# Multidisciplinary Study of Mud Emissions Following the 2016 Norcia Earthquake
## 2 Geological Setting and Sampling  
The sampling area was located in the Marche Apennine foothills, where turbidite siliciclastic sediments that fill the Messinian foredeep basin are overlapped by Mio-Pliocene marine sediments and Pleistocene continental deposits over it [38; 39; 40]. The studied area experienced compressional tectonics with NE migration of the Apennine thrust-and-fold belt during the end of the Miocene to the Early Pleistocene. The Messinian turbiditic deposits are mostly composed of peilitic and arenaceous lithofacies containing gypsum intercalations of the Laga Formation. The latter is overlapped by the Colombacci Formation, which is mainly sandy to silty shales intercalated with calcareous levels. The above formations are sharply overlapped by the Pliocene sequence, a marine sequence of alternated mudstone-sandstone lithofacies, i.e., the Argille Azzurre Formation. Quaternary continental deposits lie on top of the marine sequence and outcrop in the Monteleone di Fermo area as a gently deformed NE-dipping monoclinic [38]. Outcrops of the Argille Azzurre Formation emerge around the Monteleone di Fermo area; however, the formation continues down to considerable depths in the subsurface. The existence of mudstones at depth is one of the best conditions for developing mud volcanoes since they supply an impermeable barrier facilitating fluid overpressure development. This lithology characterizes the solids dragged by the aqueous fluids which move upward. These fluids are usually a mixture of water and hydrocarbons in liquid and gaseous states (e.g., [16]). The occurrence of resolved (or potentially resolved) gases in the aqueous fluids enables the formation of mud volcanoes, and once overpressures rise, the moving upward aqueous fluids can fluidize the mud and erupt at the surface. The sampling area was located in the eastern part of the central Apennines undergoing extension at 3.0-3.5 mm/a [41], and it is characterized by 2 major NNW-SSE-trending extensional fault systems of adjacent, west-dipping, active Quaternary faults [2]. The westernmost fault alignment extends from Gubbio to Coliforito, Norcia, and L'Aquila. The eastern system develops from Mount Vettore to Amatrice Campotosto (Mount Gorzano fault) and Gran Sasso ridge ([42; 43; 44], and references therein). The historical and instrumental seismicity occurring on some of these western structures (Gubbio 1984, M\({}_{\rm w}\) 5.6; Coliforito 1997, M\({}_{\rm w}\) 6.0; Norcia 1979, M\({}_{\rm w}\) 5.9; and L'Aquila 2009, M\({}_{\rm w}\) 6.1) indicate that this sector of the chain is active. Conversely, the seismogenic behavior of the eastern fault system has been largely debated, mainly in the geological community [42; 43; 44; 45]. The Mount Vettore and Gran Sasso faults can be considered silent in historical times [42]. The north part of the Gorzano fault was not activated in instrumental times but might be the source of the only large historical earthquake that originated in this area: the 7 October 1639 earthquake (I = IX-X MCS, M = 6.2, CPTI15, [PERSON] et al. [46]). While the southern part of  
Figure 1: Figure 1a,b is a copy of Figure 1 of [PERSON] et al. [38]. The figure shows (**a**) the epicenters of earthquakes and (**b**) the geology of the area and emission centers of mudflows. We added in (**c**) an image of emission point SV1-A (4766258 N; 375965 E) near the town of Santa Vittoria in Matenano and in (**d**) an image of emission point ML3-A (43.074429 N; 13.52854 E) near the town of Monteleone di Fermo. this fault did not show destructive historical events, it was activated during the L'Aquila 2009 sequence [44; 45; 46; 47]. Seven mud samples (Table 1) were collected in the days after the mainshock.