Why Some Regions Have More Earthquakes Than Others

Look at a global map of earthquake activity and the pattern is striking: earthquakes aren't evenly distributed. They cluster in narrow belts that ring the Pacific Ocean, cut through the Mediterranean and Middle East, and split the Atlantic down the middle. Meanwhile, vast regions—central Africa, Brazil, Australia's interior, the Sahara Desert—experience virtually no seismic activity at all.

This distribution isn't random or coincidental. Japan experiences over 1,500 earthquakes strong enough to feel every year. California records thousands of earthquakes annually, dozens of them significant. Alaska shakes more than all other U.S. states combined. Yet Florida has never experienced a damaging earthquake. Brazil, despite being nearly as large as the United States, is almost entirely earthquake-free. Central Siberia, vast and populated, rarely feels the ground move.

The difference comes down to plate tectonics and geological history. Seismically active regions sit on or near plate boundaries where Earth's rigid outer shell is breaking, colliding, or sliding. Quiet regions occupy stable plate interiors where the crust is old, cold, and strong—far from the dynamic forces that generate earthquakes.

This article explores why earthquake distribution is so uneven, which regions face the highest seismic risk and why, what makes some areas earthquake-free, and why a few regions that seem far from plate boundaries still experience significant earthquakes.

Plate Boundaries: Where Earth Is Most Active

The fundamental reason some regions have more earthquakes is simple: they're located at or near plate boundaries where tectonic forces are active.

The Three Types of Boundaries and Their Seismicity

Convergent boundaries (colliding plates):

• Highest seismic activity globally
• Produce largest earthquakes (M8.0-9.5)
• Continuous stress accumulation and release
• Examples: Pacific Ring of Fire subduction zones, Himalayan collision zone
• Why so active: Enormous forces as plates collide, large locked areas on faults

Transform boundaries (sliding plates):

• High seismic activity but smaller maximum magnitudes
• Produce up to M8.0 earthquakes typically
• Frequent moderate to large earthquakes
• Examples: San Andreas Fault (California), North Anatolian Fault (Turkey), Alpine Fault (New Zealand)
• Why active: Continuous horizontal stress, stick-slip behavior

Divergent boundaries (separating plates):

• Moderate seismic activity, usually smaller magnitudes
• Thousands of small earthquakes, few large ones
• Examples: Mid-Atlantic Ridge, East Pacific Rise, East African Rift
• Why less active: Hot, weak crust; magma intrusions release stress; frequent small events prevent large stress buildup

The Ring of Fire: Earth's Most Seismically Active Zone

The Pacific Ring of Fire demonstrates how plate boundaries create extreme seismic activity.

What Is the Ring of Fire?

Geographic extent:

• Horseshoe-shaped belt around Pacific Ocean
• ~40,000 km long
• Encompasses coasts of Asia, Americas, and Pacific islands
• Includes 75% of world's active volcanoes
• Accounts for ~90% of world's earthquakes

Why so active?

• Pacific Plate surrounded by subduction zones on nearly all sides
• Oceanic plates diving beneath continental and island arc systems
• Creates continuous chain of convergent plate boundaries
• Multiple plates colliding at different angles and speeds

Regional Breakdown of Ring of Fire Seismicity

Western Pacific (highest activity globally):

• Japan: ~1,500 felt earthquakes per year, 5-10 M6+ annually
  • Pacific Plate, Philippine Sea Plate subducting beneath Japan
  • 2011 Tohoku M9.1 killed 18,000+
  • History of devastating M7-8 earthquakes
• Indonesia: Second most seismically active country
  • Multiple subduction zones converging
  • 2004 Sumatra M9.1 generated catastrophic tsunami (230,000 deaths)
  • Frequent M6-7 earthquakes
• Philippines: Highly active, multiple subduction zones
  • Philippine Sea Plate, Eurasian Plate interactions
  • Frequent M6-7 earthquakes
  • 1990 Luzon M7.8 killed 1,600+
• Papua New Guinea: Extremely active, complex tectonics
  • Multiple plate boundaries converge
  • Frequent large earthquakes in remote areas

Eastern Pacific:

