Assessment of Primary and Secondary Environmental Effects of the 23 November 1977 San Juan Earthquake (Mw 7.4), Argentina, Using the Environmental Seismic Intensity Scale (ESI-2007)

Abstract

This study analyzes the environmental effects generated by the November 23, 1977 earthquake (Mw 7.4), whose epicenter was located in the province of San Juan, with the aim of estimating its intensity using the Environmental Seismic Intensity Scale (ESI-2007). Information from newspapers, technical reports, and scientific publications was integrated to build a detailed database of the primary and secondary effects associated with the event. The ESI-2007 methodology allowed us to delineate the most affected areas and characterize the distribution and magnitude of the observed processes. Numerous effects were documented, including the surface rupture of the Niquizanga Fault, soil liquefaction, fissures, lateral spreading, subsidence, landslides, rockfalls, and hydrological anomalies. Primary effects were concentrated along the southeastern margin of the Pie de Palo range, whereas secondary effects extended broadly across the Tulum Valley, the Bermejo Valley, and sectors of northern Mendoza. This work highlights the usefulness of the ESI-2007 scale for assessing historical earthquakes in low-population regions and provides relevant information for land-use planning and seismic-hazard mitigation.