How the Global Seismic Activity Index works

Earthquakes occur continuously worldwide. Single events, however, say little about how “active” the Earth is overall. The index therefore answers: How unusual is the currently observed global earthquake activity compared to a normal year? To do this, the seismic energy released in the last 24 hours is calculated and compared with historical values.

Only real, reported earthquake events are used for the calculation.

• Magnitude: M ≥ 3.0
• Window: rolling 24-hour window (UTC)
• Sources: international seismological institutes
• Catalog: de-duplicated multi-source dataset

Smaller events below magnitude 3.0 are intentionally excluded because global detection consistency varies strongly.

Earthquake magnitudes are logarithmic. A one-unit increase in magnitude corresponds to a much larger energy release. Therefore, the index uses a physically meaningful estimate of seismic energy in joules.

For each earthquake with magnitude M, energy E is estimated as:

log₁₀(E) = 1.5 × M + 4.8

Where:

• E is in joules
• M is the earthquake magnitude

This is a widely used approximation in seismology to compare released energy.

All energies within the last 24 hours are summed:

E_(24h) = sum of all event energies

Because the sum can span many orders of magnitude, the logarithmic value log₁₀(E_(24h)) is also used for stability and comparability.

Absolute energy values are difficult to interpret on their own. Therefore, today’s 24h energy is compared against historical values.

• Period: last 365 days
• Basis: stored daily activity snapshots

The index equals the percentile rank of the current day:

• 50 → typical (median) day
• 80 → more active than 80% of the last 365 days
• 95 → exceptionally high activity

The value is displayed as an index from 0 to 100.

For readability, the numeric value is classified:

• Quiet (0–19)
• Normal (20–39)
• Elevated (40–59)
• High (60–79)
• Very high (80–100)

This classification is for orientation only and is not a risk assessment.

The Global Seismic Activity Index:

• ❌ is not an earthquake prediction
• ❌ does not assess local risk
• ❌ does not claim an upcoming major quake

A high value only means: unusually much seismic energy was released in the last 24 hours compared to a normal year.

As with any global dataset, limitations exist:

• different magnitude types (Mw, Mb, Ml)
• reporting delays and later revisions
• regional differences in detection density
• approximate nature of the energy formula

QuakeMap24 uses a de-duplicated multi-source approach to reduce bias, but not all uncertainty can be eliminated.

The calculation is based on data from many international seismological institutes and data centers. A complete and current list of sources is available here:

👉 View data sources

You can view the current, live computed index (including the gauge/visualization) here:

👉 View the Global Seismic Activity Index live

The Global Seismic Activity Index provides:

• an objective way to contextualize global earthquake activity
• a physically meaningful energy-based measure
• a transparent, reproducible methodology