M4.9 Earthquake Strikes 20 km SE of Kastrí, Greece

A seismic event measuring magnitude 4.9 has been recorded by global monitoring networks, with the epicentre located 20 km SE of Kastrí, Greece. The earthquake occurred at 09:31 UTC on Saturday, June 20, 2026 and was detected at a focal depth of 10.0 km.

Seismological Overview

Earthquakes are the result of sudden energy release in Earth's crust, most commonly along fault lines where tectonic plates interact. This energy radiates outward as seismic waves — measured and characterised by networks of seismographs operated by agencies including the USGS, JMA, EMSC, and GFZ.

Greece and the broader Aegean region are among the most seismically active areas in Europe, positioned along the Hellenic Arc where the African Plate subducts beneath the Eurasian Plate.

Event Parameters in Detail

Magnitude: 4.9 (moment magnitude scale, Mw) — a moderate earthquake.
Depth: 10.0 km
Location: 20 km SE of Kastrí, Greece
Time: 09:31 UTC on Saturday, June 20, 2026

At a focal depth of 10.0 km, this is classified as a shallow earthquake (0–70 km). Shallow events are typically the most damaging: the seismic energy has less distance to travel before reaching the surface, resulting in stronger and more abrupt ground shaking at the epicentre.

Energy and Ground Motion

A magnitude 4.9 earthquake releases approximately approximately 30,000 tonnes of TNT — comparable to the Hiroshima atomic bomb of energy. For comparison, this exceeds the energy released by most conventional explosive events and is sufficient to shift tectonic stress in measurable ways across a wide region.

Moderate earthquakes are felt by virtually everyone near the epicentre. Strong shaking lasting 10–30 seconds can topple unsecured items, crack plaster, and cause poorly anchored objects to fall. Aftershocks are common following moderate events.

Significant damage can occur to vulnerable structures — particularly unreinforced masonry, old adobe buildings, and poorly maintained older construction. Well-engineered modern buildings are designed to withstand this level of shaking with minimal structural impact, though contents may shift and non-structural elements (ceilings, partitions) can be damaged.

Regional Seismic History

Greece accounts for approximately 50% of all seismic energy released in Europe. The Ionian Islands, Crete, and the North Aegean are historically the most active zones, though significant earthquakes can and do occur across the entire country.

Public Safety Guidance

For residents in the affected area, the immediate priority is assessing personal safety and structural integrity. The internationally recommended action during earthquake shaking is Drop, Cover, and Hold On: drop to your hands and knees, take cover under a sturdy table or desk (or protect your head with your arms if no shelter is available), and hold on until shaking stops. Do not run outside during shaking — most injuries occur when people attempt to move.

Agree on an out-of-area contact that family members can reach if local communications are disrupted. Identify two meeting points: one near your home and one further away. Practise earthquake drills, especially with children and elderly household members.

The Greek Earthquake Planning and Protection Organisation (OASP/EPPO) provides guidance and resources for residents. Standard Drop, Cover, Hold On procedures apply, and coastal residents should move inland immediately after strong shaking.

Continued Monitoring

The USGS and regional seismic networks will continue to monitor this event for aftershock activity. QuakeWatch aggregates this global data in real time — you can view all current seismic activity on our live map, or explore our earthquake science guides to learn more about the forces behind events like this one.

Building Codes and Earthquake Resilience

One of the most effective tools against earthquake damage is modern building codes that specify how structures must be designed and constructed to withstand seismic forces. Countries with active fault zones have developed increasingly sophisticated seismic design standards over the past 50 years. However, the gap between modern code-compliant buildings and older existing structures remains a critical challenge in earthquake risk reduction worldwide. Building retrofit programmes and public awareness campaigns are key components of any national earthquake preparedness strategy.