What is Earthquake?

An earthquake occurs when stress accumulated in the Earth's crust is released by the breaking of rock or sudden movement along an existing fault, sending energy outward as seismic waves. The shaking felt at the surface is not the earthquake itself but the motion created as that released energy travels through the ground and structures. An earthquake is a natural event; the scale of death and damage is strongly related to the strength of buildings, ground conditions, settlement patterns, preparedness and correct protective actions.

How earthquakes happen, faults, seismic waves, magnitude and intensity

1. What is an earthquake? The Earth's crust is neither a single piece nor motionless. As plates move very slowly, stress can accumulate in rocks. When stress exceeds rock strength, a rupture or sudden slip occurs on a fault. The released energy travels as seismic waves and shakes the ground. Most earthquakes are tectonic; volcanic activity, collapse of underground cavities and some human activities can also cause more limited shaking. 2. What are tectonic plates and faults? Tectonic plates are large and small rocky sections that form the Earth's outer part. Their boundaries may converge, diverge or slide sideways. A fault is a fracture surface or zone in the crust across which rock blocks can move relative to one another. Faults do not all have the same level of activity, and the presence of a fault on a map does not by itself show that an earthquake will occur on a specific date. 3. Hypocenter and epicenter The point inside the Earth where rupture begins is called the focus or hypocenter. Its projection on the surface is the epicenter. Earthquake depth affects how waves reach the surface and the area over which shaking is felt. Because their source is close to the surface, shallow earthquakes can produce strong shaking nearby, but damage also depends on magnitude, distance, ground conditions and building characteristics. 4. How do seismic waves travel? P waves are the fastest body waves and can travel through solids and liquids. S waves are slower, travel only through solids and move the ground perpendicular to their direction of travel. Surface waves move along the Earth's surface; their large amplitudes and long durations can make structures sway strongly. Seismometers record these motions, and differences in arrival times at multiple stations help locate an earthquake. 5. What does earthquake magnitude mean? Magnitude is a single numerical value related to energy released at the earthquake source. Moment magnitude, Mw, is widely used for large earthquakes. The scale is logarithmic, so a seemingly small increase in magnitude represents a much larger change in energy and ground motion. Calling every measurement 'Richter' is inaccurate; agencies may calculate different magnitude types according to the event and available records, and preliminary values may be revised as new data arrive. 6. Are intensity and magnitude the same? No. Magnitude is one value for the source; intensity describes the effects of shaking on people, objects, ground and structures at a particular place. The same earthquake has different intensities in different locations. Distance from the rupture, rupture direction, site amplification, building characteristics and shaking duration change the local effect. For this reason, earthquake magnitude and shaking intensity should not be used interchangeably. 7. Aftershocks, foreshocks and earthquake sequences The largest event in an earthquake sequence is called the mainshock; smaller earthquakes that then occur in the same source region are aftershocks. Their number and frequency generally decline with time, but strong aftershocks can occur and pose a danger to damaged structures. A shock that occurs before a larger event can be identified as a foreshock only after the larger earthquake happens. Not every small earthquake is a warning of a larger one. 8. Earthquake hazard and earthquake risk Hazard is the probability of strong ground motion at a location during a given period. Risk is the potential loss produced when that hazard combines with exposed people, buildings, infrastructure and vulnerability. Proximity to a fault matters but is not the only factor. Engineering, building inspection, site investigation, emergency planning and education can reduce risk; a hazard map alone cannot determine whether a particular building is safe or unsafe. 9. Why do ground and buildings change the outcome? Soft or thick sediment can amplify some seismic waves and prolong shaking. Liquefaction may develop in loose water-saturated ground, and landslides can occur on slopes. A structure's load-bearing system, material quality, compliance with its design, later alterations, maintenance and natural period relative to the shaking all affect damage. Building safety cannot be determined by looking from outside or from an internet comment; an assessment compliant with regulations must be carried out by authorized professionals.

