Abstract
Abstract. The Lorca earthquake of 11 May 2011 in the Betic Cordillera of SE Spain occurred almost exactly on the Alhama de Murcia fault, a marked fault that forms part of a NE-SW trending belt of faults and thrusts. The fault belt is reminiscent of a strike-slip corridor, but recent structural studies have provided clear evidence for reverse motions on these faults. Focal mechanisms of the main earthquake, but also of a foreshock, are strikingly consistent with structural observations on the Alhama de Murcia fault. This strengthens the conclusion that, rather than a strike-slip fault, the fault is at present a contractional fault with an oblique reverse sense of motion, presumably in response to the NW-directed motion of Africa with respect to Europe.
Highlights
On 11 May 2011 at 16:47 UTC, the city of Lorca in the Betic Cordillera of SE Spain was hit by a magnitude 5.1 earthquake
The main earthquake was preceeded by a 4.5 magnitude event for which different networks report different locations and focal depths of about 2 km east from Lorca at 0–1 km depth (United States Geological Survey, USGS), and 5 km east-northeast of Lorca at Correspondence to: R
The Internal Zone of the Betic Cordillera in SE Spain is characterized by elongate mountain ranges of mainly metamorphosed Palaeozoic and Mesozoic rocks (e.g. Egeler and Simon, 1969; Platt and Vissers, 1989), separated by intermontane basins filled with Neogene to recent continental
Summary
10 km depth (European Mediterranean Seismological Centre, EMSC). The main earthquake was followed by at least seven aftershocks with magnitudes between 2.6 and 3.9, four on the same evening, two on May and one on May (EMSC data). The fault forms part of a NE trending network of prominent faults, at first impression reminiscent of a strike-slip corridor, and bounds several Neogene and Quaternary intermontane basins (Fig. 1) This zone of prominent faults, characterized by marked seismicity Stich et al, 2003), continues into the Alboran Sea (Montenat et al, 1987; De Larouziere et al, 1988; Montenat and Ott d’Estevou, 1990) in a belt of high seismic activity (Fig. 1, inset) This short paper aims to draw attention to a remarkable consistency between the Lorca seismological data and recent structural analysis by the authors, and to emphasize that both datasets suggest oblique reverse rather than strike slip motions on significant portions of the Alhama de Murcia fault zone
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