3D monitoring of movements along West Pirin Fault

This article presents the initial results of the 3D monitoring of West Pirin Fault in the area of the village of Brezhani, SW Bulgaria. The monitoring equipment – extensometer TM71 was installed in August 2013. The data obtained from the observations until November 2018 were processed. The results show 5 stages in the dynamics of this part of the fault. One of them is associated with a coseismic effect (sharp movements) resulted from a local weak seismic event.The obtained results show that Y-axis movements are most stable, representing right-lateral strike-slip movements with a high correlation of data (coefficient of determination r2=0.866). The most active movements have been established during the last 2 years of the observations. In 2017-2018, the established rate of right-lateral strike-slip (Y axis) is 0.84 mm/a. For whole observation period the results show compression od fault zone 0.07 mm/a, right-lateral strike-slip 0.61 mm/a and reverse movements 0.09 mm/a. These results give us reason to suppose a recent activity along West Pirin Fault.