Resumen de El alud sísmico de la playa : causas y efectos: El terremoto de Bailadores, 1670
Carlos Ferrer, Jaime Laffaille
The effects of the Bailadores Earthquake in 1610 were related by friar Pedro Simon, who described in detail a violent and gigantic mass movement: La Playa Seismic Avalanche. These chronicles and detailed field surveys permitted to obtain the following parameters for this Earthquake: Magnitude 7.2 (M(L)); Maximum Intensity XI (MSK); Depth 10 km; Seismogenic source on the Bocono Fault with epicenter 3 km southwest Bailadores. The Avalanche produced by this earthquake displaced between 14 x 106 m3 and 21 x 106 m3 of material from a previously slipped mass, which fell down as an entire block and then became desintegrated. This material was moved 2,5 km toward the valley, plugging the Mocoties river and generating a water reservoir with a capacity closed to 29 x 106 m3. Approximately three months later, this natural dam broke due to water pressure and a retrogressive process, generating a 'discharge wave' which was dispersed 7 km downriver. The lithological contrast and the characteristical morphology of this event facilitated the interpretation. In this work, a five phases diagram is discussed and a model is proposed, which considers the sudden (violent) fall of material with low humidity internal content, as well as, the confinement of the air and water under pressure, and the interaction between the particles. The considered model allows to explain the high mobility and the little deformation experienced by subsoil materials.
