Spectral acceleration basin amplification factors for interface Cascadia Subduction Zone earthquakes in Canada’s 2020 national seismic hazard model
Bibliographic record
Abstract
Canada’s 2020 national seismic hazard model (CSHM 2020) provides hazard estimates for interface Cascadia Subduction Zone (CSZ) earthquakes in southwestern Canada using four ground motion models (GMMs) with equal weights. Two out of the four GMMs were derived using data primarily from subduction earthquakes in Japan so their use in CSHM 2020 includes a “Japan‐to‐Cascadia” factor to account for local site conditions. Despite this regional factor, the GMMs do not explicitly consider the amplification effects from the Georgia sedimentary basin below Metro Vancouver. This study benchmarks ground motion shaking from a suite of 30 physics‐based simulations of M 9 CSZ earthquakes, which explicitly account for basin effects for periods exceeding 1 s, to corresponding estimates from interface GMMs in CSHM 2020. Using this comparison, this study proposes site‐specific and period‐dependent basin amplification factors for a range of sites located within the Georgia sedimentary basin. The average basin amplification factors at the deepest basin location reach values as high as 2.24 and 6.29 at a 2 s period with respect to basin‐edge and outside‐basin reference locations, respectively. We evaluate the proposed factors by comparing them against long‐period amplifications observed in empirical strong motion recordings from the 2001 M 6.8 Nisqually earthquake. A framework to incorporate the proposed basin amplification factors in the calculation of CSHM 2020 uniform hazard spectra (UHS) is also proposed. The modified UHS ordinates at the deepest basin location reach values that are 58% to 271% higher, at a 2 s period, than non‐basin UHS estimates when amplification factors are calculated with respect to basin‐edge and outside‐basin reference locations, respectively.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".