Artículos científicos

URI permanente para esta colecciónhttp://10.0.96.45:4000/handle/11056/17882

Examinar

Mostrando 1 - 12 de 12

Detailed data available for recent Costa Rica earthquake.
(University of South Florida, 2013) Dixon, Timothy H.; Schwartz, Susan; Protti, Marino; Gonzalez, Victor; Newman, Andrew; Marshall, Jeff; Spotila, Jim
On 5 September 2012 a magnitude 7.6 earthquake occurred beneath the Nicoya Peninsula of northwestern Costa Rica, rupturing the subduction zone between the Cocos and Caribbean plates. In most subduction zones the locus of seismic slip lies far offshore, making it difficult to infer interface seismogenic processes from on-shore observations. In contrast, the Nicoya Peninsula lies close to the trench (within 70 kilometers), allowing observations directly over the earthquake rupture zone.
Earth's Magnetic Field Strength and the Cretaceous Normal Superchron: New Data From Costa Rica
(American Geophysical Union, 2021-03-12) Di Chiara, A.; Tauxe, L.; Staudigel, H.; Florindo, F.; Protti, M.; Yu, Y.; Wartho, J. A.; Van den Bogaard, P.; Hoernle, K.
Limitar la variabilidad a largo plazo y el promedio de la intensidad del campo magnético terrestre es fundamental para comprender las características y el comportamiento del campo geomagnético. Persisten interrogantes sobre la intensidad del campo promedio y la relación entre esta y la frecuencia de inversión, debido a la dispersión de los datos de intervalos de tiempo clave. En este estudio, nos centramos en el Supercrón Normal Cretácico (CNS; 121-84 Ma), durante el cual no se observaron inversiones. Presentamos nuevos resultados de intensidad de 41 sitios de vidrio basáltico submarino (SBG) recolectados en la Península de Nicoya y las Islas Murciélago, Costa Rica. Las nuevas y revisadas restricciones de edad 40Ar/39Ar y bioestratigráficas de estudios previos indican edades de 141 a 65 Ma. Un sitio con una edad de 135,1 ± 1,5 Ma (2σ) arrojó un resultado de intensidad confiable de 34 ± 8 µT (equivalente a un momento dipolar axial virtual, VADM, valor de 88 ± 20 ZAm2), tres sitios de 121 a 112 Ma, que abarcan el inicio del CNS, varían de 21 ± 1 a 34 ± 4 µT (53 ± 3 a 87 ± 10 ZAm2). Estos resultados del CNS son todos superiores al promedio a largo plazo de ∼42 ZAm2 y los datos de Suhongtu, Mongolia (46–53 ZAm2) y son similares a la ofiolita de Troodos, Chipre (81 ZAm2, reinterpretada en este estudio). Junto con los datos reinterpretados, los nuevos resultados de Costa Rica sugieren que la intensidad del campo geomagnético fue aproximadamente la misma antes y después del inicio del SNC. Por lo tanto, los datos no respaldan una correlación estricta entre la longitud del intervalo de polaridad y la intensidad del campo magnético.
Effect of subducting sea-floor roughness on fore-arc kinematics, Pacific coast, Costa Rica
(Geological Society of America, 1998-05-01) Fisher, Donald M.; Gardner, Thomas W.; Marshall, Jeffrey S.; Sak, Peter B.; Protti, Marino
Fault kinematics and uplift in the Costa Rican fore arc of the Middle America convergent margin are controlled to a large extent by roughness on the subducting Cocos plate. Along the northwest flank of the incoming Cocos Ridge, seafloor is characterized by short wavelength roughness related to northeast-trending seamount chains. Onland projection of the rough subducting crust coincides with a system of active faults oriented at high angles to the margin that segment the fore-arc thrust belt and separate blocks with contrasting uplift rates. Trunk segments of Pacific slope fluvial systems typically follow these margin-perpendicular faults. Regionally developed marine and fluvial terraces are correlated between drainages and acrossfaults along the Costa Rican Pacific coast. Terrace separations across block-bounding faults reveal a pattern of fore-arc uplift that coincides roughly with the distribution of incoming seamounts. Magnitude and distribution of Quaternary uplift along the Costa Rican Pacific coast suggests that, despite a thin incoming sediment pile, the inner fore arc shows an accumulation of mass—a characteristic that may be due to underplating of seamounts beneath the fore-arc high.
