A Geophysical and Field Survey in Central New Hampshire to Search for the Source Region of the Magnitude 6.5 Earthquake of 1638
Bibliographic record
Abstract
In 1638, an earthquake with an estimated MLg of 6.5 ± 0.5 struck New England and adjacent southeastern Canada producing severe shaking in Boston, Massachusetts and Trois-Rivieres, Quebec. Previously published analyses of felt reports place the possible epicenter somewhere within a broad region including NY, NH, VT and ME. The possible source region had been further refined by the application of Omori's Law rate of aftershock decay combined with estimated rupture extent based on modern seismicity, which together suggest that a seismic event of MLg 6.5 ± 0.5 could have occurred in central New Hampshire in 1638. In order to more clearly define the possible active fault for this earthquake and determine its seismotectonic framework within central New Hampshire, three geophysical methods were used to analyze recent, digitally recorded seismic data. The three methods are a relative location analysis, computation of focal mechanisms and computation of focal depths based on fundamental mode Rayleigh waves. The combined results of the analyses are consistent with a thrust fault trending NNW - SSE and possibly dipping eastward in this postulated 1638 epicentral zone. Modern earthquakes in the postulated source area of the 1638 earthquake occur at focal depths of ~3 to 10 km with many of the events occurring below 5 km, suggesting, that this is the depth range of the 1638 rupture. Depending on the depth of the pre-Silurian basement of the Central Maine Terrane, the source of the MLg 6.5 ± 0.5 earthquake of 1638 may be a basement-involved thrust fault or a reactivated east-dipping thrust fault located between the nappes of the overlying Silurian-Devonian aged metasedimentary rocks. When the postulated fault plane is projected to the surface, portions of the Pemigewasset and Merrimack Rivers are found to flow within its surface expression, which suggests that the courses of these rivers may be fault controlled. A fourth research technique, a field survey, was undertaken to search for earthquake-induced liquefaction features along the Pemigewasset, Merrimack and Winnipesaukee Rivers as well as of the Suncook River Avulsion site. Several small strata-bound soft-sediment deformation structures were found during the survey. Although some of the features may be seismically induced, they may also have formed as the result of depositional processes and therefore cannot be attributed to the 1638 earthquake.
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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 | 0.000 |
| 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".