An extreme wave event in eastern Yucatán,Mexico: Evidence of a palaeotsunami event during the Mayan times     

Javier Lario  Chris Spencer  Teresa Bardají  Ángel Marchante  Victor H. Garduño-monroy  Jorge Macias  Sergio Ortega 《Sedimentology》2020,67(3):1481-1504

The Yucatán Peninsula, Mexico, has typically been considered a tectonically stable region with little significant seismic activity. The region though, is one that is regularly affected by hurricanes. A detailed survey of ca 100 km of the eastern Yucatán and Cozumel coast identified the presence of ridges containing individual boulders measuring >1 m in length. The boulder ridges reach 5 m in height and their origin is associated with extreme wave event activity. Previously modelled tsunami waves from known seismically active zones in the region (Muertos Thrust Belt and South Caribbean Deformed Belt) are not of sufficient scale in the area of the Yucatán Peninsula to have produced the boulder ridges recorded in this study. The occurrence of hurricanes in this region is more common, but two of the most destructive (Hurricane Gilbert 1988 and Hurricane Wilma 2005) produced coastal waves too small to have created the ridges recorded here. In this paper, a new tsunami model with a source area located on the Motagua/Swan Island Fault System has been generated that indicates a tsunami event may have caused the extreme wave events that resulted in the deposition of the boulder ridges.  相似文献   

Analysis of the trends in precipitation and precipitation concentration in some climatological stations of Mexico from 1960 to 2010     

Núñez-González  Gerardo 《Natural Hazards》2020,104(2):1747-1761

Natural Hazards - Analysis of precipitation trends as well as the observed trends in precipitation concentration can be useful tools for the identification of natural hazards. This study aimed to...  相似文献   

Geomechanics of hazardous landslides   总被引：1，自引：1，他引：0  

POISEL Rainer BEDNARIK Martin HOLZER Rudolf LISCAK Pavel 《山地科学学报》2005,2(3):211-217

A catalogue of possible landslide initial failure mechanisms, taking into account the geological setting and the geometry of the slope, the joint structure, the habitus of the rock blocks, as well as the mechanical behaviour of the rocks and of the rock mass （deformation and strength parameters）, is presented. Its aim is to give geologists as well as engineers the opportunity to compare phenomena in the field and phenomena belonging to particular mechanisms and to find the mechanism occurring. The presented catalogue of initial landslide mechanisms only comprises the mechanisms having a clearly defined mechanical model that can be divided into empirical relations and into mechanical models, as well as an overview of run out models, which can be divided into empirical relations and into mechanical models.  相似文献   

Evaluating functional connectivity in a small agricultural catchment under contrasting flood events by using UAV     

Aleix Calsamiglia  Jorge Gago  Julián Garcia-Comendador  Josep Fortesa Bernat  Adolfo Calvo-Cases  Joan Estrany 《地球表面变化过程与地形》2020,45(4):800-815

Concentrated erosion, a major feature of land degradation, represents a serious problem for soil and water resources management and a threat to ecosystems. Understanding the internal mechanisms (de-)coupling sediment pathways can improve the management and resilience of catchments. In this study, concentrated erosion and deposition forms were mapped accurately through field and aerial unmanned aerial vehicle (UAV) campaigns, in order to assess the evolution of connectivity pathways over a series of three contrasted and consecutive flood events occurring between October 2016 and January 2017 (return period ranging from 0.5 to 25 years) in a small Mediterranean agricultural catchment (Can Revull, Mallorca, Spain; 1.4 km²). In addition, a morphometric index of connectivity (IC) was used to identify the potential trajectories of different concentrated erosion forms and deposition areas. IC predictions were calibrated by identifying the optimal critical thresholds, i.e. those most consistent with field observations after each of the events studied. The results found that the index performed well in predicting the occurrence and the length/area of the different type of landforms, giving kappa (κ) coefficients of variation ranging between 0.21 and 0.92 and linear correlations R² between 0.33 and 0.72. The type of landform affected the correspondence of IC predictions and field observations, with lower thresholds the greater the magnitude of their associated geomorphic processes. Rainfall magnitude proved to be a very important factor controlling the development of erosion and deposition landforms, with large differences in length/area between the contrasted events. The evolution of the observed trajectories revealed feedback dynamics between the structural and functional connectivity of the catchment, in which morphological changes determined the spatial distribution of the processes’ activity in the successive events and vice versa. © 2020 John Wiley & Sons, Ltd.  相似文献   

