Effect of 8.2 Mw Iquique Earthquake on Tall Buildings

An 8.2 Mw Earthquake struck the Chilean coast on April 1st. The epicenter was located 95km NW of Iquique. There are many 20+ story buildings in the affected area with similar characteristics than those affected in the last February 27^th 2010 Maule’s earthquake, such as a high shear wall density and 20cm thick walls with none or poor boundary transverse reinforcement. Unlike four years ago, this time no structural damage was seen in tall buildings, just small concrete cracks, natural to this kind of motion. Nonstructural damage was also much less than 2010s earthquake, limiting this kind of damage to the junction between RC walls and nonstructural partition walls. This time no blocked doors caused by short slabs remnant deformations or facade cladding damage was seen, all of them very common type of nonstructural damage in 2010.

The reason for this better performance can be explained by the smaller magnitude compared to 2010 Maule’s earthquake (8.2 Mw v/s 8.8 Mw) and better soil conditions. It should be avoided to associate the 2011 seismic code changes with this better performance since no significant difference was shown between the buildings designed before or after the code was upgraded. Finally, the long distance from the epicenter to Iquique (95 km) was a lucky factor that mitigates the earthquake´s energy before its arrival to the city.

Figure 1. Typical facade with no structural or nonstructural damage.	Figure 2. Nonstructural damage in junction of structural RC element and nonstructural partition.

Figure 3. Small cracks (width < 0.2mm) in coupling beam.