A magmatic source for fumaroles and diffuse degassing from the summit crater of Teide Volcano (Tenerife, Canary Islands): a geochemical evidence for the 2004–2005 seismic–volcanic crisis     

G. Melián  F. Tassi  N. Pérez  P. Hernández  F. Sortino  O. Vaselli  E. Padrón  D. Nolasco  J. Barrancos  G. Padilla  F. Rodríguez  S. Dionis  D. Calvo  K. Notsu  H. Sumino 《Bulletin of Volcanology》2012,74(6):1465-1483

The present work reports the results of 15 studies of diffuse CO₂ degassing performed at Teide Volcano crater (Canary Island, Spain) and the chemical and isotopic compositions of fluids discharged from a fumarolic field located at the top of the volcano as measured between 1991 and 2010. A higher contribution of magmatic gases accompanied by enhanced total diffuse CO₂ emissions were observed in relation with a seismic crisis that occurred in Tenerife Island between 2001 and 2005, with the main peak of seismic activity between April and June 2004. A significant pulse in total diffuse CO₂ emission was observed at the crater of Teide (up to 26.3?t day^?1) in 2001. In December 2003, the chemical composition of the Teide fumarole changed significantly, including the appearance of SO₂, an increase in the HCl and CO concentrations and in the C₂H₆/C₂H₄ and C₃H₈/C₃H₆ ratios, and a decrease in the H₂S, CH₄, and C₆H₆ concentrations and in the gas/steam ratio. A few months after a drastic decrease in seismic activity, the SO₂, HCl, and CO concentrations and the C₂H₆/C₂H₄ and C₃H₈/C₃H₆ ratios strongly decreased, whereas the CH₄ and C₆H₆ concentrations and the gas/steam ratios increased. According to the trends shown by both the geochemical parameters and the seismic signals late in the observation period, the risk of a rejuvenation of volcanic activity at Teide is considered to be low. The associated temporal changes in seismic activity and magmatic degassing indicate that geophysical and fluid geochemistry signals in this system are related. Future monitoring programs aimed at mitigating volcanic hazard on Tenerife Island should involve coupled geophysical and geochemical studies.  相似文献   

The different response of apparently identical structures: a far-field lesson from the Mirandola 20th May 2012 earthquake     

Silvia Castellaro  Luis Alberto Padrón  Francesco Mulargia 《Bulletin of Earthquake Engineering》2014,12(5):2481-2493

Twin structures, that is structures very similar in terms of geometry, materials, mass distribution etc., founded on the same soil and set at very close distance, are rationally expected to have an identical response to earthquakes. When this does not occur, a role is usually played by factors like the interaction with the surrounding structures or by other anomalies hidden behind the apparent similarity. We present the case of two apparently twin towers that showed a very different response to the 2012 Mirandola (Italy) earthquake ground shaking: one remained perfectly intact while the other had a wide set of fractures on secondary walls. This resulted to be the effect of several contributing factors: the stiffness of the two structures, experimentally measured, provided unexpected differences. This reflected into different modal frequencies for the two towers, with the first and second modes of the damaged tower coincident or very close to the soil resonance. The final result was a coupled soil-structure resonance, implying a much higher displacement of one tower compared to the other, under the same input motion. In Italy, insurance against earthquake damage will probably become compulsory in the near future. This case suggests that the specific soil-structure and structure-structure interaction will have to be carefully evaluated since they can critically affect even apparently identical structures.  相似文献   

Anomalous Diffuse CO2 Emissions at the Masaya Volcano (Nicaragua) Related to Seismic-Volcanic Unrest     

Germán D. Padilla  Pedro A. Hernández  Nemesio M. Pérez  Ernesto Pereda  Eleazar Padrón  Gladys Melián  José Barrancos  Fátima Rodríguez  Samara Dionis  David Calvo  Martha Herrera  Wilfried Strauch  Angélica Muñoz 《Pure and Applied Geophysics》2014,171(8):1791-1804

Anomalous changes in the diffuse emission of carbon dioxide within the Masaya caldera have been observed before two seismic events that occurred at 10 and 30 km from the observation site. Their epicenters are located, respectively, south of Managua in Las Colinas (4.3 magnitude) and the Xiloa caldera (3.6 magnitude), in 2002 and 2003, recorded by the geochemical station located at El Comalito, Masaya volcano (Nicaragua). Anomalous increases were observed, which occurred around 50 and 8 days before the main seismic event that took place in Las Colinas, and 4 days before the seismic swarm at the Xiloa caldera, with a maximum CO₂ efflux of 9.3 and 10.7 kg m^?2 day^?1, respectively. The anomalous CO₂ efflux increases remained after filtering with multiple regression analysis was applied to the CO₂ efflux time series, which indicated that atmospheric variables, during the first 4 months, explained 23 % CO₂ variability, whereas, during the rest of the time series, CO₂ efflux values are poorly controlled with only 6 %. The observed anomalies of the diffuse CO₂ emission rate might be related to pressure changes within the volcanic–hydrothermal system and/or to geostructural changes in the crust due to stress/strain changes caused before and during the earthquakes’ formation, and seem not to be related to the activity of the main crater of Masaya volcano.  相似文献   

