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

158 1 2 T H I N T E R N AT I O N A L I N Q U A M E E T I N G O N PA L E O S E I S M O L O G Y , A C T I V E T E C T O N I C S A N D A R C H A E O S E I S M O L O G Y ( PATA ) , O C T O B E R 6 T H - 1 1 T H , 2 0 2 4 , L O S A N D E S , C H I L E PATA Days 2024 K E Y W O R D S Bolivia orocline, mid-crust depth earthquakes, moment tensor (1) Observatorio San Calixto, Bolivia, (2) CEA-DASE, France, Laurent. (3) Université de la côte d’Azur au laboratoire Géoazur, France (4) CNAP, EOST/ITES, Strasbourg, France *Email: osc@osc.org.bo / bollinger@cea.fr / delouis@geoazur.unice.fr / derode@unistra.fr Fernandez M. Gonzalo A. (1) Bollinger Laurent (2) Delouis Bertrand (3) Derode Benoit (4) Nieto Mayra (1) MID-CRUSTAL EARTHQUAKES AND THEIR RELATION TO FAULTS UNDER THE BOLIVIAN OROCLINE A B S T R A C T Located in the central region of Bolivia, the department of Cochabamba is a1ectedbydestructive earthquakes.However, there is a notable lack of comprehensive documentation concerning the tectonic structures underlying these seismic events, as well as a de6nitive assessment of their seismogenic potential. The national data center, Observatorio San Calixto, has encountered challenges due to uncertainties and biases in the hypocentral locations of local earthquakes resulting from the dispersed seismic network. In response to these challenges, a temporary seismic network comprising 11 stations was established to monitor local seismic activity. The analysis of the 6rst months of the experiment reveal the presence of earthquakes clustered at midcrustal depths. One of these clusters develops at close distance or within the Main thrust system while others are located in the hangingwall on secondary faults. I N T R O D U C T I O N The Bolivian Andes result from the subduction of the Nazca oceanic plate beneath the South American continent. The system currently experiences a shortening rate of approximately 7 to 8 cm/year (Pardo-Casas, F. and Molar, P., 1987; Jarrin et al., 2023). While the majority of the shortening is absorbed at theNazca trench, about 1 cm/year is transmitted eastward and absorbed by continental subduction of the Brazilian shield beneath the Eastern Cordilleras, as illustrated in Fig. 1 (Isacks 1988; Mercier et al., 1992; Brooks B., et al., 2011; Weiss et al., 2016).