Iran's Earthquake-Prone Cities: Ancient Cities at Risk

Iran is one of the most seismically active countries in the world, experiencing on average one earthquake of magnitude 6 or greater every year. The country sits squarely in the collision zone between the Arabian and Eurasian tectonic plates, which are converging at approximately 2-3 centimeters per year. This ongoing collision has created a complex network of faults crisscrossing the Iranian plateau, placing the nation's 90 million residents in constant seismic danger.

What makes Iran's earthquake situation particularly dire is the collision between ancient urban heritage and modern population density. Many Iranian cities have existed for millennia, with building traditions developed long before seismic engineering was understood. Tehran, the capital with over 9 million residents in the city and 16 million in the greater metropolitan area, sits atop multiple active faults capable of generating magnitude 7+ earthquakes. Tabriz, with 1.7 million people, has been destroyed by earthquakes at least three times in recorded history. Mashhad, Iran's second-largest city with 3.4 million residents, sits in a highly active seismic zone.

The 2003 Bam earthquake stands as a stark illustration of Iran's vulnerability. A magnitude 6.6 earthquake struck the ancient city of Bam at 5:26 AM on December 26, killing more than 26,000 people and destroying 85% of the city's buildings. The Bam Citadel, a 2,000-year-old UNESCO World Heritage site and one of the largest adobe structures in the world, collapsed into rubble. The disaster killed a staggering proportion of the city's population—roughly one in four residents—demonstrating how traditional construction methods that served Iran for millennia become death traps when the ground shakes.

This article explores why Iran is so seismically active, which cities face the greatest earthquake threats, why traditional Iranian construction is so vulnerable to earthquakes, the specific challenge of protecting ancient urban centers and cultural heritage, how Iran's deadliest earthquakes have shaped the nation's understanding of seismic risk, and what measures are being taken—or should be taken—to protect 90 million people living on one of Earth's most active fault systems.

Iran's Tectonic Setting: Living in a Collision Zone

Understanding Iran's earthquake hazard requires understanding the massive tectonic forces compressing the Iranian plateau.

The Arabian-Eurasian Collision

The collision zone:

• Arabian Plate moving northward at 2-3 cm per year
• Colliding with Eurasian Plate
• Collision began ~35 million years ago
• Created Zagros Mountains (Iran's highest peaks)
• Entire Iranian plateau caught in collision zone

Why this creates intense seismicity:

• Continental collision cannot be "absorbed" by subduction
• Both plates too buoyant to sink into mantle
• Instead, crust deforms, folds, fractures
• Creates dense network of faults throughout region
• Stress released through frequent earthquakes

Major Fault Systems

North Tabriz Fault:

• Major right-lateral strike-slip fault in northwest Iran
• Runs directly through Tabriz (population 1.7 million)
• Capable of M7.5+ earthquakes
• Historical ruptures in 858, 1042, 1721, 1780
• 1,400+ years of documented destructive earthquakes

Main Recent Fault (Dasht-e Bayaz Fault):

• Eastern Iran fault system
• 1968 M7.3 Dasht-e Bayaz earthquake killed 12,000+
• Left-lateral strike-slip fault
• 80+ km surface rupture in 1968

Zagros Mountains Thrust System:

• Network of thrust faults in Zagros Mountains
• Extends across southern and western Iran
• Accommodates Arabia-Eurasia convergence
• Frequent M5-6 earthquakes, occasional M6-7

North Tehran Fault and Mosha Fault:

• Active faults running through northern Tehran metropolitan area
• Right-lateral strike-slip faults
• Capable of M7+ earthquakes
• Pose greatest threat to capital
• No major rupture in recorded history (ominous)

Alborz Mountain faults:

• Complex fault network in Alborz Mountains north of Tehran
• Multiple active faults capable of M6-7 earthquakes
• 1990 Manjil-Rudbar M7.4 killed 40,000+ in this region

Seismicity Patterns

Frequency:

• Average one M6+ earthquake per year
• Average one M7+ earthquake per decade
• Hundreds of M4-5 earthquakes annually
• Thousands of smaller earthquakes

Distribution:

• Northwestern Iran: Very high activity (Tabriz region)
• Northern Iran: High activity (Alborz Mountains, Tehran region)
• Eastern Iran: High activity (Dasht-e Bayaz fault system)
• Zagros Mountains: Continuous moderate activity
• Central deserts: Lower activity but not immune

Tehran: A Megacity on a Fault Line

Iran's capital presents one of the world's most serious urban earthquake threats.

