Doctor of Philosophy (Ph.D.)
Degree Granting Department
School of Geosciences
Rocco Malservisi, Ph.D.
Timothy H. Dixon, Ph.D.
Charles B. Connor, Ph.D.
Mel Rodgers, Ph.D.
Rob Govers, Ph.D.
natural hazards, potential fields, bimodal volcanism, earthquakes, fault modeling, slow slip events, volcano seismology
Volcanic and tectonic hazards such as volcanic eruptions, earthquakes and tsunamis present risks to about ~45% of the global population. They have caused at least 1.5 trillion dollars in damages worldwide since the start of the 20th century, and the costs are accelerating as population increases. In this dissertation, new data are combined with existing information and novel modeling approaches to quantify volcanic, earthquake and tsunami hazards.
The Blackfoot Reservoir Volcanic Field (BRVF) is a bimodal volcanic field on southeastern margin of the Eastern Snake River Plain in Idaho. In the BRVF, gravity anomalies reveal two shallow silicic intrusions that emplaced concurrently with rhyolitic domes in separate events. These intrusions have a cumulative volume of 50-120 km3 and suggest that large silicic eruptions (VEI ~ 5) are possible in the future.
Off the west coast of Nicaragua, the 1992 Mw 7.7 earthquake caused a large tsunami. In 2012, 150 kilometers to the southeast, there was a Mw 7.6 earthquake offshore the Nicoya Peninsula in Costa Rica that did not generate a tsunami. New stress-constrained kinematic coupling models suggest that despite the lack of a tsunami record the potential for a major one still exists. Additionally, the GPS data in Nicaragua is reconcilable with tsunami rupture models, indicating that current shallow locking is likely and a great earthquake and tsunami could be possible in the next 70 years.
Costa Rica frequently hosts Mw ~ 7 earthquakes in addition to Slow Slip Events (SSEs) every ~21 months. In 2017, an SSE occurred from May to November and coincided with the November 13 Mw 6.5 earthquake. I computed the Coulomb Failure Stress change (CFS) from the SSE resolved on the megathrust to determine if the stress change was sufficient in triggering the earthquake and evaluated the effect for a range of smoothing parameters used in the slip inversion. The CFS from the SSE is negative at the location of the earthquake and suggests that it is unlikely that the static stress change was enough to trigger the earthquake, regardless of the smoothing parameter used in the slip inversion.
Telica Volcano, Nicaragua is a persistently restless volcano that lacks a "background seismicity" that makes it difficult to discern seismicity associated with an eruption. I used repeated earthquakes, or earthquakes with similar waveforms, to reduce the signal to noise ratio and better constrain the location of small events and subsurface processes. I located two families of earthquakes beneath Telica though the uncertainties on the location are very large (>200 km) due to the limited network.
With this dissertation, I show that the volcanic, earthquake and tsunami hazard in these regions may have been underestimated and should be considered in future work.
Scholar Commons Citation
Hastings, Mitchell Scott, "Volcano and Tectonic Hazard Modeling Using Interdisciplinary Geophysical and Geodetic Methods" (2022). USF Tampa Graduate Theses and Dissertations.