Secondary Earthquake Hazards
Definition
Hazards triggered by earthquake shaking rather than the shaking itself — including tsunamis, landslides, liquefaction, fires, dam failures, and chemical releases. Often cause more damage than shaking.
Example
Fires following the 1906 San Francisco earthquake destroyed more buildings than the shaking itself.
Related Terms
Related Guides
What Is an Earthquake? A Complete Introduction
Learn what causes earthquakes, how they occur along fault lines, and why some regions experience more seismic activity than others.
Dam Safety and Seismic Risk
Dam failures during earthquakes can cause catastrophic flooding. Learn how dams are designed and evaluated for seismic safety.
The 2011 Tohoku Earthquake and Tsunami: A Complete Analysis
The 2011 M9.1 Tohoku earthquake triggered a devastating tsunami and nuclear disaster. A comprehensive analysis of one of history's worst earthquakes.
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 1906 San Francisco Earthquake: Birth of Modern Seismology
The 1906 M7.9 San Francisco earthquake and fire reshaped a city and launched modern earthquake science. The quake that changed everything.
The 1556 Shaanxi Earthquake: The Deadliest in History
The 1556 Shaanxi earthquake killed approximately 830,000 people, making it the deadliest earthquake in recorded human history.
The 1755 Lisbon Earthquake: When Philosophy Changed
The 1755 Lisbon earthquake, tsunami, and fire destroyed one of Europe's greatest cities and sparked the Enlightenment debate on natural evil.
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.
Standing in a Doorway: Why This Advice Is Outdated
Standing in a doorway during an earthquake is outdated advice that can be dangerous. Learn why Drop, Cover, Hold On is safer.
Earthquake-Proofing Your Home: A Room-by-Room Guide
Protect your home from earthquake damage with this room-by-room guide to securing furniture, appliances, and structural weak points.
Related Case Studies
The 2018 Sulawesi Earthquake: Strike-Slip Tsunami and Catastrophic Liquefaction in Palu
The earthquake that defied three textbook rules: strike-slip faults generated a destructive tsunami, the rupture propagated at supershear speed, and liquefaction flows traveled 700 meters on nearly flat ground.
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.
The 1995 Kobe Earthquake: The Disaster That Transformed Japan's Building Codes
The earthquake that exposed fatal weaknesses in Japan's pre-1981 building stock, leading to the most sweeping seismic engineering reforms in history and proving that building codes save lives.
The 1970 Ancash Earthquake: The Deadliest Earthquake in South American History
The deadliest earthquake in South American history, where a 50-million-cubic-meter avalanche from Mount Huascaran traveled at 300 km/h to bury the town of Yungay, killing 92% of its population.
The 1923 Great Kanto Earthquake: When Fire Destroyed Tokyo
The earthquake that proved fire -- not shaking -- is the primary killer in dense urban areas, with 38,000 people perishing in a single fire tornado.
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.