Fore-arc motion and Cocos Ridge collision in Central America
(American Geophysical Union, 2009-05-07) LaFemina, Peter; Dixon, Timothy H.; Govers, Rob; Norabuena, Edmundo; Turner, Henry; Saballos, Armando; Mattioli, Glen; Protti, Marino; Strauch, Wilfried
We present the first regional surface velocity field for Central America, showing crustal response to interaction of the Cocos and Caribbean plates. Elastic half-space models for interseismic strain accumulation on the dipping subduction plate boundary fit the GPS data well and show strain accumulation offshore and beneath the Nicoya and Osa peninsulas in Costa Rica but not in Nicaragua. Since large subduction zone earthquakes occur in Nicaragua, we suggest that interseismic locking in Nicaragua and some other parts of Central America occurs but is mainly shallow, <20 km depth, too far offshore to be detected by our on-land GPS measurements. Our data also show significant trench-parallel motion for most of the region, generally interpreted as due to oblique convergence and strong mechanical coupling between subducting and overriding plates. However, trench-parallel motion is also observed in central Costa Rica, where plate convergence is normal to the trench, and in the Nicaraguan fore arc, where trench-parallel motion is fast, up to 9 mm a 1, but mechanical coupling is low. A finite element model of collision (as opposed to subduction) involving the aseismic Cocos Ridge also fits the GPS surface velocity field, most significantly reproducing the pattern of trench-parallel motion. We infer that buoyant, thickened CNS-2-Cocos Ridge crust resists normal subduction and instead acts as an indenter to the Caribbean plate, driving crustal shortening in southern Costa Rica and contributing to trench-parallel fore-arc motion in Costa Rica and perhaps Nicaragua as a type of tectonic escape.
High-resolution gravity survey: Investigation of subsurface structures at Poás volcano, Costa Rica
(Universidad Nacional, Costa Rica, 2003-08-03) Fournier, Nicolas; Rymer, Hazel; Williams-Jones, Glyn; Brenes, Jorge
Bouguer gravity surveys have long been used to investigate sub-surface density contrasts. The main sources of error in previous surveys have been the determination of relative elevations of stations and the effect of topography (removed via the terrain correction). The availability of high precision Kinematic GPS data now facilitates generation of high-resolution Digital Elevation Models that can help to improve the accuracy of relative elevation determination and the terrain correction. Here we describe a highresolution gravity survey at Poás volcano, Costa Rica. Our gravity modelling identifies small pockets of magma at shallow depths which relate to successive magma intrusion through time and shows that the persistent degassing in the eastern part of the crater is related to local deformation at the top of the volcano and changes in the fracture network, rather than to the presence of a shallow magma intrusion.
Horizontal subduction and truncation of the Cocos Plate beneath central Mexico
(American Geophysical Union, 2008-09-27) Pérez-Campos, Xyoli; Kim, YoungHee; Husker, Allen; Davis, Paul M.; Clayton, Robert W.; Iglesias, Arturo; Pacheco, Javier F.; Singh, Shri K.; Manea, Vlad Constantin; Gurnis, Michael
Based on analysis of data from a trans-Mexico temporary broadband seismic network centered on Mexico City, we report that the subducting Cocos Plate beneath central Mexico is horizontal, and tectonically underplates the base of the crust for a distance of 250 km from the trench. It is decoupled from the crust by a very thin low viscosity zone. The plate plunges into the mantle near Mexico City but is truncated at a depth of 500 km, probably due to an E-W propagating tear in the Cocos slab. Unlike the shallow slab subduction in Peru and Chile, there is active volcanism along the Trans Mexican Volcanic Belt (TMVB) that lies much further inland than regions to either side where subduction dip is not horizontal. Geodynamical modeling indicates that a thin weak layer such as imaged by the seismic experiment can explain the flat subduction geometry.
Magma plumbing processes for persistent activity at Poás volcano, Costa Rica
(American Geophysical Union Advancing Earth, 2005-04-21) Rymer, Hazel; Locke, Corinne A.; Brenes, jorge; Williams-Jones, Glyn
New microgravity data from the active crater of Poás volcano, Costa Rica, collected in 2002 – 2004 extends the existing dataset to provide a unique 20-year time series. These data show that gravity has decreased monotonically in the north and east of the crater over the last 5 years, whilst it has increased to the west and remained approximately constant in the south. These changes are interpreted in terms of convective recharge within dendritic intrusions beneath the crater, with overall down-welling in the north and up-welling in the west. The data reveal a 5 –10 year periodicity in sub-crater mass movement, but overall, the upper part of the conduit system appears to have maintained a state of mass equilibrium.
