JOURNAL OF QUATERNARY SCIENCE (2004) 19(3) 219–227 Copyright ß 2004 John Wiley & Sons, Ltd. Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jqs.838 Small-scale faulting, topographic steps and seismic ruptures in the Alhambra (Granada, southeast Spain) J. M. AZAN ˜ O ´ N, 1 * A. AZOR, 1 G. BOOTH-REA 2 and F. TORCAL 3,4 1 Departamento de Geodina ´mica, Universidad de Granada, Campus de Fuentenueva, 18002-Granada, Spain 2 GEOMAR, Wischhofstr. 1-3, D-24148 Kiel, Germany 3 Departamento de Ciencias Ambientales, Universidad Pablo de Olavide, Sevilla, Spain 4 Instituto Andaluz de Geofı ´sica y Prevencio ´n de Desastres Sı ´smicos, Granada 18071, Spain Azan ˜o ´ n, J. M., Azor, A., Booth-Rea, G. and Torcal F. 2004. Small-scale faulting, topographic steps and seismic ruptures in the Alhambra (Granada, southeast Spain). J. Quaternary Sci., Vol. 19 pp. 219–227. ISSN 0267-8179. Received 17 September 2003; Revised 25 November 2003; Accepted 10 December 2003 ABSTRACT: The Alhambra (14th century AD) in Granada (southeast Spain) is built at the summit of a Pliocene to Lower Pleistocene conglomeratic formation. Tens of small-scale normal faults crop out along the northern hillslope of the Alhambra, which have a N130–N150  E strike, dipping 65–75  mostly to the southwest. These are closely spaced faults (approximately 5–30 m) with centimetre to several metre displacements. Several topographic steps in this area coincide with hectometre- to kilometre-scale faults with the same kinematics as the small-scale ones. Some of these faults appear to be active and related to the present seismicity detected in this region, and associated with the cracks and other damage observed in the Alhambra. Several focal mechanisms calculated in this study are in accordance with the dominant NW–SE orientated normal faults. We interpret that the topographic steps of these faults are a consequence of repeated earthquakes during the past 800 ka. The last large earthquake of approximately 5.1 magnitude in this area occurred in 1431, destroying the Alixares Palace, the Arabian fence and part of the Alhambra wall. We consider the seismic risk associated with these faults to be moderate, as the displacement is partitioned into several hectometre- to kilometre-scale faults. Copyright ß 2004 John Wiley & Sons, Ltd. KEYWORDS: active tectonics; normal faults; co-seismic damage; Betic Cordillera. Introduction One of the most picturesque features of the Alhambra (14th century AD), the most visited monument in Europe, is its empla- cement on the summit of a red hill that dominates a flat area, namely the Granada Depression, where most of Granada city is located. From a geological point of view, this area surrounded by mountains, where Tertiary and Quaternary sediments crop out, is known as the Granada Basin (Fig. 1). This basin, located in the central sector of the Betic Cordillera, is one of the most seismically active zones in the Iberian Peninsula (e.g. Morales et al., 1999; Mun ˜oz et al., 2002; Galindo-Zaldı ´var et al., 2003; Sanz de Galdeano et al., 2003). There is substantial historical evidence for several important earthquakes that must have occurred in 1431, 1526, 1806, 1911 and 1956 in the northeast- ern sector of the Granada Basin. However, the Alhambra has remained standing during the past six centuries and the degree of seismic damage to its structure is far from significant. There are three possible reasons for this apparent good state of preser- vation: (i) stability resulting from the mechanical behaviour of the conglomeratic formation on which the Alhambra is founded, (ii) the moderate magnitude of the seismicity in the Granada Basin and (iii) the lack of important seismic active faults in the neighbourhood of the Alhambra. The substratum of the Alhambra hill is a conglomeratic formation which reduces the amplification of the seismic waves with respect to softer sedimentary rocks, such as the silts and clays cropping out basinwards. This site effect is difficult to evaluate, except when a large magnitude earthquake occurs (e.g. Chin and Aki, 1991; Wen et al., 2002). The seismicity in the Granada Basin can be qualified as recurrent but nevertheless moderate (magnitudes between 2 and 5). The absence of important seismogenic faults in the Alhambra area remains a controversial issue, because well exposed fault- scarps occur only between the basement and the sediments of the Granada Basin. However, the good preservation of these fault-scarps has an obvious lithological control, i.e. the foot- wall is made up of high-strength rocks of the basement, whereas the hanging wall is made up of mostly soft sedimen- tary rocks. In this paper, we concentrate on the geological fea- tures of the Alhambra hill that could be considered indicative of very recent seismic activity. Particularly, we describe (i) * Correspondence to: J. M. Azan ˜o ´ n, Departamento de Geodina ´mica, Universidad de Granada, Campus de Fuentenueva, 18002-Granada, Spain. E-mail: jazanon@ugr.es