Earthquakes in Türkiye, prediction claims, preparedness and protective actions during shaking

10. Earthquake reality and the hazard map in Türkiye Türkiye lies in a broad tectonic region where the African, Arabian and Eurasian plates interact. It contains many active faults, especially the North Anatolian and East Anatolian fault systems and the extensional system in the Aegean region. AFAD's Earthquake Hazard Map of Türkiye shows expected ground-motion levels; it is not a direct continuation of the old earthquake-zone classification. It does not replace parcel, site or building risk analysis; local ground studies and engineering assessment are still required. 11. Can the time of an earthquake be predicted? Current science cannot reliably specify an earthquake's exact day, time, location and magnitude in advance. Long-term hazard studies and probabilities can be prepared, but they are not predictions for a particular day. An early-warning system does not predict either: after an earthquake starts, it detects fast waves and attempts to provide seconds of warning before more damaging waves arrive. Claims giving a precise date based on animal behavior, weather, clouds, planetary positions or one small shock are not reliable scientific evidence. 12. Secondary earthquake hazards Beyond shaking, earthquakes can cause fires, gas leaks, electrical faults, water and transport disruption, landslides, rockfall, liquefaction and coastal tsunamis. Damage to dams, industrial facilities and hazardous-material infrastructure can create additional risks. Planning should cover these cascading effects, not only building collapse. A person on the coast who feels strong or prolonged shaking should move away from the shore and toward higher ground after shaking stops when waiting for an official warning would be unsafe. 13. Preparing the home and workplace If you have concerns about a building, seek information from authorized institutions and engineering professionals. Secure cupboards, shelves, televisions and other objects that could topple using appropriate methods; place heavy objects on lower shelves and keep exits clear. Decide in advance on a family communication plan, safer indoor locations, an out-of-area contact and the nearest official assembly area. Practice Drop, Cover and Hold On. Include the specific needs of children, older people, disabled people and pets. 14. What belongs in an emergency kit? For the first 72 hours, prepare water, durable food, regular medicines, first-aid supplies, a flashlight, batteries or a power source, a whistle, seasonally suitable clothing, hygiene items, masks, some cash and copies of important documents, tailored to the household. Consider baby, disability and pet needs separately. Everyone should know where the kit is, and expiry dates for food, water, batteries and medicines should be checked regularly. A kit complements rather than replaces building safety and a family plan. 15. What should you do during an earthquake indoors? Do not panic and run toward stairs, elevators, balconies or exits. Move away from windows, glass, exterior walls and objects that may topple; DROP, COVER your head and neck, and HOLD ON beside or under sturdy furniture. Do not jump outside while shaking continues. If you are in bed and no heavy object could fall on you, protect your head with a pillow. If you use a wheelchair, lock the wheels and protect your head and neck. Attempt to shut off gas or electricity only after the shaking and only if it is safe. 16. What should you do outdoors or in a vehicle? In an open area, move away from buildings, walls, balconies, glass, trees, poles and power lines; crouch and protect your head. If driving, stop in a safe place without endangering traffic, away from bridges, tunnels, overpasses, buildings and power lines, and remain in the vehicle until shaking stops. Where there is a tsunami threat, move away from the sea and toward higher ground after shaking. In a metro, train, stadium or crowded venue, follow staff and official announcements. 17. What should you do immediately after an earthquake? First check yourself and people nearby for injuries; if trained, provide first aid within safe limits. Leave a damaged building carefully by the stairs, not the elevator, and do not re-enter until authorities say it is safe. If you smell gas, do not light a flame, use a match or touch electrical switches; turn off the valve only if safe and move away. Repeat Drop, Cover and Hold On during aftershocks. Keep phone lines free except for emergencies, prefer text messages, and follow official assembly-area and authority instructions. 18. Reliable information, psychological resilience and frequently asked questions After an earthquake, rely on verified statements from AFAD, governorates, municipalities, emergency services and other authorized institutions. Do not share old footage, unverified missing-person lists, locations or aid appeals without checking them. Give children calm, accurate and age-appropriate information; seek professional support if intense fear, sleeplessness or loss of daily function persists. 'Is a doorway always safe?' No; unless specifically reinforced, a doorway in a modern building may provide no special protection. 'Do small earthquakes prevent a large one?' Generally no; the energy they release is far smaller than that of a major earthquake. 'Can I enter before aftershocks end?' Do not enter a damaged building without an official or technical safety assessment. 'Should I run outside during shaking?' When you are indoors and shaking continues, AFAD's core guidance is Drop, Cover and Hold On. Source basis: AFAD — What Is an Earthquake?; AFAD — Measures Before, During and After an Earthquake; AFAD — Earthquake Hazard Map of Türkiye; USGS — Earthquake Magnitude, Energy Release and Shaking Intensity. Sources checked on 11 October 2026.