Joint Inversion of SPREE Receiver Functions and Surface Wave Dispersion Curves for 3‐D Crustal and Upper Mantle Structure Beneath the U.S. Midcontinent Rift
Bibliographic record
Abstract
Abstract Broadband seismograms from the EarthScope Transportable Array and Superior Province Rifting EarthScope Experiment (SPREE) deployments are used to map the crust and uppermost mantle structures beneath the failed Midcontinent Rift (MCR) of Minnesota/Wisconsin, USA. The results suggest the existence of a variable zone of mafic underplating that is up to 20 km thick (40–60 deep). We jointly invert receiver functions and Rayleigh wave dispersion curves to quantify the region's crustal and mantle shear‐wave velocity structure. Basin sediment thicknesses are mildly asymmetric about the rift axis, with thickest regions immediately beneath the rift. 3‐D modeling shows anomalous lower crust and crust‐mantle transitions beneath the MCR. Sub‐MCR crustal thicknesses are generally >50 km with lower crust Vs of 4.0–4.2 km/s. Away from the MCR, the crust is typically ∼40 km thick. Strong variations in apparent crustal thickness are found along the MCR, increasing significantly in places. An additional layer of shear velocities intermediate between typical lower crust and upper mantle velocities (4.1–4.6 km/s) exists beneath most of the MCR which is thickest beneath the rift axis and pinches out away from the rift. This structure corroborates previous proposals of the presence of an underplated layer near the Moho. Results cannot distinguish between different mechanisms of emplacement (e.g., mafic interfingering within a subsequently down‐dropped lower crust vs. development of a high‐density pyroxenitic residuum at the top of the mantle). Also observed are anomalously high (>4.7 km/s) sub‐rift shear‐wave velocities at ∼70–90‐km depths, suggesting the presence of cold, depleted upper mantle material.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.001 | 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".