• Chile: Most powerful earthquake ever recorded (1960 M9.5)
  • Nazca Plate subducting beneath South America
  • Averages one M8+ earthquake per decade
  • 2010 M8.8 killed 525
• Peru: Continuation of same subduction zone
  • Frequent M6-8 earthquakes
  • 1970 Ancash M7.9 killed 70,000+ (mostly from landslide)
• Ecuador & Colombia: Nazca Plate subduction continues
  • 2016 Ecuador M7.8 killed 676
• Central America: Cocos Plate subduction
  • Mexico, Guatemala, El Salvador, Nicaragua, Costa Rica all highly active
  • 2017 Mexico M8.2 killed 98

North American Pacific Coast:

• Alaska: More earthquakes than rest of U.S. combined
  • Pacific Plate subducting beneath North America
  • 40,000+ earthquakes per year (most small)
  • 1964 M9.2—second largest earthquake ever recorded
  • Averages 20-30 M5+ earthquakes per year
• Pacific Northwest (Washington, Oregon, Northern California):
  • Juan de Fuca Plate subducting beneath North America
  • Currently in quiet period (ominous)
  • Capable of M9+ earthquakes
  • Last major earthquake: 1700 M9.0
• California: Transform boundary, not subduction
  • San Andreas Fault system
  • 10,000+ earthquakes per year (most imperceptible)
  • Several M6+ earthquakes per decade

Southwest Pacific:

• New Zealand: Highly active, complex tectonics
  • Pacific Plate subducting beneath North Island
  • Alpine Fault (transform) through South Island
  • 2011 Christchurch M6.3 killed 185
  • 2016 Kaikōura M7.8—one of most complex ruptures ever recorded
• Tonga-Kermadec Arc: Very active but remote
  • Pacific Plate subducting steeply
  • Frequent M6-7 earthquakes
  • Low impact due to ocean location

The Alpide Belt: The Second Most Active Seismic Zone

Extending from the Mediterranean through the Middle East to the Himalayas and Indonesia, this belt accounts for ~5-6% of global seismicity.

What Is the Alpide Belt?

Geographic extent:

• Stretches from Mediterranean Sea to Southeast Asia
• ~15,000 km long
• Encompasses southern Europe, Middle East, Central Asia, Himalayas
• Second most seismically active belt after Ring of Fire

Why active?

• African and Arabian plates colliding with Eurasia
• Indian plate colliding with Eurasia (forming Himalayas)
• Complex zone of continental collision
• Multiple smaller plates caught in collision

Regional Seismicity in the Alpide Belt

Mediterranean region:

• Turkey: Among most seismically active countries
  • Three tectonic plates colliding (African, Arabian, Eurasian)
  • North Anatolian Fault—major transform fault
  • 1999 İzmit M7.6 killed 17,000+
  • 2023 Kahramanmaraş M7.8 killed 59,000+
• Greece: Very active, Mediterranean subduction
  • Frequent M5-6 earthquakes
  • Occasional M7+ events
• Italy: Active despite being in "stable" Europe
  • Complex collision zone
  • 2016 Central Italy M6.2 killed 299
  • 2009 L'Aquila M6.3 killed 309

Middle East:

• Iran: One of most seismically active countries
  • Arabian Plate colliding with Eurasia
  • Complex network of faults
  • 2003 Bam M6.6 killed 26,000+
  • Frequent M6-7 earthquakes
• Afghanistan & Pakistan: High seismic activity
  • Extension of Himalayan collision zone
  • 2005 Kashmir M7.6 killed 87,000+

Himalayan region:

• Nepal, Bhutan, Northern India: India-Eurasia collision
  • Most dramatic continental collision on Earth
  • 2015 Nepal M7.8 killed 9,000
  • Capable of M8+ earthquakes
  • Major earthquake overdue on some segments
• Tibet: Frequent earthquakes from crustal deformation
  • 2008 Sichuan M7.9 killed 87,000+

Mid-Ocean Ridges: Hidden Seismic Activity

The longest mountain chain on Earth is also highly seismically active—we just don't notice because it's underwater.

