majiayu000 /classify-anomaly - Multi-Proxy Discrimination Skill
Purpose
Apply the multi-proxy discrimination framework to classify geochemical anomalies as SEISMIC, CLIMATIC, VOLCANIC, or COMPOUND (CVSE). This is the core methodology for distinguishing earthquake signals from false positives.
Usage
/classify-anomaly <d18O_z> <d13C_z> [--MgCa Z] [--recovery YEARS] [--date YEAR]
Examples:
/classify-anomaly -2.46 +1.60 # Basic two-proxy
/classify-anomaly -2.16 N/A --MgCa +1.60 # Missing δ13C, use Mg/Ca
/classify-anomaly -3.77 -1.18 --date 1275 # Check volcanic correlation
/classify-anomaly -3.6 -2.36 --recovery 46 # With recovery time
Discrimination Framework
Primary Decision Tree
Is there a significant anomaly (|z| ≥ 2.0)?
├─ NO → NORMAL (no event detected)
└─ YES → Check proxy coupling...
│
├─ COUPLED (δ18O and δ13C both anomalous, same sign)
│ └─ Coupling ratio < 2.0 → **SEISMIC CANDIDATE**
│
├─ DECOUPLED (δ18O anomalous, δ13C normal or opposite)
│ ├─ Volcanic correlation? → **VOLCANIC**
│ └─ No volcanic correlation → **CLIMATIC** (drought/wet)
│
└─ δ13C ONLY anomalous (δ18O normal)
└─ Check geogenic CO₂ sources → **SEISMIC CANDIDATE**
Proxy Rules
| Proxy | Seismic Signal | Climatic Signal | Volcanic Signal |
|---|---|---|---|
| δ18O | Negative (deep water) | Variable | Negative (wet) |
| δ13C | Positive > -8‰ (geogenic CO₂) | Negative < -10‰ (biogenic) | Variable |
| Mg/Ca | Positive (old water) | Negative (dilution) | Variable |
| Coupling ratio | < 2.0 (COUPLED) | > 3.0 (DECOUPLED) | > 3.0 (DECOUPLED) |
| Recovery time | 5-71 years | 1-7 years | 1-3 years |
Coupling Ratio Calculation
Coupling ratio = |δ18O_z| / |δ13C_z|
< 2.0 → COUPLED (seismic)
2.0-3.0 → AMBIGUOUS
> 3.0 → DECOUPLED (climatic/volcanic)
Recovery Time Assessment
| Duration | Classification | Example |
|---|---|---|
| 1-3 years | VOLCANIC | Samalas 1257 recovery |
| 3-7 years | CLIMATIC | Drought recovery |
| 10-30 years | SEISMIC | Typical earthquake |
| 30-71 years | MAJOR SEISMIC | Lapa Grande ~96 CE (71 yr) |
Temporal Shape (Mg/Ca)
| Shape | Onset Rate | Classification |
|---|---|---|
| SHARK FIN | > 0.5 σ/mm | SEISMIC (rapid onset) |
| HUMP | < 0.5 σ/mm | CLIMATIC (gradual onset) |
Classification Output
## Anomaly Classification: [Date/Window]
### Input Metrics
| Metric | Value | Notes |
|--------|-------|-------|
| δ18O z-score | -2.46σ | Significant negative |
| δ13C z-score | +1.60σ | Marginal positive |
| Mg/Ca z-score | +2.25σ | Significant positive |
| Recovery time | 15 years | Extended |
| Coupling ratio | 1.54 | COUPLED |
### Discrimination Tests
| Test | Result | Interpretation |
|------|--------|----------------|
| δ18O significance | ✓ PASS | z ≤ -2.0 |
| δ13C coupling | ✓ PASS | Same direction, ratio < 2 |
| Mg/Ca elevation | ✓ PASS | Deep/old water signature |
| Recovery duration | ✓ PASS | > 10 years |
| Volcanic correlation | ✗ NONE | No major eruptions ±5 years |
### CLASSIFICATION: **SEISMIC CANDIDATE** (Tier 1)
**Confidence**: HIGH
**Evidence tier**: Tier 1 (multi-proxy)
**Rationale**:
- Coupled proxies (ratio 1.54) indicate Chiodini mechanism
- Elevated Mg/Ca confirms deep water mobilization
- Extended recovery (15 yr) rules out volcanic/climatic
- No volcanic forcing in time window
Evidence Tiers
| Tier | Requirements | Confidence |
|---|---|---|
| Tier 1 | Multi-proxy (δ18O + Mg/Ca OR δ13C) + recovery > 10 yr + no volcanic | HIGH |
| Tier 2 | δ18O + historical documentation OR single additional proxy | MODERATE |
| Tier 3 | Single proxy OR weak correlation | LOW |
Volcanic Correlation Check
When --date is provided, check against major eruptions:
| Date Window | Major Eruptions | VSSI (Tg S) |
|---|---|---|
| 1255-1260 CE | Samalas 1257 | 59.42 |
| 1228-1235 CE | Unknown 1230 | 23.78 |
| 1105-1115 CE | Unknown 1108 | 19.16 |
| 1452-1458 CE | Kuwae 1452 | 31.06 |
| 1808-1816 CE | Unknown 1809 + Tambora 1815 | 22.10 + 26.03 |
If date ±5 years overlaps major eruption AND proxies are DECOUPLED → VOLCANIC
Output Classifications
| Classification | Criteria |
|---|---|
| SEISMIC | Coupled proxies, no volcanic, recovery > 10 yr |
| CLIMATIC | Decoupled proxies, no volcanic |
| VOLCANIC | Decoupled proxies, volcanic correlation |
| CVSE | Compound event: volcanic + seismic + hydrological |
| EQUIVOCAL | Insufficient evidence to classify |
CVSE (Compound Volcanic-Seismic Event) Criteria
All THREE must be present:
- Volcanic forcing - Documented eruption in ice cores
- Seismic signal - Mg/Ca or δ13C proxy confirmation
- Hydrological expression - Documented floods or aquifer disruption
Known CVSEs:
- 1285 Italy (UE6 + earthquake + Genoa floods)
- 936 Belize (Eldgjá + seismic + global floods)
- 853 Pacific NW (Churchill VEI 6 + Cascadia S + drought)
Example Full Analysis
User: /classify-anomaly -3.77 -1.18 --date 1275 --recovery 3
Classification Analysis:
Input:
- δ18O z = -3.77σ (EXTREME NEGATIVE)
- δ13C z = -1.18σ (not significant)
- Date: ~1275 CE
- Recovery: 3 years
Tests:
- Coupling ratio: 3.77/1.18 = 3.19 → DECOUPLED
- Volcanic check: 1257 Samalas (59.42 Tg S) within 18 years
- Recovery: 3 years (volcanic range)
CLASSIFICATION: **VOLCANIC**
Rationale:
- Decoupled signature (δ18O >> δ13C)
- Temporal proximity to 1257 Samalas (largest eruption in 2000 years)
- Short recovery (3 yr) matches volcanic pattern
- NOT seismic despite extreme δ18O
This is the documented Samalas volcanic response at Yok Balum.
Important Notes
- Missing δ13C - Use Mg/Ca as substitute coupling test
- Uncertainty propagates - Single proxy = Tier 3 max
- CVSE is rare - Requires ALL THREE components
- Recovery time is diagnostic - "Order of magnitude gap" between volcanic (1-3 yr) and seismic (10-71 yr)
- Update ANOMALY_CATALOG.md - After classification with approval