<![CDATA[El 27 de febrero de 2010 ocurrió un terremoto Mw=8,8 en el centro-sur de Chile que provocó alzamientos y subsidencias cosísmicas. El litoral de la Región del Biobío tuvo alzamiento cosísmico que generó el ensanchamiento de playas, la emersión de la plataforma de abrasión marina, desecamiento de ríos y humedales y muerte de biota intermareal. Por el contrario, el litoral entre las regiones de Valparaíso y O'Higgins experimentó subsidencia cosísmica que provocó una disminución del ancho de las playas, profundización de ríos, sumergencia de barras litorales e inundación de vegetación y su desecación. El tsunami arrastró arenas litorales y vegetación hacia el interior. Las arenas del litoral que quedaron sueltas, fueron redepositadas en 2010 y 2011 debido a las marejadas, ensanchando playas, reconstruyendo aquellas que habían disminuido por la subsidencia cosísmica así como las barras litorales.]]>

Among Mediterranean regions, the South-Central Zone of Chile (SCZCh) portrays a landscape where wildfires constantly and historically occur, many times damaging ecosystems, lives and livelihoods. Since 2010, this zone has entered a period of unprecedented drought that has contributed to wildfire rising trends. Wildfire occurrence and intensity in this zone can be associated with three main factors: climate and land cover as conditioning factors, and human activity as a triggering factor. This paper evaluates wildfire hazard for the SCZCh, based on environmental susceptibility to wildfire occurrence, using numerical regional climate and wildfire modeling for the 2002–2005 historical period and for the mid and late 21st-century under the RCP8.5 climate change scenario. Results indicate high skill in matching spatial patterns of fire spot occurrence and density in the historical period, as well as the ability to simulate seasonal behavior in wildfire environmental susceptibility, consistent with national historical statistics. The fire hazard in SCZCh will slightly increase in all seasons for both 2041–2050 and 2091–2100 periods, especially southward, with a long-term spatial homogenization of medium levels of hazard in Central Valley and Coastal Range, between 0 and 1000 m a.s.l. These results combined with the current homogeneous extensive exotic species plantations dominated by inflammable tree species in SCZCh might facilitate the occurrence of large wildfires under the projected 21st-century climate regime.

Wildfire risk is latent in Chilean metropolitan areas characterized by the strong presence of wildland–urban interfaces (WUIs). The Concepción metropolitan area (CMA) constitutes one of the most representative samples of that dynamic. The wildfire risk in the CMA was addressed by establishing a model of five categories (near zero, low, moderate, high, and very high) that represent discernible thresholds in fire occurrence, using geospatial data and satellite images describing anthropic–biophysical factors that trigger fires. Those were used to deliver a model of fire hazard using machine learning algorithms, including principal component analysis and Kohonen self-organizing maps in two experimental scenarios: only native forest and only forestry plantation. The model was validated using fire hotspots obtained from the forestry government organization. The results indicated that 12.3 % of the CMA's surface area has a high and very high risk of a forest fire, 29.4 % has a moderate risk, and 58.3 % has a low and very low risk. Lastly, the observed main drivers that have deepened this risk were discussed: first, the evident proximity between the increasing urban areas with exotic forestry plantations and, second, climate change that threatens triggering more severe and large wildfires because of human activities.

Los ambientes lacustres de montaña son altamente sensibles a modificaciones climáticas y antrópicas, el lago Laja en Chile central presenta modificaciones severas en los últimos años, impactando toda su cuenca. Mediante el análisis diacrónico de imágenes satelitales multitemporales Landsat (1986-2016), con clasificación supervisada (ENVI) y evaluados los cambios (Idrisi Andes), buscamos definir los principales factores que explicarían los cambios en este sistema lacustre, mediante el análisis de las coberturas de suelo, la distribución de los derechos de agua y los datos climáticos. Se observa una reducción de precipitaciones de 1500-2000 mm a 970-780 mm anuales y un aumento sostenido de la temperatura entre 1,3-1,6 °C, además se reconocieron fluctuaciones de la cobertura de superficie inundada del lago de 9.994,63 ha (1985) a 5.135,6 ha (2013), es decir, una reducción en el período de 48,6%. Entonces el retroceso sistemático del lago Laja no se explica por las variaciones climáticas analizadas, lo que nos lleva a inferir que el causante externo principal de este proceso es la acción antrópica, expresada en la presión y competencia por el uso del recurso hídrico entre actores con desiguales relaciones de poder: centrales hidroeléctricas, pequeños-medianos agricultores, habitantes del sector y empresarios del turismo.

The Tirúa-Mocha Island area (38.2°-38.4° S) in southern Chile has been affected by two megaearthquakes in only 50 years: the 1960 Mw=9.5 Valdivia earthquake and 2010 Mw=8.8 Maule earthquake. We studied in the field the vertical ground movements occurred during the interseismic period between both earthquakes and the coseismic period of 2010 Maule earthquake and 2011 Mw=7.1 Araucanía earthquake. During the 1960 earthquake, vertical coseismic ground movements are typical of subduction related earthquakes with Mocha Island, located close to the trench, experienced bigger ground uplift (150 cm) than that occurred in Tirúa (-20 cm), place located in the continental margin at the latitude of Mocha Island. Then during the 1960-2010 interseismic period, the 1960 coseismic uplift remained at Mocha Island unlike the normal interseismic subsidence that occurred northward at Arauco Peninsula and Santa María Island. Also Tirúa experienced the biggest interseismic uplift (180 cm) in all the area affected later by 2010 Maule earthquake. Then during the 2010 Mw=8.8 Maule earthquake an anomalous vertical coseismic ground uplift occurred in the study area, opposite to that of 1960 since Mocha Island experienced lower (25 cm) ground uplift than Tirúa (90 cm). Subsequently, during the Araucanía 2011 earthquake a ground uplift in Mocha Island (50 cm) and subsidence at Tirúa (20 cm) occurred. These unexpected vertical ground movements can be explained by the existence of an upper plate splay fault located below the sea bottom between Tirúa and Mocha Island: the Tirúa-Mocha splay fault. Considering the last seismic cycle, the activity of this fault would have started after the 1960 Valdivia earthquake. During 2010 Maule earthquake, the main slip occurred at Tirúa Mocha splay fault. Finally during 2011 Araucanía earthquake, the slip occurred mainly at the updip of Wadati-Benioff plane with probable normal activity of Tirúa-Mocha splay fault. Simple elastic dislocation models considering the Wadati-Benioff plane and the Tirúa-Mocha splay fault activity, can account for all the vertical ground movements observed during 1960 earthquake, the 1960-2010 interseismic period, the 2010 Maule earthquake and the 2011 Araucanía earthquake.