Field and seismic evaluation of the block-and-ash flows emplaced from eruption columns of the 2005 Vulcanian explosions at Volcán de Colima,Mexico     

Vyacheslav M. Zobin  Gerardo Carrasco-Núñez  Víctor R. Vargas-Gutiérrez 《Bulletin of Volcanology》2016,78(4):27

  相似文献   

Gemini 3D spectroscopy of BAL+IR+Fe ii QSOs – II. IRAS 04505−2958, an explosive QSO with hypershells and a new scenario for galaxy formation and galaxy end phase     

S. Lípari  M. Bergmann  S. F. Sanchez  B. Garcia-Lorenzo  R. Terlevich  E. Mediavilla  Y. Taniguchi  W. Zheng  B. Punsly †  A. Ahumada  D. Merlo 《Monthly notices of the Royal Astronomical Society》2009,398(2):658-700

  相似文献   

CCD Washington photometry of three highly field star contaminated open clusters in the third Galactic quadrant     

A.E. Piatti  J.J. Clariá  M.C. Parisi  A.V. Ahumada 《New Astronomy》2009,14(1):97-108

We present CCD photometry in the Washington system C and T₁ passbands down to T₁ ～ 19.5 magnitudes in the fields of Czernik 26, Czernik 30, and Haffner 11, three poorly studied open clusters located in the third Galactic quadrant. We measured T₁ magnitudes and C ? T₁ colors for a total of 6472 stars distributed throughout cluster areas of 13.6′ × 13.6′ each. Cluster radii were estimated from star counts in appropriate-sized boxes distributed throughout the entire observed fields. Based on the best fits of isochrones computed by the Padova group to the (C ? T₁, T₁) color-magnitude diagrams (CMDs), we derived color excesses, heliocentric distances and ages for the three clusters. These are characterized by a relatively small angular size and by a high field star contamination. We performed a firm analysis of the field star contamination of the CMDs and examined different relationships between the position in the Galaxy of known open clusters located within 1 kpc around the three studied ones, their age and their interstellar visual absorption. We confirm previous results in the sense that the closer the cluster birthplace to the Galactic plane, the higher the interstellar visual absorption. We also found that the space velocity dispersion perpendicular to the Galactic plane diminishes as the clusters are younger. The positions, interstellar visual absorptions, ages, and metallicities of the three studied clusters favor the hypothesis that they were not born in the recently discovered Canis major (CMa) dwarf galaxy before it was accreted by the Milky Way.  相似文献   

Spectral analysis of climate cycles to predict rainfall induced landslides in the western Mediterranean (Majorca,Spain)     

Juan Antonio Luque-Espinar  Rosa María Mateos  Inmaculada García-Moreno  Eulogio Pardo-Igúzquiza  Gerardo Herrera 《Natural Hazards》2017,89(3):985-1007

In the present work, spectral analysis has been applied to determine the presence and statistical significance of climate cycles in long-term data series from different rainfall and gauging stations located in the Tramuntana Range, in the north-western sector of the island of Majorca. Climate signals recorded previously in the Mediterranean region have been identified: the ENSO, NAO, HALE, QBO and Sun Spot cycles as well as others related to solar activity; the most powerful signals correspond to the annual cycle, followed by the 6-month and NAO cycles. The incorporation of data derived from gauging stations contributes to better climate signal detection as local and exceptional influences are eliminated. Simulations have been performed for each rainfall/gauging station, using the most significant climate cycles obtained by means of the power spectrum. A good correlation between rainfall/flow values and simulated cycles has been obtained. The NAO and ENSO cycles are the most influential in the rainy periods, and specifically the NAO cycle, where a good correlation between episodes of high rainfall/flow and high values of ANAOI can be observed. At a second stage, landslides dated and recorded in the Tramuntana Range since 1954 (174 events) have been correlated with the simulated cycles obtaining good results, as the landslide events match rainfall peaks well. The correlation for the past decade (since 2005), when a detailed landslide inventory is available, also reveals a coincidence between landslide events and climate cycles, and specifically NAO and ENSO cycles. That is the case of the period 2008–2010, when numerous mass movements took place, and when the largest movement of the inventory was recorded. Results show a potential rainy period in the Tramuntana Range for the coming years (with maximum values around year 2021), when conditions similar to those related to the 2008–2010 event could take place again. The methodology presented in this work can contribute to the prediction of temporal, extreme hydrological events in order to design short-/medium-term mitigation strategies on a regional scale.  相似文献   

