Study of the Accelerogram Destructiveness of NAZCA Plate Subduction Earthquakes

Abstract eng:
A comprehensive and systematic study of the destructiveness of earthquakes originated by the subduction of the Nazca plate under the South American plate during the last 60 years is presented. The Nazca plate subduction is an extreme case among the world subduction types, it is characterized to be one of the youngest plate and to have the highest convergence velocity. This youth of the Nazca plate means that it has a surface with a high density of asperities, and the high convergence velocity produces the highest seismicity zone of the world. Furthermore, this high seismicity produces different types of large magnitude subduction earthquakes (Ms>7.5) along the Pacific coast of Chile and Peru every five years, which allows to estimate destructiveness with accelerograms, using an important data base. Nazca subduction accelerograms are characterized by high PGA values, larger than 0.6g and large acceleration response spectra. Despite these large values at the site of accelerographic stations, only moderate damage is observed. The study of the Nazca Plate accelerograms destructiveness capacity is done comparing their horizontal destructiveness potential factor PDH with the MSK intensity at the accelerographic station site, obtaining a good correlation between these two values. Also it is concluded that despite the high magnitude of the Nazca plate subduction earthquakes and their high peak ground acceleration, the associated macroseismic intensity values represent moderate level of damage for structures with seismic design. The intensity of zero crossings of Nazca plate accelerograms is found to be very high and it is the main reason of their moderate damage capacity.

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