Earthquakes: Types and Causes

What is an Earthquake?

• A sudden release of energy in the Earth's crust, causing seismic waves to propagate through the Earth or along its surface
• Caused by movement along faults, volcanic activity, or human activities such as injection of fluids into the ground

Types of Earthquakes

• Tectonic earthquakes: result from movement along faults, plate boundaries, and plate tectonics
• Volcanic earthquakes: caused by movement of magma and gas beneath a volcano
• Collapse earthquakes: result from collapse of underground caverns or voids
• Human-induced earthquakes: caused by human activities such as injection of fluids, mining, and construction

Earthquake Characteristics

• Magnitude: measure of the size of an earthquake, usually measured on the moment magnitude scale (Mw)
• Intensity: measure of the effects of an earthquake at a particular location, usually measured on the Modified Mercalli Intensity Scale (MMI)
• Depth: distance from the Earth's surface to the earthquake's epicenter
• Epicenter: point on the Earth's surface directly above the earthquake's hypocenter (focus)
• Hypocenter: location of the earthquake's focus, where the seismic waves originate

Seismic Waves

• P-waves: primary waves, compressional waves that travel through the Earth's crust and mantle
• S-waves: shear waves, waves that travel through the Earth's crust and mantle, but not through the core
• Surface waves: waves that travel along the Earth's surface, causing the most damage

Measuring Earthquakes

• Seismometers: instruments that detect and record seismic waves
• Seismographs: records of seismic waves, used to determine earthquake characteristics
• GPS: Global Positioning System, used to measure ground deformation and movement

Earthquake Hazards

• Ground shaking: most common hazard, causing damage to buildings and infrastructure
• Landslides: triggered by earthquakes, can cause further damage and loss of life
• Tsunamis: large ocean waves triggered by earthquakes, can cause widespread damage and loss of life
• Liquefaction: process where soil or sediment becomes fluid-like during an earthquake, can cause damage to structures and infrastructure

What is an Earthquake?

• An earthquake is a sudden release of energy in the Earth's crust, causing seismic waves to propagate through the Earth or along its surface.
• Earthquakes can be caused by movement along faults, volcanic activity, or human activities such as injection of fluids into the ground.

Types of Earthquakes

• Tectonic earthquakes result from movement along faults, plate boundaries, and plate tectonics.
• Volcanic earthquakes are caused by movement of magma and gas beneath a volcano.
• Collapse earthquakes result from collapse of underground caverns or voids.
• Human-induced earthquakes are caused by human activities such as injection of fluids, mining, and construction.

Earthquake Characteristics

• Magnitude is a measure of the size of an earthquake, usually measured on the moment magnitude scale (Mw).
• Intensity is a measure of the effects of an earthquake at a particular location, usually measured on the Modified Mercalli Intensity Scale (MMI).
• Depth is the distance from the Earth's surface to the earthquake's epicenter.
• Epicenter is the point on the Earth's surface directly above the earthquake's hypocenter (focus).
• Hypocenter is the location of the earthquake's focus, where the seismic waves originate.

Seismic Waves

• P-waves are primary waves, compressional waves that travel through the Earth's crust and mantle.
• S-waves are shear waves, waves that travel through the Earth's crust and mantle, but not through the core.
• Surface waves are waves that travel along the Earth's surface, causing the most damage.

Measuring Earthquakes

• Seismometers are instruments that detect and record seismic waves.
• Seismographs are records of seismic waves, used to determine earthquake characteristics.
• GPS (Global Positioning System) is used to measure ground deformation and movement.

Earthquake Hazards

• Ground shaking is the most common hazard, causing damage to buildings and infrastructure.
• Landslides are triggered by earthquakes, can cause further damage and loss of life.
• Tsunamis are large ocean waves triggered by earthquakes, can cause widespread damage and loss of life.
• Liquefaction is a process where soil or sediment becomes fluid-like during an earthquake, can cause damage to structures and infrastructure.