Artículo Científicos

URI permanente para esta colecciónhttps://hdl.handle.net/11056/32225

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Crustal Velocity Structure Beneath The Western Andes of Colombian Using Receiver-Function Inversion
(ELSEVIER, 2013-12-01) Monsalve, Hugo; Pacheco, Javier F.; Vargas, Carlos A.; Morales, Yorly A.
Analysis of teleseismic records obtained in two broadband seismic stations of three components located on the Andean region of Colombia is presented in this work. The two stations are located at the Western Cordillera (WC), station BOL, and at the Central Cordillera (CC), station PBLA. The analysis of seismograms was performed by inversion of the receiver functions (RF) in order to obtain the crustal velocity structure beneath the receivers. The receiver function is a spectral ratio obtained from teleseismic earthquakes recorded by broadband seismic stations, which allows the calculation of the velocity structure beneath the receiver by removing source effects in the horizontal components of the seismic traces. Data stacking was performed in order to improve signal to noise ratio and then the data was inverted by using two optimization algorithms: a genetic algorithm (GA), and a simulated annealing algorithm (SA). The present work calculates the receiver functions using teleseismic earthquakes at epicentral distances (Δ) ranging between 30° and 90° and recorded at the two stations within the years 2007 and 2009.
Yield estimate (230 kt) for a Mueller-Murphy model of the 3 september 2017, North Korean nuclear test (mbNEIC = 6.3) from teleseismic broadband P waves assuming extensive near-source damage
(AGU Advancing Earth and Space Sciences, 2018-09-21) Chaves, Esteban J.; Lay, Thorne; Voytan, Dimitri P.
The 3 September 2017 underground nuclear test (mbNEIC= 6.3) is the largest of six announced North Korean explosions. The event generated many P wave seismograms at global broadband seismic stations with good signal-to-noise ratio for periods less than ~5 s. Instrument deconvolution provides 435 stable broadband P wave ground displacement records in the period range 0.1 to 5.0 s. These are stacked in 26 azimuth/distance windows to average path and receiver effects. Waveform stacks and average amplitude of 4-Hz ground displacements are modeled assuming a Mueller-Murphy explosion source modelfor a granite source medium. Nonelastic pP delays consistent with burial depths in the mountainous source topography are considered, and explosion yield and an average constant-Q attenuation operator areestimated by fitting the waveforms. For a source depth of 750 m in heavily damaged environment, the estimated yield = 230 ± 50 kt andt*= 0.78 ± 0.03 s.
Plant Responses to Volcanically Elevated CO2 in Two Costa Rican Forests
(Copernicus Publications, 2019-04-01) Bogue, Robert R.; Schwandner, Florian M.; Fisher, Joshua B.; Pavlick, Ryan; Magney, Troy S.; Famiglietti, Caroline A.; Cawse-Nicholson, Kerry; Yadav, Vineet; Linick, Justin P.; North, Gretchen B.; Duarte, Eliecer
We explore the use of active volcanoes to determine the short- and long-term effects of elevated CO2 on tropical trees. Active volcanoes continuously but variably emit CO2 through diffuse emissions on their flanks, exposing the overlying ecosystems to elevated levels of atmospheric CO2. We found tight correlations (r2=0.86 and r2=0.74) between wood stable carbon isotopic composition and co-located volcanogenic CO2 emissions for two of three investigated species (Oreopanax xalapensis and Buddleja nitida), which documents the long-term photosynthetic incorporation of isotopically heavy volcanogenic carbon into wood biomass. Measurements of leaf fluorescence and chlorophyll concentration suggest that volcanic CO2 also has measurable short-term functional impacts on select species of tropical trees. Our findings indicate significant potential for future studies to utilize ecosystems located on active volcanoes as natural experiments to examine the ecological impacts of elevated atmospheric CO2 in the tropics and elsewhere. Results also point the way toward a possible future utilization of ecosystems exposed to volcanically elevated CO2 to detect changes in deep volcanic degassing by using selected species of trees as sensors.
Earthquake Potential in Costa Rica Using Three Scenarios for the Central Costa Rica Deformed Belt as Western Boundary of the Panama Microplate
(ELSEVIER, 2019-10-04) Carvajal-Soto, Luis Alejandro; Ito, Takeo; Protti, Marino; Kimura, Hiroshi
El Cinturón Deformado de Costa Rica Central (CCRDB) es una zona de fallamiento difuso que representa el límite occidental de la Microplaca de Panamá. Utilizando el método de Monte Carlo con Cadenas de Markov y bajo tres escenarios de distribución espacial del CCRDB, analizamos la deformación cortical intersísmica en Costa Rica y sus alrededores a partir de los resultados de las observaciones del Sistema Global de Navegación por Satélite (GNSS) para Costa Rica, Nicaragua y Panamá. Asumimos que la deformación cortical intersísmica observada en la superficie es resultado de los efectos cinemáticos del movimiento de bloques tectónicos rígidos, la deformación elástica debida a las interacciones en la interfaz de los bloques y la tensión interna dentro de los bloques tectónicos. Suponiendo que el momento sísmico en las interfaces de subducción y continentales se acumula únicamente como una deformación elástica y luego se libera cosísmicamente, las tasas de acumulación de momento sísmico resultantes reflejan la capacidad de producir terremotos de magnitud Mw > 8 a lo largo de la convergencia de la Placa de Cocos y terremotos de magnitud Mw > 7 a lo largo de las interfaces continentales. Si bien estos son los valores que arroja el modelo, los escasos datos históricos sugieren que este potencial sísmico podría estar sobreestimado, pero la sismicidad histórica en Costa Rica aún es insuficiente para descartar niveles de potencial sísmico más altos.

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