Empirical Site Response for POLARIS Stations in Southern Ontario, Canada
Bibliographic record
Abstract
It is well known that local geology, particularly overburden, can greatly increase ground shaking during an earthquake; the best method for determining the degree of amplification remains controversial, however. The so-called site response is a localized resonant amplification of seismic wave motion that is largely controlled by the thickness, shear modulus, and viscosity of soft soil layers. Accurate knowledge of site-response spectra is important for understanding potentially destructive amplification that could occur during a large earthquake, as well as for calibration of seismic networks. In the absence of cosited measurements of ground motion in deep bedrock and at the surface, site response must be estimated either by numerical computation, based on detailed knowledge of the properties of near-surface layers, or by empirical means. A number of different empirical methods for determining site response are in common use, with various authors citing advantages of one technique over another. The objectives of this study are twofold. Our first purpose is to report empirical site-response spectra for 18 stations (Table 1) of the recently installed POLARIS seismograph network in southern Ontario, Canada (Atkinson et al. , 2003). This network is equipped with Guralp CMG-ESP three-component broadband seismometers and Nanometrics Libra digitizers. Data are digitally sampled at 100 Hz and transmitted in near real-time via satellite to two data-collection centers in London and Ottawa, Ontario. The Ontario POLARIS stations were deployed commencing in late 2001 and cover a roughly rectangular area within the lower Great Lakes region, with a station spacing of 50-100 km (Figure 1). Near-surface layers at these sites depend on local conditions and range from unweathered Precambrian bedrock to fractured Paleozoic limestone, to thick Quaternary till deposits. As a consequence of the variable near-surface conditions, we observe a wide range of site-response spectra. View this table: TABLE 1 POLARIS Stations in Southern Ontario Used for This …
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.005 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".