Publication Date:
2022-05-04
Description:
Time-dependent, or 4-D, microgravity changes observed at the Laguna del Maule volcanic
field, Chile, since 2013, indicate significant (1.5 × 10^11 kg) ongoing mass injection. Mass injection is focused
along the Troncoso fault, and subparallel structures beneath the lake at 1.5–2 km depth, and is best
modeled by a vertical rectangular prism source. The low-density change (156 to 307 kg/m3) and limited
depth extent suggest a mechanism of hydrothermal fluid intrusion into existing voids, or voids created by
the substantial uplift, rather than deeper-sourced dike intrusion of rhyolite or basalt magma. Although the
gravity changes are broadly spatially coincident with ongoing surface deformation, existing models that
explain the deformation are deeper sourced and cannot explain the gravity changes. To account for this
discrepancy and the correspondence in time of the deformation and gravity changes, we explore a coupled
magmatectonic interaction mechanism that allows for shallow mass addition, facilitated by deeper magma
injection. Computing the strain, and mean, normal, and Coulomb stress changes on northeast trending
faults, caused by the opening of a sill at 5 km depth, shows an increase in strain and mean and normal
stresses along these faults, coincident with the areas of mass addition. Seismic swarms in mid-2012 to the
west and southwest of the mass intrusion area may be responsible for dynamically increasing permeability
on the Troncoso fault, promoting influx of hydrothermal fluids, which in turn causes larger gravity changes
in the 2013 to 2014 interval, compared to the subsequent intervals.
Description:
Published
Description:
3179–3196
Description:
4V. Dinamica dei processi pre-eruttivi
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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