The Global Ridge System

Extent and activity:

• 65,000 km of spreading ridges encircling the globe
• Thousands of earthquakes annually
• Most are small (M3-5)
• Rarely exceed M6.5
• Low hazard because remote and underwater

Major ridge systems:

• Mid-Atlantic Ridge: Splits Atlantic Ocean
  • Extends from Arctic to Antarctic
  • Continuous seismic activity
  • Exposed in Iceland (where we can study it)
• East Pacific Rise: Eastern Pacific spreading center
  • Fastest-spreading ridge globally
  • Very frequent small earthquakes
• Indian Ocean Ridges: Multiple spreading centers
  • Southwest Indian Ridge, Southeast Indian Ridge
  • Moderate seismic activity

Why Ridge Earthquakes Are Small

Several factors limit magnitude:

• Hot, weak crust near ridges
• Magma intrusions release stress continuously
• Thin lithosphere limits rupture area
• Frequent small earthquakes prevent stress buildup
• Low differential stress

Seismically Quiet Regions: Where Earthquakes Don't Happen

Vast areas of Earth experience almost no earthquake activity. Understanding why reveals much about Earth's structure.

Characteristics of Quiet Regions

What they have in common:

• Located in stable plate interiors (cratons)
• Far from any plate boundaries
• Old, cold, strong crust
• Minimal active faulting
• Low tectonic stress

Major Seismically Quiet Regions

South America interior:

• Brazil: Nearly entire country earthquake-free
  • Center of South American Plate
  • Stable Precambrian shield
  • No significant earthquakes in recorded history
  • Amazonian craton—some of oldest, most stable crust on Earth
• Why so quiet: Thousands of kilometers from nearest plate boundary (Andes)

African interior:

• Central and Southern Africa: Very low seismicity
  • Ancient cratons (Congo, Kalahari)
  • Minimal tectonic activity
  • Exception: East African Rift (active divergent boundary)
• Sahara Desert: Essentially earthquake-free
  • Center of African Plate
  • Far from active margins

Australian interior:

• Central Australia: Extremely low seismicity
  • Ancient craton
  • Does experience rare intraplate earthquakes
  • But vastly quieter than coastal regions

Northern Asia interior:

• Central Siberia: Very quiet
  • Stable Siberian craton
  • Far from plate boundaries
  • Occasional small earthquakes but no major activity

North America interior:

• Canadian Shield: Minimal seismicity
  • Ancient Precambrian shield
  • Some of oldest rock on Earth
  • Very stable
• Parts of U.S. Midwest and South: Low activity
  • Florida: Zero damaging earthquakes in recorded history
  • Wisconsin, Minnesota: Very rare small earthquakes
  • Exception: New Madrid Seismic Zone (intraplate anomaly)

Antarctica interior:

• East Antarctica very quiet
• West Antarctica more active (different geology)
• Limited monitoring, so true activity level uncertain

Intraplate Earthquakes: The Puzzling Exceptions

Some regions far from plate boundaries still experience significant earthquakes—these require special explanation.

What Are Intraplate Earthquakes?

Definition:

• Earthquakes occurring within plate interiors
• Far from active plate boundaries
• Account for ~5% of global seismicity
• Often unexpected and therefore particularly dangerous

Why they occur:

• Ancient faults within plates can be reactivated
• Plate boundary stresses transmitted into plate interiors
• Mantle processes can create stress from below
• Post-glacial rebound in formerly glaciated areas
• Localized zones of weakness concentrate stress

Major Intraplate Seismic Zones

New Madrid Seismic Zone (Central United States):

• Missouri, Arkansas, Tennessee, Kentucky
• Ancient failed rift (~600 million years old)
• 1811-1812: Three M7.0-8.0+ earthquakes
  • Rang church bells in Boston
  • Temporarily reversed flow of Mississippi River
  • Felt across half the United States
• Current activity: ~200 small earthquakes per year
• Future risk: ~7-10% probability of M7.0+ in 50 years
• Major concern: Region unprepared for large earthquakes

Charleston Seismic Zone (South Carolina):

• 1886 M7.3 earthquake destroyed Charleston
  • 60 deaths
  • Felt from Boston to Chicago to Cuba
• Cause still debated
• Low current seismicity
• Unknown recurrence interval