Performance evaluation of active wireline heave compensation systems in marine well logging environments     

Tanzhuo Liu  Gerardo Iturrino  David Goldberg  Eric Meissner  Kerry Swain  Clayton Furman  Peter Fitzgerald  Nathan Frisbee  Joe Chlimoun  John Van Hyfte  Ron Beyer 《Geo-Marine Letters》2013,33(1):83-93

The basic functionality and performance of a new Schlumberger active wireline heave compensation system on the JOIDES Resolution was evaluated during the sea trial and a 3-year period of the IODP Phase II operations. A suite of software programs was developed to enable real-time monitoring of the dynamics of logging tools, and assess the efficiency of wireline heave compensation during downhole operations. The evaluation of the system effectiveness was performed under normal logging conditions as well as during stationary tests. Logging data were analyzed for their overall quality and repeatability, and to assess the reliability of high-resolution data such as formation microscanner (FMS) electrical images. This revealed that the system reduces 65–80 % of displacement or 88–98 % variance of downhole tool motion in stationary mode under heave conditions of ±0.2–1.5 m and water depths of 300–4,500 m in open holes. Under similar water/heave conditions, the compensator system reduces tool displacement by 50–60 %, or 75–84 % variance in downhole tool motion during normal logging operations. Such compensation efficiency (CE) is comparable to previous compensation systems, but using advanced and upgradeable technologies, and provides 50–85 % heave motion and heave variance attenuation. Moreover, logging down/up at low speeds (300–600 m/h) reduces the system’s CE values by 15–20 %, and logging down at higher speeds (1,000–1,200 m/h) eliminates CE values by 55–65 %. Considering the high quality of the logging data collected, it is concluded that the new system can provide an improved level of compensation over previous systems. Also, if practically feasible, future integration of downhole cable dynamics as an input feedback into the current system could further improve its compensation efficiency during logging operations.  相似文献   

Full frequency-range transient solution for compressional waves in a fluid-saturated viscoacoustic porous medium1     

Jos M. Carcione  Gerardo Ouiroga-Goode 《Geophysical Prospecting》1996,44(1):99-129

An analytical transient solution is obtained for propagation of compressional waves in a homogeneous porous dissipative medium. The solution, based on a generalization of Biot's poroelastic equations, holds for the low- and high-frequency ranges, and includes viscoelastic phenomena of a very general nature, besides the Biot relaxation mechanism. The viscodynamic operator is used to model the dynamic behaviour associated with the relative motion of the fluid in the pores at all frequency ranges. Viscoelasticity is introduced through the standard linear solid which allows the modelling of a general relaxation spectrum. The solution is used to study the influence of the material properties, such as bulk moduli, porosity, viscosity, permeability and intrinsic attenuation, on the kinematic and dynamic characteristics of the two compressional waves supported by the medium. We also obtain snapshots of the static mode arising from the diffusive behaviour of the slow wave at low frequencies.  相似文献   

Recurrent magma mingling in successive ignimbrites from Amealco caldera, central Mexico     

Gerardo J. Aguirre-Díaz 《Bulletin of Volcanology》2001,63(4):238-251

The Amealco Tuff is a widespread (>2880 km²), trachyandesitic to rhyolitic pyroclastic deposit in the central Mexican Volcanic Belt that was erupted from the Amealco caldera at 4.7ǂ.1 Ma. It includes three major ignimbrites, each showing complex mingling of pumice fragments and matrix glass with andesitic to rhyolitic compositions. The different glasses are well mingled throughout each of the pyroclastic-flow deposits. Mingling of glasses may have occurred just before and during the explosive eruptions that produced the pyroclastic flows, as the distinct melts had insufficient time to homogenize. Mingling of glasses is evident in each of the three separate major ignimbrites of the Amealco Tuff; thus, the processes that caused it were repetitive. It is infered that the repetitive mingling of melts was due to repeated mafic magma inputs to an evolved magma chamber.  相似文献   