The City and Its Faults

Population concentration:

• City proper: 9+ million people
• Greater metropolitan area: 16+ million people
• Nearly 20% of Iran's entire population
• Political, economic, cultural center of nation

Fault systems:

• North Tehran Fault: Runs along northern edge of city
• Mosha Fault: Northeast of Tehran
• Rey Fault: South of Tehran
• Multiple smaller faults throughout region
• Some faults run directly beneath densely populated areas

The Threat

Earthquake potential:

• North Tehran and Mosha faults capable of M7+ earthquakes
• No major historical rupture on these faults (concerning)
• Stress accumulating for centuries
• When rupture occurs, it will be catastrophic

Damage scenarios:

• M7.0 earthquake on North Tehran Fault: estimated 50,000-200,000+ deaths
• Up to 50% of buildings could be damaged or destroyed
• Critical infrastructure (hospitals, fire stations) would be damaged
• Landslides in northern Tehran (built on slopes of Alborz Mountains)
• Economic damage: hundreds of billions of dollars

Why Tehran is so vulnerable:

• Rapid unplanned growth: City expanded rapidly without adequate planning
• Building quality varies enormously: Modern high-rises alongside ancient structures
• Building code enforcement: Inconsistent, particularly in informal settlements
• Density: Extremely dense population in vulnerable buildings
• Topography: Northern Tehran on steep slopes prone to landslides
• Soil conditions: Parts built on soft alluvial deposits (amplifies shaking)

Historical Earthquakes Near Tehran

1830 Tehran earthquake:

• Estimated M7.0-7.2
• 45,000+ deaths
• Destroyed much of Tehran (then much smaller city)
• Nearly 200 years ago—stress has been building since

1962 Buyin-Zahra earthquake:

• M7.1 about 150 km west of Tehran
• 12,000+ deaths
• Demonstrated potential for large earthquakes in region

1990 Manjil-Rudbar earthquake:

• M7.4 about 200 km northwest of Tehran
• 40,000+ deaths
• Felt strongly in Tehran
• Caused panic but limited damage to capital
• Wake-up call about Tehran's vulnerability

Efforts to Address Tehran's Risk

Building codes:

• Iran has relatively modern building codes
• Designed to withstand M7.0 earthquakes
• BUT enforcement is major problem
• Corruption, cost-cutting lead to non-compliance
• Many buildings constructed illegally without permits

Retrofit programs:

• Some efforts to retrofit older buildings
• But scale of problem overwhelming
• Millions of vulnerable structures
• Limited resources for comprehensive program

Proposals to move capital:

• Periodically discussed due to earthquake risk
• Also air pollution, water scarcity concerns
• But politically and economically impractical
• Tehran remains capital despite risks

The 2003 Bam Earthquake: A City Erased

The Bam earthquake demonstrated the catastrophic vulnerability of traditional Iranian construction.

December 26, 2003, 5:26 AM

The earthquake:

• M6.6 earthquake struck Bam, southeastern Iran
• Epicenter just outside city
• Shallow depth: only 10 km
• Strike-slip faulting on previously unknown fault

Timing made it worse:

• 5:26 AM—most people asleep in homes
• Winter—families sleeping indoors
• Friday (weekend in Iran)—people at home, not at work
• Building collapses occurred when occupancy highest

The Devastation

Death toll:

• Official death toll: 26,271
• Some estimates as high as 43,000
• Population of Bam: approximately 100,000
• One in four residents killed
• 30,000+ injured
• 75,000+ homeless

Building damage:

• 85% of buildings destroyed or severely damaged
• Nearly complete destruction in old city center
• Hospitals collapsed, hampering rescue efforts
• All three hospitals in Bam destroyed
• Emergency services overwhelmed

The Bam Citadel (Arg-e Bam):

• 2,000-year-old UNESCO World Heritage site
• Largest adobe structure in world
• Stood for two millennia
• Collapsed almost completely in seconds
• Massive loss of cultural heritage
• Symbol of how ancient construction techniques fail in earthquakes

Why So Deadly?

