Group B, Poster #216, Ground Motions

Exploring Basin Amplification within the Reno Metropolitan Area in Northern Nevada Using 3D Scenarios

John N. Louie, Eric Eckert, Lauren M. Lewright, Michelle Scalise, Aditya Prathap, & Ken Smith
Poster Image: 

Poster Presentation

2022 SCEC Annual Meeting, Poster #216, SCEC Contribution #11968 VIEW PDF
The Reno metropolitan area (located within the Truckee Meadows in northern Nevada) is subjected to significant seismic risk, primarily resulting from the region’s proximity to the Mount Rose fault system and the urban area’s presence within a large complex of thin (< 1 km thick) sedimentary sub-basins. Numerous paleoseismic studies have shown the Mount Rose fault system has a history of producing large Holocene earthquakes. To help explore this hazard, we used SW4, a physics-based wave-equation modeling tool, to develop a suite of non-ergodic scenarios at low frequency (<1 Hz) as well as the Reno ShakeOut Scenario at <3.1 Hz. The 3.1 Hz scenario uses a grid with a minimum spacing of... 20 m with eight points per minimum wavelength to perform a full 3D simulation for a potential magnitude 6.3 earthquake within the Mount Rose fault system. This calculation is limited to a minimum shear-wave velocity (Vs min) of 500 m/s. Results at 3 Hz indicate that there is a potential for widespread and variable ground shaking at modified Mercalli intensity (MMI) magnitudes between VII and VIII (very strong to severe ground shaking), with some areas achieving violent (IX and X) motions. Distributions of high shaking are controlled by proximity to the rupture, geotechnical shear-wave velocity, topography; and significantly, basin geometry. Comparisons between SW4 peak ground velocity (PGV) computations, and PGV estimates calculated from the Campbell and Bozorgnia empirical ground-motion model emphasize the degree to which very thin basins may result in greater hazard than is currently predicted. Non-ergodic scenarios for small earthquakes in and around the city suggest basin amplifications commonly exceed a factor of 4 between 0.3 and 0.8 Hz. These amplifications develop despite the thickness of low-velocity sediments below Reno rarely exceeding 1 km. This information helps improve our understanding of regional risk by highlighting these significant basin effects and the local variability that is likely to occur with any large seismic event.