Active tectonics around the Cusco city, Peru: record of earthquakes in the last 14,000 years, from paleosismological data

Abstract

The seismic activity of Peru has its origin in the convergent margin, where the Nazca plate subducts under the South American plate, a process that generates friction and accumulation of stress, reflected in deformation of the crust and superficial earthquakes (<30km of depth). Cusco was affected by earthquakes in 1950, 1650 and recently in 1986, the first two, major earthquakes of magnitudes greater than 7 MM (Silgado,1978). The Tambomachay active geological fault is located four kilometers to the north of the city of Cusco, and belongs to a large and wide deformation zone, where the structures have NWSE and E-W trends, known as the Zurite-Cusco- Urcos-Sicuani Fault System (Benavente et al., 2013). Recent studies show clear morphological and structural evidence of Quaternary activity on these structures (Sébrier et al., 1985; Mercier et al., 1992; Cabrera, 1988; Benavente et al, 2013), so they should be classified as an important seismogenic source; however, there has not been complete characterization to assess the seismic hazard to the city of Cusco, which currently houses over ~500,000 inhabitants. In this research investigation, we present a paleoseismological study of the western sector of the Tambomachay Fault. We present displacement rates, recurrence intervals and ages of recent seismic events