The extent of damage to the building stock (in the sense of damage grade) due to the Magnitude 8.8 Chile earthquake can be evaluated as moderate till minor. However, extensive the damage has been assessed in some major afflicted areas (e.g. Constitucion, Dichato) due to the tsunami.

The reasons for the moderate earthquake damages could be the result of the large distance of the epicenter and due to the different design philosophy of the building code and its practical application in Chile.

Because of the high frequency of earthquake occurrence, generally, the engineers like to avoid damages in the structures after an earthquake. In other countries damages are allowed at special points (locations) and in a defined extent (“Performance-based Design”).

Chile is located in a very active seismic region; therefore, the country experienced the strong earthquake shacking periodically (e.g. 1960, 1985). The main reason of the high seismicity is the movement (several cm per year) of the Nasca-Plate under the South-American-Plate which results in the increase of stress in the region.

The large number of undamaged or only slightly damaged buildings confirms that the right lessons were driven from the strong earthquakes in the past and implemented in an effective manner. 

The enormously high magnitude of the earthquake could be estimated here in Weimar at the real-time registration of the Bauhaus-Station, just few minutes after the event.

In the framework of this mission, instruments were temporarily installed at different buildings to measure the building response due to the aftershocks. Some stronger events were recorded, which would be interesting and relevant for the design in German Earthquake regions.

The transfer of the experiences from previous earthquakes could be found in the preferred construction types, too. Next to the traditionally adobe clay, simple masonry and wood structures (which are still often used particularly in the rural regions) massive reinforced concrete wall structures dominates in the region, which in the past behaves quite well under earthquake loads.

Also many buildings are constructed as confined masonry which offers pretty well earthquake resistance as experienced world-wide.

Apart from the high magnitude of the earthquake and following tsunami, the damages to the multi-story RC buildings were main investigation aspect during the stay in Chile. The main tasks included the identification and reasons of the damages and in particular, the transfer of the gained experiences to other regions.

Like almost every major earthquake, there were spectacular damage cases in the structures due to strong earthquake shaking, which makes the engineers aware of the specific defects in the structure. They are usually due to the unfavorable overlapping of several damage causing parameters.

Infrastructure:

Following the main event and the several aftershocks, substantial damages to the infrastructure occurred. Some bridges suffered tremendous damage collapsed and many more had to be closed for the traffic. Furthermore, numerous cracks and large settlements were observed in the streets.

Special structures:

Single isolated special structures (Silos) suffered total loss and collapsed. The reasons for the stability failure have to be investigated in each specific case.

Simple residential buildings:

Total collapse of buildings due to the earthquake occurred mainly to adobe constructions. But, also, that there were examples which were damaged but didn’t failed/collapsed.

Multistorey residential buildings:

Damages to structures design by engineers were mainly happen at multi-story buildings with more than 10 floors, which could be, because of the special characteristic of the earthquake motion and the behavior of the weak, amplifying subsoil. The Eigen frequencies of this type of structure approximately match with the long period frequency content of the earthquake, which is not fully considered in the current code.

Another reason could be the change of the construction and design philosophy during the last years. Because of different influences, the thickness of structural wall elements was dropped to around 15cm from 30cm, which had mainly contributed to the damage of the buildings.

In the Tsunami affected cities of Dichato and Constitución, the damages caused by the shaking of the earthquake were relatively small. Only minor damage could be observed at topographically higher located buildings..

Especially the simple, adobe structures as well as the lightweight wooden constructions were totally destroyed by the tsunami (sometimes partially). But also more massive construction types sustain heavy damages, e.g. scouring of the foundation.

In dependence of the form of the coast, different impacts of damage could be observed. The exact situations still have to be analyzed and investigated. Especially, there are different information and observation available at the moment about the number and height of the tsunami waves.

In general, the coastal area of Chile is prepared for Tsunami, but the focus seems to have been on the evacuation of the affected area. It should be considered that the last tsunami occurred in this region 50 years ago.

A comparison of the effects due to the tsunami after the Sumatra-Andamanen-Earthquake 2004 can provide the basis of the other coastal features and construction methods for future.