Optimum size and density of surface grid arrays for retrieving accurate shear-tensile fracturing of microearthquakes     

Yi Ren  Yongtao Gao  Shunchuan Wu  Václav Vavryčuk 《Geophysical Prospecting》2020,68(8):2347-2360

Surface arrays became an important tool for monitoring the induced seismicity in hydraulic fracturing experiments and for assessing the impact of fluid injection on the fracturing process of microearthquakes. The layout of sensors plays a key role in this task because it controls the accuracy of event locations and retrieved seismic moment tensors. We simulate various configurations of grid sensor arrays characterized by a different number of sensors, array span, sensor spacing, depth of sources and various shear/tensile source mechanisms of events. The moment tensor inversion is carried out using synthetically calculated P-wave amplitudes with added random noise. A bias in the solutions is evaluated by errors in the double-couple percentage of inverted moment tensors because the double-couple errors inform us about the sensitivity of the network to detect the shear/tensile fracturing mode of induced microearthquakes. The results show that the accuracy of the double-couple percentage is mostly controlled by the offset-to-depth ratio R defined as the ratio of half of the network size to the event depth. The optimum value of R is in the range of 0.75–1.5 irrespective of the type of the focal mechanism. If 121 (11 × 11) sensors are distributed in a regular grid and recorded data are characterized by a 10% random noise, the double-couple error is less than 6%. This error increases, if R is not optimum or if the number of sensors is reduced. However, even sparse arrays with 49 (7 × 7) or 16 (4 × 4) sensors can yield a reasonable accuracy, provided the surface grid arrays are designed to have an optimum size.  相似文献   

Using visibility analysis to improve point density and processing time of SfM-MVS techniques for 3D reconstruction of landforms     

Álvaro Gómez-Gutiérrez  Trent Biggs  Napoleon Gudino-Elizondo  Paz Errea  Esteban Alonso-González  Estela Nadal Romero  José Juan de Sanjosé Blasco 《地球表面变化过程与地形》2020,45(11):2524-2539

Image network geometry, including the number and orientation of images, impacts the error, coverage, and processing time of 3D terrain mapping performed using structure-from-motion and multiview-stereo (SfM-MVS). Few studies have quantified trade-offs in error and processing time or ways to optimize image acquisition in diverse topographic conditions. Here, we determine suitable camera locations for image acquisition by minimizing the occlusion produced by topography. Viewshed analysis is used to select the suitable images, which requires a preliminary digital elevation model (DEM), potential camera locations, and sensor parameters. One aerial and two ground-based image collections were used to analyse differences between SfM-MVS models produced using: (1) all available images (ALL); (2) images selected using conventional methods (CON); and (3) images selected using the viewshed analysis (VIEW). The resulting models were compared with benchmark point clouds acquired by a terrestrial laser scanner (TLS) and TLS-derived DEMs. The VIEW datasets produced denser point clouds (28–32% more points) and DEMs with up to 66% reduction in error compared with CON datasets due to reduction of gaps in the DEM. VIEW datasets reduced processing time by 37–76% compared with ALL, with no reduction in coverage or increase in error. DEMs produced with ALL and VIEW datasets had similar slope and roughness, while slight differences that may be locally important were observed for the CON dataset. The new method helps optimize SfM-MVS image collection strategies that significantly reduce the number of images required with minimal loss in coverage or accuracy over complex surfaces. © 2020 John Wiley & Sons, Ltd.  相似文献   

High-latitude dust deposition in snow on the glaciers of James Ross Island,Antarctica     

Jan Kavan  Daniel Nývlt  Kamil Láska  Zbyněk Engel  Michaela Kňažková 《地球表面变化过程与地形》2020,45(7):1569-1578

