The structure of the Earth’s crust at the junction of the Siberian craton and Sayan–Baikal Fold Belt was studied along the Bayandai Village–Cape Krestovskii profile (85 km long) by a set of geological and geophysical methods: structural survey, interpretation of long-distance photographs, emanation survey, electrical prospecting with self-potential (SP) and direct-current (DC) resistivity profiling, magnetotelluric sounding, magnetic survey, and hydrogeochemical sampling of water objects. Interpretation of the data refined the main features of the tectonic structure of western Cisbaikalia and revealed the disruption pattern and hierarchic zone–block structure of the Earth’s crust. The Obruchev fault system (≈50 km wide), which is the northwestern shoulder of the Baikal Rift, is the main interblock zone of the studied region. It consists of the Morskoi, Primorskii, and Prikhrebtovyi interblock zones, traced from depths of tens of kilometers and widening near the surface owing to superior structures. The studies gave an insight into the regularities in the occurrence of interblock zones and the criteria for their identification in different geologic-geophysical fields. An efficient complex of methods for mapping the Earth’s crust zone–block structure is proposed.