Implications of geomorphological research for recent and prehistoric avalanches and related hazards at Huascaran,Peru

Detailed research of superficial deposits below the northern peak of Huascaran (Cordillera Blanca) provides new information on the limits of a paleo-avalanche originating from this mountain. Geomorphological mapping of the sediments identified glacial deposits, deposits from historical rock-debris avalanches and huge boulders from a paleo-avalanche. Schmidt Hammer rock-hardness tests were used to distinguish between the several generations of rock-debris avalanches, but largely failed to distinguish between the much older moraine and the paleo-avalanche sediments. Thus, only the field geomorphological mapping proved to be reliable for identifying the limits of the paleo-avalanche. The limits identified as granite boulders deposited over volcanic rocks were found to extend 30 m further up the opposite valley slope than previously had been mapped. This larger extent implies a greater volume and/or greater mobility for the prehistoric event.     

Implications of subsurface thermal–hydraulic–mechanical processes associated with glaciation on Shield flow system evolution and performance assessment

A deep geologic repository (DGR) situated on the Canadian Shield will be subject to long-term climate change that will markedly alter surface conditions as a result of glaciation and permafrost penetration. Systematic, two-dimensional and three-dimensional coupled thermal–hydraulic–mechanical finite-element simulations with varying degrees of coupling, including depth-dependent salinity (represented as a change in groundwater density) and temperature-dependent density and viscosity, were undertaken to address the implications of glaciation on groundwater flow system dynamics as it could affect DGR performance. The modelling domain consisted of a 1.6-km deep sub-regional scale (≈100 km²) fractured Shield flow system. Initial and transient thermal, hydraulic and mechanical boundary conditions were developed from two realizations of the University of Toronto Glacial Systems Model of the last Laurentide glaciation. Results indicate that during the glacial loading/unloading cycle, for this particular conceptual model, there is limited penetration of glacial meltwaters to depth and small residual anomalous hydraulic head. During glacial coverage, the mechanical factor of safety increases in the moderately fractured and sparsely fractured rock mass, but principal effective stress reorientation also occurs. Given the assumed nonglacial in situ state of stress and mechanical properties, the fracture zones were predicted to be less stable under glacial conditions.

Seismicity pattern of the Betic Cordillera(southern Spain) derived from the fractal properties of earthquakes and faults

Several studies on earthquake occurrence and associated faulting have demonstrated that both phenomena have a scale-invariant behavior which can be analyzed by means of a set of non-integer dimensions(Dq) describing their fractal properties and the calculation of multi-fractal spectra.It is the case that the behavior of these spectra is asymptotic at the ends of the variation interval of q,which is a real number that enters into the definition of the partition function of the dataset.The difference between the extreme values,called multi-fractal spectrum slope,is used to investigate the heterogeneity of the spatial distribution of earthquakes and fault systems.In this paper we focus on the Betic Cordillera,southeastern Spain,which is commonly considered the contact between the Eurasian and African plates and has an important seismic activity in the context of the Iberian Peninsula.Some of the most conspicuous Iberian earthquakes,such as the 1829 mb6.3 Torrevieja and the 1884 mb6.1 Alhama de Granada earthquakes occurred in this mountain range and both reached intensity X.The present work implies a new analysis based on the slope of multi-fractal spectra and referred to the historical seismicity of the region,specifically b-value(frequency distribution of earthquakes respect to magnitude),epicentral location,seismic energy and faulting.On this basis we propose a seismotectonic zonation that is contrasted with the stress state and the geodynamical evolution of the Betic Cordillera.     

Crustal velocity structure beneath the western Andes of Colombian using receiver-function inversion

Analysis of teleseismic records obtained in two broadband seismic stations of three components located on the Andean region of Colombia is presented in this work. The two stations are located at the Western Cordillera (WC), station BOL, and at the Central Cordillera (CC), station PBLA. The analysis of seismograms was performed by inversion of the receiver functions (RF) in order to obtain the crustal velocity structure beneath the receivers. The receiver function is a spectral ratio obtained from teleseismic earthquakes recorded by broadband seismic stations, which allows the calculation of the velocity structure beneath the receiver by removing source effects in the horizontal components of the seismic traces. Data stacking was performed in order to improve signal to noise ratio and then the data was inverted by using two optimization algorithms: a genetic algorithm (GA), and a simulated annealing algorithm (SA). The present work calculates the receiver functions using teleseismic earthquakes at epicentral distances (Δ) ranging between 30° and 90° and recorded at the two stations within the years 2007 and 2009.Delay times between P and PS waves converted at the Moho boundary were used to constrain the velocity structure. The receiver functions at the stations were generated from seismic events within a broad range of back azimuth. Data from gravity and magnetism were also used during the geophysical survey. The depth of the Moho boundary was found to be at 40 km in the WC beneath station BOL and at 43 km in the CC beneath station PBLA. The upper crust, with a thickness of 5 km, is characterized by a shear wave velocity of about 3.0 km s⁻¹; the shallower layers, at approximately 1.0 km, have shear wave velocities between 2.2 and 2.6 km s⁻¹, which corresponds to sediments overlying the upper crust. These observations support the hypothesis of a thickness of the crust at the root of the mountain range to be between 32 and 50 km. The calculated receiver functions were compared with artificial ones generated from the inversion of 48000 models of horizontal layers for each station using a GA and an SA that allowed a satisfactory coverage of all the sample space in order to avoid non-unique solutions. Beneath station BOL a moderate low-velocity zone (LVZ) was found, which was caused by accretionary processes of the ophiolite complex in the WC.     

