The Magnitude 6.2 Reno ShakeOut Scenario
Eric Eckert MS Thesis Defense
Paleoseismic studies indicate that large Holocene earthquakes have occurred within the Mount Rose Fault system. Since these events preceded the creation of seismic networks, ground motion recordings are unavailable, complicating seismic hazard assessments. Physics based seismic hazard analysis is helping others fill these gaps by using the wave equation to predict ground shaking for potential earthquake scenarios, as demonstrated by Bielak et al. (2010) with the Great California ShakeOut Scenario and by Rodgers et al. (2019) through the construction of Hayward rupture scenarios within the Bay Area. Leveraging similar technology enabled the construction of the Reno ShakeOut Scenario, a 3D simulation for a potential magnitude 6.2 earthquake within the Mount Rose Fault system in Reno, Nevada. The ShakeOut Scenario was run with SW4, a powerful wave equation solver using a single kinematic rupture generated with the Graves and Pitarka (2010) method.
Development of the PointsToModels Python library enabled aggregation of selected ReMi Vs30 measurements and gravimetry results into a continuous 3D raster file. Model quality was evaluated by comparing simulations of the Thomas Creek (2015 Mw 4.4) and Mogul (2008 Mw 5.0) events to ground-truth seismic records. The execution of the magnitude 6.2 Reno ShakeOut Scenario builds on these results, enhancing our collective understanding of regional seismic risk, indicating that there is a potential for wide-spread ground shaking at the Modified Mercalli Intensity scale (MMI) magnitudes between VII and VIII (very strong to severe ground shaking), with small areas achieving violent (IX) motions. Distributions of high shaking is controlled by proximity to the rupture, Vs30 values and most significantly basin thickness. Comparisons between SW4 peak ground velocity (PGV) calculations, and PGV estimates computed from the Campbell & Bozorgnia (2008) empirical ground motion model (GMM) indicate that there is significant basin amplification occurring. The 2018 USGS National Seismic Hazard Model (NHSM) forecasts a 10% chance of this region experiencing severe ground shaking and a 2% chance of violent shaking within the next 50 years. Since the GMMs used by the National Hazard model assume no basins and firm 760 m/s soil, it is likely that the actual risk is higher in some areas within the ShakeOut domain. The Reno ShakeOut Scenario enhances our understanding of seismic hazard within the Reno basin by indicating ranges and distributions of potential ground motions.
Related NBMG publication: Planning scenario for a major earthquake in western Nevada