Multiscale postseismic behavior on a megathrust: the 2012 Nicoya earthquake, Costa Rica
(American Geophysical Union, 2015-06-17) Malservisi, Rocco; Schwartz, Susan Y.; Voss, Nicholas; Protti, Marino; Gonzalez, Victor; Dixon, Timothy H.; Jiang, Yan; Newman, Andy V.; Richardson, Jacob; Walter, Jacob I.; Voyenko, Denis
La Península de Nicoya, en el noroeste de Costa Rica, se encuentra sobre una sección del megaembotamiento de subducción a lo largo de la Fosa Mesoamericana. El 5 de septiembre de 2012, un megaembotamiento de magnitud de momento 7,6 se produjo bajo una densa red de estaciones GPS y sísmicas continuas. Muchas de las estaciones GPS registraron el evento a alta frecuencia, 1 Hz o mejor. Analizamos la evolución temporal y espacial de la deformación superficial tras el terremoto. Nuestros resultados muestran que la ruptura principal fue seguida por un deslizamiento posterior significativo dentro de las primeras 3 h posteriores al evento principal. El comportamiento del desplazamiento superficial puede representarse mediante procesos de relajación con tres tiempos característicos: 7, 70 y más de 400 días. Suponemos que el tiempo de relajación largo corresponde a la relajación viscoelástica y el tiempo de relajación intermedio corresponde al deslizamiento posterior en la falla principal. El tiempo de relajación corto puede representar una combinación de deslizamiento posterior rápido, ajuste poroelástico en la corteza superior u otros procesos. Durante los primeros meses posteriores al terremoto, el deslizamiento posterior probablemente liberó una cantidad significativa del déficit de deslizamiento aún presente tras la ruptura cosímica, en particular el buzamiento ascendente de la ruptura. El deslizamiento posterior parece estar limitado por el buzamiento ascendente de las regiones afectadas por deslizamientos lentos previos al terremoto, lo que sugiere que ambos procesos se ven influenciados por diferentes propiedades de fricción.
Quantifying recent pyroclastic and lava flows at Arenal Volcano, Costa Rica, using medium-footprint lidar
(American Geophysical Union Advancing Earth and Space Sciences, 2006-11-03) Hofton, M. A.; Malavassi, E.; Blair, J. B.
Arenal volcano is a small, active stratovolcano in Costa Rica. In 1998 and 2005, NASA’s Laser Vegetation Imaging Sensor (LVIS) was used to collect wide-swath 3- dimensional topographic images of the volcano. The LVIS is a full-waveform, scanning, medium-sized footprint, airborne laser altimeter system. By digitally recording the shape of the returning laser pulse (waveform), the LVIS provides a precise and accurate view of both the sub-canopy and canopy-top topographies as well as the vertical and horizontal structure of vegetation at 15– 25 m horizontal resolution. By comparing georeferenced waveform data collected in 1998 and 2005, we mapped lava and pyroclastic flows deposited during this period. The active crater grew by 3.82 m yr 1. A flow volume estimate of 2.19 107 m3 (Dense Rock Equivalent of 1.89 107 m3 or 0.085 m3s 1) Nwas obtained for the period 1998 to 2005. Precise elevation and elevation change data such as those provided by the LVIS are essential to calculate eruption volume and to study magma-supply dynamics, as well as assess the danger posed by the volcano to the local population from hazards such as pyroclastic flows.
Seismic tomography and earthquake locations in the Nicaraguan and Costa Rican upper mantle
(American Geophysical Union, 2008-07-30) Syracuse, Ellen M.; Abers, Geoffrey A.; Fischer, Karen; MacKenzie, Laura; Rychert, Catherine; Protti, Marino; González, Víctor; Strauch, Wilfried
The Central American subduction zone exhibits large variations in geochemistry, downgoing plate roughness and dip, and volcano locations over a short distance along the arc. Results from joint inversions for Vp, Vp/Vs, and hypocenters from the Tomography Under Costa Rica and Nicaragua (TUCAN) experiment give insight into its geometry and structure. In both Costa Rica and Nicaragua, the intermediate-depth seismic zone is a single layer no more than 10 to 20 km thick. Tomographic images show that throughout Nicaragua and Costa Rica the slowest mantle P wave velocities appear below and behind the volcanic front, indicating likely zones of highest temperature extending 80 to 120 km depth. A sheet of high Vp/Vs, thought to be caused by melt, is imaged directly beneath the Nicaraguan volcanoes, whereas a weaker, broader anomaly is imaged beneath the Costa Rican volcanoes, potentially indicating a greater extent of melting beneath Nicaragua. Within the downgoing plate, anomalously low velocities occur at least 20–30 km below Wadati-Benioff zone seismicity, to depths of 140 km beneath Nicaragua and to 60 km depth beneath Costa Rica. They indicate 10–20% serpentinized upper mantle of the downgoing plate beneath Nicaragua, similar to that inferred from refraction seaward of the trench, but continuing to subarc depths. This unusually hydrated lithosphere may introduce more water into the Nicaraguan mantle, initiating increased amount of melting and fluid flux to the arc.