Adobe and unreinforced masonry construction:

• Bam's traditional buildings built from adobe (sun-dried mud bricks)
• Adobe has almost no tensile strength
• Walls crack and collapse when shaken
• Heavy roofs (often with earth covering for insulation) crush occupants
• Unreinforced masonry similarly vulnerable

Building characteristics:

• Thick, heavy walls
• No reinforcement or connections between structural elements
• Walls simply stacked, not tied together
• Roofs not properly connected to walls
• When shaking begins, structures fall apart

Why magnitude 6.6 was so destructive:

• M6.6 is moderate by global standards
• In well-built areas, might cause limited damage
• 2014 Napa, California M6.0 killed 1 person
• 2003 Bam M6.6 killed 26,000+
• Difference: building construction quality
• Same magnitude, vastly different outcomes

The Response and Recovery

International aid:

• Massive international response
• Countries worldwide sent rescue teams
• United States provided aid despite strained relations
• Demonstrated humanitarian cooperation transcending politics

Reconstruction:

• Bam rebuilt with earthquake-resistant construction
• New building codes enforced
• Citadel reconstruction ongoing (painstaking archaeological process)
• City substantially recovered but never regained former population

Lessons:

• Traditional construction methods inadequate for seismic zones
• Building codes must be enforced, not just written
• Cultural heritage sites need seismic protection
• Moderate magnitude earthquakes can be catastrophic with poor construction

Other Earthquake-Prone Iranian Cities

Tehran is not alone—many Iranian cities face severe earthquake threats.

Tabriz: A City Repeatedly Destroyed

The city:

• Population: 1.7 million
• Northwestern Iran, near Turkish and Armenian borders
• Ancient city, capital of Iran at various periods
• Major commercial and cultural center

Seismic setting:

• North Tabriz Fault runs directly through city
• Capable of M7.5+ earthquakes
• Complex tectonic environment with multiple active faults

Historical earthquakes:

• 858 CE: Massive earthquake destroyed city, ~200,000 deaths (medieval estimate)
• 1042 CE: Another destructive earthquake, tens of thousands killed
• 1721 CE: M7.3-7.7, destroyed much of city, 80,000+ deaths
• 1780 CE: M7.4, destroyed city again, 50,000+ deaths
• At least four total destructions in recorded history

Modern vulnerability:

• Much larger population than historical periods
• Mix of modern and traditional construction
• Many older buildings highly vulnerable
• North Tabriz Fault last major rupture: 1780 (245 years ago)
• Stress accumulating for another major earthquake

Mashhad: Holy City in Seismic Zone

The city:

• Population: 3.4 million (Iran's second-largest city)
• Major pilgrimage destination (Imam Reza shrine)
• 20+ million pilgrims visit annually
• Concentrated population and tourism infrastructure

Seismic threat:

• Located in seismically active northeastern Iran
• Multiple active faults in region
• 1673 earthquake destroyed much of city
• Regular moderate earthquakes (M5-6)

Special concerns:

• Large transient population (pilgrims)
• Many pilgrims unfamiliar with city, earthquake procedures
• Mass gatherings at shrine complex (can hold 700,000+ people)
• Panic during earthquake could cause stampede

Shiraz: Cultural Capital at Risk

The city:

• Population: 2 million
• Cultural and historical center
• Near Persepolis and other ancient sites
• Major tourism destination

Seismic setting:

• Zagros Mountain fold-and-thrust belt
• Multiple active faults
• Moderate seismicity (frequent M4-5, occasional M6)

Qom: Religious Center

The city:

• Population: 1.3 million
• Major Shia religious center
• Theological schools and seminaries
• Pilgrimage destination

Seismic threat:

• Located on active faults
• 1962 earthquake (epicenter near Qom) killed hundreds
• Many historical religious buildings highly vulnerable

The Construction Challenge: Ancient Methods Meet Modern Hazards

Traditional Iranian construction techniques are catastrophically vulnerable to earthquakes.

Adobe Construction

What is adobe?

• Sun-dried mud bricks
• Clay mixed with straw, shaped, dried in sun
• Used for thousands of years in Iran
• Excellent thermal properties (cool in summer, warm in winter)
• Locally available, inexpensive materials
• Well-suited to Iran's climate—but not to earthquakes

Why adobe fails in earthquakes:

• No tensile strength (easily cracks)
• Heavy mass but no ductility
• Walls not connected to each other or to roof
• Shaking causes walls to crack and separate
• Heavy roof collapses, crushing occupants
• Complete collapse common even in moderate earthquakes

Unreinforced Masonry

Traditional masonry construction:

• Brick or stone walls stacked with mortar
• No steel reinforcement
• Heavy, rigid structures
• Cannot flex or absorb seismic energy

Earthquake vulnerability:

• Walls crack at mortar joints
• Out-of-plane failure (walls topple outward)
• Floors and roofs lose support, collapse
• Parapets and chimneys fall into streets
• Extremely dangerous to occupants

