Issue 45

F. Brandão et alii, Frattura ed Integrità Strutturale, 45 (2018) 14-32; DOI: 10.3221/IGF-ESIS.45.02 17 mically active area, where in 1980 an earthquake of magnitude of 5.2 m b was registered in the Pacajús city. The seismic activity in the northeast region of Ceará State, more precisely, in the Sobral region, is very old and it is the second most important in the Brazilian northeast, being preceded only by the region of the edge of the Bacia Potiguar, that includes a large part of the State of Rio Grande do Norte and the eastern part of the Ceará State. Since 2008 an intense seismic activ- ity in the Sobral region has been observed, where several earthquakes have occurred and the big of these was occurred on 05/21/2008, of 4.2 m b magnitude. The geographical position of the event and the seismogram recorded by the Riachuelo station (RCBR), located at Riachuelo-RN at approximately 572 km away from Sobral city, are shown in Fig. 2. These events have caused damage in some buildings. Figure 2 : (a) geographical position of the earthquake of magnitude 4.2 m b registered in 05/21/2008 (black circle) and (b) Seismogram of the event, where BH1 represents the component E-W, BH2 represents the component N-S and BHZ represents the vertical com- ponent (adapted from [25]). Figure 3 : Seismic zones of Brazil [20]. Until 2005, the Brazil did not have a seismic code; only in 2006 the “NBR 15421: Design of seismic resistant structures – Procedure” was published [20]. The current Brazilian norm requires that the structures on the Brazilian territory must be designed and built in order to withstand the effects of seismic loads. This standard defines the seismic loads, according to the Brazilian seismicity, and the methods of design and evaluation of the structures to be used. According to [26], for the elaboration of NBR 15421, a large study was developed in which a comparative analysis of the seismic technical standards of six South American countries was carried out observing their geographical continuity with Brazil. This allowed to de- (a) (b)