporting lack of vertical continuity of the Campotosto fault (e.g. Buttinelli et al. 2018). The cumulative seismic moment release calculated using the geodetic dataset is 9.29 × 10 17 Nm, corresponding to an Mw ~6 earthquake. This estimate is larger than the cumulative seismic moment of all the seismic events with M>4 occurred in the corresponding time period (6.01 × 10 17 Nm), suggesting that a fraction (~35%) of the overall deformation occurring during and after the 18 January 2017 Campotosto seismic sequence can be associated to aseismic processes. Our results show also that the inferred slip distribution is complementary with respect to the previous L’Aquila 2009 seismic sequence affecting the southern half of the Campotosto fault (Cheloni et al. , 2014), suggesting the activation of different portions of the seismogenic fault