majiayu000 /zscore - Quick Z-Score Analysis Skill
Purpose
Rapidly calculate z-scores for speleothem δ18O, δ13C, and other proxy data to identify significant anomalies. This is the core analysis workflow used multiple times per session.
Usage
/zscore <cave_name_or_entity_id> [--start YEAR] [--end YEAR] [--proxy PROXY] [--threshold Z]
Examples:
/zscore YOKI # All Yok Balum data
/zscore CRC-3 --start 1850 --end 1950 # Crystal Cave 1850-1950
/zscore "Bàsura" --proxy d18O,d13C # Multiple proxies
/zscore 390 --threshold 2.5 # Higher significance threshold
Workflow
Step 1: Get Cave Data
Use MCP tools to retrieve data:
# Search for cave
sisal_search_caves region="Italy" min_samples=50
# Get samples for specific entity
sisal_get_samples entity_id="123"
Step 2: Extract Proxy Measurements
From the returned data, extract:
d18O_measurement- Oxygen isotope values (‰ VPDB)d13C_measurement- Carbon isotope values (‰ VPDB)interp_age- Interpolated age (years BP)year_CE- Calendar year (1950 - interp_age)
Step 3: Calculate Baseline Statistics
For the full record (or specified baseline period):
δ18O: μ = mean(d18O), σ = std(d18O)
δ13C: μ = mean(d13C), σ = std(d13C)
Step 4: Calculate Z-Scores
For each measurement:
z = (measurement - μ) / σ
Step 5: Identify Anomalies
Apply threshold (default |z| ≥ 2.0):
| Z-Score Range | Classification |
|---|---|
| z ≤ -3.0 | EXTREME NEGATIVE |
| -3.0 < z ≤ -2.0 | SIGNIFICANT NEGATIVE |
| -2.0 < z < +2.0 | Normal |
| +2.0 ≤ z < +3.0 | SIGNIFICANT POSITIVE |
| z ≥ +3.0 | EXTREME POSITIVE |
Step 6: Generate Output Table
## Z-Score Analysis: [Cave Name]
**Entity**: [entity_id]
**Data range**: [start] - [end] CE
**Measurements**: [N] δ18O, [N] δ13C
### Baseline Statistics
| Proxy | Mean (μ) | Std Dev (σ) | N |
|-------|----------|-------------|---|
| δ18O | -X.XX‰ | X.XX‰ | N |
| δ13C | -X.XX‰ | X.XX‰ | N |
### Anomalies (|z| ≥ 2.0)
| Year CE | δ18O (‰) | δ18O z | δ13C (‰) | δ13C z | Classification |
|---------|----------|--------|----------|--------|----------------|
| ~1394 | -6.23 | -2.16σ | N/A | N/A | SIGNIFICANT NEG |
| ~1285 | -6.89 | -2.46σ | N/A | N/A | SIGNIFICANT NEG |
### Time Windows of Interest
[Group consecutive anomalies into windows]
| Window | Duration | Peak δ18O z | Peak δ13C z | Notes |
|--------|----------|-------------|-------------|-------|
| 1280-1295 CE | 15 yr | -2.46σ | N/A | Possible seismic |
Interpretation Guidelines
δ18O Anomalies
| Direction | Typical Cause |
|---|---|
| Negative (z < -2) | Increased deep/old water contribution OR wetter conditions |
| Positive (z > +2) | Increased evaporation OR drier conditions |
δ13C Anomalies
| Direction | Typical Cause |
|---|---|
| Negative (z < -2) | More biogenic CO₂ (soil respiration) |
| Positive (z > +2) | More geogenic CO₂ (earthquake/volcanic) OR prior calcite precipitation |
Coupled vs Decoupled
| Pattern | δ18O | δ13C | Interpretation |
|---|---|---|---|
| COUPLED | Anomaly | Anomaly (same direction) | SEISMIC (Chiodini mechanism) |
| DECOUPLED | Anomaly | Normal OR opposite | CLIMATIC (drought, volcanic) |
Output Format
The skill outputs:
- Cave metadata (entity, coordinates, coverage)
- Baseline statistics table
- All anomalies table (sorted by |z|)
- Time windows of interest (grouped anomalies)
- Quick interpretation (coupled/decoupled assessment)
MCP Tools Used
| Tool | Purpose |
|---|---|
sisal_search_caves |
Find cave entity ID |
sisal_get_samples |
Download measurements |
Advanced Options
Multi-Proxy Analysis
/zscore YOKI --proxy d18O,d13C,MgCa
Specific Time Window
/zscore CRC-3 --start 1890 --end 1900 # Around 1896 earthquake
Higher Threshold
/zscore "Bàsura" --threshold 2.5 # More stringent (fewer false positives)
Baseline Period
/zscore YOKI --baseline 1800-1900 # Use specific period for μ/σ
Example Full Output
## Z-Score Analysis: Crystal Cave (CRC-3)
**Entity**: 456
**Coordinates**: 36.59°N, 118.82°W
**Data range**: 873 - 2006 CE
**Measurements**: 1,054 δ18O
### Baseline Statistics
| Proxy | Mean (μ) | Std Dev (σ) | N |
|-------|----------|-------------|---|
| δ18O | -8.23‰ | 0.42‰ | 1,054 |
### Anomalies (|z| ≥ 2.0)
| Year CE | δ18O (‰) | δ18O z | Classification |
|---------|----------|--------|----------------|
| ~1741 | -9.72 | -3.54σ | **EXTREME NEG** |
| ~1896 | -9.13 | -2.14σ | SIGNIFICANT NEG |
| ~1910 | -9.72 | -3.54σ | **EXTREME NEG** |
| ... | ... | ... | ... |
**Total anomalies**: 47 (4.5% of record)
### Top 5 Most Extreme
1. ~1741 CE: z = -3.54σ (Pre-Spanish earthquake?)
2. ~1910 CE: z = -3.54σ (Known M6.0 Bishop)
3. ~1929 CE: z = -2.61σ (Known M5.5 Independence)
4. ~1896 CE: z = -2.14σ (Known M6.3 Independence)
5. ~1984 CE: z = -2.71σ (Known M6.1 Round Valley)
### Interpretation
✓ Modern earthquakes (1896, 1910, 1929, 1984) all show z ≤ -2.0
✓ Pre-Spanish ~1741 anomaly consistent with Rose Canyon/Kern Canyon event
✓ Cave shows reliable seismic sensitivity
Important Notes
- Z-scores are relative - Compare within same cave record
- Resolution matters - Annual vs decadal samples affect detection
- Missing data - Note gaps in record around anomalies
- Multi-proxy preferred - Single proxy anomaly is weaker evidence
- Follow up with /classify-anomaly - For full seismic vs climatic discrimination