Date of Award
Doctor of Philosophy (PhD)
Mary M. Miller
I describe four investigations of crustal deformation at spatial scales of cm to hundreds of km, and temporal scales of minutes to decades.
With suitable geometry, strainmeters and creepmeters can be used in combination to quantify the propagation direction, velocity, amplitude and location of aseismic slip on a fault. I quantify creep events from a generalized form of the wave equation in terms of three variables, a decay function (ω), a propagation velocity, vp and a slip amplitude.
In the Yellowstone caldera strainmeters monitor loading arising from a seiche on Lake Yellowstone. To explain the high Q factor (i.e. the remarkable persistence) of the seiche I invoke a positive feed-back process whereby hydrothermal vents in the floor of the lake interact with bottom pressure fluctuations associated with lake level oscillations. This is believed to be the first observation of a thermally driven seiche.
GPS data revealed that limited afterslip occurred following the 2015 Mw=7.8 Gorkha earthquake, despite the associated observation that subsurface strain exceeded 10E-5 near the southern margins of rupture. In a published article we hypothesize that blind thrust faults similar to the Gorkha earthquake transfer latent strain to up-dip regions of shallow thrust faults, and that this strain is exploited as additional slip in future earthquakes.
Finally, I use GPS data from 151 sites in Colombia, Venezuela and Panama to identify the rate of loading and probable location of a potential future 8
Mencin, David James, "Periodic and Static Strain Investigations with Borehole Strainmeters and GPS" (2018). Geological Sciences Graduate Theses & Dissertations. 139.