Potential damage and losses in a repeat of the 1910 Adra (Southern Spain) earthquake

Abstract

The town of Adra (Almeria Province, South-Eastern Spain) has been seriously affected by historical damaging earthquakes in 1487, 1522, two in 1804 and in 1910 with epicentres offshore in the Alboran Sea that reached onshore an estimated maximum intensity of VIII, IX, VIII, VIII–IX and VII–VIII, respectively. Additionally, in the instrumental period, several seismic series near the city affected it with moderate structural damages like the recent one of 1993–1994, when two main earthquakes of magnitude 5.0 and 4.9 cause serious damage in mid-rise reinforced concrete buildings sited on soft soils. Consequently, the town can be affected by moderate to destructive earthquakes, so this paper provides an initial assessment of the potential impact and the consequences (in terms of structural damage, economic and human losses) if the 1910 Adra earthquake hit the city again. The results point out that buildings damage are mainly concentrated in the soft soils areas of the city and that the non-engineered buildings, especially the oldest one, have the highest vulnerability, and therefore, the structural damage is higher, while seismically designed structures show a better behaviour showing less damage. Additionally, mid- and high-rise buildings have more extensive damage than low-rise buildings. Besides, the reinforced concrete buildings with waffled-slab floors, built previously to the first Spanish seismic code (NCSE-94), show, also, important damage. In summary, we have obtained that 474 ± 160 and 973 ± 78 buildings will be affected by complete and extensive damage, respectively, that is around 40% of the buildings in the city.