Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

164 PATA Days 2024 C O N C L U S I O N S Mid-crustal seismic clusters are evidenced in Cochabamba region (the core of the Bolivian orocline). The POB seismic network was designed to complement the national network and to better resolve the relationship between regional seismicity and geological structures. During the initial months of acquisition, 439 earthquakes (with M L > 0.2) were documented. Most of these seismic events occur within the first 20 km, amidst the basal decollement of the thrust system and the surface. This result suggests that the local earthquakes are much shallower than what was previously presented in the national catalog. We interpret that part of this seismicity is a consequence of the activity of the main thrust system, as described further south in Bolivia (Isacks, 1988) and in Argentina (Ammirati et al., 2022). This is confirmed by the focal mechanism of the largest shock recorded during the first 6 months of the experiment, a M L 4.3 that occurred on May 18th 2022. Another cluster of earthquakes that occur in the hanging wall (the vicinity of Sipesipe, west side of Cochabamba) appear to fall at the contact between tectonic slivers. However, note that strike- slip faults similar in orientation to the Cochabamba fault develop on both sides of the basin. Finally, reverse faulting activity is demonstrated at mid-crustal depths in the vicinity of the most frontal ramps, in a region where we suspect the down-dip extension of partially or fully locked fault segments of the frontal thrust system. A C K N O W L E D G E M E N T S The project was developed within the framework of the long- lasting collaboration between CEA-DASE, France and OSC, Bolivia. We are very grateful to the Gobernacion of Cochabamba, especially to Dr. Fernando Fernandez (head of the UGR) and his team.