Morphologic description of the Punta Cola rock avalanche and associated minor rockslides caused by the 21 April 2007 Aysén earthquake (Patagonia, southern Chile) Descripción morfológica de la avalancha de rocas de Punta Cola y deslizamientos de rocas asociados causados por el terremoto de Aysén del 21 de abril de 2007 (Patagonia, sur de Chile)

The 21 April 2007 Aysén earthquake triggered hundreds of landslides in the epicentral area, including several large-volume rock avalanches that caused tsunamis in the Aysén fjord. This study is part of a larger project aiming to better understand the conditioning factors controlling size and distribution of earthquake-triggered landslides. The focus is set on the largest rockslide that occurred at Punta Cola. Using a high-resolution digital surface model created from terrestrial laser scanning, a detailed geomorphologic map of the rockslide scars and the rock avalanche deposits on land was made. This map permitted to establish the sequence of events: the failure of the rockslide main compartment led to a rock avalanche that crossed the valley and ran up on the opposite valley flank before turning downstream and impacting the fjord and creating a tsunami. Afterwards, another rockslide compartment failed and piled up 80 m thick deposits in the valley. Seven minor rockslides occurred in the Punta Cola valley after the main rock avalanche. The volumes of rockslides and associated deposits were estimated using the sloping local base level technique that allows computing the possible pre-rockslide topography and the bedrock-deposits interface. These volume computations give 22.4 Mm3 for the Punta Cola rockslide, which is significantly more than previous estimates (12 Mm3). The on-shore deposits of the main rock avalanche have a volume of 13.7 Mm3 and approximately 14.4 Mm3 are deposited in the fjord. This study highlights the additional information on rockslides and rock avalanches that can be obtained from high-resolution 3D data and mapping. El terremoto de Aysén del 21 de abril de 2007 generó cientos de remociones en masa en la zona epicentral, incluyendo varias avalanchas de roca de gran volumen que causaron tsunamis en el fiordo Aysén. Este estudio es parte de un proyecto orientado a una mejor comprensión de los factores que controlan el tama o y distribución de remociones en masa generadas por sismos. El estudio se centra en el deslizamiento de mayor tama o, ocurrido en el sector de Punta Cola. Mediante el uso de un modelo de terreno digital de alta resolución creado a partir de un escaneo láser terrestre, se preparó un mapa geomorfológico de las zonas de arranque y depósitos de la avalancha de roca, el cual permite establecer la secuencia de eventos: la falla de la sección mayor de deslizamiento derivó a una avalancha de roca que cruzó el valle trepando el flanco opuesto antes de girar hacia aguas abajo e impactar el fiordo generando un tsunami. Poster