## 2 Geological and Geomorphological Context  
Mallorca is located in the western Mediterranean, which is the largest emerged terrain of the Balearic Promontory, which constitutes the prolongation of the Betic Cordillera into the Mediterranean basin (East Spain; Figure 1) [16]. The promontory is bounded by two large extensional structures: the \"Valencia Through\" to the north and the \"Emile Baudot Scarp\" to the south [16,17]. This last one is a c. 1 km high submarine escarpment defining the northern border of the Algerian Basin [16]. The island is internally defined by a NE-SW trending basin-and-range structure, with important extensional Neogene basins [17], such as the Palma Bay Basin, The Central Inca Basin, and the Alcudia Basin (Figure 1). The NE-SW Sencelles Fault (SCF) bounds the Inca Basin to the south and is the main extensional structure of Mallorca Island (Figure 1). The fault has been active along the last c. 19 Ma (early Miocene), with a maximum accumulated throw of 750 m [18,19]. Modern gravity and borehole data [17] support the north-to-south half-graben model previously proposed for the Inca Basin [18,19,20] with the depocenter close to the Sencelles Fault (Figure 2), where the maximum thickness of Plio-Quaternary deposits (-120 m) is reached [14]. Synthetic reverse faults and antiform structures occur in the hanging wall of the SCF, affecting the entire post-tortonian sequence (Figure 2). The Messinian sequence includes a lagoon-reef complex buried by the so-called Terminal Complex (_Bonanova Fm. and _Santayi Fm._). These are formed by the littoral brackish to mangrove facies grading occasionally to grey marks with gypsums attributed to the end of the Messinian [17]. The broad syncline is eventually filled by the Lower Pliocene (_Son Mir Fm._) and the Upper Pliocene (_St. Jordi Fm._) littertoral series which are also deformed by the SCF. The fault cuts the whole Neogene sequence filling the Inca Basin, which is accommodated in a broad syncline and offset by high-angle antithetic normal faults dipping to the NW (Figure 2). These structures occasionally cut the Upper Pliocene littoral calcarenites (_St. Jordi Fm._) (Figures 1 and 2) forming NW-wards facing bedrock fault scarps with important accumulations of Quaternary alluvial deposits (~60 m thick) at the downthrown blocks [20]. The distal alluvial deposits are back-tilted and hold fossil remains of the extinct caprine _Myotragus balearcius_ (Figure 3), endemic to the island during the Pleistocene [18]. However, geophysical data indicate that the maximum thickness of Quaternary deposits in the Sta. Eugenia sector hardly surpasses 10 m, linked to the creek of Torrent de Solleric and Holocene in age [17,20]. Consequently, geologic and geomorphologic evidence prove the activity of the SCF from Late Pliocene to recent times with a mean throw of around 100 m for the last ~3 Ma [20]. This fault (7 km long) has been subdivided into two main segments based on their structural and geomorphological features [20]: The Sencelles and the Sta. Eugenia segments are separated by the rock salient of Puig Son Segui (Figure 3). However, some authors lengthen this fault 6 km to the NE in a poorly defined third section (Llubi Segment), where the fault displays a suspect dominant left-lateral strike-slip behavior [21] and generates a small pull-apart basin (Figure 3). In any case, although the fault displays some strike-slip features (e.g., rock salients, sag ponds, die-out anticlines; Figure 3), its overall geometry and kinematics at the surface fit better to that of the normal fault scarps described in the literature [8,9,12,15]. This study is focused on the easternmost segment of the fault (Sta. Eugenia Segment), with a length of about 2.8 km between the rock salient of Puig Son Segui  
Figure 1: The geological and structural framework of Mallorca Island, showing the location of the main Quaternary basins, neotectonic faults, related thermal springs, seismic activity, and the macroseismic area of the 1851 CE Palma Earthquake (Sa Cabaneta-Marrati).