/validate-cave - Modern Earthquake Validation Skill

Purpose

Systematically test if a speleothem cave record detects known modern earthquakes. This validates the paleoseismic methodology and builds the 50+ validation matrix.

Usage

/validate-cave <cave_name_or_entity_id> [--start YEAR] [--end YEAR] [--radius KM]

Examples:

/validate-cave CRC-3                     # Crystal Cave (California)
/validate-cave YOKI --start 1970 --end 2010
/validate-cave "Lapa Grande" --radius 50
/validate-cave Ko-1                      # Kocain (Turkey)

Workflow

Step 1: Identify Cave & Get Coordinates

1. Search SISAL using sisal_search_caves MCP tool
2. Get cave metadata: entity_id, coordinates, site name
3. Determine data coverage: earliest/latest sample dates

# Example MCP call
sisal_search_caves region="California" min_samples=50

Step 2: Search for Modern Earthquakes

Use earthquake_search MCP tool to find earthquakes near cave:

# Default: M≥5.0, 100 km radius, 1900-2025
earthquake_search lat=36.59 lon=-118.82 min_magnitude=5.0 radius_km=100

Filter results:

• Keep only earthquakes within cave data timespan
• Note earthquakes outside timespan (for documentation)

Step 3: Download Cave Data

Use sisal_get_samples MCP tool:

sisal_get_samples entity_id="123"

Extract:

• δ18O measurements with dates
• δ13C measurements (if available)
• Mg/Ca measurements (if available)

Step 4: Calculate Baseline Statistics

For all cave data:

δ18O: μ = mean(d18O_measurement), σ = std(d18O_measurement)
δ13C: μ = mean(d13C_measurement), σ = std(d13C_measurement)

Step 5: Test Each Earthquake

For each earthquake within cave data coverage:

1. Define test window: earthquake_year ± 10 years
2. Extract data in window: All samples within ±10 years
3. Calculate z-scores: z = (measurement - μ) / σ
4. Find extreme values: Most negative AND most positive z-score
5. Apply detection threshold:
   • |z| ≥ 2.0 → DETECTED
   • |z| < 2.0 → NOT DETECTED

Step 6: Generate Results Table

| Date | Magnitude | Distance (km) | Cave Data? | δ18O z | Detection | Notes |
|------|-----------|---------------|------------|--------|-----------|-------|
| 1976-02-04 | M7.5 | 30 km | ✓ Yes | +1.32σ | ✗ NO | Below threshold |
| 1896-07-21 | M6.3 | 48 km | ✓ Yes | -3.54σ | **✓ YES** | Strong signal |

Step 7: Calculate Statistics

Detection rate = (detections / tests_with_data) × 100%

Example:
- Total earthquakes found: 9
- Earthquakes with cave coverage: 6
- Detections (z ≥ 2.0): 1
- Non-detections: 5
- **Detection rate: 16.7%**

Step 8: Update VALIDATION_MATRIX_50PLUS.md

Add/update cave section in paleoseismic_caves/VALIDATION_MATRIX_50PLUS.md:

### [Cave Name] ([Country]) - [N] Earthquakes

**Cave coordinates**: [lat]°N, [lon]°W
**Data coverage**: [start] - [end] CE
**Cave entity**: [entity_id] (SISAL)

#### Modern Earthquakes:

[Results table]

**Detection rate**: X/Y (Z%)

**Notes**: [Interpretation, hypotheses for non-detections]

Detection Criteria

Threshold	Interpretation
z ≥ +2.0 or z ≤ -2.0	DETECTED (significant anomaly)
1.5 ≤	z
	z

Interpreting Results

High Detection Rate (≥60%)

• Cave is sensitive to earthquakes
• Methodology validated for this setting
• Prehistoric detections are credible

Moderate Detection Rate (30-60%)

• Cave may be selective (certain magnitudes/distances)
• Need to identify detection threshold
• Prehistoric detections need scrutiny

Low Detection Rate (<30%)

• Cave may be insensitive after certain date
• Check for cave changes (flowpath, aquifer)
• Prehistoric detections HIGHLY UNCERTAIN

Zero Detection (0%)

• Critical concern (like Yok Balum)
• Investigate: (a) Cave sensitivity, (b) Tectonic setting, (c) Data quality
• Prehistoric "detections" may not be seismic

Output Format

The skill outputs:

1. Cave metadata box (coordinates, coverage, entity_id)
2. Earthquake search summary (N earthquakes found, N testable)
3. Full results table (all earthquakes with test results)
4. Statistics summary (detection rate, range tested)
5. Interpretation (what results mean for methodology)
6. Update to VALIDATION_MATRIX_50PLUS.md (with approval)

MCP Tools Used

Tool	Purpose
sisal_search_caves	Find cave in SISAL database
sisal_get_samples	Download δ18O/δ13C/Mg measurements
earthquake_search	Search USGS catalog near cave
calc_distance	Verify earthquake-cave distances
calc_pga	Calculate expected ground acceleration

Example Full Workflow

User: /validate-cave CRC-3

Claude:
1. Searching SISAL for CRC-3 (Crystal Cave)...
   - Entity ID: 123
   - Coordinates: 36.59°N, 118.82°W
   - Data: 873-2006 CE (1,054 δ18O measurements)

2. Searching USGS catalog (M≥5.0, 100km, 1900-2025)...
   - Found 11 earthquakes
   - 9 within cave data coverage (873-2006 CE)

3. Calculating z-scores...
   - Baseline: μ=-8.23‰, σ=0.42‰

4. Testing each earthquake...
   [Results table]

5. RESULTS:
   - Detections: 9/9
   - Detection rate: **100%** ✓✓✓

6. INTERPRETATION:
   Crystal Cave shows PERFECT detection of modern earthquakes.
   This validates the methodology for California Sierra Nevada setting.

Would you like me to update VALIDATION_MATRIX_50PLUS.md with these results?

Important Notes

1. Document BOTH detections AND non-detections - Publication requires honest statistics
2. Non-detection ≠ failure - May indicate distance/magnitude thresholds
3. 0% detection is significant - Yok Balum 0% rate is scientifically valuable
4. Check data quality - Missing samples around earthquake = inconclusive, not non-detection
5. Consider tectonic setting - Strike-slip vs thrust vs subduction may behave differently