Influences of type of wave and angle of incidence on seismic bending moments in pile foundations          下载免费PDF全文

J. M. Zarzalejos  J. J. Aznárez  L. A. Padrón  O. Maeso 《地震工程与结构动力学》2014,43(1):41-59

When analysing the seismic response of pile groups, a vertically‐incident wavefield is usually employed even though it does not necessarily correspond to the worst case scenario. This work aims to study the influences of both the type of seismic body wave and its angle of incidence on the dynamic response of pile foundations. To this end, the formulation of SV, SH and P obliquely‐incident waves is presented and implemented in a frequency‐domain boundary element‐finite element code for the dynamic analysis of pile foundations and piled structures. Results are presented in terms of bending moments at cap level of single piles and 3 × 3 pile groups, both in frequency and in time domains. It is found that, in general, the vertical incidence is not the most unfavourable situation. In particular, obliquely‐incident SV waves with angles of incidence smaller than the critical one, a situation in which the mechanism of propagation of the waves in the soil changes and surface waves appear, yield bending moments much larger than those obtained for vertically‐incident wavefields. It is also shown that the influence of pile‐to‐pile interaction on the kinematic bending moments becomes significant for non‐vertical incidence, especially for P and SV waves. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Crater Lake Temperature Changes of the 2005 Eruption of Santa Ana Volcano,El Salvador,Central America     

P. A. Hernández  N. M. Pérez  J. C. Varekamp  B. Henriquez  A. Hernández  J. Barrancos  E. Padrón  D. Calvo  G. Melián 《Pure and Applied Geophysics》2007,164(12):2507-2522

A sudden eruption at Santa Ana occurred on 1 October 2005, producing an ash-and-gas plume to a height in excess of 10 km above the volcano. Several days before, thermal infrared images of the crater provided precursory signals of the eruption. A significant increase in the extent and intensity of the fumarolic field inside the crater rim and of the surface temperature of the crater’s lake was observed. Changes in energy input was also estimated to explain the increase in lake temperature based on energy/mass balance calculations.  相似文献   

Precursory Subsurface 222Rn and 220Rn Degassing Signatures of the 2004 Seismic Crisis at Tenerife, Canary Islands     

Nemesio M. Pérez  Pedro A. Hernández  Eleazar Padrón  Gladys Melián  Rayco Marrero  Germán Padilla  José Barrancos  Dácil Nolasco 《Pure and Applied Geophysics》2007,164(12):2431-2448

Precursory geochemical signatures of radon degassing in the subsurface of the Tenerife Island were observed several months prior to the recent 2004 seismic-volcanic crisis. These premonitory signatures were detected by means of a continuous monitoring of ²²²Rn and ²²⁰Rn activity from a bubbling CO₂-rich gas spot located at 2.850 m depth inside a horizontal gallery for groundwater exploitation at Tenerife. Multivariate Regression Analysis (MRA) on time series of the radon activity was applied to eliminate the radon activity fluctuation due to external variables such as barometric pressure, temperature and relative humidity as well as power supply. Material Failure Forecast Method (FFM) was successfully applied to forecast the anomalous seismicity registered in Tenerife Island in 2004. The changes in the ²²²Rn/²²⁰Rn ratio observed after the period of anomalous seismicity might suggest a higher gas flow rate and/or changes in the vertical permeability induced by seismic activity.  相似文献   

SO2 Emission from Active Volcanoes Measured Simultaneously by COSPEC and mini-DOAS   总被引：1，自引：0，他引：1  

José Barrancos  José I. Roselló  David Calvo  Eleazar Padrón  Gladys Melián  Pedro A. Hernández  Nemesio M. Pérez  Millán M. Millán  Bo Galle 《Pure and Applied Geophysics》2008,165(1):115-133

