Stress field
- Simulation of volcanic deformation at Stromboli: the unwrapped InSAR (WP2) displacement map is used as a noise data set (img. 1); we added a complex source (img. 2) to the real noise data; the result provides a realistic signal (img. 3).
- For the test data set provided above, we invert the complex signal (img. 1) and compute the residual (img. 2) - more than 95% of the signal can be explained by this model.
- Volumetric strain change for the best fitting model to the above described synthetic deformation test data set
Motivation
Previous studies have shown that changes in the stress field can trigger volcanic eruptions or unrest. Part of this work package is to investigate the changes of the static stress field that are resulting from deformation sources, such as earthquakes, magma influx into/from magma chambers, dikes intrusions, or gravitational flank movement.
The data of deformation is provided by the work-packages WP 1 and WP 2. The combination of ground control tools and spatially covering InSAR data hence allows to assess the chronology of deformation and its deformation sources (e.g. an propagating dike), and herewith to develop models that aim for a time-series analysis of the static stress field.
Goals and Work plan
It is foreseen to invert surface deformation data in order to obtain the geometry and slip distribution of the source. The source parameters resulting from the inverse models will then be used in an automatic forward modeling technique. This allows estimating the state of stress indirectly, by forward analysis of the sources of dislocation that best explain a measured surface displacement.
The automatic combination of the inversion and forward models in near real-time is challenging and shall be further developed during this project. The sources of deformation are analytically and thereafter numerically represented by a set of dislocation sources, with the aim to retrieve more complex and more realistic finite sources. Solid algorithms are currently developed for isotropic, homogeneous half-space approximations. Here we found that an iterative approach of the Genetic Algorithm or the Simulated Annealing procedure provide best results in considerably short computation times. The deliverables of this work include the quantification of:
- the normal stress at preferred intrusive rift zones,
- the volumetric strain and pore pressure change at levels of potential magma chambers and hydrothermal activity, and
- the Coulomb failure stress at active faults that can be compared to earthquake locations.
The result of inversion provides us with an analytical model for the source of deformation. As illustrated below, via forward calculation we are able to obtain more information about the resulting strain field. This allows quantify stress changes associated with the deformation at nearby structures like tectonic faults, hydrothermal regions or even neighboring volcanic centers. This product shall be available in a Geographic Information System and be comparable to other activity parameters.