Definition of Lateral Spread Displacement for Regional Risk Assessments of Pipeline Vulnerability
Bibliographic record
Abstract
Terasen Gas Inc. (Terasen) operates a natural gas supply and distribution system situated within one of the zones of the highest seismic activity in Canada. The region encompasses significant areas underlain by marine, deltaic, and alluvial soil deposits, some of which are considered to be susceptible to liquefaction and large ground movements when subjected to earthquake ground shaking. Terasen undertook an assessment of seismic risks to its transmission and key intermediate pressure pipelines in the Lower Mainland in 1994 [1]. The seismic assessment focused on approximately 500 km of steel pipelines ranging from NPS 8 to NPS 42 and operating at pressures from 1900 to 4020 kPa. The 1994 risk assessment provided the basis for detailed site-specific assessment and seismic upgrade programs to retrofit its existing system to reduce risks to acceptable levels. While the general approach undertaken in 1994 remains technically sound, advancements have been made over the past 15 years in the understanding of earthquake hazards and their impact on pipelines. In particular, estimates of the earthquake ground shaking hazard in British Columbia as published by Geological Survey of Canada (GSC) have recently been updated and incorporated into the 2005 National Building Code of Canada (NBCC). In addition, empirical methods of estimating lateral spread ground displacements have been improved as new case-history information has become available. Given these changes, Terasen decided in 2009 to reexamine the seismic risk to Terasen’s pipelines. The scope of the updated seismic risk study was expanded over that in 1994 to include pipelines on Vancouver Island and the Interior of British Columbia. For regional assessments, estimates of lateral spread displacements are necessarily based upon empirical formulations that relate displacement to variables of earthquake severity (earthquake magnitude and distance), susceptibility to liquefaction (density, grain size, fines content), and topography (distance from a river bank or ground slope). Implementing empirical formulae with the results of probabilistic seismic hazard calculations is complicated by the fact that the empirical approach requires earthquake magnitude and distance, as a parametric couple, to be related to the ground shaking severity. However, but such a relationship does not exist in the estimates of mean or modal earthquake magnitude and distance disaggregated from a probabilistic seismic hazard analysis. This paper presents an overview of the approach to regional risk assessment undertaken by Terasen and discusses the unique approach adopted for determining lateral spread displacements consistent with the probabilistic seismic hazard analysis.
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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 | 0.003 | 0.006 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.004 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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 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".