Central and Eastern Canada:

• Scattered intraplate seismicity
• 1988 Saguenay M5.9 (Quebec)
• Ancient fault systems occasionally reactivate
• Post-glacial rebound contributes

Australian intraplate earthquakes:

• 1989 Newcastle M5.6 killed 13
  • Australia's most damaging earthquake
  • Region had no known earthquake history
• Scattered moderate earthquakes across continent
• Stress from distant plate boundaries transmitted inward

Central China:

• Not at plate boundary but still active
• 1556 Shaanxi M8.0—deadliest earthquake in history (~830,000 deaths)
• 1976 Tangshan M7.5 killed 242,000+
• Stresses from India-Eurasia collision transmitted eastward

Fennoscandia (Scandinavia):

• Frequent small earthquakes in Sweden, Norway, Finland
• Post-glacial rebound—land rising after ice sheet removal
• Rising ~1 cm/year
• Creates stress, triggers earthquakes
• Demonstrates earthquakes can occur for non-tectonic reasons

Why Intraplate Earthquakes Are Dangerous

Unique hazards:

• Unexpected: Occur in areas with no earthquake culture or preparedness
• Building codes inadequate: Structures not designed for earthquakes
• Efficient wave propagation: Old, cold crust transmits seismic waves farther
• Larger felt area: Same magnitude affects much larger region than at plate boundaries
• Unpredictable recurrence: Irregular intervals between earthquakes (centuries to millennia)

Example of wave propagation difference:

• M6.0 in California: Strongly felt within ~50 km
• M6.0 in central U.S.: Strongly felt within ~200 km
• Same energy, but older crust transmits waves more efficiently

Why This Distribution Isn't Changing

The pattern of seismically active and quiet regions has been stable for millions of years—and will remain so.

Plate Motions Are Constant

Timescales:

• Plates move at 1-10 cm per year
• Directions and speeds relatively constant over millions of years
• Changes occur, but very slowly
• Current plate boundaries will remain active indefinitely

What this means:

• California will continue shaking as long as San Andreas Fault is active (millions more years)
• Japan will remain highly seismically active (subduction continuing)
• Pacific Ring of Fire will remain most active zone globally
• Brazil will remain earthquake-free (unless new plate boundary forms)

New Plate Boundaries Can Form

Continental rifting:

• East African Rift is creating new plate boundary
• Eventually will split Africa into two plates
• Already producing significant earthquakes
• Process takes millions of years

Other examples:

• Red Sea—former continental rift, now ocean basin
• Atlantic Ocean—opened when Pangaea rifted apart
• These demonstrate that plate boundaries do evolve
• But on timescales far longer than human civilization

Special Cases: Unusual Seismic Patterns

Hawaii: Intraplate But Active

Why Hawaii has earthquakes:

• Located in middle of Pacific Plate (far from boundaries)
• But sits over volcanic hotspot
• Magma movement creates earthquakes
• Volcanic loading flexes crust
• Most earthquakes related to volcanic activity, not tectonics
• Can produce M6-7 earthquakes

Iceland: Divergent Boundary on Land

Unique situation:

• Mid-Atlantic Ridge exposed above sea level
• Island literally being torn apart by plate divergence
• Frequent earthquakes and volcanic eruptions
• We can walk on and study active plate boundary
• Earthquakes typically M5-6, occasional M6.5+

Yellowstone: Hotspot in Continental Interior

Why Yellowstone has earthquakes:

• Located in stable North American interior
• But sits above massive volcanic hotspot
• Frequent earthquake swarms (thousands in weeks)
• Related to magma movement and hydrothermal activity
• Usually M2-4, occasionally M5-6
• Not tectonic in origin

Human-Induced Seismicity: A New Category

Human activities can trigger earthquakes in regions that would otherwise be quiet.

