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Caracterización geotécnica y geomecánica de la roca de falla de la falla activa de Alhama de Murcia

Publicated to:Geogaceta. (62): 7-10 - 2017-01-01 (62), DOI:

Authors: Rodríguez Soto, Pablo; Tsige, Meaza; Insua Arévalo, Juan M; Martínez Díaz, José Jesús; Rodríguez Escudero, Emilio; Jiménez Molina, David

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Abstract

We present the results of the mechanical parameters of natural clay rich fault-rock (fault gouge) from one of the most active faults in the Iberian Peninsula, Alhama de Murcia Fault (FAM). FAM shows segments partially formed by exhumed fine grained fault gouge (FG) with a 50-80 m thickness developed mainly in a brittle regime. It is composed mainly by mica (muscovite and paragonite) and quartz, the clay minerals are mainly illite with some caolinite. The FG shows a notable tectonic fabric characterized by the preferred orientation of plate-like minerals arranged in an anastomosing texture which controls the mechanical behavior of the fault. Undisturbed samples, taken from two fault observatory boreholes, have been used for laboratory tests. The result of the study shows that there is important variability in strength properties depending on the stress orientation in relation to fabric. The friction angle (φ) varies between very low values (16ᵒ-26ᵒ) for planes oriented favorably to the tectonic fabric to very high values (>50ᵒ) for planes unfavorably oriented. This high value of friction angle was also obtained in reconstructed and not oriented FG samples.

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