The 2010 Mw=8.8 Maule earthquake, which occurred in the subduction contact between the Nazca and the South American tectonic plates off the coast of Chile, represents an important opportunity to improve understanding of the distribution and controls for the generation of landslides triggered by large megathrust earthquakes in subduction zones. This paper provides the analysis of the comprehensive landslide inventory for the Maule earthquake between 32.5° S and 38.5° S°. In total 1226 landslides were mapped over a total area of c.120,500 km 2 , dominantly disrupted slides. The total landslide volume is c. 10.6 Mm 3. The events are unevenly distributed in the study area, the majority of landslides located in the Principal Andean Cordillera and a very constrained region near the coast on the Arauco Peninsula, forming landslide clusters. Statistical analysis of our database suggests that relief and lithology are the main geological factors controlling coseismic landslides, while the seismic factor with higher correlation with landslide occurrence is the ratio between peak horizontal and peak vertical ground accelerations. The results and comparison with other seismic events elsewhere suggest that the number of landslides generated by megathrust earthquakes is lower than events triggered by shallow crustal earthquakes by at least one or two orders of magnitude, which is very important to consider in future seismic landslide hazard analysis.

On the 21st of April 2007, the Aysén Fjord earthquake (Mw 6.2) in southern Chile (45.3°S, 73.0°W) triggered hundreds of landslides in the epicentral area along the fjord coast and surroundings. Some of these landslides induced large tsunami waves within the fjord causing fatalities and damaging several salmon farms, the most important economic activity of the area. The landslides included rock slides and avalanches, rock falls, shallow soil and soil-rock slides, and debris flows. The earthquake was the climax of a seismic swarm that began 3 months earlier. The seismicity is associated with tectonic activity along the Liquiñe-Ofqui fault zone (LOFZ), a major structural feature of the region. The earthquake-induced landslides were mapped and classified from field observations and remote sensing analysis. The landslide areas and epicentral distances are within the expected range for the earthquake magnitude according to worldwide data, while the position of landslides on the slopes strongly suggests topographic amplification effects in triggering the failures. The location of the landslides is also clearly related to some of the main fault branches of the LOFZ. The seismic event has configured a new situation of seismic and landslide hazard in the Aysén region and along the LOFZ, where the presence of towns and economic infrastructure along the coasts of several fjords constitutes a potential risk that was not considered before this seismic event.

The April 21, 2007 shallow crustal earthquake (Mw 6.2) in the Aisén Fjord area triggered hundreds of landslides around the epicentral zone. Among those, several rock slope failures such as rock slides, rock falls and rock avalanches were induced on the steep fjord slopes. The violent impact of the disrupted rock masses into the fjord generated local tsunamis that caused ten fatalities and extensive damage to salmon farms located along the fjord shores. Field observations suggested that geotechnical and geomorphological factors controlled the landslide locations and failure modes, associated with the presence of faults and topographic relief, respectively. This event is an example of a geological hazard that has not been previously addressed in the Chilean Patagonian fjordland, revealing the need for identifying and understanding these geological phenomena in future hazard assessments in the region.

We address the question of whether all large‐magnitude earthquakes produce an erosion peak in the subaerial components of fluvial catchments. We evaluate the sediment flux response to the Maule earthquake in the Chilean Andes (Mw 8.8) using daily suspended sediment records from 31 river gauges. The catchments cover drainage areas of 350 to around 10,000 km2, including a wide range of topographic slopes and vegetation cover of the Andean western flank. We compare the 3‐ to 8‐year postseismic record of sediment flux to each of the following preseismic periods: (1) all preseismic data, (2) a 3‐year period prior to the seismic event, and (3) the driest preseismic periods, as drought conditions prevailed in the postseismic period. Following the earthquake, no increases in suspended sediment flux were observed for moderate to high percentiles of the streamflow distribution (mean, median, and ≥75th percentile). However, more than half of the examined stations showed increased sediment flux during baseflow. By using a Random Forest approach, we evaluate the contributions of seismic intensities, peak ground accelerations, co‐seismic landslides, hydroclimatic conditions, topography, lithology, and land cover to explain the observed changes in suspended sediment concentration and fluxes. We find that the best predictors are hillslope gradient, low‐vegetation cover, and changes in streamflow discharge. This finding suggests a combined first‐order control of topography, land cover, and hydrology on the catchment‐wide erosion response. We infer a reduced sediment connectivity due to the postseismic drought, which increased the residence time of sediment detached and remobilized following the Maule earthquake.

ABSTRACT. The April 21, 2007 shallow crustal earthquake (Mw 6.2) in the Aisén Fjord area triggered hundreds of landslides around the epicentral zone. Among those, several rock slope failures such as rock slides, rock falls and rock avalanches were induced on the steep fjord slopes. The violent impact of the disrupted rock masses into the fjord generated local tsunamis that caused ten fatalities and extensive damage to salmon farms located along the fjord shores. Field observations suggested that geotechnical and geomorphological factors controlled the landslide locations and failure modes, associated with the presence of faults and topographic relief, respectively. This event is an example of a geological hazard that has not been previously addressed in the Chilean Patagonian fjordland, revealing the need for identifying and understanding these geological phenomena in future hazard assessments in the region. RESUMEN. Inestabilidades de laderas de roca generadoras de tsunami durante el terremoto de Aisén del 21 de abril de 2007, sur de Chile (45.5º S).El 21 de abril de 2007 un terremoto superfi cial cortical (Mw 6,2) en el área del Fiordo Aisén desencadenó cientos de remociones en masa en la zona epicentral. Entre éstas, se generaron varias inestabilidades en laderas rocosas escarpadas, tales como deslizamientos, caídas y avalanchas de rocas. El violento impacto de las masas disgregadas de roca en las aguas del fiordo generó tsunamis locales, que causaron diez víctimas fatales y un importante daño en granjas salmoneras ubicadas a lo largo de las costas del fi ordo. Observaciones de terreno sugieren controles geotécnicos y geomorfológicos en la ubicación y modos de falla de las remociones en masa, asociados a la presencia de fallas y relieve abrupto, respectivamente. Este evento es un ejemplo de un tipo de peligro geológico que no ha sido previamente detectado ni abordado en los fiordos de la Patagonia Chilena, revelando la necesidad de identifi car y comprender estos fenómenos geológicos en futuras evaluaciones de peligro en la región.