Acoustic and seismic imaging of the Adra Fault (NE Alboran Sea): in search of the source of the 1910 Adra earthquake

• Published in: Natural hazards and earth system sciences Vol. 12; no. 11; pp. 3255 - 3267
• Main Authors: Grà cia, E, Bartolome, R, Lo Iacono, C, Moreno, X, Stich, D, Martínez-Diaz, J. J, Bozzano, G, Martínez-Loriente, S, Perea, H, Diez, S, Masana, E, Dañobeitia, J. J, Tello, O, Sanz, J. L, Carreño, E, EVENT-SHELF Team
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 07.11.2012; Copernicus Publications
• Subjects: Earthquakes; Marine; Radiocarbon dating; Seismic reflection surveying; Seismic tomography; Seismology; MED, Alboran Sea; MED, Spain, Andalucia, Almeria
• ISSN: 1684-9981; 1561-8633; 1684-9981
• DOI: 10.5194/nhess-12-3255-2012

Recently acquired swath-bathymetry data and high-resolution seismic reflection profiles offshore Adra (Almería, Spain) reveal the surficial expression of a NW–SE trending 20 km-long fault, which we termed the Adra Fault. Seismic imaging across the structure depicts a sub-vertical fault reaching the seafloor surface and slightly dipping to the NE showing an along-axis structural variability. Our new data suggest normal displacement of the uppermost units with probably a lateral component. Radiocarbon dating of a gravity core located in the area indicates that seafloor sediments are of Holocene age, suggesting present-day tectonic activity. The NE Alboran Sea area is characterized by significant low-magnitude earthquakes and by historical records of moderate magnitude, such as the Mw = 6.1 1910 Adra Earthquake. The location, dimension and kinematics of the Adra Fault agree with the fault solution and magnitude of the 1910 Adra Earthquake, whose moment tensor analysis indicates normal-dextral motion. The fault seismic parameters indicate that the Adra Fault is a potential source of large magnitude (Mw ≤ 6.5) earthquakes, which represents an unreported seismic hazard for the neighbouring coastal areas.