Stresses induced by magma chamber inflation altered by mechanical
layering and layer dip
Abstract
Understanding the stress distribution around shallow magma chambers is
vital for predicting eruption sites and magma propagation directions. To
achieve accurate predictions, comprehensive insight into the stress
field surrounding magma chambers and near the surface is essential.
Existing stress models for magma chamber inflation often assume a
homogenous elastic half-space or a heterogeneous crust with varying
mechanical properties in horizontal layers. However, as many volcanoes
have complex, non-horizontal, and heterogeneous layers, we enhance these
assumptions by considering mechanically diverse layers with varying
dips. We employed the Finite Element Method (FEM) to create numerical
models simulating two chamber shapes: a circular form and a sill-like
ellipse. The primary condition was a 10 MPa excess pressure within the
magma chamber, generating the stress field. Layers dips by 20-degree
increments, with differing elastic moduli, represented by stiffness
ratios (EU/EL) ranging from 0.01 to 100. Our findings validate prior
research on heterogeneous crustal modeling, showing that high stiffness
ratios disrupt stress within layers and induce local stress rotations at
mismatched interfaces. Layer inclination further influences stress
fields, shifting the location of maximum stress concentration over
varying distances. This study underscores the significance of accurately
understanding mechanical properties, layer dip in volcanoes, and magma
chamber geometry. Improving predictions of future eruption vents in
active volcanoes, particularly in the Andes with its deformed, folded,
and non-horizontal stratified crust, hinges on this knowledge. By
expanding stress models to incorporate complex geological structures, we
enhance our ability to forecast eruption sites and the paths of magma
propagation accurately.