Modern Construction Issues

Building code problems:

• Iran has modern seismic building codes
• Codes based on international standards
• Problem: enforcement inconsistent
• Corruption allows non-compliant construction
• Developers cut corners to reduce costs
• Inspectors bribed or overwhelmed

Concrete frame buildings:

• Common in modern Iranian cities
• Can be earthquake-resistant if properly designed and built
• BUT many cut corners:
  • Inadequate reinforcement steel
  • Poor concrete quality
  • Inadequate connections between elements
  • Soft first story (retail/parking) without proper reinforcement
• Result: buildings that look modern but are highly vulnerable

The Retrofit Challenge

Scale of the problem:

• Millions of vulnerable buildings across Iran
• Many in densely populated urban areas
• Retrofitting expensive and disruptive
• Limited resources for comprehensive program

Cultural heritage concerns:

• Many historic buildings cannot be demolished
• Retrofitting must preserve historical character
• Balancing preservation with safety extremely difficult
• Some structures essentially impossible to make earthquake-safe

Iran's Deadliest Earthquakes: A Century of Disasters

Iran's earthquake history is a catalog of recurring catastrophes.

Major Earthquakes Since 1900

1909 Silakhor earthquake (M7.4):

• Western Iran
• 5,000-6,000 deaths

1962 Buyin-Zahra earthquake (M7.1):

• Northwest Iran
• 12,000+ deaths
• Qazvin province devastated

1968 Dasht-e Bayaz earthquake (M7.3):

• Eastern Iran
• 12,000+ deaths
• 80 km surface rupture
• Scientifically important—well-documented rupture

1978 Tabas earthquake (M7.4):

• Eastern Iran
• 15,000-25,000 deaths
• City of Tabas essentially destroyed
• 85% of buildings collapsed

1990 Manjil-Rudbar earthquake (M7.4):

• Northwest Iran, Gilan province
• 40,000-50,000 deaths (estimates vary)
• 100,000+ injured
• 500,000+ homeless
• Felt strongly in Tehran (200 km away)
• Major wake-up call about seismic risk

2003 Bam earthquake (M6.6):

• Southeastern Iran
• 26,000+ deaths
• Detailed earlier in article

2012 East Azerbaijan earthquakes (M6.4, M6.3):

• Northwest Iran, near Tabriz
• Two large earthquakes 11 minutes apart
• 306 deaths
• Thousands injured

2017 Iran-Iraq earthquake (M7.3):

• Kermanshah province, western Iran
• 630+ deaths (mostly in Iran)
• Thousands injured
• Demonstrated ongoing seismic activity in Zagros Mountains

Cumulative Toll

20th-21st century deaths:

• Over 126,000 deaths from earthquakes since 1900
• Hundreds of thousands injured
• Millions made homeless
• Enormous economic losses
• Incalculable cultural heritage losses

Preparedness and Mitigation Efforts

Iran faces enormous challenges in reducing earthquake risk.

What's Being Done

Building codes:

• Modern codes comparable to international standards
• Updated based on earthquake lessons
• Require earthquake-resistant design
• But enforcement remains major problem

Seismic monitoring:

• National seismic network operated by IIEES (International Institute of Earthquake Engineering and Seismology)
• Monitors earthquake activity across country
• Provides data for hazard assessment
• Early warning system under development

Public education:

• Earthquake drills in schools
• Public awareness campaigns
• Emergency preparedness information
• But reach and effectiveness vary

Research:

• IIEES conducts earthquake research
• Studies fault systems and seismic hazards
• Develops improved construction techniques
• International collaboration on earthquake science

What Needs to Be Done

Enforcement of building codes:

• Strict enforcement critical
• Codes worthless without compliance
• Requires political will and resources
• Anti-corruption measures essential

Retrofitting existing buildings:

• Millions of vulnerable structures exist
• Comprehensive retrofit program needed
• Prioritize high-occupancy buildings
• Schools, hospitals, government buildings first
• Then residential buildings in high-risk areas

Urban planning:

• Restrict development near active faults
• Ensure adequate open spaces for post-earthquake assembly
• Plan evacuation routes
• Distribute critical facilities geographically

Emergency preparedness:

• Stockpile emergency supplies
• Train search and rescue teams
• Develop coordinated response plans
• Regular drills and exercises

The Bottom Line

Iran's position in the collision zone between the Arabian and Eurasian plates makes it one of the most seismically active countries on Earth. The ongoing convergence at 2-3 centimeters per year creates a complex network of faults that crisscross the Iranian plateau, generating on average one magnitude 6+ earthquake every year and a magnitude 7+ earthquake every decade. With 90 million people living and working atop this seismically active landscape, Iran faces an earthquake crisis that combines ancient urban heritage, rapidly growing modern cities, and construction practices that range from vulnerable traditional methods to poorly enforced modern codes.

