The fault network in the southern foot of Rila Mountains, SW BulgariaThe fault network in the southern foot of Rila Mountains, SW Bulgaria

Southwestern slopes of Rila Mountain and northern parts of the Mesta graben are one of the least studied areas in terms of brittle tectonics. We carried out studies in the area around Bachevo and Dobarsko villages aiming to observe the fault zone network. The Bachevo fault zone is defined as Paleogene–Eocene Low-Angle Normal Fault that later underwent strike-slip and normal fault reactivation. The zone is an important tectonic boundary, separating the ca. 56 Ma Kapatnik granite from the Ograzhden Unit. Another important and possibly younger extensional zone is the Semkovo Fault. The relationships between the both zones are unclear. In terms of the Quaternary tectonics, it is important to differentiate between the Semkovo fault and the active Southeastern Rila Normal Fault. There are no data about Quaternary activity of the Bachevo fault zone.