We measured SO₂ emission rate from six volcanoes in Latin America (Santa Ana, El Salvador; San Cristóbal and Masaya, Nicaragua; Arenal and Poás, Costa Rica; Tungurahua and Sierra Negra, Ecuador) and from Mt. Etna, Italy, using two different remote sensing techniques: COSPEC (COrrelation SPECtrometer) and miniDOAS (miniaturized Differential Optical Absorption Spectroscopy). One of the goals of this study was to evaluate the differences in SO₂ emission rates obtained by these two methods. The observed average SO₂ emission rates measured during this study were 2688 t·d⁻¹ from Tungurahua in July 2006, 2375 t·d⁻¹ in September 2005 and 480 t·d⁻¹ in February 2006 from Santa Ana, 1200 t·d⁻¹ in May 2005 from Etna, 955 t·d⁻¹ in March 2006 and 1165 t·d⁻¹ in December 2006 from Masaya, 5400 t·d⁻¹ of March 7, 2006 and 265 t·d⁻¹ in March 2006 from San Cristobal, 113 t·d⁻¹ in April 2006 from Arenal, 104 t·d⁻¹ in April 2006 from Poás and 11 t·d⁻¹ in July 2006 from Sierra Negra volcano. Most of the observed relative differences of SO₂ emission measurements from COSPEC and miniDOAS were lower than 10%.  相似文献   

Diffuse CO₂ emission rate from Pululahua and the lake-filled Cuicocha calderas,Ecuador     

Eleazar Padrón  Pedro A. Hernández  Theofilos Toulkeridis  Nemesio M. Pérez  Rayco Marrero  Gladys Melián  Giorgio Virgili  Kenji Notsu 《Journal of Volcanology and Geothermal Research》2008

We report herein the first results of two soil CO₂ efflux surveys carried out at Cuicocha lake-filled and Pululahua caldera volcanic systems, Ecuador. A total of 172 and 217 soil CO₂ efflux measurements were taken at the surface environment of Pululahua and Cuicocha calderas respectively, by means of the “accumulation chamber” method during the summer of 2006 to constrain the total CO₂ output from the studied area. Soil CO₂ efflux values ranged from non-detectable up to 48.5 and 141.7 g m^{− 2} d^{− 1} for Cuicocha and Pululahua calderas respectively. In addition, probability graphs were used to distinguish the existence of different geochemical populations. Sequential Gaussian Simulation was used to construct an average map for 100 simulations and to compute the total CO₂ emission at each studied area: 106 and 270 t d^{− 1} (metric tons per day) for Cuicocha (13.3 km²) and Pululahua (27.6 km²) volcanoes respectively.  相似文献   

Seismic response of bridge piers on pile groups for different soil damping models and lumped parameter representations of the foundation     

Francisco González  Luis A. Padrón  Sandro Carbonari  Michele Morici  Juan J. Aznárez  Francesca Dezi  Graziano Leoni 《地震工程与结构动力学》2019,48(3):306-327

This paper presents a wide parametric study aimed at elucidating the influence, on the computed seismic response of bridge piers, of two related aspects of the model: (1) the adoption of the classical hysteretic or the causal Biot's damping models for the soil and (2) the use of two different lumped parameter models of different complexity and accuracy to approximate the impedances of the pile foundation. A total of 2072 cases, including different superstructures, pile foundations, soil deposits, and seismic input signals, are studied. The results are presented so that the influence of the different parameters involved in the analysis can be assessed. From an engineering point of view, both lumped parameter models provide, in general, sufficiently low errors. The choice of the most adequate model for each case will depend not only on the configuration of the structure and the soil-foundation system but also on the assumed soil damping model, whose influence on the computed seismic responses is relevant in many cases. The nonphysical behaviour provided by the classical hysteretic damping model for the soil at zero frequency generates issues in the process of fitting the impedance functions. It is also found that larger deck displacements are predicted by Biot's model due to the higher damping at low frequencies provided by the classical hysteretic damping model.  相似文献   

On soil-structure interaction in large non-slender partially buried structures     

J. Vega  J. J. Aznárez  A. Santana  E. Alarcón  L. A. Padrón  J. J. Pérez  O. Maeso 《Bulletin of Earthquake Engineering》2013,11(5):1403-1421

This paper addresses the seismic analysis of a deeply embedded non-slender structure hosting the pumping unit of a reservoir. The dynamic response in this type of problems is usually studied under the assumption of a perfectly rigid structure using a sub-structuring procedure (three-step solution) proposed specifically for this hypothesis. Such an approach enables a relatively simple assessment of the importance of some key factors influencing the structural response. In this work, the problem is also solved in a single step using a direct approach in which the structure and surrounding soil are modelled as a coupled system with its actual geometry and flexibility. Results indicate that, quite surprisingly, there are significant differences among prediction using both methods. Furthermore, neglecting the flexibility of the structure leads to a significant underestimation of the spectral accelerations at certain points of the structure.  相似文献