Finite rupture properties of the 2011 Lorca earthquake
DOI:
https://doi.org/10.21701/bolgeomin.123.4.002Keywords:
apparent source-time functions, directivity, Lorca earthquake, source parameters, ruptureAbstract
On 11 May 2011 an earthquake (Mw = 5.2) hit the region of Murcia (Spain), shaking mainly the city of Lorca and causing extensive personal and material damage. We have estimated that it involved an oblique reverse-faulting mechanism with a shallow hypocentre (4.6 km) at only 5.5 km epicentral distance from Lorca city centre. Double-difference relocations yield a rupture length of ~ 4 km and suggest a propagation of the rupture from the northeast to the southwest along the Alhama de Murcia fault. We obtained apparent source-time functions at each station using empirical Green’s function deconvolution and applying the 4.6 Mw foreshock and the 3.9 Mw aftershock, both of them with a similar location and mechanism. Two methods of deconvolution were used: spectral division and iterative time domain. Both methods gave consistent, stable results, revealing a clear “directivity effect”. We have modelled apparent durations with a unilateral and asymmetric bilateral rupture, in both cases obtaining a rupture directivity of ~N215°E towards Lorca, which may have contributed to the unfavourable scenario caused by this event.
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Junta de Andalucía
Grant numbers P09-RNM-5100
