Model comparison of volcanic aerosol forcing and climate impact of tropical and extratropical eruptions

<p>Major volcanic eruptions increase sulfate aerosols in the stratosphere. This causes a large-scale dimming effect with significant surface cooling and stratosphere warming. However, the climate impact differs for tropical and extratropical eruptions, and depends on the eruption season and height, and volcanic volatiles injections. In order to study different volcanic aerosol forcing and their climate impact, we perform simulations based on the fully coupled Community Earth System Model version 2 (CESM2) with the version 6 of the Whole Atmosphere Community Climate Model (WACCM6) with prognostic stratospheric aerosol and chemistry. In this study, explosive eruptions at 14.6 N and 63.6 N in January and July injecting 17 MT and 200 MT SO<sub>2</sub> at 24 km with and without halogens are simulated, in line with Central American Volcanic Arc and Icelandic volcanic eruptions. Simulated changes in the stratospheric sulfate and halogen burdens, and related impacts on aerosol optical depth, radiation, ozone and surface climate are analyzed. These simulated volcanic eruption cases will be compared with simulations based on the aerosol-climate model MAECHAM5-HAM.</p>

Preliminary results on the characterisation of the Guaycume fault (El Salvador) from geodetic and seismological data

<p>The Guaycume fault is a right-lateral strike-slip structure located in Western El Salvador, within the El Salvador Fault Zone (ESFZ). The ESFZ consists of a strike-slip fault system extending through the Central American Volcanic Arc, on the western margin of the Chortís block, where the Cocos plate subducts under the Caribbean plate.</p><p>The Guaycume fault has been proposed as a possible source for the Mw 6.4 1917 El Salvador destructive earthquake, presenting high seismic potential in close proximity to San Salvador (Alonso-Henar et al., 2018). Its geomorphological expression has been clearly identified (Martinez-Diaz et al., 2016); however, few specific studies are currently published, and its behaviour and kinematics remain widely unknown. Notably, there is a lack of precise information about the amount of deformation that this fault currently absorbs of the westward movement (relative to the Chortís block) of the forearc sliver.</p><p>We process GNSS data in the area from 2007 to 2020 in order to retrieve the GNSS velocity field surrounding the Guaycume fault. We use these data to perform a thorough kinematic study, updating the previously existing slip rates (Staller et al., 2016). Combined with seismological data, this information allows us to understand the seismic cycle of the fault to a better extent, thus leading to a better comprehension of its seismic potential.</p>

Using ambient noise tomography to image tectonic and magmatic features of the Irazú-Turrialba volcanic complex at regional and local scales

<p>Passive seismology in volcanically active locations provides a valuable insight into the structural and evolutionary characteristics of subsurface magmatic features. The Irazú-Turrialba Volcanic Complex (ITVC) consists of a twin-system of volcanoes in Costa Rica, located at the south-eastern end of the Central American Volcanic Arc (CAVA). The ITVC represents a noticeable delineation of this subduction arc sequence, influenced by the formation of the Panama microplate and potentially driven by the Central Costa Rican Deformation belt (CCRDB). This volcanic arc is formed by the subduction of the Cocos Plate, beneath the Caribbean plate. This is an interesting twin-volcanic system consisting of the close-system of Irazú, and actively-venting open-system of Turrialba. Utilizing ambient noise tomography (ANT), 3D shear-wave velocity models are retrieved and compared to previously determined major tectonic features at both regional and local scales</p> <p> </p> <p>Data were collected from 20 temporary broadband seismic stations, forming a network around the ITVC, and supplemented by 45 permanent stations from the regional networks (OVSICORI & RSN). We used the continuous noise readings from vertical components to compute cross-correlation functions. We then used Rayleigh wave group-velocity dispersion curves to perform an inversion to obtain 2D group velocity maps at both regional and local scales. A further inversion step was undertaken to obtain 3D shear-wave velocity models of the regional features of the Central American Volcanic Arc and more local-scale features of the plumbing system beneath the ITVC. Features determined in the inversions are compared to the literature-established, large-scale and local tectonic features, creating an image of the twin-system complex. In particular, we compare the subsurface magmatic features of the ITVC to establish the impact of local and regional faulting on the shape of the internal plumbing structure, and to determine whether ANT can effectively constrain these known tectonic features.</p> <p> </p> <p>We establish an improved understanding of the ITVC whole-system plumbing, and the regional velocity anomalies attributed to other Costa Rican volcanic systems within the Central American Volcanic Arc and relation to the tectonics.</p>