THE POLITICS OF CRUSTAL FAULTS: ISSUES AND CONTROVERSIES AROUND THE SAN RAMÓN FAULT IN CHILE

Abstract

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 indeed paid increasing attention to crustal seismicity, especially after the recent Mw 7.0 Pichilemu (2010) and Mw 6.7 Pisagua (2014) shallow intraplate earthquakes. Although the San Ramón Fault (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 in the media and amongst politicians. Running for ~30km 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 santiaguinos. Moreover, 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). In this article, we discuss the rise of a conflict around the SRF. The conflict 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 stakeholders (academics, policymakers, privates, and civil society). The discussion includes the scientific disagreement amongst academics regarding the fault’s activity and seismogenic potential, and the political need for action as the SRF hazard becomes word-of-mouth and some stakeholders start demanding 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