Articles | Volume 12, issue 12
Nat. Hazards Earth Syst. Sci., 12, 3631–3643, 2012
Nat. Hazards Earth Syst. Sci., 12, 3631–3643, 2012

Research article 12 Dec 2012

Research article | 12 Dec 2012

The role of near-field interaction between seismic waves and slope on the triggering of a rockslide at Lorca (SE Spain)

P. Alfaro1, J. Delgado1, F. J. García-Tortosa2, J. J. Giner1, L. Lenti3, C. López-Casado4, S. Martino5, and G. Scarascia Mugnozza5 P. Alfaro et al.
  • 1Dpt. Ciencias de la Tierra y del Medio Ambiente, Universidad de Alicante, Ap. Correos 99, 03080 Alicante, Spain
  • 2Dpt. Dpto. Geología, Universidad de Jaén, Campus Las Lagunillas, 23071 Jaén, Spain
  • 3Institut français des sciences et technologies des transports, de l'aménagement et des réseaux (IFSTTAR), 58 Boulevard Lefebvre, 75732 Paris Cedex 15, France
  • 4Dpt. Física Teórica y del Cosmos, Facultad de Ciencias, Campus Fuentenueva, Universidad de Granada, 18003 Granada, Spain
  • 5Dipartimento di Scienze della Terra, Università di Roma "Sapienza", P.le. Moro 5, 00185 – Roma, Italy

Abstract. A ~1000 m3 rockslide occurred close to Lorca (SE Spain) during the main shock (Mw = 5.1) of the May 2011 seismic sequence. The location of the rockslide, within 10 km of the earthquake epicenter and along the southern slope of a valley in which similar geological conditions occur on both slopes of the valley, suggests a significant near-field effect due to local seismic response. This could be related to the specific interaction between the topography and the obliquely propagating seismic waves.

A dynamic stress strain numerical model was constructed using the FLAC 7.0 finite difference code to back analyze the Lorca rockslide event and relate its occurrence to both the local seismic amplification and the interaction between seismic waves and local topography. The results indicate that only for seismic waves with incidence angles in the range 0°–50° are the occurred slope instabilities expected. These results do not significantly change when varying the values for either stiffness or strength parameters within the range of the experimental data.