What Magnitude Earthquake Is Dangerous?

Not all earthquakes are dangerous. Most earthquakes are too small to feel, and even many earthquakes you can feel cause no damage. So what magnitude becomes dangerous?

Quick Answer

Magnitude 5.0 and above can cause damage in populated areas. However, the danger depends on depth, distance from populated areas, and building quality.

Earthquake Magnitude Scale Explained

Magnitude 1.0-2.9 (Micro)

Not felt by people. Detected only by seismographs. Happens millions of times per year globally. These earthquakes release very little energy and pose zero danger.

Magnitude 3.0-3.9 (Minor)

Often felt but rarely causes damage. About 130,000 per year worldwide. People describe these as feeling like a truck passing by or a brief vibration. Windows may rattle, hanging objects may swing slightly.

Magnitude 4.0-4.9 (Light)

Felt by most people indoors. Can cause dishes to rattle and pictures to fall. Noticeable shaking but usually no structural damage. About 13,000 per year globally.

At this magnitude, you'll definitely know it's an earthquake. Items on shelves may fall, suspended lights swing noticeably, and parked cars rock slightly. However, well-built structures remain undamaged.

Magnitude 5.0-5.9 (Moderate)

This is where earthquakes become potentially dangerous. Can cause damage to poorly constructed buildings. Well-built buildings usually survive with minor damage like cracked plaster or broken windows. About 1,300 per year worldwide.

In areas with poor building codes, M5.0+ earthquakes can cause building collapses and casualties. In areas with modern building codes (like California or Japan), damage is typically limited to older unreinforced structures.

Magnitude 6.0-6.9 (Strong)

Definitely dangerous in populated areas. Can cause substantial damage within 100 km of the epicenter. About 130 per year globally.

Expected damage:

• Older buildings may collapse or suffer severe damage
• Modern buildings experience moderate damage
• Chimneys and parapets fall
• Underground pipes break
• Landslides in hilly areas
• People have difficulty standing

Magnitude 7.0-7.9 (Major)

Serious damage over large areas. Can be felt hundreds of kilometers away. About 15 per year globally. These earthquakes make international news and often require humanitarian response.

Expected impacts:

• Most masonry buildings destroyed
• Even well-built structures suffer damage
• Bridges collapse
• Large cracks in the ground
• Massive landslides
• Tsunamis if underwater

Examples: 2010 Haiti earthquake (M7.0, 200,000+ deaths), 2011 Christchurch, New Zealand (M6.3 aftershock caused most damage).

Magnitude 8.0+ (Great)

Catastrophic damage across areas several hundred kilometers wide. About 1 per year globally. These are the earthquakes that reshape landscapes and trigger international relief efforts.

Examples: 2011 Tohoku, Japan (M9.1), 2004 Indian Ocean (M9.1), 1906 San Francisco (M7.9).

Why Depth Matters

A magnitude 6.0 earthquake at 10 km depth is much more dangerous than the same magnitude at 100 km depth. Shallow earthquakes release their energy closer to the surface, causing stronger shaking.

Depth categories:

• Shallow (0-70 km): Most destructive. Energy concentrated near surface.
• Intermediate (70-300 km): Less surface damage. Longer, rolling motion.
• Deep (300+ km): Rarely cause damage. May not even be felt.

The devastating 2011 Christchurch earthquake was only M6.3 but occurred at just 5 km depth, directly under the city. This shallow depth concentrated enormous energy at the surface, killing 185 people despite the "moderate" magnitude.

Building Quality Is Critical

Modern earthquake-resistant buildings can withstand magnitude 7.0+ earthquakes with minimal damage. However, older unreinforced masonry buildings can collapse in magnitude 5.0 earthquakes.

Building Code Comparison

Countries with strict codes (Japan, California, Chile):

• M5.0: Minor damage, no collapses
• M6.0: Moderate damage, rare collapses
• M7.0: Significant damage but most buildings survive

Countries with lax codes:

• M5.0: Some building collapses possible
• M6.0: Widespread collapses, major casualties
• M7.0: Catastrophic destruction

Example: The 2010 M7.0 Haiti earthquake killed over 200,000 people largely due to poor building construction. A similar M7.0 earthquake in California or Japan would cause far fewer casualties.

Distance from Epicenter

The further you are from the epicenter, the less dangerous the earthquake:

• At epicenter: Full force, maximum damage
• 50 km away: Reduced shaking, less damage
• 100+ km away: Gentle rolling motion, minimal damage

The Bottom Line

Earthquake danger depends on multiple factors:

• Magnitude 5.0+: Potentially dangerous
• Magnitude 6.0+: Definitely dangerous in populated areas
• Magnitude 7.0+: Major disaster requiring international response

But remember: A M5.5 shallow earthquake under a city with poor building codes can be deadlier than a M7.0 deep earthquake far from population centers.

Prepare for Earthquakes

If you live in an earthquake zone:

• Know if your building meets modern earthquake codes
• Secure heavy furniture and appliances
• Create an emergency kit
• Practice "Drop, Cover, Hold On"
• Consider earthquake insurance