Injection-Induced Earthquakes

Oklahoma: From quiet to highly active:

• Historically very low seismicity
• 2008-2016: Seismicity increased 1000x
• Caused by wastewater injection from oil/gas operations
• Injection changes pore pressure on faults
• Triggered M5.0-5.8 earthquakes
• Injection rates reduced, seismicity declining

Other examples:

• Texas, Arkansas, Ohio—injection-related earthquakes
• Demonstrates that quiet regions can become active
• But activity ceases when injection stops

Reservoir-Induced Seismicity

How dams can trigger earthquakes:

• Large reservoirs add enormous weight to crust
• Water infiltrates fractures, changing pore pressure
• Can trigger earthquakes on existing faults
• Examples: China, India, various countries
• Typically M4-6, rarely larger

The Bottom Line

The uneven distribution of earthquakes across Earth's surface is not random—it's the direct consequence of plate tectonics. Regions that experience frequent, powerful earthquakes sit on or near plate boundaries where Earth's rigid outer shell is actively breaking, colliding, or sliding. Quiet regions occupy stable plate interiors where the crust is old, cold, strong, and far from the dynamic forces that generate earthquakes.

The Pacific Ring of Fire—a horseshoe-shaped belt of subduction zones surrounding the Pacific Ocean—accounts for roughly 90% of the world's earthquakes. Japan, Indonesia, Chile, Alaska, and the Pacific Northwest all sit along this belt, experiencing thousands of earthquakes annually. The Alpide Belt, stretching from the Mediterranean through the Middle East to the Himalayas, accounts for another 5-6% of global seismicity. These two belts alone explain the vast majority of earthquake activity worldwide.

Meanwhile, vast regions experience almost no earthquake activity. Brazil, central Africa, Australia's interior, the Sahara Desert, and central Siberia are all located in the stable interiors of tectonic plates, thousands of kilometers from active boundaries. The crust in these regions is ancient—often billions of years old—cold, and extraordinarily strong. Without the dynamic stresses of plate boundaries, these regions remain seismically quiet and will continue to do so for millions of years to come.

The small percentage of earthquakes that occur within plate interiors—intraplate earthquakes—present a particular challenge. The New Madrid Seismic Zone in the central United States, despite being thousands of kilometers from the nearest plate boundary, produced three magnitude 7-8+ earthquakes in 1811-1812. The 1886 Charleston earthquake destroyed that city despite South Carolina having no known earthquake history. These events demonstrate that ancient faults within plates can be reactivated, though the mechanisms remain debated and recurrence intervals are highly irregular.

What makes intraplate earthquakes especially dangerous is the combination of unexpected location, inadequate building codes, and efficient seismic wave propagation. A magnitude 6.0 earthquake in central North America will be felt strongly over an area several times larger than the same magnitude earthquake in California because the old, cold crustal rock transmits seismic waves more efficiently. Combined with populations unprepared for earthquakes and buildings not designed to withstand them, this creates significant vulnerability in regions that rarely shake.

The pattern is clear and stable. Plate boundaries are seismically active—they have been for millions of years and will continue to be for millions more. Plate interiors are quiet and will remain so unless new plate boundaries form through processes like continental rifting, which takes millions of years. The plates themselves move at steady, predictable rates. The San Andreas Fault will continue generating earthquakes. The Pacific Ring of Fire will continue dominating global seismicity. Brazil will remain earthquake-free.

Understanding this pattern enables rational earthquake preparedness. Resources can be concentrated where earthquakes actually occur rather than being spread uniformly. Building codes can be tailored to regional seismic hazard. Populations at risk can be educated about earthquake safety while those in quiet regions can focus on other hazards. The distribution of earthquakes is not a mystery—it's the predictable consequence of Earth's dynamic surface, where rigid plates float on a slowly flowing interior, constantly moving, colliding, and breaking in an endless tectonic dance.

Additional Resources

Explore earthquake activity in specific regions: Learn about high-risk areas like California, the Pacific Northwest, Alaska, Chile, Turkey, and Mexico City. Understand the intraplate anomaly of the New Madrid Seismic Zone. Learn how Tokyo became earthquake-prepared and how plate tectonics creates earthquakes. Discover what happens underground during earthquakes, why depth matters, why earthquakes cannot be predicted, and what earthquake swarms are. Find safety basics in our comprehensive FAQ, and observe global earthquake patterns on our real-time map.