224 research outputs found
Melt inclusion evidence for long term steady-state volcanism at Las Sierras-Masaya volcano, Nicaragua
No full textLas Sierras-Masaya volcanic system is a persistently active basaltic caldera complex in Nicaragua. While there has been almost no juvenile material erupted since 1772, Masaya volcano has been persistently degassing for >150 years. An additional unusual behaviour for the Las Sierras-Masaya volcanic complex is its ability to produce large caldera-forming basaltic Plinian eruptions with the most recent occurring about 1800 years ago.
Here we present melt inclusion analyses that provide constraints on the magmatic system over time. Melt inclusions hosted in plagioclase and olivine crystals were analyzed for major, trace and volatile elements (S, Cl, F, H2O). The data supports a consistent parental magmatic source with restricted compositional variability explained by simple fractional crystallization of plagioclase, olivine, clinopyroxene and magnetite at a nearly constant temperature. This broadly agrees with previous whole rock geochemical studies showing that the overall chemical signature of volcanic products at Masaya has remained largely unchanged for ~60,000 years and that both shallow fractionation and degassing processes dominate the whole evolution of the magmatic series. Based on volatile element in melt inclusions and gas composition and flux measurements, we determine the magmatic flux to be ~0.19 km3 yr−1 implying that up to 47 km3 of magma may have degassed since the last effusive eruption. As at other persistently active basaltic volcanoes (e.g., Mt. Etna, Italy; Kilauea, Hawaii, USA), this magmatic flux must involve significant endogenous storage which is likely accommodated by extensional tectonics. However, Masaya volcano differs in its apparent simplicity with respect to its stable chemistry and its fully interconnected magmatic system.Peer reviewedFinal article publishedMasaya volcanoMagmatism and extensional tectonicsVolatile budgetsMelt inclusion geochemistryPersistent degassin
Masaya en algunas gestas nicaragüenses
No full textAt the beginning of the Hispanic conquest of Nicaragua, the region was under the rule of Chorotega, Maribio and Nicaraguan lordships. After the conquest, the indigenous communities were forced to pay taxes for the benefit of encomenderos and the Spanish crown itself. Upon the arrival of the Spanish conquerors, Masaya and the rest of Los Pueblos were part of one of the Chorotega lordships, that of the Dirianes, established about five centuries before. The most representative theatrical work that existed in the Kingdom of Guatemala during the colonial period was El Güegüence or Macho Ratón, a comedy by an unknown author, written in Masaya (Nicaragua) around 1673, a time when the main economic activity was the production of indigo dye, an activity that made transportation flourish. Patachos and trains, led by muleteers, traveled all the royal roads of the Kingdom of Guatemala, carrying loads of indigo, silver, gold and remittances from the royal estate to the Golfo Dulce, in Guatemala, or to the port of Veracruz, in Mexico, and bringing on his return wine, olives, plums, cloth, weapons. During the colonial period, encomenderos, landowners, magistrates and religious authorities committed multiple abuses against the indigenous population of Masaya through the tribute they had to pay twice a year, as well as through the seizure of their communal and ejidal lands, and through of distribution and personal services that forced them to work on estates and stately homes.En los inicios de la conquista hispana de Nicaragua, la región estaba bajo el dominio de señoríos chorotegas, maribios y nicaraos. Después de la conquista, las comunidades indígenas fueron obligadas a tributar en beneficio de encomenderos y de la misma corona española. Al arribo de los conquistadores españoles, Masaya y el resto de Los Pueblos eran parte de uno de los señoríos chorotegas, el de los dirianes, constituido unos cinco siglos antes.La obra teatral más representativa que hubo en el Reino de Guatemala durante el período colonial fue El Güegüence o Macho Ratón, comedia de autor desconocido, escrita en Masaya (Nicaragua) hacia 1673, época en que la actividad económica principal era la producción de tinte añil, actividad que hizo florecer el transporte. Patachos y recuas, dirigidos por arrieros recorrían todos los caminos reales del Reino de Guatemala, llevando cargas de añil, plata, oro y remesas de la hacienda real hacia el golfo Dulce, en Guatemala, o al puerto de Veracruz, en México, y trayendo en su retorno vino, aceitunas, ciruelas, telas, armas. Durante el período colonial, encomenderos, terratenientes, corregidores y autoridades religiosas cometieron múltiples atropellos contra la población indígena de Masaya por medio del tributo que debía pagar dos veces al año, así como a través del arrebato de sus tierras comunales y ejidales, y por medio del repartimiento y servicios personales que los obligaba a trabajar en las haciendas y casas señoriales
Seismic imaging based on Joint Migration Inversion: Handling missing low frequencies and horizontally propagating waves
No full textSeismic imaging is a significant technology to provide the image of the subsurface in several fields such as hydrocarbon exploration/production and civil engineering. A fundamental problem in seismic imaging is that both the depth reflectivity and velocity distribution of the subsurface have to be predicted by only seismic events observed at the surface, and it still remains a challenging research topic. Joint migration inversion (JMI) is one of the seismic waveform imaging algorithms that were recently proposed. JMI is capable of simultaneously estimating velocity and reflectivity models of the subsurface by exploiting reflected waves including internal multiples. The seismic modeling algorithm in the JMI process is a method termed full wavefield modeling (FWMod), which is a one-way propagator-based reflection modeling algorithm, including higher-order scattering and transmission effects. In this thesis, two directions to improve the accuracy of seismic imaging based on JMI are discussed. On one hand, an extension of FWMod is proposed to correctly deal with not only reflected waves but refracted/diving waves via one-way propagators in the horizontal direction, and this method is extended to a new JMI algorithm. On the other hand, we assume that only reflected waves including internal multiples are utilized in the imaging based on JMI and present two novel methods for the inversion and pre-processing: 1) iterative reflectivity-constrained velocity estimation, 2) surface amplitude correction via learning from synthetic models for land seismic data. The reflectivity-constrained velocity estimation is employed to improve the accuracy of the estimated velocity by exploiting the estimated reflectivity in the JMI process. The surface amplitude correction process is introduced to mitigate the influence of the amplitude variations caused by source/receiver response sensitivities and the difference of the features between observed land seismic data and the simulated data by the used imaging scheme. The numerical and field data examples for both land and marine cases demonstrate that the proposed approach is capable of effectively estimating reflectivity and velocity model, even though the low frequency components of the observed data are absent.ImPhys/Acoustical Wavefield Imagin
Generation and detection of ultrabroadband infrared wave exceeding 200 THz
No full textBy focusing a hollow-fiber compressed intense 10–fs pulse and its second harmonic in air, an ultrabroadband infrared pulse with a spectral range of 1–200 THz is generated through a plasma. Coherent detection of the signal up to 100 THz is achieved with electro–optic sampling and THz air-breakdown-coherent-detection. The drastic dependence on the orientation of the second harmonic crystal is clarified in a range of 100–200 THz. From these, the whole frequency components are confirmed to be generated from the AC biased plasma and phase-locked
Gapless Sensitive Detection of Ultrabroadband Infrared Pulses Using Single Crystal of Diamond
No full textGeneration and detection of ultrabroadband coherent infrared pulses with frequencies up to 200 THz using air plasma and 10 fs pulses
No full textUltrabroadband coherent electric field from far infrared to 200 THz using air plasma induced by 10 fs pulses
No full textPhase-sensitive THz nonlinear spectroscopy in high-T<inf>c</inf> superconductor thin film
No full textUltrabroadband infrared pulse ranging from terahertz region to near infrared using air for both generation and detection
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