Table 2.
Probability-tree exercises to assist eruption forecasting.
| Date | Probability of eruption in 2 weeks | Probability eruption increases (2 weeks) | Probability eruption stay same (2 weeks) | Probability eruption lessens (2 weeks) | Maximum VEI 1 (2 weeks) | Maximum VEI 2 (2 weeks) | Maximum VEI 3 (2 weeks) | Maximum VEI ≥ 4 (2 weeks) |
|---|---|---|---|---|---|---|---|---|
| 20-Sep | 0.50 ± 0.10 | 0.45 | 0.45 | 0.10 | ||||
| 23-Sep | 0.70 ± 0.10 | 0.45 | 0.45 | 0.10 | ||||
| 02-Oct | 0.60 ± 0.10 | 0.45 | 0.45 | 0.10 | ||||
| 17-Oct | 0.50 ± 0.20 | 0.45 | 0.25 | 0.20 | 0.10 | |||
| 15-Nov* | 0.40 ± 0.20 | 0.45 | 0.25 | 0.20 | 0.10 | |||
| Post-Eruption Initiation | ||||||||
| 11-Dec | 0.55 | 0.40 | 0.05 | 0.55 | 0.28 | 0.17 | ||
| 24-Jan | 0.20 | 0.70 | 0.10 | 0.75 | 0.20 | 0.05 | ||
| 12-Mar | 0.25 | 0.60 | 0.15 | 0.90 | 0.09 | 0.01 | ||
*In only the 15-Nov event tree, the relative likelihood that eruptions would be phreatic vs. magmatic was added to the tree and estimated at 80%:20%.