## 4 Results and Discussion  
### Seismic Reflection Survey  
The trace of the seismic profile is perpendicular to the mapped Banos fault (Figures 1 and 2) that bound the Bailen Basin. Therefore, it is expected that it will allow the detection of other possible subparallel structures associated with the same fracturing system. In addition, the different mechanical behaviour of the lithologies studied should allow differentiating the described units, as well as deducing lateral thickness changes in the profile. In the upper part of the seismic profile in Figure 3, materials attributable to the Miocene are represented in two shades of yellow (M1 + M2). At the base of this unit, there are levels that contain moderate-amplitude reflectors (M1), which are interpreted as sandstones and are related to the upper aquifer (Figure 3). The thicknesses obtained using an interval velocity of 1900 m/s [35] fit the depths to the base of the Miocene found in boreholes 1 and 2. Underlying the Miocene unit, the Triassic unit appears, represented in shades of pink in the seismic profile (Figure 3). One hundred seismic traces are represented, corresponding to 1500 m on the horizontal axis of the profile. This short distance is sufficient to detect changes in the thickness of the Triassic unit. At the NW end (trace 510), it covers a two-way time of 0.08 s, which corresponds to a thickness of 88 m (with an estimated interval velocity of 2200 m/s). In contrast, at the SE end (trace 420), the Triassic unit covers a greater two-way time, approximately 0.15 s, which is correlated with a thickness of 165 m. The estimated interval velocity to the base of the Triassic (2200 m/s) is verified in boreholes 1 and 2, where the thicknesses are 120 and 130 m, respectively. Within the Triassic unit, maximum increase in wave amplitudes are also detected in the seismic trace, which are correlated with levels of sandstones and conglomerates. They are especially abundant at the base of the Triassic unit but also appear in the middle part (SE sector). The increase in wave amplitude associated to the Triassic base corresponds to the lower aquifer (T1 in Figure 3). Laterally, this base reflector may be lost due to changes in thickness or even due to the wedging of the basal conglomerates (between traces 460-470), as seen in outcrops in the northwestern sector of the Banos fault. In the lower part of the profile, the acoustic basement consists of the folded phyllites of the Palaeozoic basement, which are characterized by a discontinuous reflectivity, which generates chaotic features and disorganized seismic facies (Figure 3). Figure 3: Seismic reflection profile and interpretation (see location in Figure 2). The positions of boreholes 1 and 2 are indicated. T1: conglomerate and sandstones of the lower Triassic (lower aquifer); T2: lutites of the upper Triassic; M1: rudites and calcarenites from the basal Miocene unit (upper aquifer); M2: marks from the upper Miocene. The seismic reflection profile in Figure 3 also shows a series of faults that affect the basement and the sedimentary cover. The most obvious difference is between seismic traces 470 and 475 (Fault 2 in Figure 3). The reflectors sink towards the SE by approximately 0.05 s, which corresponds to the 50 m throw detected in the two boreholes. This fracture affects the base and the sedimentary cover. Although the faults affect the Late Miocene and are, therefore, of a later age, the thickness changes in the Triassic suggest previous pulses that affected the subsidence and the sedimentation rate already in the Triassic. Furthermore, it should be noted that the lack of information in the first 0.06 s of the seismic profile makes it impossible to know if the highest part of the Miocene is also affected or, on the contrary, fossilizes the structure. This creates some uncertainty about the age of the last pulse of the fault. In addition to this fault, the morphology of the reflectors suggests the presence of another fault with a smaller throw around seismic trace 490 (Figure 3).