Performance of the Earthen Arg-e-Bam (Bam Citadel) during the 2003 Bam, Iran, Earthquake

Abstract

The Arg-e-Bam (Bam Citadel; in Farsi, arg means citadel) is a remarkable example of the earthen architecture and construction that was heavily damaged in the 2003 Bam, Iran, earthquake, which occurred on 26 December 2003. This paper presents the hypothesis that the collapse of the walls was caused largely by a combination of the effects of (1) the additive changes made to the walls, particularly in recent restorations, which resulted in variations in the density and response to vibrations of different layers of unfired earth construction in the walls, and (2) extensive damage from termites and loss of the cohesion of the clay from degradation and excessive drying out, all of which interacted with the earthquake vibrations of unusually high-frequency in such a way that many walls effectively burst from the loss of cohesion and subsidence of their clay internal cores. Concern is raised about the possibility of similar risks to other earthen monumental structures in future earthquakes.