CORRELATIONS BETWEEN LARGE SCALE LANDSLIDES AND SEISMOGENIC FAULT AFTER THE FEBRUARY 13, 2001 EL SALVADOR EARTHQUAKE

The February 13, 2001, strike-slip earthquake (Mw 6.6) struck the central region of El Salvador (Central America), inside the Caribbean plate overriding the subducting Cocos plate, at a hypocentral depth of 10 km. The earthquake sequence took place inside the Great Interior Valley, crossed along its whole length by the El Salvator dextral-slip fault system. The valley hosts also a chain of Quaternary and active volcanoes that extend across the country from east to west. According to Canora et al. (2010), the 13 February earthquake was associated to a 21 km long rupture of the San Vicente fault segment of the El Salvador fault zone. The rightlateral strike-slip surface rupture had a maximum surface displacement of 0.60 m, without any significant vertical component. An earlier destructive earthquake had occurred one month before the February event, on January 13 (Mw 7.7), within the subducting Cocos plate 40 km off the Salvadorian coast. The latter was the largest seismic event occurred in El Salvador in more than 50 years. It caused 900 fatalities and severe damage, mainly due to earthquakeinduced landslides. Although the February 13 event was smaller in magnitude than the January earthquake, it caused substantial damage and more than 300 deaths. The most devastating impact of the 2001 earthquakes was the triggering of hundreds of landslides, some of which damaged and destroyed towns, roads and other lifelines, also causing serious damages to the local economy based on coffee plantations and other agricultural productions. Among the landslides generated by the February event, there were some with estimated volume ranging between 800,000 to 12,000,000 m3. These large landslides were markedly distributed in the region of maximum seismic intensity, in a narrow belt along the surface rupture zone. Comprehensive analysis reveals that these large catastrophic landslides could be specifically tied to the main seismotectonic structure of the El Salvador fault zone, i.e., be directly caused by the fault slip. This observation can be quite relevant for future hazard assessment.