  In this letter we study chaotic dynamical properties of an asymmetrically
coupled one-dimensional chain of maps. We discuss the existence of coherent
regions in terms of the presence of defects along the chain. We find out that
temporal chaos is instantaneously localized around one single defect and that
the tangent vector jumps from one defect to another in an apparently random
way. We quantitatively measure the localization properties by defining an
entropy-like function in the space of tangent vectors.
