Modeling surface deformation on Kilauea volcano: constraints from the elastic properties of basalt
Academic Affiliation: Graduate, University of Arizona, Geosciences
Science Mentor: Shimon Wdowinski, University of Miami
Katherine Faye Fornash is a graduate student in Geoscience at the University of Arizona. She was a 2009 and 2010 RESESS intern. Her 2009 summer research focused on geochemical evidence for flat-slab subduction in Cenozoic Western North America. Katherine is a runner, hiker, and avid reader.
Magmatic-induced crustal deformation models have been used for decades to make inferences about the geometry of magma chambers and subsurface magmatic processes, such as dike emplacement and magmatic migration. However, the accuracy of such models, and thus the interpretations derived from them, are heavily dependent on the rheology and elastic properties of the interstitial rocks. Accordingly, the elastic parameters of a suite of basaltic surface rocks were determined in order to improve elastic deformation models of Kilauea volcano and to better constrain the relationship between the observed surface deformation and the magmatic activity in the subsurface.
The elastic moduli of interest were calculated from compressional and shear wave velocities, which were measured under both dry and saturated conditions using the pulse transmission technique. In general, values obtained for the Young’s modulus (E= 30 GPa- 55 GPa), shear modulus (m= 13 GPa- 21 GPa), and Bulk modulus (K= 20 GPa-50 GPa) were lower than the typical values used in elastic deformation models, whereas the average value for Poisson’s ratio (0.27) was close to the assumed value of 0.25 for crustal materials. Little-to-no variation was observed between measurements conducted in dry conditions versus those in saturated conditions.
These reduced values suggest that previous elastic deformation models, which use elastic parameters (E= 73 GPa, m= 30 GPa) averaged over the entire crust, may have overestimated the pressure change required to produce the observed pattern of surface deformation, especially in the case of volcanoes with shallow magma reservoirs, such as Kilauea.