Unreinforced Masonry (URM)
Definition
Brick or block construction without steel reinforcement, which is extremely vulnerable to earthquake shaking. URM buildings account for the majority of earthquake fatalities worldwide.
Example
The 2023 Turkey earthquakes collapsed thousands of URM buildings, killing over 50,000 people.
Related Terms
Related Guides
Unreinforced Masonry: The Most Dangerous Building Type
Unreinforced masonry buildings kill more people in earthquakes than any other type. Learn the risks and how communities address this deadly legacy.
How to Evaluate Your Building's Seismic Safety
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The Evolution of Building Codes After Major Earthquakes
Every major earthquake reveals building failures that reshape building codes. Trace the evolution of seismic design standards from 1906 to today.
The 2010 Haiti Earthquake: Disaster and Response
The 2010 M7.0 Haiti earthquake killed over 200,000 people. Learn why the devastation was so extreme and the lessons for earthquake preparedness.
The 1976 Tangshan Earthquake: China's Deadliest Disaster
The 1976 M7.5 Tangshan earthquake killed an estimated 242,000 people. The deadliest earthquake of the 20th century.
The 1556 Shaanxi Earthquake: The Deadliest in History
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The 2015 Nepal Earthquake: The Gorkha Quake
The 2015 M7.8 Nepal earthquake devastated Kathmandu and triggered avalanches on Everest. A study in building vulnerability and international response.
The 1989 Loma Prieta Earthquake: The World Series Quake
The 1989 M6.9 Loma Prieta earthquake struck during the World Series, collapsing freeways and exposing soft-story building dangers.
The 1923 Great Kanto Earthquake: Tokyo's Destruction
The 1923 M7.9 Kanto earthquake destroyed Tokyo and Yokohama, killing over 140,000. The firestorms were deadlier than the shaking itself.
Do You Need Earthquake Insurance? A Complete Guide
Homeowners insurance doesn't cover earthquakes. Learn who needs earthquake insurance, what it costs, and how to decide if it's worth the premium.
Related Case Studies
The 2023 Turkey-Syria Earthquakes: A Double Mainshock That Killed 59,000
The deadliest earthquake disaster of the 2020s, notable for its unprecedented double mainshock sequence and the subsequent criminal prosecution of contractors for building code violations.
The 2015 Nepal Earthquake: When the Himalayas Shifted and Kathmandu Trembled
The earthquake that demonstrated the Himalayas' ongoing collision in real time, with GPS measurements showing Nepal shifted 3 meters south, while only partially releasing centuries of accumulated tectonic strain.
The 2011 Christchurch Earthquake: How a M6.2 Aftershock Destroyed a City Center
One of the few cases where an aftershock was more devastating than its mainshock, with a M6.2 at just 5 km depth producing 2.2g ground acceleration that obliterated Christchurch's city center.
The 2010 Haiti Earthquake: How a Magnitude 7.0 Killed 316,000 People
The deadliest earthquake relative to magnitude in modern history, demonstrating that building quality and governance -- not earthquake size -- determine whether people live or die.
The 2008 Sichuan Earthquake: 87,000 Dead Along the Longmenshan Fault
The earthquake that forced China to confront endemic building code violations after thousands of 'tofu-dreg' school buildings collapsed while adjacent government structures survived, killing over 5,000 children.
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Frequently Asked Questions
The epicenter is the point on the Earth's surface directly above the hypocenter (focus) where the earthquake rupture begins. It is typically reported as latitude and longitude coordinates. The strongest shaking usually occurs near the epicenter, though local soil conditions and fault geometry can shift the zone of maximum damage.
A seismograph (or seismometer) is an instrument that detects and records ground motion caused by seismic waves. Modern broadband seismometers can detect movements smaller than the width of an atom. Networks of seismographs around the world enable scientists to locate earthquakes and determine their magnitude within minutes.
P-waves (primary waves) are compressional waves that travel fastest through rock, arriving first at seismic stations. S-waves (secondary waves) are shear waves that arrive later but cause more ground shaking. P-waves travel through solids, liquids, and gases; S-waves only travel through solids. The time difference between them helps determine earthquake distance.
The hypocenter (or focus) is the point within the Earth where an earthquake rupture initiates. It is described by latitude, longitude, and depth. The vertical distance between the hypocenter and the surface directly above is the earthquake's depth, which strongly influences how the earthquake is felt at the surface.
Seismology is the scientific study of earthquakes and the propagation of seismic waves through the Earth. It encompasses earthquake detection, location, and characterization; Earth's internal structure; seismic hazard assessment; and earthquake engineering. Seismologists use data from global seismograph networks to study these phenomena.