Along‐strike variations in the shallow seismic velocity structure of the Seattle fault zone: Evidence for fault segmentation beneath Puget Sound
Bibliographic record
Abstract
Around 1100 years ago, the Seattle fault, which trends east‐west beneath Puget Sound and the greater Seattle metropolitan area, experienced a M > 7 earthquake. We present high‐resolution images of the shallow P wave velocity variation across the fault zone. These images were obtained by tomographic inversion of the first arrivals recorded along two north‐south oriented seismic reflection lines shot within Puget Sound near Seattle. Just beneath the seafloor, the fault zone includes uplifted Tertiary rocks with seismic velocities in the range of 2300 to 2600 m s −1 . These velocities contrast markedly with values of ∼1600 m s −1 in shallow Holocene sediments. South of the Seattle fault zone volcanic rocks of the Crescent Formation, which exhibit velocities >3700 m s −1 , are identified at depths of only 900 m. Seismic velocities of around 2600 m s −1 , which represent Oligocene rocks, are found in the hanging wall of the Seattle fault beneath eastern Puget Sound. In the west, lower, 2300 m s −1 seismic velocities occur, probably due to the presence of Miocene rocks, which are not found in the east. Along‐strike velocity variations arise from the folding of Tertiary rocks and the presence of distinct fault splays, including a north striking tear fault characterized by depressed seismic velocities that was intersected by the eastern seismic line. Along‐strike differences in the uplift of Tertiary rocks beneath Puget Sound are likely associated with the existence of a segment boundary of the Seattle fault system.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.001 |
| 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".