TH score update: VOLCANO

[matamadio]

Hazard Processing Method

• Data Source: VEI buffered polygons (GeoPackage)
• Unit: VEI (Volcanic Explosivity Index)
• Default Value Threshold: 2 (not used for scoring)
• Default Area Threshold: 3%

Workflow:

1. Perform spatial intersection with admin units
2. If no intersection: Score = -1 (not affected - outside volcano hazard zone)
3. Calculate intersection area as percentage of admin unit area
4. Find maximum VEI where intersection area ≥ area threshold %
5. If max VEI = 0 (no VEI meets area threshold): Score = -1 (not affected)
6. Remap qualifying VEI to hazard score using ranges:
   • VEI < 2 → Score 0 (no hazard)
   • VEI 2-3 → Score 0
   • VEI 3-4 → Score 1
   • VEI 4-5 → Score 2
   • VEI > 5 → Score 3

Scoring Logic:

• Outside VEI buffers → Score -1 (not affected)
• Inside buffers but no VEI meets area threshold → Score -1 (not affected)
• Maximum qualifying VEI determines score (0-3)
• Value threshold parameter is disabled (area-based only)

Output Columns:

• VEI_max: Maximum qualifying VEI value
• Hazard_score: Final remapped score

---

Comparison

New score distribution: ADM2

New score distribution: URBAN

[matamadio]

Original (2019) vs. 2025 Update

Data Overview

• Original Dataset: 38,229 administrative regions (ADM2 level)
• 2025 Dataset: 39,370 administrative regions (ADM2 level)
• High-Quality Matches: 33,207 regions (90%+ matching confidence)
• Unmatched Original: 5,022 regions
• Unmatched 2025: 6,268 regions

Technical Notes

• Hazard ranks: -1 = N/A, 0 = Very Low, 1 = Low, 2 = Medium, 3 = High
• Original data used text codes (VLO, LOW, MED, HIG), converted to numeric for easier comparison (delta)
• Matching threshold: 90% similarity required for inclusion in analysis
• Medium-quality matches (70-90%) available in separate sheet for manual review

Matching Method

Fuzzy string matching using hierarchical location names (Country | Admin1 | Admin2).
Only high-quality matches (≥90% similarity) were used for hazard comparison.

---

• Regions Compared: 1,316
• Agreement: 55.5% (731 unchanged)
• Net Trend: Downgrades (542 downgrades vs 43 upgrades)
• Average Change: -1.16 ranks
• Notable Shifts:
  • High risk regions decreased from 1,045 to 681

Comment

The new dataset filters out most ancient eruptions, leaving only active volcano and with VEI > 2. This reflects in a general score downgrade, with several risk locations entirely disappearing e.g. continental africa and asia, which makes sense to me but I defer to @stufraser1