The Seismicity of the Western Lake Ontario Area: Results from the Southern Ontario Seismic Network (SOSN), 1992-2001
Bibliographic record
Abstract
The Southern Ontario Seismic Network (SOSN) consists of eleven three-component short-period seismic stations, located mainly in the Toronto-Hamilton-Niagara area of Ontario, Canada. The network has been in operation by the University of Western Ontario (UWO) for Ontario Power Generation (OPG) since 1991 with the purpose of obtaining information on the seismicity and seismic hazards of a region of southern Ontario in which a number of nuclear power stations are located. Over the past decade, an average of more than ten local earthquakes per year in the western Lake Ontario area was detected by the SOSN. Most of the events were in the 2–3 magnitude ( M N ) range. The largest events during this time took place in the surrounding regions—Pymatuning, northwestern Pennsylvania (285 km southwest from Toronto, just south of Lake Erie, 25 September 1998, M N 5.4), northern Ontario/Quebec border (325 km north of Toronto, 1 January 2000, M N 5.2), Ashtabula, Ohio (262 km southwest of Toronto, 26 January 2001, M N 4.4), and Au Sable Forks, New York (436 km east of Toronto, 20 April 2002, M N 5.1). The largest earthquake ( M N 3.8) in the western Lake Ontario region during the past ten years occurred on 26 November 1999 in Lake Ontario, 16 km southeast of the town of Pickering, which lies just east of Toronto. The estimated location uncertainty (±2 km) is significantly better than that which was possible before 1991. The focal depths, though poorly constrained for most events, are shown to lie in the 3–15 km range, well within the Grenvillian rocks of the Precambrian Shield. The new seismicity map shows that a definite pattern is emerging in the SOSN data set in Lake Ontario, one which is significantly different from the past historical earthquake patterns obtained when the instrumental coverage was poor. Most events occur in scattered clusters in the western part of Lake Ontario and the northwestern corner of New York State. The area of seismicity does not extend significantly to the north of western Lake Ontario and appears to end to the west rather abruptly along a 30 km small fault line running from south of Hamilton in a north-northeasterly direction to Burlington, Ontario. Although the area of seismicity coincides with a region of linear magnetic anomaly trends (suggesting a strong structural fabric in the basement rocks), the correlation of seismicity of the new SOSN data set with magnetic lineaments is still unclear. The cause of the seismicity is speculated to be related to water flows along various fissures below the lake. It is known from induced seismicity studies of reservoirs that the presence of fluids can cause earthquakes by changing the pore pressure and reducing the friction along any faults which may be present. From seismic reflection studies, dipping structures and shear zones have been imaged to extend southeastward under Lake Ontario. This may explain why most of the earthquakes are occurring under the lake or southeast of the lake.
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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 | 0.003 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| Insufficient payload (model declined to judge) | 0.002 | 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".