Revision of the Applicability of the NGA's in South America, Chile - Argentina.

Abstract:

In South America, larger magnitude seismic events originate in the subduction zone between the Nazca and Continental plates, as opposed to crustal events. Crustal seismic events are important in areas very close to active fault lines; however, seismic hazard analyses incorporate crust events related to a maximum distance from the site under study. In order to use crustal events as part of a seismic hazard analysis, it is necessary to use the attenuation relationships which represent the seismic behavior of the site under study. Unfortunately, in South America the amount of compiled crustal event historical data is not yet sufficient to generate a firm regional attenuation relationship. In the absence of attenuation relationships for crustal earthquakes in the region, the conventional approach is to use attenuation relationships from other regions which have a large amount of compiled data and which have similar seismic conditions to the site under study. This practice permits the development of seismic hazard analysis work with a certain margin of accuracy.

In South America, in the engineering practice, new generation attenuation relationships (NGA-W) are used among other alternatives in order to incorporate the effect of crustal events in a seismic hazard analysis. In 2014, the NGA-W Version 2 (NGA-W2) was presented with a database containing information from Taiwan, Turkey, Iran, USA, Mexico, Japan, and Alaska.

This paper examines whether it is acceptable to utilize the NGA-W2 in seismic hazard analysis in South America. A comparison between response spectrums of the seismic risk prepared in accordance with NGA-W2 and actual response spectrums of crustal events from Argentina is developed in order to support the examination. The seismic data were gathered from equipment installed in the cities of Santiago, Chile and Mendoza, Argentina.