Could the Granada fault produce a catastrophic earthquake?



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Azañón, J.M. and García Mayordomo, Julián and Insúa Arévalo, Juan Miguel and Rodríguez Peces, Martín Jesús (2009) Could the Granada fault produce a catastrophic earthquake? In 8th International Workshop on Seismic Microzoning and Risk Reduction, 15-18 de marzo de 2009, Aguadulce (Almería).

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The City of Granada is placed at the margin of a flat area known as the Granada Basin (Betic Cordillera, SE Spain) surrounded by mountains. The seismic activity in the
Granada Basin is high, with a large number of earthquakes, all of them of moderate to low magnitude (Mb≤5.5). Historically, earthquakes in this area have produced important material damage and human casualties; however, it is hard to evaluate their magnitude. Seismicity has its origin mostly at depths between 5 and 17 km and the focal
mechanisms indicate a present stress field dominated by a tensional tensor with an associated NE-SW extensional axis. The sedimentary cover of the Granada Basin is mostly coeval with the activity of faults that bound the basin, which have controlled the stratigraphic architecture. These faults are normal, mostly with a NW-SE orientation,
and dipping towards the SW. Basinwards migration of the extensional front has exhumed the footwalls of older faults, uplifting the previous Tortonian sedimentary
cover, which presently outcrops as emerged ranges at the margins of the basin. This work presents preliminary results of a paleoseismic study of the Granada Fault, an
NW-SE active normal fault that produces a Plio-Quaternary throw of 300 m. According to these data, slip rate has been estimated in 0.38 mm/y (Sanz de Galdeano et al.,
2003). Several palaeosoils, Pleistocene in age, have been affected by this fault. Three different events can be recognized from the accumulative throw. The vertical slip per event ranges from 5 to 7 cm. Following the empirical relationship between moment magnitude and average displacement proposed by Wells and Coppersmith (1994), a
magnitude between 5.9 and 6.0 can be preliminary assessed for these events. The palaeosoils were sampled and dated using the Thermoluminiscence method to constrain
these estimates.

Item Type:Conference or Workshop Item (Paper)
Uncontrolled Keywords:Paleoseismicity, Slip ranges, Seismic hazard, Central Betics
Subjects:Sciences > Geology
Sciences > Geology > Seismology
Sciences > Geology > Geodynamics
ID Code:20811
Deposited On:16 Apr 2013 10:21
Last Modified:17 Apr 2015 11:45

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