A Seismic Socio-Environmental Conflict: Controversies Around the San Ramón Fault, Chile

This empirical case study addresses the rise of a seismic socio-environmental conflict associated to the potential seismicity of the San Ramón Fault (SRF). Running for over 30 km along the foothills of Santiago, the capital of Chile, the SRF has recently been classified as active, becoming a ‘new’ hazard for nearly 2 million people.

The seismicity of Chile is mainly controlled by large subduction zones in the Nazca and South American plates’ interface, ca. 150 km from the Chilean coast, which generated the well-known Mw 9.5 Valdivia (1960) and Mw 8.8 Maule (2010) earthquakes. Besides large subduction events, less-studied crustal earthquakes can cause great destruction due to their shallow hypocentres. Local scientists have paid increasing attention to crustal seismicity, especially after the Mw 7.0 Pichilemu (2010) and Mw 6.7 Pisagua (2014) shallow intraplate earthquakes. Although the SRF is one of the Chilean crustal faults with slower slip rate (ca. 0.3-0.4 mm/yr), it is by far the most popular. Some researchers have estimated that the next occurrence of the up-to-Mw-7.5 earthquakes in the SRF, with an 8000-year recurrence, is geologically imminent (± 500 yr).

The conflict involving the SRF stems from an official narrative about the hazard that the fault represents and the policy (re)actions to this knowledge. We focus on the tensions generated amongst stakeholder groups, including the scientific disagreement regarding the fault’s activity and damaging potential, and the political need for action associated to the SRF becoming word-of-mouth and demands for disaster risk mitigation. Touching upon disaster risk reduction and urban development issues, the conflict around the SRF unveils the challenges of seismic risk governance in the context of urban and crustal faults.