Field Survey of the 27 February 2010 Chile Tsunami

On 27 February 2010, a magnitude M _w?=?8.8 earthquake occurred off the coast of Chile??s Maule region causing substantial damage and loss of life. Ancestral tsunami knowledge from the 1960 event combined with education and evacuation exercises prompted most coastal residents to spontaneously evacuate after the earthquake. Many of the tsunami victims were tourists in coastal campgrounds. The international tsunami survey team (ITST) was deployed within days of the event and surveyed 800?km of coastline from Quintero to Mehuín and the Pacific Islands of Santa María, Mocha, Juan Fernández Archipelago, and Rapa Nui (Easter). The collected survey data include more than 400 tsunami flow depth, runup and coastal uplift measurements. The tsunami peaked with a localized runup of 29?m on a coastal bluff at Constitución. The observed runup distributions exhibit significant variations on local and regional scales. Observations from the 2010 and 1960 Chile tsunamis are compared.     

Identifying advantages and drawbacks of two hydrological models based on a sensitivity analysis: a study in two Chilean watersheds

ABSTRACT

Hydrological modelling has undergone constant growth with the increase in information processing capabilities. Hydrological models have traditionally been used to study the effects of climate change on management and land-use changes and for water resources planning, among other purposes. The aim of this study was to determine and analyse the advantages of the HBV and HYMOD models, which are commonly used in hydrology on daily and monthly time scales. A regional sensitivity analysis was used to compare the processes that take on greater importance at different time scales in the two models. As a result, it was found that quick precipitation–runoff processes prove to be better represented in the HBV model, while slow, time-aggregated processes are better represented by the HYMOD model. This study confirms that both models are adequate for rain-dominated basins, such as those of the study area. Additionally, the HBV model proved to be more robust in comparison to HYMOD.     

Abrupt vegetation changes during the last glacial to Holocene transition in mid‐latitude South America

A pollen record from the Huelmo site (ca. 41°30′S) shows that vegetation and climate changed at millennial time‐scales during the last glacial to Holocene transition in the mid‐latitude region of western South America. The record shows that a Nothofagus parkland dominated the landscape between 16 400 and 14 600 ¹⁴C yr BP, along with Magellanic Moorland and cupressaceous conifers. Evergreen North Patagonian rainforest taxa expanded in pulses at 14 200 and 13 000 ¹⁴C yr BP, following a prominent rise in Nothofagus at 14 600 ¹⁴C yr BP. Highly diverse, closed canopy rainforests dominated the lowlands between 13 000 and 12 500 ¹⁴C yr BP, followed by the expansion of cold‐resistant podocarps and Nothofagus at ca. 12 500 and 11 500 ¹⁴C yr BP. Local disturbance by fire favoured the expansion of shade‐intolerant opportunistic taxa between 10 900 and 10 200 ¹⁴C yr BP. Subsequent warming pulses at 10 200 and 9100 ¹⁴C yr BP led to the expansion of thermophilous, summer‐drought resistant Valdivian rainforest trees until 6900 ¹⁴C yr BP. Our results suggest that cold and hyperhumid conditions characterised the final phase of the Last Glacial Maximum (LGM), between 16 400 and 14 600 ¹⁴C yr BP. The last ice age Termination commenced with a prominent warming event that led to a rapid expansion of North Patagonian trees and the abrupt withdrawal of Andean ice lobes from their LGM positon at ca. 147 000 ¹⁴C yr BP. Hyperhumid conditions prevailed between 16 400 and 13 000 ¹⁴C yr BP, what we term the ‘extreme glacial mode’ of westerly activity. This condition was brought about by a northward shift and/or intensification of the southern westerlies. The warmest/driest conditions of the last glacial–interglacial transition occurred between 9100 and 6900 ¹⁴C yr BP. During this period, the westerlies shifted to an ‘extreme interglacial mode’ of activity, via a poleward migration of stormtracks. Our results indicate that a highly variable climatic interval lasting 5500 ¹⁴C years separate the opposite extremes of vegetation and climate during the last glacial‐interglacial cycle, i.e. the end of the LGM and the onset of the early Holocene warm and dry period. Copyright © 2003 John Wiley & Sons, Ltd.     

Colour Hue and Texture Evaluation for 3D Symbolization of Indoor Environments Using RGB-D Data

In this work an evaluation procedure of the use of colour hue and texture for 3D symbolization of indoor environments using RGB-D data is presented. The main characteristics of the proposed method involve RGB-D cameras to collect colour and depth data and the evaluation of the visual variables colour hue and texture combined with visual aspects such as lighting and camera configuration for the symbolization of 3D indoor environments. High quality coloured point clouds of indoor environments are obtained with the Kinect sensor and then registered and processed in order to create 3D models. These sets of point clouds can be detected, recognized and classified under one of the three following main categories: ceiling, wall or floor. After classification is done, the resulting point clouds are properly treated as 3D triangular meshes in the MeshLab software. These meshes are then filtered to form complete surfaces which are then refined before being considered for visual variable application. We evaluated the proposed method on several indoor environments to show that it efficiently combines the colour and depth data obtained from RGB-D cameras with different parameters defined for the visual variables colour hue and texture for 3D symbolization of indoor environments.     

