 |
| Titel |
Numerical model for the evaluation of Earthquake effects on a magmatic system. |
| VerfasserIn |
Deepak Garg, Antonella Longo, Paolo Papale |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250121489
|
| Publikation (Nr.) |
 EGU/EGU2016-240.pdf |
|
|
|
|
|
| Zusammenfassung |
| A finite element numerical model is presented to compute the effect of an Earthquake on the
dynamics of magma in reservoirs with deformable walls. The magmatic system is hit by a
Mw 7.2 Earthquake (Petrolia/Capo Mendocina 1992) with hypocenter at 15 km diagonal
distance. At subsequent times the seismic wave reaches the nearest side of the magmatic
system boundary, travels through the magmatic fluid and arrives to the other side of the
boundary. The modelled physical system consists in the magmatic reservoir with a thin
surrounding layer of rocks. Magma is considered as an homogeneous multicomponent
multiphase Newtonian mixture with exsolution and dissolution of volatiles (H2O+CO2).
The magmatic reservoir is made of a small shallow magma chamber filled with
degassed phonolite, connected by a vertical dike to a larger deeper chamber filled with
gas-rich shoshonite, in condition of gravitational instability. The coupling between the
Earthquake and the magmatic system is computed by solving the elastostatic equation
for the deformation of the magmatic reservoir walls, along with the conservation
equations of mass of components and momentum of the magmatic mixture. The
characteristic elastic parameters of rocks are assigned to the computational domain at the
boundary of magmatic system. Physically consistent Dirichlet and Neumann boundary
conditions are assigned according to the evolution of the seismic signal. Seismic forced
displacements and velocities are set on the part of the boundary which is hit by wave.
On the other part of boundary motion is governed by the action of fluid pressure
and deviatoric stress forces due to fluid dynamics. The constitutive equations for
the magma are solved in a monolithic way by space-time discontinuous-in-time
finite element method. To attain additional stability least square and discontinuity
capturing operators are included in the formulation. A partitioned algorithm is used to
couple the magma and thin layer of rocks. The magmatic system is highly disturbed
during the maximum amplitude of the seismic wave, showing random to oscillatory
velocity and pressure, after which it follows the natural dynamic state of gravitational
destabilization. The seismic disturbance remarkably triggers propagation of pressure
waves at magma sound speed, reflecting from bottom to top, left and right of the
magmatic system. A signal analysis of the frequency energy content is reported. |
|
|
|
|
|
|