C. E. Jacob's Study on the Prospective and Hypothetical Future of the Mining of the Ground Water Deposited Under the Southern High Plains of Texas and New Mexico     

W. Brutsaert  Gerardo Wolfgang Gross  Ralph M. McGehee 《Ground water》1975,13(6):492-505

  相似文献   

Magnitude and Frequency of Flooding in the Tagus Basin (Central Spain) over the Last Millennium     

Gerardo Benito  Andrés Díez-Herrero  María Fernández de Villalta 《Climatic change》2003,58(1-2):171-192

A relational database using Access, and an interface based on a Geographical Information System (GIS) with ArcView program, were created to allow spatial-temporal analysis of documentary flood data collected for the Tagus basin (Central Spain). High flood frequencies were registered in the periods: AD 1160–1210 (3%), 1540–1640 (11%; peak at 1590–1610), 1730–1760 (5%), 1780–1810 (4%), 1870–1900 (19%), 1930–1950 (17%) and 1960–1980 (12%). Flood magnitudes of those documentary events were estimated at four sites (Aranjuez, Toledo, Talavera and Alcántara) along the Tagus River using HEC-RAS Computer program, matching the calculated water surface profiles with historical references of flood stage. The largest floods took place during the periods AD 1168–1211 (Toledo and Talavera), AD 1658–1706 (Talavera), AD 1870–1900, and AD 1930–1950 (Aranjuez, Toledo, Talavera and Alcántara). The temporal distribution of flood magnitude and frequency is discussed within the context of climatic variability experienced by the Iberian Peninsula. Although flood producing mechanisms of Atlantic and Mediterranean basins of the Iberian Peninsula are related to different, independent atmospheric patterns, there is a clear coincidence between most periods showing high flood frequencies. These periods of high flooding seem to correspond to the initial and final decades of periods with climate deterioration described at the continental scale. This suggests that climatic variability over the last millennium has induced a response in hydrological extremes (positive or negative), irrespective of the flood-producing mechanism.  相似文献   

Mineralization of organic material and bacterial dynamics in Mississippi River plume water     

Wayne S. Gardner  James B. Cotner  Brian J. Eadie  Joann F. Cavaletto  Ronald Benner  Gerardo Chin-Leo 《Estuaries and Coasts》1994,17(4):816-828

Net remineralization rates of organic matter and bacterial growth rates were observed in dark-bottle incubation experiments conducted in July–August and February with water samples collected from sites in the Mississippi River plume of the Gulf of Mexico. Our objectives were to measure site-specific degradation rates of labile dissolved and particulate organic matter, quantify the potential importance of bacteria in these processes, and examine the kinetics of degradation over time. Unfiltered samples, and samples treated to remove (or dilute out) particles larger than bacteria, were enclosed in 9-1 bottles and incubated in the dark for 3–5 d. Respiration rates and inorganic compound accumulation rates were higher in summer than in winter and were highest in unfiltered surface samples at sites of intermediate salinities where phytoplankton were most abundant. The ratio of ammonium accumulation to oxygen removal in summer experiments suggested that the mineralized organic material resembled “Redfield” stoichiometry. Chemical fluxes were greater in bottles containing large (>1–3 μm) particles than in the bottles with these particles removed, but bacterial activities were generally similar in both treatments. These results suggest that particle consumers were an important component of total organic matter degradation. However, these experiments may have underestimated natural bacterial degradation rates because the absence of light could affect the production of labile organic substrates by phytoplankton. In agreement, with this hypothesis, bacterial growth rates tended to decrease over time in summer in surface plume waters where phytoplankton were abundant. In conjunction with other data, our results indicate that heterotrophic processes in the water column are spatially and temporally dependent on phytoplankton production.  相似文献