Fault Segment
Definition
A distinct section of a larger fault system with characteristic slip behavior. Different segments may rupture independently or together in a cascade, affecting earthquake magnitude.
Example
The Cascadia subduction zone may rupture in segments or as a single M9+ event.
Related Terms
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 2016 Kumamoto Earthquakes: A Double Mainshock That Rewrote Seismic Hazard Rules
The earthquake doublet that overturned the assumption that the first large shock is always the mainshock, forcing Japan to revise its public messaging and early warning protocols.
The 1999 Izmit Earthquake: North Anatolian Fault Rupture at Turkey's Industrial Heart
The latest in a remarkable 60-year westward migration of M7+ earthquakes along the North Anatolian Fault, with stress calculations now pointing directly at Istanbul for the next major rupture.
The 1906 Ecuador-Colombia Earthquake: The M8.8 Megathrust That Defined the Northern Andes Hazard
The earthquake that established the segmented rupture model for subduction zones, as its 500 km rupture was partially re-ruptured in three subsequent earthquakes -- a textbook case of megathrust supercycles.
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.