Tehran presents perhaps the world's most serious urban earthquake threat. The capital and its surrounding metropolitan area hold over 16 million people—nearly 20% of Iran's entire population—living directly above multiple active faults capable of magnitude 7+ earthquakes. The North Tehran and Mosha faults have not ruptured in recorded history, suggesting centuries of stress accumulation. When these faults inevitably rupture, casualties could range from 50,000 to over 200,000, with economic damage in the hundreds of billions of dollars. The city's rapid, often unplanned expansion has created a mix of modern high-rises, traditional construction, and informal settlements, with building quality varying enormously and code enforcement inconsistent at best.

The 2003 Bam earthquake stands as a stark illustration of Iran's vulnerability. A magnitude 6.6 earthquake—moderate by global standards—killed more than 26,000 people in a city of approximately 100,000 residents. One in four residents died because traditional adobe and unreinforced masonry construction simply collapsed when the ground shook. The 2,000-year-old Bam Citadel, one of the world's largest adobe structures and a UNESCO World Heritage site, crumbled into rubble in seconds, demonstrating how construction methods that served Iran for millennia become death traps in earthquakes. By comparison, California's 2014 Napa earthquake at magnitude 6.0 killed one person—the difference was building construction quality.

Iran's earthquake history over the past century reads as a catalog of recurring disasters: 12,000 deaths in the 1962 Buyin-Zahra earthquake, 12,000 in the 1968 Dasht-e Bayaz earthquake, 15,000-25,000 in the 1978 Tabas earthquake, 40,000-50,000 in the 1990 Manjil-Rudbar earthquake, 26,000+ in the 2003 Bam earthquake. The cumulative toll exceeds 126,000 deaths since 1900, with hundreds of thousands injured and millions made homeless. Each disaster demonstrates the same fundamental problem: buildings that cannot withstand the shaking that Iran's tectonic setting guarantees will occur repeatedly.

The challenge facing Iran is immense. Millions of vulnerable buildings exist across the country—adobe structures in rural areas and small cities, unreinforced masonry in historic urban centers, and modern concrete buildings constructed without adequate seismic design or enforcement. Traditional construction techniques that evolved over millennia in response to Iran's climate prove catastrophic when earthquakes strike. Modern building codes exist and are reasonably sophisticated, but enforcement is inconsistent, corruption enables non-compliant construction, and developers cut corners to reduce costs. The result is buildings that may look modern but collapse when shaken.

Iran has made progress. Building codes have been updated, seismic monitoring networks operate nationwide, public education programs raise awareness, and research institutions study earthquake hazards. The government and scientific community understand the risks. But understanding the problem is not the same as solving it. Comprehensive retrofitting of existing vulnerable buildings would cost billions of dollars and require decades of sustained effort. Strict enforcement of building codes requires political will and anti-corruption measures. Urban planning restrictions on development near active faults must be implemented and maintained despite development pressures.

The plates will continue converging. Stress will continue building on locked faults. Earthquakes will continue striking Iranian cities. The only questions are when, where, and whether Iran will be adequately prepared. For ancient cities like Tabriz, destroyed by earthquakes at least four times in recorded history, the pattern is clear—another major earthquake is not a matter of if, but when. For Tehran, with 16 million people living above faults that have not ruptured in living memory, the stakes could not be higher. Iran's approach must balance the reality of limited resources with the certainty of future disasters, prioritizing strict building code enforcement for new construction, retrofitting the most vulnerable existing buildings, and ensuring that when the inevitable earthquake strikes, response systems are ready to save as many lives as possible.

Additional Resources

Explore earthquake topics relevant to Iran: Understand how plate tectonics creates earthquakes, discover what happens underground during earthquakes, and learn the mathematical patterns earthquakes follow. See why some regions have more earthquakes than others and explore other regions along the Alpide Belt including Turkey's earthquake threat. Learn about how earthquake depth affects damage, why earthquakes cannot be predicted, and earthquake swarms. Compare with Ring of Fire countries like Chile's resilience strategies, Tokyo's preparedness, New Zealand's approach, and Indonesia's challenges. Find earthquake safety basics in our comprehensive FAQ, and observe Iran's frequent earthquakes on our real-time map.