Seismic Microzonation of Concepción City


Abstract eng:
Chile is one of the most seismically active countries in the world, because it is located in the subduction zone generated by the convergence of the South American and Nazca plates. In this context, the city of Concepcion has been affected by destructive earthquakes and tsunamis. The last major seismic event in the region was the February 27, 2010 Mw = 8.8, Maule earthquake, which destroyed buildings of adobe and unreinforced masonry and caused damage in reinforced concrete buildings located in Concepcion, ranging from slight damage to the collapse of the Alto Rio building. Among the factors to be studied in order to understand the variability of damages observed in Concepcion, there is the site effect, due to the city is on a basin with layers of sediment of variable thickness. Also, we must consider the location of asperities in the contact between the Nazca and South American plates, which characterized acceleration records obtained in the February 27, 2010 earthquake. In addition, in the design point of view it was observed that the response spectra of the Maule earthquake, recorded at the center of Concepcion, do not match the response spectra of the seismic design code for the area. This work seeks to generate a seismic microzonation to better assess the seismic demand in Concepcion by performing a Probabilistic Seismic Hazard Analysis (PSHA) and using a simple methodology to include the site effect. An improved model of the 3D geometry of the interface between the plates is obtained using geophysical datasets, and hypocenters of the seismic activity in the area. The attenuation curves for rock of Abrahanson 2016 [1], Idini et al 2016 [2], Contreras- Boroschek 2015 [3] and Zaho 2006 [4], are used. Based on H/V spectra ratio for two stations in Concepción, and the response modification factors proposed by Idini [2,5], which depend on the soil period, the response spectra for accelerations and pseudo-displacements on soil, are calculated. Seismic hazard analysis includes information on the location of the asperities. Results obtained show that their inclusion does not significantly modifies the results due to asperity closeness to the site under study. Acceleration and displacement isoseismic maps for PGA, and spectral periods of 0.3s and 1s considering 475 years return period, are obtained. It is concluded that rigid structures will have high acceleration demand in the entire Concepción, and flexible structures will have high displacement and ductility demand (above 30 cm) in areas with soil period above 0.8s. In addition, the seismic demand (acceleration and displacement) for seven buildings with more than 5 stories and demolition order after the Maule earthquake, were analyzed.

Contributors:
Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
Rights:
Text je chráněný podle autorského zákona č. 121/2000 Sb.



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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 4492.:
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