Tectonic evolution of the Málaga Basin (Betic Cordillera). Regional implications

Abstract

During the Neogene (uppermost Aquitanian-Lower Burdigalian, Tortonian and Pliocene), three successive marine episodes took place in the present-day Malaga Basin. The first of these affected a wide area of the Belic Internal Zones and was brought to an abrupt conclusion by the westward displacement of these Zones, together with important horizontal movements associated with N70-100 direction strike-slip faults and the superposition of materials from the Campo de Gibraltar. The two other marine episodes were clearly controlled by vertical movements of NW-SE and NK-SW faults, caused by a clear E-W distension which, according to regional data, was associated with some compression in an approximately N-S direction. The area has also been affected, although to a lesser extent, by the uplift of the Betic Cordillera from the Upper Miocene to the present day.     

Intercomparison of the total storage deficit index (TSDI) over two Canadian Prairie catchments

Retrieval of the terrestrial moisture storage dataset from the Gravity Recovery and Climate Experiment (GRACE) satellite remote sensing system is possible when the catchment of interest is of large spatial scale. These dataset are of paramount importance for the estimation of the total storage deficit index (TSDI), which enables the characterization of a particular drought event from the perspective of the terrestrial moisture storage over that catchment. Incidentally, the GRACE gravity signal over the 13,000 km² Upper Assiniboine River Basin on the drought-prone Canadian Prairie is so poor therefore making the computation of the total storage deficit index for this basin infeasible. Consequently, the estimation of the terrestrial moisture storage from other reliable sources becomes imperative in order to enable the computation of the TSDI over this basin.This study explores the utilization of the Variable Infiltration Capacity (VIC) model, a physically based, spatially distributed hydrologic model to simulate the total moisture storage over the Upper Assiniboine River Basin which was then employed in the estimation of the TSDI over this basin for subsequent characterization of the recent Prairie-wide drought. Interestingly, the temporal patterns in the computed TSDI from the VIC model reveal a strong resemblance with the same drought characterization undertaken over the larger adjacent Saskatchewan River Basin, which was accomplished utilizing terrestrial moisture storage from the GRACE-based approach. Additionally, these independent techniques employed in the characterization of the last Prairie drought over the two adjacently situated basins resulted in similar drought severity classification from the standpoint of the total moisture storage deficits over these basins. This study has therefore shown that in the computation of the total storage deficit index over small-scale catchments during anomalous climatic conditions that propagate extreme dryness through the terrestrial hydrologic systems, simulations of the total water storage from a structurally sound model such as the VIC model could be resourceful for the computation of the monthly total storage deficit index if no constraint is placed on the availability of accurate meteorological forcing.     

Effect of shipping activity on warming trends in the Canadian Arctic

This paper presents a detailed account of the effect of shipping activity on the increasing trends of air temperatures in the Canadian Arctic region for the period of 1980–2018. Increasing trend of temperature has gained significant attention with respect to shipping activities and sea ice area in the Canadian Arctic. Temperature, sea ice area and shipping traffic datasets were investigated, and simple linear regression analyses were conducted to predict the rate of change(per decade) of the average temperature, considering winter(January) and summer(July) seasons. The results indicate that temperature generally increased over the studied region. Significant warming trend was observed during July, with an increase of up to 1℃, for the Canadian Arctic region. Such increasing trend of temperature was observed during July from the lower to higher latitudes. The increase in temperature during July is speculated to increase the melting of ice. Results also show a decline in sea ice area has a significant positive effect on the shipping traffic, and the numbers of marine vessel continue to increase in the region. The increase in temperature causes the breaking of sea ice due to shipping activities over northern Arctic Canada.     

A PRELIMINARY VALIDATION STUDY OF THE SEASONAL FORECAST OF CCCMA MODEL OVER CHINA

In this study we validate the raw ensemble mean forecasts of the CCCma's GCM2 modelagainst surface temperature and precipitation data obtained from 160 Chinese stations.It is foundthat despite the lagre biases,the model was able to produce seasonal anomalies that haveproperties that are reasonably close to those that are observed.This anomaly is the quantity ofinterest when forecasting seasonal climatic conditions.The root mean squared difference(RMSD)between the forecast and observed anomaly leads us to be modestly optimistic about the prospectsfor using dynamical models to forecast the interannual variability of some meteorological elements.The correlation analysis of the forecast and observation also supports the result given by theRMSD analysis and provides a tool for identify the forecast confidence level in various regions,     

HYDROLOGICAL FUNCTION OF A MOUNTAIN FEN AT LOW ELEVATION UNDER DRY CONDITIONS

Mountain fens are limited in their spatial extent but are vital ecosystems for biodiversity, habitat, and carbon and water cycling. Studies of fen hydrological function in northern regions indicate the timing and magnitude of runoff is variable, with atmospheric and environmental conditions playing key roles in runoff production. How the complex ecohydrological processes of mountain fens that govern water storage and release as well as peat accumulation will respond to a warmer and less snowy future climate is unclear. To provide insight, we studied the hydrological processes and function of Sibbald fen, located at the low end of the known elevation range in the Canadian Rocky Mountains, over a dry period. We added an evapotranspiration function to the Spence hydrological function method to better account for storage loss. When frozen in spring and early summer, the fen primarily transmits water. When thawed, the fen's hydrological function switches from water transmission to water release, leading to a summertime water table decline of nearly 1 m. Rainfall events larger than 5 mm can transiently switch fen hydrological function to storage, followed by contribution, depending on antecedent conditions. The evapotranspiration function was dominant only for a brief period in late June and early July when rainfall was low and the ground was still partially frozen, even though evapotranspiration accounted for the largest loss of storage from the system. This research highlights the mechanisms by which mountain peatlands supply baseflow during drought conditions, and the importance of frozen ground and rainfall in regulating their hydrological function. The study has important implications for the sustainability of low elevation mountain fens under climate change.