Impact Of Surface Processes Research Articles

The Impact of Large Erosional Events and Transient Normal Stress Changes on the Seismicity of Faults

AbstractThe long‐term erosion of steep landscapes is punctuated by dramatic erosional events that can remove significant amount of sediments within a timescale shorter than a seismic cycle. However, the role of such large erosional events on seismicity is poorly understood. We use QDYN, a quasi‐dynamic numerical model of earthquake cycles to investigate the effect of a large erosional event on seismicity. The progressive evacuation of landslide sediments is modeled by a transient normal stress decrease. We show that erosional events with a shorter duration compared with the duration of a seismic cycle can significantly increase the seismicity rate, even for small stress changes. Moreover, large erosional events with a shorter period compared with the earthquake nucleation timescale can change earthquake size distribution by triggering more small events. Those results suggest that large erosional events can significantly affect seismicity, illustrating in turn the short‐term impact of surface processes on tectonics.

The Impact of Surface Processes on the J–V Characteristics of Organic Solar Cells

In this article, the impact of surface recombination on the J–V characteristics of organic solar cells (OSC) was analyzed. The investigation was carried out using the drift-diffusion model in which the surface recombination of holes and electrons on both electrodes, anode and cathode, were taken into account through boundary conditions. In order to perceive the individual influence of the surface recombination, the equilibrium thermionic concentrations for holes and electrons on contact interfaces were neglected. As the reference point of our analysis, the measured In2O5Sn/ poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)/ poly(3-hexylthiophene-2,5-diyl): indene-C60 bisadduct /Al solar cell J–V curve was reproduced by our model. The surface recombination velocities (SRVs) for electrons and holes on both contacts were further varied and J–V curves were generated. For simplicity, it was assumed that diffusion current dominates at contacts. For the sake of systematization, three categories of SRV values were introduced, S —small for blocking contact, L —large for conductive contact, and M —medium for contact which is neither blocking nor conductive. The analysis was conducted for different ratios of electron and hole mobilities. It was established that in order to obtain regular J-shape J–V characteristics in OSCs, both contacts should be conductive, for both holes and electrons. This implies that the concept of contact selectivity in OSCs should be reexamined in terms of its physical description and relation to the SRVs values.

Hydrologic and microclimate characterizations of Thornton's Cave, West-Central Florida (USA)

A cave’s environment is controlled by a suite of factors unique to the environments in which they formed, including, but not limited to, regional geologic and climate settings. These factors collectively owe to wide variations in cave biology, geomorphology and overall speleogenesis. This report combines local climate, hydrologic, and CO2 data collected over the course of a two-year study at Thornton’s Cave, a partially-flooded cave in the West-Central Florida karst belt, to characterize its current environment and yield insight regarding how changes in regional climate and hydrology impact its past and future speleogenesis. Data loggers continuously monitoring cave and surface air temperatures, water levels and surface rainfall documented immediate responses in the cave to long- and short-term fluctuations in these parameters at the surface. Atmospheric CO2 in the cave and at the surface demonstrate seasonal trends, though the cave maintains higher concentrations and lower δ13C of CO2 than the surface, suggesting decomposition of organic matter, and to a lesser degree macroorganisms are contributing proportionally more CO2 to the cave. Collectively, these interpretations provide insight on the impact of surface processes on cave formation here, and suggest that a biotic model of speleogenesis using bacterially-sourced CO2 as a component of dissolution may be possible. Further, they can be used to further the understanding of the karstification in West-Central Florida and analogous karst regions.

Impact of surface processes on the growth of orogenic wedges: Insights from analog models and case studies

Interaction between surface processes and deep tectonic processes plays a key role in the structural evolution, kinematics and exhumation of rocks in orogenic wedges. The deformation patterns observed in analogue models applied to natural cases of present active or ancient mountain belts reflect several first order processes that result of these interactions. Internal strain partitioning due to mechanical behaviour of a thrust wedge has a strong impact on the vertical component of displacement of tectonic units that in return favour erosion in domains of important uplift. Such strain partitioning is first controlled by tectonic processes, but surface processes exert a strong feed back on wedge dynamics. Indeed, material transfer in thrust wedges not only depends on its internal dynamics, it is also influenced by climate controlled surface processes involving erosion and sedimentation. Effects of erosion are multiple: they allow long term localization of deformed domains, they favour important exhumation above areas of deep underplating and combined with sedimentation in the foreland they contribute to maintain the wedge in a critical state for long time periods. The simple models illustrate well how mountain belts structure, kinematics of tectonic units and exhumation are determined by these complex interactions.