A simple and general methodology to calibrate seismic instruments for debris flow quantification: application to Cotopaxi and Tungurahua volcanoes (Ecuador)     

Andrade  S. Daniel  Almeida  Stefanie  Saltos  Emilia  Pacheco  Daniel  Hernandez  Stephen  Acero  Wilson 《Landslides》2022,19(3):747-759

Debris flows are hazardous phenomena occurring at volcanoes, and monitoring them has proved as challenging as imperative in several cases. The use of seismic instruments to measure and study the physical properties of debris flows has witnessed significant progress in the last years, with the use of improved sensors, innovative methodologies and high-resolution analysis. However, the application of such studies to the practical task of providing early warnings remains limited by the significant amount of infrastructural and technological resources commonly required for their deployment. In Ecuador, debris flows at volcanoes are detected by means of seismic instruments which are usually part of broader monitoring networks, thus requiring calibration to provide quantitative information about the flows and feed early-warning systems. In the present work, a theoretical approach based on the Buckingham Π-theorem is used to determine an expression that linearly correlates the seismic signal produced by a transiting debris flow with its discharge rate, for instruments installed in different substrata and at variable distances from the drainage. The expression is experimentally tested with Acoustic Flow Monitors and Broad-band seismometers installed in the vicinity of drainages at Tungurahua and Cotopaxi volcanoes, where actual debris flows occurred in relation to eruptive activity. The experiments consist in comparing the measured peak amplitude values of the seismic signal envelopes with the estimated peak discharge rates of several events. The results confirm the validity of the theoretical expression with linear correlations observed between the seismic amplitudes and the discharge rates, thus defining calibration expressions that can be generally applied to varied environments and instruments. The seismic instruments calibrated through this methodology can provide instantaneous and reliable predictions of debris flow discharge rates within less than an order of magnitude and only requiring limited data processing and storage. Such level of prediction could help to improve early warning systems based on seismic instruments installed in locations where more developed instrumental arrays are unavailable or unpractical.

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Microclimatic variation of thermal comfort in a district of Lisbon (Telheiras) at night   总被引：1，自引：0，他引：1  

H. Andrade  M.-J. Alcoforado 《Theoretical and Applied Climatology》2008,92(3-4):225-237

Summary The microclimatic spatial variation of air temperature, wind speed, radiative fluxes and Physiological Equivalent Temperature (PET) was studied in Telheiras, a northern district of the city of Lisbon. The main goal was to assess how to improve outdoor thermal conditions based on research results. An empirical model was developed to estimate PET in Telheiras under different weather types; the model allows the continuous spatial representation of PET, using a Geographical Information System (GIS) and can be used in other areas of Lisbon. Although there is a small microclimatic variation in air temperature, the PET presents a much stronger variation, due to the influence of wind and radiative fluxes. Urban geometry, expressed by the Sky View Factor (SVF), is the main factor controlling the microclimatic diversity of the neighbourhood. The coolest conditions occur in open areas (centre of large courtyards and marginal areas) and the warmest in streets with low SVF that are sheltered from the wind. Authors’ address: H. Andrade and M.-J. Alcoforado, Centro de Estudos Geográficos, Universidade de Lisboa, Alameda da Universidade, 1600-214 Lisboa, Portugal  相似文献   

Continental and marine contributions to formation of mangrove sediments in an Eastern Amazonian mudplain: The case of the Marapanim Estuary     

Maria Do Perpetuo Socorro Progene Vilhena  Marcondes Lima Da Costa  José Francisco Berrêdo 《Journal of South American Earth Sciences》2010,29(2):427-438

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Primordial magnetic fields constrained from CMB anisotropies on dynamo cosmology     

