Seismic Tremors and Magma Wagging During Explosive Volcanism
Bibliographic record
Abstract
Low frequency volcanic tremor is a common feature of explosive volcanism and a key ingredient in assessments of volcanic hazard. Most models for volcanic tremor rely on specific properties of the geometry, structure and constitution of volcanic conduits, as well as the gas content of the erupting magma. Mark Jellinek and David Bercovici use a model of a silicic magma rising in a conduit as a columnar plug to demonstrate that, for most geologically relevant conditions, the magma column will oscillate or 'wag' against the restoring force of a highly vesicular annulus of sheared bubbles at observed tremor frequencies. They also find that the frequencies produced are relatively insensitive to the conduit structure and geometry. Most models for volcanic tremor rely on specific properties of the geometry, structure and constitution of volcanic conduits as well as the gas content of the erupting magma. Here, a model is used of a silicic magma rising in a conduit as a columnar plug to demonstrate that, for most geologically relevant conditions, the magma column will oscillate or 'wag' against the restoring force of a highly vesicular annulus of sheared bubbles at observed tremor frequencies. The frequencies produced are relatively insensitive to the conduit structure and geometry. Volcanic tremor is a ubiquitous feature of explosive eruptions. This oscillation persists for minutes to weeks and is characterized by a remarkably narrow band of frequencies from about 0.5 Hz to 7 Hz (refs 1–4). Before major eruptions, tremor can occur in concert with increased gas flux and related ground deformation5,6,7. Volcanic tremor is thus of particular value for eruption forecasting6,8. Most models for volcanic tremor rely on specific properties of the geometry, structure and constitution of volcanic conduits as well as the gas content of the erupting magma. Because neither the initial structure nor the evolution of the magma-conduit system will be the same from one volcano to the next, it is surprising that tremor characteristics are so consistent among different volcanoes. Indeed, this universality of tremor properties remains a major enigma. Here we employ the contemporary view that silicic magma rises in the conduit as a columnar plug surrounded by a highly vesicular annulus of sheared bubbles9,10. We demonstrate that, for most geologically relevant conditions, the magma column will oscillate or ‘wag’ against the restoring ‘gas-spring’ force of the annulus at observed tremor frequencies. In contrast to previous models, the magma-wagging oscillation is relatively insensitive to the conduit structure and geometry, which explains the narrow band of tremor frequencies observed around the world. Moreover, the model predicts that as an eruption proceeds there will be an upward drift in both the maximum frequency and the total signal frequency bandwidth, the nature of which depends on the explosivity of the eruption, as is often observed.
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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) | 0.005 | 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".