Why do buildings collapse in earthquakes? Building for safety in seismic areas. Robin Spence

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Why do buildings collapse in earthquakes? Building for safety in seismic areas - Robin Spence


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Stone masonry building in the Kutch district damaged in the Bhuj earthquake.

Photo depicts brick masonry building with reinforced concrete floors damaged in the Bhuj earthquake. Photo depicts reinforced concrete building in the Kutch district and typical damage patterns. Photo depicts damage to a reinforced concrete building in Bhuj, and view of the same building in satellite image, arrow showing viewing direction.

      Source: Saito et al. (2004).

      The final toll of dead and injured shows that altogether 13 481 people were killed in the earthquake (Jain et al. 2002). There were more than 166 000 injured, 20 000 of them seriously. From medical reports, it is clear that both death and injury were mainly the result of traumas associated with the collapse of buildings. Over 1000 school students and teachers were killed, though because it was a public holiday many schools were closed. There were also more adult female than male deaths (Murty 2005). There can be little doubt, though, that failure of weak masonry walls and the resulting collapse of dwellings was the main cause of death, and the magnitude of the death toll is a reflection of the very wide area over which heavy ground shaking was observed, combined with the weakness of the typical masonry buildings.

      2.2.2 The 26.12.2003 Bam Earthquake: Mw6.6, about 27 000 Deaths

      The massive death toll in Bam has been attributed to the extreme weakness of the adobe houses which are inhabited by the majority of the population. This method of building has been documented in the World Housing Encyclopedia (Maheri et al. 2005).

      Adobe construction is an appropriate response to the climate of Southern Iran, given high day–night temperature swings, and also the lack of timber available for construction. At the time of the earthquake, this was still the predominant way of building in Bam. But in the event of an earthquake its weakness is extreme. The problems include (Maheri et al. 2005):

       Thick heavy walls, which attract large lateral seismic forces.

       Lack of connections between perpendicular walls.

       Heavy domed or vaulted mud roofs, exerting lateral pressure on walls.

       Poor quality of the adobe units (local sun‐dried mud).

       Poor quality of mortar and bonding.

       Lack of foundations.

       Limited maintenance.

Photo depicts high-resolution satellite imagery of the centre of Bam taken (left) before and (right) after earthquake, clearly indicating the extent of the damage.

      Source: DigitalGlobe.

Photo depicts failure of adobe dwelling in the Bam earthquake.

      Source: World Housing Encyclopedia. Reproduced with permission of EERI.

      2.2.3 The 26.12.2004 Indian Ocean Earthquake and Tsunami: Mw = 9.1, 225 841 Deaths


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