L. C. Garcia de Andrade 《Astrophysics and Space Science》2010,330(2):347-351

Magneto-curvature stresses could deform magnetic field lines giving rise to back reaction and restoring magnetic stresses (Tsagas in Phys. Rev. Lett., 2001). Barrow and Tsagas (Phys. Rev. D, 2008) have shown that in Friedman universe the expansion slows down in its spatial section of negative Riemann curvature. Earlier, Chicone and Latushkin (Proc. Am. Math. Soc. 125(11):3391, 1995) proved that fast dynamos in compact 2D manifold implies negatively constant Riemannian curvature. Here one applies the Barrow-Tsagas ideas to cosmic dynamos of negative curvature. Fast dynamo, covariant stretching of Riemann slices of cosmic Lobachevsky plane is given. Inclusion of advection term on dynamo equations (Clarkson and Marklund in Mon. Not. R. Astron. Soc., 2005) is considered. In advection absence, slow dynamos are also obtained. It is shown the viscous and restoring forces on stretching particles decrease, as magnetic rates increase. From COBE data ( $\frac{{\delta}B}{B}\approx{10^{-5}}$ ), one is able to compute the stretching $\frac{{\delta}V^{y}}{V^{y}}=1.5\frac{{\delta}B}{B}\approx{1.5{\times}10^{-5}}$ . Zeldovich et al. have computed the maximum magnetic growth rate as γ _max ≈8.0×10^?1 t ^?1. From COBE data a lower growth rate as γ _COBE ≈6.0×10^?6 t ^?1, is well-within Zeldovich et al estimate. Instead of Harrison value $B\approx{t^{\frac{4}{3}}}$ one obtains a lower primordial field B≈10^?6 t which yields B≈10^?6 G at 1 s Big Bang time.  相似文献   

Metal fluxes to the sediments of the Moulay Bousselham lagoon,Morocco   总被引：2，自引：0，他引：2  

Asmae Mhamdi Alaoui  Mohamed Choura  Mohamed Maanan  Bendahhou Zourarah  Marc Robin  Maria Freitas Conceição  César Andrade  Mehdi Khalid  Christian Carruesco 《Environmental Earth Sciences》2010,61(2):275-286

The metal content in surface sediments (0–2 cm, 26 samples), in a sediment core (120, 1 cm slices), taken from Moulay Bousselham (Morocco) was investigated. Concentrations of Al, Fe, Mn, Pb, Zn, Cu, Ni, Cr, Cd, As, and Hg were evaluated in surface and cored sediments of Moulay Bousselham lagoon. Significantly high concentrations in μg g⁻¹ dw of Pb (31.7–6.2), Zn (758.9–167), Cu (310.7–22), Ni (96–10.5), Cr (113–18.9), Cd (0.84–0.02), As (1–0.1), and Hg (0.61–0.02) were found in sediment samples from Moulay Bousselham lagoon. Calculated enrichment factors [EF_Me = (Me/Al)_sample/(Me/Al)_background], using Al as a normalizer, and correlation matrices showed that metal pollution in Merja Zerga of Moulay Bousselham lagoon was the product of anthropogenic sources, while the metal content in Merja Kehla was of natural origins. The results suggest that a major change in the sedimentary regime of the lagoon, associated with internal trapping and re-distribution of heavy metal, has been occurring in the past few decades. The cause would appear to be the construction of a Nador Canal at the lagoon. Probable effects concentrations (PEC) were often exceeded for heavy metals in the lagoon sediments, especially for Zn, Cu, Ni, and Cr, and four stations, stations MZ-11, MZ-12, MZ-13, MZ-14, MZ-16, and MZ-17, had multiple metals at presumptively toxic levels. These comparisons suggest that sediment metal levels in the river are clearly high and probably pose an environmental risk at some stations. The levels of most of the metals were not greatly enriched, a consideration that is of the utmost importance when contamination issues are at stake. Metal concentrations found in Moulay Bousselham lagoon were comparable to aquatic systems classified as contaminated from other regions of the world.  相似文献   

    