Changing fire regimes in the temperate rainforest region of southern Chile over the last 16,000 yr

A high-resolution macroscopic charcoal record from Lago Melli (42°46′S, 73°33′W) documents the occurrence of forest fires in the lowlands of Isla Grande de Chiloé, southern Chile, over the last 16,000 yr. Our data suggest that fire activity in this region was largely modulated by the position/intensity of the southern westerlies at multi-millennial time scales. Fire activity was infrequent or absent between 16,000-11,000 and 8500-7000 cal yr BP and was maximal between ∼ 11,000-8500 and 3000-0 cal yr BP. A mosaic of Valdivian/North Patagonian rainforest species started at ∼ 6000 cal yr BP, along with a moderate increase in fire activity which intensified subsequently at 3000 cal yr BP. The modern transition between these forest communities and the occurrence of fires are largely controlled by summer moisture stress and variability, suggesting the onset of high-frequency variability in summer precipitation regimes starting at ∼ 5500 cal yr BP. Because negative anomalies in summer precipitation in this region are teleconnected with modern El Niño events, we propose that the onset of El Niño-like variability at ∼ 5700-6200 cal yr BP led to a reshuffling of rainforest communities in the lowlands of Isla Grande de Chiloé and an increase in fire activity.     

Preference for Grassland Heterogeneity: Implications for Biodiversity in the Great Plains

The Great Plains of the United States is a grassland region managed primarily for homogeneity associated with production agriculture. The resulting decline of obligate fauna makes enhancing biodiversity an increasingly important ecological goal. A survey was administered to land managers and the general population in ranching regions of Nebraska, Kansas, Oklahoma, and the Texas Panhandle. This research explores the preferred characteristics of privately owned grasslands among ranchers and the general population for vegetation structure and biodiversity. Results indicate a knowledge gap between biodiversity and the vegetation heterogeneity required to support it. Preference for grassland structure is seen as a sociocultural driver of decisions on management practices that constrain adoption of heterogeneity management. Conserving biodiversity and enhancing ecosystem services provided by heterogeneous grasslands can be accomplished by demonstrating that conservation advantages of heterogeneity and production agriculture are compatible.     

Gravitational deformation and inherited structural control on slope morphology in the subduction zone of north‐central Chile (ca. 29–33°S)

Subduction zones provide direct insight into plate boundary deformation and by studying these areas we better understand tectonic processes and variability over time. We studied the structure of the offshore subduction zone system of the Pampean flat‐slab segment (ca. 29–33°S) of the Chilean margin using seismic and bathymetric constraints. Here, we related and analysed the structural styles of the offshore and onshore western fore‐arc. Overlying the acoustic top of the continental basement, two syn‐extensional seismic sequences were recognised and correlated with onshore geological units and the Valparaíso Forearc Basin seismic sequences: (SII) Pliocene‐Pleistocene and (SI) Miocene‐Pliocene (Late Cretaceous (?) to Miocene‐Pliocene) syn‐extensional sequences. These sequences are separated by an unconformity (i.e. Valparaíso Unconformity). Seismic reflection data reveal that the eastward dipping extensional system (EI) recognised at the upper slope can be extended to the middle slope and controlled the accumulation of the older seismic package (SI). The westward dipping extensional system (EII) is essentially restricted to the middle slope. Here, EII cuts the eastward dipping extensional system (EI), preferentially parallel to the inclination of the older sequences (SI), and controlled a series of middle slope basins which are filled by the Pliocene‐Pleistocene seismic sequence (SII). At the upper slope and in the western Coastal Cordillera, the SII sequence is controlled by eastward dipping faults (EII) which are the local reactivation of older extensional faults (EI). The tectonic boundary between the middle (eastern outermost forearc block) and upper continental slope (western coastal block) is a prominent system of trenchward dipping normal fault scarps (ca. 1 km offset) that resemble a major trenchward dipping extensional fault system. This prominent structural feature can be readily detected along the Chilean erosive margin as well as the two extensional sets (EI and EII). Evidence of slumping, thrusting, reactivated faults and mass transport deposits, were recognised in the slope domain and locally restricted to some eastern dipping faults. These features could be related to gravitational effects or slope deformation due to coseismic deformation. The regional inclination of the pre‐Pliocene sequences favoured the gravitational collapse of the outermost forearc block. We propose that the structural configuration of the study area is dominantly controlled by tectonic erosion as well as the uplift of the Coastal Cordillera, which is partially controlled by pre‐Pliocene architecture.     

Shallow-level differentiation of phonolitic lavas from Sumaco Volcano,Ecuador

Sumaco Volcano is located in the rear-arc of Ecuador and produces phonolitic alkaline lavas hosting a unique assemblage of minerals including haüyne and titanaugite. The most mafic lavas are picrobasalts that contain titanaugite as the primary mineral phase; the most evolved tephri-phonolite lavas contain titanaugite?+?anorthoclase?+?haüyne. Titanaugite forms at middle to deep crustal pressures, whereas haüyne is only stable at shallow depths in highly oxidizing conditions. The Sumaco mineral assemblages and geochemistry indicate that fractionation of the titanaugite- and haüyne-bearing assemblage took place over a range of pressures from 5 to 25 kbar (14–75 km), with at least 50% of differentiation taking place at shallow crustal levels. Minerals record multiple cycles of recharge and mixing accompanied by an increase in fO₂ and sulfur concentration during differentiation. Mantle-like Sr and Nd isotope values (⁸⁷Sr/⁸⁶Sr = 0.70406–0.70423; ¹⁴³Nd/¹⁴⁴Nd = 0.512880–0.512913) indicate minimal crustal assimilation. Sumaco’s unique geochemical composition is not observed in the nearby volcanoes Antisana, Pan de Azucar or El Reventador suggesting that its unique magma source is confined to this volcano. The high temperature and sulfate-saturated conditions at shallow depths suggest that magma ascends rapidly to a shallow reservoir where the majority of crystallization and recharge takes place prior to eruption. An important conclusion of this research is that Sumaco does not represent typical rear-arc subduction processes, and caution should be used when using Sumaco as an end-member to evaluate across-arc processes in the Northern Volcanic Zone.