earthquakes

Course: Earthquake-Resistant Design (CE584)
Institution: University of Gaziantep, Faculty of Engineering, Department of Civil Engineering
Instructor: Asso. Prof. Dr. Esra M. Güneyisi
Student Presenters: Mustafa Mohammed Rashid, Mustafa Fahmi Hasan
Date of Presentation: 11 November 2013

An earthquake, also known as a quake, tremor, or temblor, results from the sudden release of energy in the Earth’s crust, creating seismic waves.
Seismicity refers to the frequency, type, and size of earthquakes in an area measured by seismometers.

Tectonic Plates: The Earth's outer surface is divided into tectonic plates that constantly move, causing stress to build up along plate boundaries.
Release of Stress: An earthquake occurs when the stress from plate movement is released.
Earthquake-Prone Areas: Most earthquakes are found along the Circum-Pacific seismic belt known as the "Ring of Fire," with 95% of the world’s earthquakes occurring at active plate boundaries (e.g., the Philippines, Japan, California, Alaska, South America).

Intensity measures the size and effects of an earthquake at Earth's surface, commonly represented on the Modified Mercalli Scale.

Different intensity scales exist; the most commonly used in the U.S. are the Modified Mercalli Scale and the Rossi-Forel Scale.
Unlike magnitude, which is a single value for each earthquake, intensity can vary based on the location.

Intensity and Effects

describes how people perceive the earthquake's vibrations:
- I-III: People notice slight vibrations.
- IV-VI: Moderate damage; people run outdoors.
- VII-IX: Heavy damage; structures may collapse.
- X-XII: Great destruction; significant ground cracks and displacement.

Scale Levels:
- I: Instrumental, not felt.
- II: Weak, felt by a few indoors.
- III: Slight, hanging objects swing.
- IV: Moderate, noise from rattling objects.
- V: Strong, furniture moved; damage begins.
- VI: Very Strong, significant structural damage.
- VII: Destructive, considerable damage in buildings.
- VIII: Violent, most buildings damaged.
- IX: Intense, serious destruction.
- X: Extreme, total destruction.
- XI: Catastrophic, ground deformation; evidence of landslides.

Magnitude quantifies the energy released during an earthquake, generally a single number reflecting the earthquake's strength.
Developed by Charles Richter in 1935, the magnitude scale compares the amplitude of seismic waves.
The seismic moment is a modern metric that reflects the energy released more accurately than the Richter scale.

Intensity measures effects on people and structures, while Magnitude measures the energy released from the earthquake’s source.

Intensity varies based on location, influenced by building structures, depth of the quake, and distance from the epicenter.

Historical data on notable earthquakes provides insight into the relationship between magnitude and recorded intensity, indicating trends and outcomes of significant seismic events.

Accelerographs: Tools that record ground acceleration during earthquakes.
Accelerograms: Data representations of ground acceleration, velocity, and displacement.

Earthquakes are natural disasters caused by tectonic plate movements, and understanding their intensity and magnitude is essential for disaster readiness and resilience planning.