Fault zone structure and seismic slip localization in dolostones, an example from the Southern Alps, Italy

► The Borcola Pass Fault Zone (BPFZ) is a strike-slip fault zone cutting dolomitic host rocks. ► The damage zone of the BPFZ is cut by secondary faults exploiting pre-existing joints. ► Microstructures of dolostone-cutting slip zones suggest coseismic fluidization. ► Structural complexity of the BPFZ is comparable with that of active seismogenic faults cutting carbonates.