DInSAR Coseismic Deformation of the May 2011 M&amp;lt;sub&amp;gt;w&amp;lt;/sub&amp;gt; 5.1 Lorca Earthquake (southeastern Spain)

T Frontera,R Arbiol,G Khazaradze,A Echeverria,A Concha,F Pérez,X Goula,E Suriñach,P Blanco

doi:10.5194/se-3-111-2012

DInSAR Coseismic Deformation of the May 2011 M&lt;sub&gt;w&lt;/sub&gt; 5.1 Lorca Earthquake (southeastern Spain)

T Frontera, R Arbiol + Show 7 more

Open Access

https://doi.org/10.5194/se-3-111-2012

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Abstract

Abstract. The coseismic superficial deformation at the region of Lorca (Murcia, southeastern Spain) due to the Mw 5.1 earthquake on 11 May 2011 was characterized by a multidisciplinary team, integrating information from DInSAR, GPS and numerical modelling techniques. Despite the moderate magnitude of the event, quantitative information was obtained from the interferometric study of a pair of TerraSAR-X images. The DinSAR results defined the trace of the fault plane and evidenced uplift of the hanging wall block in agreement with the estimated deformation obtained through an elastic rupture dislocation numerical model. Meanwhile for the footwall block, interferometric results showed that tectonic deformation is masked by an important subsidence related to groundwater extraction previously identified at the area of study. Horizontal crustal deformation rates and velocity vectors, obtained from GPS stations existent at the area, were also coherent with the tectonic setting of the southern margin of the Iberian Peninsula and with the focal mechanism calculated for the Lorca event. The analysis of a continuous GPS site in Lorca showed good agreement with the horizontal N–S direction component relative to the numerical model and tectonics of the region. This is the first time at this seismic active area that a multi-technique analysis has been performed immediately after the occurrence of a seismic event, comparing the existing deformation data with a theoretical numerical model based on estimated seismic rupture dislocation.

Highlights

On 11 May 2011, two shallow moderate magnitude earthquakes occurred at less than 5 km northeast of the city of Lorca (Murcia, southeastern Spain)
The GPS data considered in this study consist of the analysis of one continuous GPS (CGPS) station located in Lorca (LORC) and six campaign data belonging to the CuaTeNeo (Cuantificacion de la Tectonica actual y Neotectonica) geodetic network, which was established in 1996 to quantify the current rates of crustal deformation in the eastern part of the Betic Cordillera (Colomina et al, 1999)
Using the numerical model as reference for the coseismic displacement, we found a good agreement between the DInSAR measurements (3 cm) and the model estimated values (4 cm) on the northern hanging wall block of the fault

Summary

Introduction

On 11 May 2011, two shallow moderate magnitude earthquakes occurred at less than 5 km northeast of the city of Lorca (Murcia, southeastern Spain). On 6 August 2002, an earthquake occurred 40 km west of Mula near the town of Bullas It had a magnitude of Mw 4.6 and a maximum intensity of V (EMS) (Buforn et al, 2005). In the same town on 29 January 2005, there was another earthquake near Bullas (Buforn et al, 2006) with a magnitude of Mw 4.7; the IGN (2005) assigned a maximum intensity of VII (EMS). This last earthquake was more damaging than the one in 2002, probably due to the weakening effect produced by the 2002 previous shock on some structures. This supposed mislocation might have been due to the generation of aftershocks in a zone with high concentration of the static Mohr-Coulomb stresses out of the FAM plane

GPS data

DInSAR analysis

Numerical model of coseismic vertical deformation

Discussion and conclusions