Trabajo presentado en el 17th International Seismix Symposium, celebrado en Aviemore (Escocia), del 15 al 20 de mayo de 2016, The Alhama de Murcia fault (AMF) is one of the
most active faults of the Iberian Peninsula and
the source of the Lorca 2011 earthquake that
caused significant demage including several
casualties. This NE-SW oblique (strike slip-reverse movement) fault, extended up to 100 km,
has been extensively mapped to characterize
its surface structure but almost no information
is available of the structure and geometry at
depth. As a result of the Lorca 2011 earthquake
and its devastating effects in the population a
need for better knowledge of the AMF became
mandatory. Accordingly, InterGEO project pursues to understand the seismic behaviour of
the fault and determine its relevance in seismic
hazard. In order to achieve this, a multidisciplinary approach is used including detailed geological mapping, paleoseismic trenches, borehole logging and geophysical characterization., The main aim is to characterize the AMF in the
sorroundings of the Lorca city ,from surface to
depth, in the most interesting fault segments., Research supports: CGL2014-56548-P, 2009-SGR-1595 ,
CGL2013-47412-C2-1-P, Peer reviewed

vEGU21: Gather Online | 19-30 April 2021, In Spring 2011 (11th of May), the vicinity of Lorca city (Murcia, SE Iberian Peninsula) was hit by two main seismic shocks that reach a maximum magnitude of 5.2 Mw. The earthquake caused serious widespread damage in the city and its surroundings. Similar events have affected the area regularly in the past (for example: on May 6,1977, 4.2 mg). These events are distributed along a relatively broad band (roughly NE-SW oriented) parallel to the coast, associated to the activation of the Alhama de Murcia Fault (AMF), an oblique-slip (reverse-strike-slip) fault system located in the Eastern Betics Shear Zone. The current study aims to characterize the shallow subsurface across some of the surface outcrop of a few of the main faults that lie within this seismogenic strike-slip fault system. Six normal-incidence seismic reflection profiles were acquired in the area crossing the AMF and the Carrascoy fault, among others). This study focuses on the determination of the shear-wave velocity depth model by applying Multichannel Analysis of Surface Waves (MASW), using the shot records of the seismic reflection profiles. The 1D velocity-depth functions acquired were pasted together to obtain the final 2D velocity models. The hand-picked dispersion curves were inverted using two different approaches to address the consistency of the inversion schemes. The final models reveal relevant differences across the different fault zones, reflecting the heterogeneity and lateral variability that characterizes a complex seismogenic zone, a most probably, diffuse plate boundary., This research is supported by: Generalitat de Catalunya (AGAUR) grant 2017SGR1022 (GREG); EU (H2020) 871121 (EPOS-SP); EIT-RawMaterials 17024 (SIT4ME), CGL2013-47412-C2-1-P.

X Congreso Geológico de España, 5-7 Julio 2021, Vitoria - Gasteiz, La estructura profunda de la falla de Alhama de Murcia (AMF) ha sido caracterizada mediante el análisis de ondas superficiales identificados en datos de reflexión sísmica superficial de alta resolución. El análisis multicanal de ondas de superficie (MASW) es usado para desentrañar un modelo 2D de Vs y para obtener imágenes de la geometría del sistema de fallas en profundidad. El área de estudio incluye segmentos de la AMF ubicados en el área de La Salud. Se han utilizado dos enfoques para lograr modelos de velocidad bien restringidos de la zona de falla. Por un lado, se han limpiado los datos utilizado un flujo de procesado convencional diseñado para aumentar su ratio de señal/ruido. Por el otro, se ha usado el enfoque de Occam para invertir las curvas de dispersión de ondas de superficie digitalizadas. Los perfiles 1D de profundidad de las Vs fueron estimados en los dominios de disparo y de CDP. Se obtuvieron modelos de velocidad-profundidad 2D relativamente bien resueltos mediante la interpolación de las funciones de velocidad-profundidad 1D. Estos modelos de velocidad 2D ayudan a restringir en profundidad la geometría de la zona de falla hasta los 100 m que se caracteriza por una anomalía de baja velocidad relativamente amplia que se correlaciona en la superficie con la expresión de la falla., The deep structure of the Alhama de Murcia Fault (AMF) is characterized by means of the analysis of surface waves identified in shallow high resolution seismic reflection data. Multichannel analysis of surface waves (MASW) is used to unravel the 2-D S-wave velocity model and image the depth geometry of the fault system. The study area includes segments of the fault located in La Salud area. Two approaches have been used to achieve a well constrained velocity model in the AMF fault zone. Conventional seismic reflection processing work flow has been used to clean the seismic data and increase its S/N ratio. Occam's approach has been used to invert the digitized surface wave dispersion curves. 1D shear wave velocity-depth profiles were estimated in shot and CDP domains. Relatively well resolved 2D velocity-depth models were obtained by composite of the 1D Velocity-depth functions. These composite 2D-velocity models are able to constrain the depth geometry of the fault zone up to 100 m depth. The fault zone is indicated by a relatively broad low velocity anomaly that correlates with the fault’s surface expression., We would thank for the data permission to project of InterGEO (CGL2013-47412- C2-1-P) ICTJA-CSIC. The Ministry of Education and Culture of the Republic of Indonesia is thanked for main author’s PhD scholarship. JA is funded by MICINN (IJC2018-026335-I).