Seismically-induced landslides in the Betic Cordillera (S Spain) J. Delgado a,n , J.A. Pela ´ ez b , R. Toma ´s a , F.J. Garcı ´a-Tortosa c , P. Alfaro d , C. Lo ´ pez Casado e a Dpt. Ingenierı ´a de la Construccio ´n, OO.PP. e I.U, Escuela Polite´cnica Superior, Universidad de Alicante, 03080 Alicante, Spain b Dpt. Fı ´sica, Campus Las Lagunillas s/n, Universidad de Jae ´n, 23071 Jae´n, Spain c Dpt. Geologı ´a, Campus Las Lagunillas s/n, Universidad de Jae´n, 23071 Jae ´n, Spain d Dpt. Ciencias de la Tierra y M.A. Facultad de Ciencias, Universidad de Alicante, 03080 Alicante, Spain e Dpt. Fı ´sica Teo ´rica y del Cosmos, Facultad de Ciencias, Universidad de Granada, Av. Severo Ochoa s/n, 18071 Granada, Spain article info Article history: Received 27 April 2010 Received in revised form 3 January 2011 Accepted 19 April 2011 Available online 18 May 2011 abstract A database of seismically-induced landslides in the Betic Cordillera is presented. Data included were classified according to landslide typology. Most of them ( E80%) correspond to small size, disrupted landslides (including rock/earth falls and earth slides that disorganize as mass-movement progresses) and the remaining consist mainly of coherent landslides (slumps in soils and rock-slides). Deep seated induced landslides are uncommon in the study zone and have occurred only after the few events of large magnitude reported in the Cordillera. Data available show that events of small magnitude (M w o5.0) can induce instabilities in the study zone for comparatively large distances ( 410 km) when compared with available upper bound curves for maximum epicentral distances for seismic induced landslides, that concentrate along areas prone to landsliding, like river banks or slopes on soft materials, which points out the importance of the role of slope susceptibility on the occurrence of instabilities during earthquakes. Landslides in the database are then analyzed and a power-law relationship that relates earthquake size, measured as epicentral intensity (I o ), to maximum distance of induced landslide valid for the study zone is proposed. Although included data represent a clear partial and incomplete dataset, they show the landslide state of knowledge for this region. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction A great effort has been made in the last two decades to study and understand the problem of landslides induced by earthquakes. Because this indirect effect of shaking can be widespread, its effect may cause a major disruption in society, causing significant economic losses and deaths. This was the case for the events of Alcoy (1620) or Arenas del Rey (1884) in South Spain, where several counties and towns were severely damaged by seismic induced landslides. Several techniques are in use to address this topic and support planning decisions towards earthquake-triggered landslide risk management (e.g., [1–5]). Each one has its own requirements and implies the use of different kinds of data. Choosing among them is frequently a question of scale and availability of data: the more rigorous ones are employed for site specific studies, where detailed information about subsoil materials and properties are available, while the more generic ones are more appropriate for regional studies, where detailed data are rarely accessible. Although seismically-induced landslides have been known for a long time in the Betic Cordillera, S Spain, there are still few studies about this topic and they have been focused on studying limited areas within the cordillera (e.g., [6–13]) or describing single landslide topics [14]. No attempt has been made to develop a database for such landslides or to determine relationships between landslide occurrence and shaking parameters of events. In this paper we present for the first time a regional database compiled for landslides induced by earthquakes occurred in the Betic Cordillera (Fig. 1). Although this database is incomplete, it represents a step forward for the progress in the knowledge of this phenomenon in the area. This database comprises landslides induced by two types of earthquakes: historical earthquakes, most of them moderate to strong events (6.0–7.0 M w ), and recent events (1945 to present) of low magnitude ( r5.0 M w ). 2. Seismotectonic framework Seismicity in the Betic Cordillera is conditioned by the contact between the Eurasian and the African plates. NUVEL-1 model [15] reveals a NW-SE to NNW-SSE convergence rate of 4–6 mm/year between Southern Spain and Africa. In this geodynamic setting, NW-SE to NNW-SSE compression is combined with NE-SW extension [16]. In general, the Betic Cordillera is characterized by a continuous scattered low to moderate seismicity (Mo5.5; Fig. 1) inducing a low to moderate seismic hazard [17,18]. In any case, some destructive Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/soildyn Soil Dynamics and Earthquake Engineering 0267-7261/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.soildyn.2011.04.008 n Corresponding author. Tel.: þ34 965 903 400x2122; fax: þ34 965 909 862. E-mail addresses: Jose.delgado@ua.es (J. Delgado), japelaez@ujaen.es (J.A. Pela ´ ez), Roberto.tomas@ua.es (R. Toma ´ s), gtortosa@ujaen.es (F.J. Garcı ´a-Tortosa), Pedro.alfaro@ua.es (P. Alfaro), clcasado@ugr.es (C. Lo ´ pez Casado). Soil Dynamics and Earthquake Engineering 31 (2011) 1203–1211