CHARACTERIZATION OF SEICHE LOAD INDUCED STRAIN IN THE YELLOWSTONE CALDERA

The Yellowstone volcanic field is one of the largest and most active volcanic systems in the world. Understanding and putting constrains on the subsurface structure and rheology is important in assessing the dynamics and development of the Yellowstone magmatic system. This project seeks to expand on the previous work by using additional data sets from absolute pressure gauges and borehole strainmeters to better characterize the nature of deformation (and subsequently rheological properties) in the Yellowstone Caldera. Three absolute pressure gauges were deployed from August 2014 to September 2015 in a campaign in Yellowstone Lake, with a total of 38 weeks of data collected over three recording intervals. Spectral analysis of the lake data shows that there are several seiches of varying frequencies occurring year round on the lake with the most prominent seiche having a period of ~78 minutes. Analysis of the data from strainmeters in the caldera show that there is regular measureable deformation occurring at periods between ~58 to ~80 minutes, at both previously established and recently added stations, both near the shore and across the caldera. This periodic deformation is caused by the load on the Earth’s crust of the seiche waves in the Lake with the similar period. The largest deformations occur during the largest seiches (> 5cm vertical displacement). Strain at stations near the lake is an order of magnitude higher than that across the caldera. By understanding the relationship between the seiche induced strain near and distant from the lake we can better constrain the nature of deformation in the caldera and therefore the subsurface structure.