TH scores update: EARTHQUAKE

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Hazard Processing Method

• Data Source: 4 return periods (RP250, RP475, RP975, RP2475) - PGA rasters
• Unit: PGA-g
• Default Value Thresholds:
  • RP50=120
  • RP100=100
  • RP1000=80
  • RP10000=60
• Default Area Threshold: 5%

Workflow:

1. Extract all pixel values for each RP raster within each admin unit
2. Calculate mean (for reporting) and area percentage (% of pixels > value threshold)
   • Note: The mean value is calculated and stored in output columns (RP{X}_mean) but is NOT used for scoring. Only the area percentage determines the score.
3. Check if area threshold % met per RP
4. Score = count of RPs meeting threshold (0-4)
5. Special case: If NO pixels exceed threshold in ALL RPs → Score -1 (not affected)

Scoring Logic:

• 4 RPs meet threshold → Score 3
• 3 RPs meet threshold → Score 2
• 2 RP meets threshold → Score 1
• 1 RPs meet threshold → Score 0
• No pixels > threshold in any RP → Score -1 (not affected by cyclones)

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Comparison

Comment: switching from zonal mean to area threshold avoid to flatten out extreme values. Using 4 RPs allow to better define not-affected areas (grey).

New score distribution: ADM2

New score distribution: URBAN

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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.

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• Regions Compared: 18,367
• Agreement: 58.4% (10,726 unchanged)
• Net Trend: Balanced (3,662 upgrades vs 3,979 downgrades)
• Average Change: -0.12 ranks
• Notable Shifts:
  • Medium → High: 3,094 regions (significant!)
  • High risk regions increased from 2,436 to 5,237

Comment

The original score approach (zonal mean) flatted out extreme values, leading to mostly average scores; the new approach retains these extrene values (both high and low), and as a consequenze the score distribution resemble a log instead of a normal curve. This allows risk hotspots to emerge more clearly, e.g. the african rift.