P- and S-wave velocity models incorporating the Cascadia subduction zone for 3D earthquake ground motion simulations, Version 1.6—Update for Open-File Report 2007–1348

Abstract

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit https://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation:Stephenson, W.J., Reitman, N.G., and Angster, S.J., 2017, P-and S-wave velocity models incorporating the Cascadia subduction zone for 3D earthquake ground motion simulations, version 1. AcknowledgmentsThe V P and V S property volumes of model V1.6 were greatly improved by feedback from end-users including Art Frankel (U.S. Geological Survey [USGS]), Andy Delorey (Los Alamos National Laboratory), and John Vidale (University of Washington). We thank Jack Odum and Robert Williams (USGS) for their technical reviews, which greatly improved this manuscript. Special thanks to Jordan Bretthauer (USGS) for assistance in developing figure 1 of this report. Discussions with numerous collaborators and other interested parties seeking components of the model for their research helped prompt us to formally complete this updated documentation. This research was supported by funding from the USGS Earthquake Hazards Program. IntroductionIn support of earthquake hazards studies and ground motion simulations in the Pacific Northwest, threedimensional (3D) P-and S-wave velocity (V P and V S , respectively) models incorporating the Cascadia subduction zone were previously developed for the region encompassed from about 40.2°N. to 50°N. latitude, and from about 122°W. to 129°W. longitude ( fig. 1). This report describes updates to the Cascadia velocity property volumes of model version 1.3 ([V1.3]; Stephenson, 2007), herein called model version 1.6 (V1.6). As in model V1.3, the updated V1.6 model volume includes depths from 0 kilometers (km) (mean sea level) to 60 km, and it is intended to be a reference for researchers who have used, or are planning to use, this model in their earth science investigations. To this end, it is intended that the V P and V S property volumes of model V1.6 will be considered a template for a community velocity model of the Cascadia region as additional results become available. With the recent and ongoing development of the National Crustal Model (NCM; Boyd and Shah, 2016), we envision any future versions of this model will be directly integrated with that effort. BackgroundThe Cascadia subduction zone stretches for over 1,000 km, from the Mendocino Triple Junction off the northern California coast northward to Vancouver Island, Canada ( fig. 2). The primary reasons for developing these model volumes are (1) for simulat...

Source‐Dependent Amplification of Earthquake Ground Motions in Deep Sedimentary Basins

“…We use a 3‐D finite difference velocity‐stress code (Liu & Archuleta, ) applied to a 3‐D seismic velocity model for the Cascadia subduction zone that includes the Puget Lowland basins (i.e., Seattle, Tacoma, and Everett basins; Stephenson et al, ) to simulate long‐period wave propagation up to a frequency of 1 Hz. Each point source is described using a Brune () source time function and a rise time of 0.5 s. The 3‐D seismic velocity model for Cascadia was developed using a variety of geophysical measurements, including shallow seismic reflection profiling, gravity modeling, and seismic tomography using local and regional earthquakes, ambient noise, and active sources.…”

“…Map of the Puget Lowland showing the depth to a shear wave velocity of 2.5 km/s and the locations of the Seattle, Tacoma, and Everett basins based on Stephenson et al (). Locations of point source earthquakes used in the 3‐D simulations are also shown.…”

Estimating economic losses of midrise reinforced concrete shear wall buildings in sedimentary basins by combining empirical and simulated seismic hazard characterizations

“…Compared with the other basins in the western United States, Seattle has the largest maximum value of Z 2.5 , which is equal to 6.9 km. 26 As a result, the spectral accelerations from the 2014 to the 2018 NSHM Uniform Hazard Spectrum (UHS) for a hazard level with a 2% probability of exceedance in 50-year is approximately 50% larger for periods in the range of 1-4 s. Increases in spectral acceleration due to basin amplification are larger at longer periods. For instance, the increase in spectral acceleration at a period of 0.2 s is only 15%, whereas for a 2.0 s period, the increase is 66%.…”

Calibration of the U.S. Geological Survey National Crustal Model

“…Deviations for the Seattle and Salt Lake City models were not investigated. The Seattle model available from ScienceBase (Stephenson, 2017) provides a model with only 500 m of vertical resolution, which is insufficient for comparison. In the Salt Lake City model, little to no deviation from the measured data probably exists because of the way in which the model was constructed.…”