High-latitude dust (HLD) depositions on four glaciers of James Ross Island (the Ulu Peninsula) were analysed. The deposition rate on the selected glaciers varies from 11.8 to 64.0 g m⁻², which is one order of magnitude higher compared to the glaciers in Antarctica or elsewhere in the world. A strong negative relationship between the sediment amount and altitude of a sampling site was found. This is most likely caused by the higher availability of aeolian material in the atmospheric boundary layer. General southerly and south-westerly wind directions over the Ulu Peninsula – with exceptions based on local terrain configuration – help to explain the significantly lower level of sediment deposition on San Jose Glacier and the high level on Triangular Glacier. X-ray fluorescence (XRF) spectrophotometry was used to estimate the relative proportions of the main and trace (lithophile) elements in the sediment samples. Both the sediment amount and the XRF results are analysed in a depth profile at each locality and compared among the glaciers, suggesting long-range transport of fine mineral material from outside James Ross Island. The distribution of aeolian sediment among the glaciers corresponds well with the prevailing wind direction on the Ulu Peninsula. © 2020 John Wiley & Sons, Ltd.  相似文献   

Streamflow elasticity,in a context of climate change,in arid Andean watersheds of north-central Chile     

Cristián Barrera  Jorge Núñez Cobo  Maxime Souvignet  Jorge Oyarzún 《水文科学杂志》2020,65(10):1707-1719

ABSTRACT

Based on a future temperature increase of 0.5°C and precipitation decrease of 25%, the climate elasticity of streamflow to precipitation and temperature changes in 12 Andean watersheds of the Coquimbo Region, north-central Chile, was assessed. Also, the possible relationships between this elasticity and specific physiographic characteristics of the watersheds (area, average elevation, slope distribution, terrain roughness, slope orientation, vegetation cover) were studied. Climate elasticity of streamflow ranged between 0 and 2.8. Watersheds presenting higher elevations, with a fairly well-balanced distribution of slope exposure tend to exhibit lower elasticity, which could be explained by the contribution of snowfall to the hydrological regime, more significant in those watersheds. Results should be considered when downscaling climate model projections at the basin scale in mountain settings. Finally, uncertainties in the approach, given by factors such as streamflow seasonality, data availability and representativeness and watershed characteristics, and therefore the scope of the results, are discussed.  相似文献   

An iterative technique to delineate protection buffers for wetlands in regions subject to intensive groundwater pumping     

H.F. Aristizábal 《水文科学杂志》2019,64(8):885-899

Wetlands are vulnerable to groundwater extraction, which has proven detrimental to aquatic ecosystems around the planet. As wetlands rank among the world’s most endangered ecosystems, versatile strategies are required to protect them. This paper provides a modelling-based method to delineate protection buffers in wetlands subject to groundwater extraction. The technique is sufficiently flexible to cater to a wide variety of conditions, and simple enough to underpin management decisions on a daily basis. A numerical model is used to obtain a map of the critical rate of groundwater abstraction, based on the distance between wetlands and suitable discharge thresholds. The outcomes determine the allowed pumping rate at any point under steady and transient-state conditions. A new iteration is developed every time a new pumping allowance is made. This procedure is demonstrated by means of hypothetical scenarios, as well as by a case study application in the Valle del Cauca region, Colombia.  相似文献   

Spatial and seasonal patterns of flood change across Brazil   总被引：1，自引：1，他引：0  

D. Bartiko  D. Y. Oliveira  N. B. Bonumá 《水文科学杂志》2019,64(9):1071-1079

Brazil has some of the largest rivers in the world and has the second greatest flood loss potential among the emergent countries. Despite that, flood studies in this area are still scarce. In this paper, we used flood seasonality and trend analysis at the annual and seasonal scales in order to describe flood regimes and changes across the whole of Brazil in the period 1976–2015. We identified a strong seasonality of floods and a well-defined spatio-temporal pattern for flood occurrence. There are positive trends in the frequency and magnitude of floods in the North, South and parts of Southeast Brazil; and negative trends in the North-east and the remainder of Southeast Brazil. Trends in the magnitude (frequency) were predominant in the winter (summer). Overall, floods are becoming more frequent and intense in Brazilian regions characterized by wet conditions, and less frequent and intense in drier regions.  相似文献