Phaedon Kyriakidis  Andre G. Journel 《Mathematical Geology》2000,32(7):893

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Travelling ionospheric disturbance properties deduced from Super Dual Auroral Radar measurements     

J. W. MacDougall  D. A. Andre  G. J. Sofko  C.-S. Huang  A. V. Koustov 《Annales Geophysicae》2001,18(12):1550-1559

Based on modeling of the perturbations in power and elevation angle produced by travelling ionospheric disturbances (TIDs), and observed by the Super Dual Auroral Radar Network, procedures for determining the TID properties are suggested. These procedures are shown to produce reasonable agreement with those properties of the TIDs that can be measured from simultaneous ionosonde measurements. The modeling shows that measurements of angle-of-elevation perturbations by SuperDARN allows for better determination of the TID properties than using only the perturbations of power as is commonly done.On sabbatical from Department Electrical Engineering, University of Western Ontario, London, Ontario, Canada  相似文献   

Gold distribution in lateritic profiles in South America, Africa, and Australia: applications to geochemical exploration in tropical regions     

Marcondes Lima da Costa   《Journal of Geochemical Exploration》1993,47(1-3)

Gold, a principal ore commodity, is sought in third world countries, which are situated mainly in the tropics, where extensive lateritic terrains exist. The high value of gold on the international market and balance of payment problems cause gold to be especially important. Present intensive propecting for gold in the Third World countries are, for those reasons, in lateritic terrains. Laterites, formed during the Tertiary and the Recent in inner tropical morphoclimatic zones covered by dense rain forests, in places such as the Amazon region and West Africa, are presently undergoing strong weathering and erosion that truncates lateritic profiles. Consequently, the thick soils still forming today cover in different places, different parts of truncated profiles. Samples of thick soils taken from the surface down, may begin not at the original top of the laterite but somewhere along the profile. Inasmuch as elements in lateritic profiles are not homogeneously distributed, problems in interpretation can result. Gold distribution in non-truncated laterites tends to be sigmoidal in distribution. Two convexities (highest contents) can be distinguished: one in surficial iron crusts or equivalents, the other at the base of saprolite. The sigmoidal curve can be cut off, strongly modified, or concealed by tropical weathering. The intense weathering can diminish concentrations, i.e., elements can be dispersed. Geochemical exploration becomes difficult, because interpretations of the geochemical anomalies based on high concentrations becomes unreliable. If the amount of truncation of lateritic profiles can be assessed, weak or even negative anomalies can become as good or better than strong anomalies.  相似文献   

Hydrocarbon contamination in mussels from Guanabara Bay     

Azevedo LA  de Andrade Brüning IM  Moreira I 《Marine pollution bulletin》2004,49(11-12):1120-1122

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Beyond Modelling: Linking Models with GIS for Flood Risk Management     

Zerger  Andre  Wealands  Stephen 《Natural Hazards》2004,33(2):191-208

Spatially explicit hydrodynamic flood models can play animportant role in natural hazard risk reduction. A key element of these models that make them suitable for riskreduction is the ability to provide time-series inundation information about the onset, duration and passingof a hazard event. Such information can be critical for landuse planning, for mapping evacuation egress routes,and for locating suitable emergency shelters to name only a few risk treatments. This research contends that abarrier to effective risk reduction is providing disaster managers with access to model results in a structured andflexible framework that allows consequences of different hazard scenarios to be assessed and mapped. Toaddress these limitations, a framework has been developed that links a commercial relational databasemanagement system with a GIS-based decision support system. The framework utilises industry standard dataexchange protocols and results in efficient time-series hazard data management. A case study based in Cairns,in far-north coastal Australia is presented to illustrate how the system has been developed. Results show that theframework reduces data volumes significantly, while making pre-run modelled inundation results rapidly accessibleto disaster managers. Of note is the ability of the framework to present results in terms of risk to buildings,roads and other spatial features in urban regions, and to provide answers to relatively complex risk questions.  相似文献