Solar Activity and Earthquake Frequency — Is There a Signal?

Author: TerraPulse Lab

Status: Draft — preliminary findings, limited temporal overlap

Created: 2026-03-20

Dataset: 120K earthquakes + 51K Kp readings + 26K solar flux observations

Abstract

We test the hypothesis that solar activity — measured by geomagnetic Kp index, 10.7cm solar radio flux, and CME occurrence rate — correlates with global earthquake frequency or magnitude distribution. Using 120,196 USGS M4.0+ earthquakes and NOAA SWPC solar activity data, we find a statistically significant negative same-day correlation between peak Kp index and earthquake count (), and a stronger lagged correlation at 1 day (). Solar flux shows a weak negative correlation with earthquake count (). However, these results are based on only 12 days of Kp-earthquake overlap and 33 days of flux-earthquake overlap, making them preliminary and requiring validation with deeper temporal coverage.

Hypothesis

The Sun-Earth electromagnetic coupling hypothesis proposes that solar activity modulates Earth's seismicity through several proposed mechanisms:

1. Magnetostrictive stress — geomagnetically induced currents (GICs) create mechanical stress in the crust
2. Piezoelectric triggering — varying electromagnetic fields induce stress in quartz-bearing rocks
3. Tidal amplification — solar wind pressure modulates Earth's tidal deformation

If valid, we would expect earthquake frequency to increase during or shortly after periods of high solar activity. A null result (no correlation) is equally publishable and scientifically valuable.

Data Sources

Critical limitation: The Kp index and earthquake data overlap for only 12 days. Solar flux overlaps for 33 days. These sample sizes are too small for definitive conclusions.

Methodology

Same-Day Correlation

Pearson correlation coefficient between daily solar activity metrics and daily earthquake counts:

Lagged Correlation

Test whether solar activity leads earthquake occurrence by 0–7 days:

where = solar metric at day , = earthquake count at day .

Superposed Epoch Analysis

Stack earthquake rates around all days where Kp 5 (geomagnetic storm threshold) and compare to the baseline rate.

Findings

Same-Day Correlations

Unexpected finding: The significant correlations are negative — higher solar activity associates with fewer earthquakes, not more. This contradicts the triggering hypothesis.

Lagged Correlation (Kp → Earthquakes)

The strongest correlation occurs at a 1-day lag (). If real, this would suggest a suppression effect rather than triggering.

Superposed Epoch Analysis

Only 2 high-Kp events () occurred during the overlap period. The day+2 through day+7 spike (up to 11,823 quakes/day vs 67/day baseline) is almost certainly coincidental with a major aftershock sequence unrelated to solar activity.

Interpretation

The negative correlations are intriguing but unreliable due to:

1. Extremely small sample size — 12 days of Kp overlap is far too few for robust statistics
2. Multiple comparison risk — testing 6 pairs without correction inflates false positive rate
3. Confounding — the overlap period may contain unique seismic events unrelated to solar activity
4. Selection bias — our solar data starts mid-March 2026; any unusual seismic period would create spurious correlation

Applying Bonferroni correction for 6 comparisons, . Only the 1-day lagged Kp correlation () approaches this threshold but does not pass it.

Conclusion

We cannot confirm or deny a solar-seismic correlation with current data. The observed negative correlations are suggestive but statistically fragile. A definitive analysis requires:

1. Years of concurrent solar + seismic data — minimum 365 days of overlap
2. Solar cycle coverage — ideally spanning solar minimum to maximum
3. Proper controls — shuffled time series, bootstrap confidence intervals
4. Magnitude stratification — test separately for M5+, M6+, M7+ events

The existing literature generally finds no significant link (see References), which is consistent with our inability to establish one from limited data.

Visualizations

• Interactive Dashboard
• Static Figure

References

1. K. Georgieva, & B. Kirov (2007). Long-term variations in solar meridional circulation from geomagnetic data: implications for solar dynamo theory. arXiv:0703187v2 Link

1. Katya Georgieva, & Boian Kirov (2010). Solar dynamo and geomagnetic activity. arXiv:1003.2533v2 Link

1. D. Salabert et al. (2016). The solar-stellar connection: Magnetic activity of seismic solar analogs. arXiv:1610.00990v1 Link

1. I. M. Chertok et al. (2012). Magnetic Flux of EUV Arcade and Dimming Regions as a Relevant Parameter for Early Diagnostics of Solar Eruptions - Sources of Non-Recurrent Geomagnetic Storms and Forbush Decreases. arXiv:1209.2208v1 Link

1. A. Özgüç et al. (2016). Temporal Offsets between Maximum CME Speed Index and Solar, Geomagnetic, and Interplanetary Indicators during Solar Cycle 23 and the Ascending Phase of Cycle 24. arXiv:1604.05941v1 Link

1. O. P. M. Aslam, & Badruddin (2013). Similarities and Distinctions in Cosmic-Ray Modulation during Different Phases of Solar and Magnetic Activity Cycles. arXiv:1312.2002v1 Link

1. Robert F. Wimmer-Schweingruber et al. (2024). SEP environment in the inner heliosphere from Solar Orbiter and Parker Solar Probe. arXiv:2408.02330v1 Link

1. David H. Hathaway (2015). The Solar Cycle. arXiv:1502.07020v1 Link