The synchronous occurrence of shallow tremor and very low frequency earthquakes offshore of the Nicoya Peninsula, Costa Rica
(American Geophysical Union, 2013-03-05) Walter, Jacob I.; Schwartz, Susan Y.; Protti, Marino; Gonzalez, Victor
The occurrence of transient, shallow slow slip at seismogenic zones has important implications for earthquake and tsunami hazards. Here we provide evidence that a tremor and slow slip event occurred at shallow depth offshore of the Nicoya Peninsula, Costa Rica, in August 2008. The temporal coincidence of offshore tremor, very low frequency earthquakes (VLFEs), motions consistent with slow slip on the plate interface on western coastal GPS stations, and a pressure transient in an IODP borehole all indicate slow slip occurring at shallow depths. Large ocean loading stresses on the shallow plate interface modulate tremor activity, with the peak Coulomb stress forced by semi-diurnal ocean tides correlating with tremor productivity. Based on beamforming data, we constrain that the VLFE activity occurs in the same region as the tremor and slow slip. The presence of slow slip at shallow depth has important implications for the up-dip extent of earthquake rupture. The proximity of the 5 September 2012, Mw 7.6 megathrust earthquake to slow slip, tremor, and VLFE activity in the 2008 event suggests abrupt frictional transitions from locked to conditionally stable behavior on the plate interface offshore of the Nicoya Peninsula.
Tracking Formation of a Lava Lake From Ground and Space: Masaya Volcano (Nicaragua), 2014–2017
(American Geophysical Union, 2018-02-22) AIUPPA, Alessandro; de Moor, J. Marteen; Arellano, Santiago; Coppola, Diego; Francofonte, Vincenzo; Galle, Bo; Giudice, Gaetano; Liuzzo, Marco; Mendoza, Elvis; Saballos, Armando; Tamburello, Giancarlo; Battaglia, Angelo; Bitetto, Marcello; Gurrieri, Sergio; Laiolo, Marco; Mastrolia, Andrea; Moretti, Robertto
A vigorously degassing lava lake appeared inside the Santiago pit crater of Masaya volcano (Nicaragua) in December 2015, after years of degassing with no (or minor) incandescence. Here we present an unprecedented-long (3 years) and continuous volcanic gas record that instrumentally characterizes the (re)activation of the lava lake. Our results show that, before appearance of the lake, the volcanic gas plume composition became unusually CO2 rich, as testified by high CO2/SO2 ratios (mean: 12.2 6 6.3) and low H2O/CO2 ratios (mean: 2.3 6 1.3). The volcanic CO2 flux also peaked in November 2015 (mean: 81.3 6 40.6 kg/s; maximum: 247 kg/s). Using results of magma degassing models and budgets, we interpret this elevated CO2 degassing as sourced by degassing of a volatile-rich fast-overturning (3.6–5.2 m3 s21) magma, supplying CO2-rich gas bubbles from minimum equivalent depths of 0.36–1.4 km. We propose this elevated gas bubble supply destabilized the shallow (<1 km) Masaya magma reservoir, leading to upward migration of vesicular (buoyant) resident magma, and ultimately to (re)formation of the lava lake. At onset of lava lake activity on 11 December 2015 (constrained by satellite-based MODIS thermal observations), the gas emissions transitioned to more SO2-rich composition, and the SO2 flux increased by a factor 40% (11.4 6 5.2 kg/s) relative to background degassing (8.0 kg/s), confirming faster than normal (4.4 versus 3 m3 s21) shallow magma convection. Based on thermal energy records, we estimate that only 0.8 of the 4.4 m3 s21 of magma actually reached the surface to manifest into a convecting lava lake, suggesting inefficient transport of magma in the near-surface plumbing system.

Examinar

Examinando Artículos científicos por browse.metadata.rights "Attribution-NonCommercial-ShareAlike 4.0 International"