2020
Autores
Mendes, VB; Barbosa, SM; Carinhas, D;
Publicação
JOURNAL OF APPLIED GEODESY
Abstract
In this study, we estimate vertical land motion for 35 stations primarily located along the coastline of Portugal and Spain, using GPS time series with at least eight years of observations. Based on this set of GPS stations, our results show that vertical land motion along the Iberian coastline is characterized, in general, by a low to moderate subsidence, ranging from -2.2 mm yr(-1) to 0.4 mm yr(-1), partially explained by the glacial isostatic adjustment geophysical signal. The estimates of vertical land motion are subsequently applied in the analysis of tide gauge records and compared with geocentric estimates of sea level change. Geocentric sea level for the Iberian Atlantic coast determined from satellite altimetry for the last three decades has a mean of 2.5 +/- 0.6 mm yr(-1), with a significant range, as seen for a subset of grid points located in the vicinity of tide gauge stations, which present trends varying from 1.5 mm yr(-1) to 3.2 mm yr(-1). Relative sea level determined from tide gauges for this region shows a high degree of spatial variability, that can be partially explained not only by the difference in length and quality of the time series, but also for possible undocumented datum shifts, turning some trends unreliable. In general, tide gauges corrected for vertical land motion produce smaller trends than satellite altimetry. Tide gauge trends for the last three decades not corrected for vertical land motion range from 0.3 mm yr(-1) to 5.0 mm yr(-1) with a mean of 2.6 +/- 1.4 mm yr(-1), similar to that obtained from satellite altimetry. When corrected for vertical land motion, we observe a reduction of the mean to E1.9 +/- 1.4 mm yr(-1). Actions to improve our knowledge of vertical land motion using space geodesy, such as establishing stations in co-location with tide gauges, will contribute to better evaluate sea level change and its impacts on coastal regions.
2020
Autores
Zafrir, H; Barbosa, S; Levintal, E; Weisbrod, N; Ben Horin, Y; Zalevsky, Z;
Publicação
FRONTIERS IN EARTH SCIENCE
Abstract
Long-term monitoring of Rn-222 and CO2 at a depth of several dozen meter at the SdeEliezer site, located within one of the Dead Sea Fault Zone segments in northern Israel, has led to the discovery of the clear phenomenon that both gases are affected by underground tectonic activity along the Dead Sea Fault Zone. It may relate to pre-seismic processes associated with the accumulation and relaxation of lithospheric stress and strain producing earthquakes. This approach assumes that meteorological influences on physico-chemical parameters are limited at depth since its strength diminishes with the increase of the overlay layer thickness. Hence, the monitoring of natural gases in deep boreholes above the water table enables to reduce the climatic-induced periodic contributions, and thus to identify the specific portion of the radon signals that could be related to regional tectonic pre-seismic activity. The plausible pre-seismic local movement of the two gases at depth is identified by the appearance of discrete, random, non-cyclical signals, wider in time duration than 20 h and clearly wider than the sum of the width of the periodic diurnal and semidiurnal signals driven by ambient meteorological parameters. These non-cyclical signals may precede, by one day or more, a forthcoming seismic event. Hence, it is plausible to conclude that monitoring of any other natural gas that is present at depth may show a similar broadening signal and may serve as a precursor too. The necessary technical conditions enabling to distinguish between anomalous signals of gases that may be induced locally by pre-seismic processes at depth, and the relatively low periodic signals that are still established at depth related to external climatic conditions, are presented in detail.
2020
Autores
Chen, X; Barbosa, S; Mäkelä, A; Paatero, J; Monteiro, C; Guimarães, D; Junninen, H; Petäjä, T; Kulmala, M;
Publicação
Abstract
2020
Autores
Rousseau, D; Barbosa, S; Bagniewski, W; Boers, N; Cook, E; Fohlmeister, J; Goswami, B; Marwan, N; Rasmussen, SO; Sime, L; Svensson, A;
Publicação
Abstract
2020
Autores
dos Santos, PL; Freigoun, MT; Martin, CA; Rivera, DE; Hekler, EB; Romano, RA; Perdicoulis, TPA;
Publicação
IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY
Abstract
System identification approaches have been used to design an experiment, generate data, and estimate dynamical system models for Just Walk, a behavioral intervention intended to increase physical activity in sedentary adults. The estimated models serve a number of important purposes, such as understanding the factors that influence behavior and as the basis for using control systems as decision algorithms in optimized interventions. A class of identification algorithms known as matchable-observable linear identification has been reformulated and adapted to estimate linear time-invariant models from data obtained from this intervention. The experimental design, estimation algorithms, and validation procedures are described, with the best models estimated from data corresponding to an individual intervention participant. The results provide insights into the individual and the intervention, which can be used to improve the design of future studies.
2020
Autores
Azevedo Perdicoúlis, T; Jank, G; Lopes dos Santos, P;
Publicação
Systems of Systems - Engineering, Modeling, Simulation and Analysis [Working Title]
Abstract
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