The orientation of faulting associated with volcano-tectonic earthquakes
follows the stress field there, as with tectonic earthquakes. Therefore,
stress changes associated with volcanic activity change fault
orientations or focal mechanisms. Zhan et al. (2022) observed temporal
changes of focal mechanisms associated with volcanic unrest. They
decomposed the stress field into the ambient differential stress,
volcano loading, and the stress change by the dike intrusion; they then
evaluated their relative contributions to constrain the magnitude of the
ambient differential stress that is consistent with the observation.
This study indicates that focal mechanisms can be used to monitor the
stress state of an active volcano. Combining focal mechanisms with other
geophysical observables, such as seismic anisotropy and geodetic
measurements, will give us more precise assessments of the stress state,
leading to better forecasts of volcanic activity.