Quaternary International 158 (2006) 96–109 Liquefaction phenomena associated with historical earthquakes in San Juan and Mendoza Provinces, Argentina Laura P. Perucca à , Stella M. Moreiras Consejo Nacional de Investigaciones Cientı´ficas y Tecnolo´gicas (CONICET), Gabinete de Neotecto´nica, INGEO, Facultad de Ciencias Exactas, Fı´sicas y Naturales, Universidad Nacional de San Juan, Av. Ignacio de La Roza y Meglioli s/n, 5400 San Juan, Argentina Available online 26 July 2006 Abstract Mendoza and San Juan provinces which represent the most seismically active regions of Argentina have been affected by at least nine destructive earthquakes with magnitudes X6.3 in the period 1861–1997. During these events, earthquake-induced liquefaction processes have caused the most severe damages in properties and fields impacting adversely on regional development and economy. Analysing historical liquefaction data we corroborated the relation between liquefaction phenomenon with sediment grain size and depth of phreatic level. We also noted that even the distance from liquefaction features to epicentres increases with earthquake magnitude, previous empirical relations for distance/magnitude are not enough accurate to predict liquefaction feature distance. Moreover, we suggest that when physical conditions of terrain are suitable, liquefaction phenomenon can occur even at greater distances than those established by empirical manner. In addition, regarding potential risk for this seismically region, the most liquefaction vulnerability areas were established taken into account the historical data and the presence of Holocene–Pleistocene deposits with present higher phreatic level. Our findings are essential for future proper territorial planning and they should be useful for minimize economical losses caused by secondary effects in these seismic regions of Argentina. r 2006 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction San Juan and Mendoza provinces are located between 281 to 341S and 671 to 701W(Fig. 1). At this latitude (271 to 321S), the subduction angle of the Nazca plate tends to be sub-horizontal (o141) at 100 km depth (Stauder, 1973; Barazanghi and Isacks, 1976; Smalley and Isacks, 1987, 1990; Smalley et al., 1993) which is mainly indicated by intense seismic activity from about 5–50 km depth. This activity decreases between 90 and 150 km depth (INPRES, 1993). The geologic record also shows that the inhomo- geneity in the subduction angle has a direct relationship with the tectonic and morphologic style (Jordan et al., 1983), different in the southern and northern portions (Barazanghi and Isacks, 1976, Jordan et al., 1983) and approximately concentrating 80% of the Quaternary deformation in the Argentinean territory (Costa et al., 2000). Almost all the historical and instrumental seismicity records, and the scarce well-known historical ruptures, are concentrated on a belt located between 311 and 331S. Liquefaction processes have been commonly analysed for the evaluation of potential seismic hazard (Moretti et al., 1995; Obermeier, 1994; Paredes and Perucca, 2000; Perucca and Moreiras, 2003) as they are well known as a secondary effect of earthquakes causing damage. Liquefac- tion features are rare mainly because of poor structure preservation, and therefore the compilation of historical documents is essential. Liquefaction features have been described in most worldwide seismic regions but they have been underestimated in Mendoza and San Juan provinces which represent the most seimically active regions of Argentina. At least nine destructive earthquakes (1861, 1894, 1903, 1917, 1920, 1927, 1929, 1944 and 1977) have affected the development and economy of these provinces during the last 150 years. The critical economical losses caused by these earthquakes have been previously eval- uated by INPRES (1982, 1993, 1995). Although the secondary seismic effects including liquefaction were neglected, they were widespread and spectacular during the seismic shaking and a great part of damage was ARTICLE IN PRESS 1040-6182/$ - see front matter r 2006 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2006.05.023 à Corresponding author. Tel./fax: +54 0264 4265103. E-mail addresses: lperucca@unsj-cuim.edu.ar (L.P. Perucca), moreiras@lab.cricyt.edu.ar (S.M. Moreiras).