Abstract
Abstract. In recent decades, finite-element modelling (FEM) has become a very popular tool in volcanological studies and has even been used to describe complex system geometries by accounting for multiple reservoirs, topography, and heterogeneous distribution of host rock mechanical properties. In spite of this, the influence of geological information on numerical simulations is still poorly considered. In this work, 2D FEM of the Colima Volcanic Complex (Mexico) is provided by using the Linear Static Analysis (LISA) software in order to investigate the stress field conditions with increasingly detailed geological data. By integrating the published geophysical, volcanological, and petrological data, we modelled the stress field considering either one or two magma chambers connected to the surface via dykes or isolated (not connected) in the elastic host rocks (considered homogeneous and non-homogeneous). We also introduced tectonic disturbance, considering the effects of direct faults bordering the Colima Rift and imposing an extensional far-field stress of 5 MPa. We ran the model using the gravity in calculations. Our results suggest that an appropriate set of geological data is of pivotal importance for obtaining reliable numerical outputs, which can be considered a proxy for natural systems. Beside and beyond the importance of geological data in FEM simulations, the model runs using the complex feeding system geometry and tectonics show how the present-day Colima volcanic system can be considered in equilibrium from a stress state point of view, in agreement with the long-lasting open conduit dynamics that have lasted since 1913.
Highlights
Magmatism and tectonism are strongly related to regional and local stress fields, affecting both the orientation of faults and the location of volcanic vents (Geyer et al, 2016)
Following successful application in mechanical engineering, the use of finite-element modelling (FEM) has been extensively introduced in volcanology in order to investigate the effects of topography, lithologic heterogeneities, tectonic stresses, and the gravity field on the stress of volcanic systems (e.g. Cailleau et al, 2003, 2005; Buchmann and Conolly, 2007; Manconi et al, 2009; Masterlark et al, 2012) including volcanoes (e.g. Fujita et al, 2013; Charco and Galán del Sastre, 2014; Coco et al, 2016; Ronchin et al, 2015; Hickey et al, 2015; Cabaniss et al, 2018; Rivalta et al, 2019)
The local stress around a volcanic feeding system depends on the geometry of the magma plumbing system, including the chamber(s) and dykes forming it, and on the mechanical properties of the host rock around it (e.g. Marti and Geyer, 2009), especially on changes in the Young modulus (e.g. Gudmundsson, 2011; Jeanne et al, 2017; Heap et al, 2020)
Summary
Magmatism and tectonism are strongly related to regional and local stress fields, affecting both the orientation of faults and the location of volcanic vents (Geyer et al, 2016). 5.4 GPa for volcanic rocks, Heap et al, 2020), but young and non-welded pyroclastic units may be very soft In the last decade, few investigations have been carried out to assess the influence of the amount and quality of geological data on FEM computations (Kinvig et al, 2009; Norini et al, 2010, 2019; Cianetti et al, 2012; Ronchin et al, 2013; Chaput et al, 2014) To bridge this gap, in this work we use the Linear Static Analysis (LISA) software (version 8.0; https://www.lisafea.com/, last access: 10 December 2020) to study the subsurface field state in the Colima Volcanic Complex (CVC, Mexico) at increasing geological detail. The FEM was run starting from simple homogeneous vs. stratified lithology of the subsurface in successively more detail through the addition of single and double magma chambers, feeder dykes, faults, and extensional far-field tectonic stress (Fig. 1b)
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