EARTHQUAKES!!Earth Science

Mr. Barry

Focus and Epicenter

Focus: the point where an earthquake originates

Epicenter: the point on Earth’s surface directly above the focus

Fault: location along which an earthquake originates

Earthquake Waves

Seismic Waves: vibrations of the ground during an earthquake

Primary Waves (P-waves): squeeze and pull rocks in the same direction along the direction the wave is traveling

Earthquake Waves

Secondary Waves (S-Wave): cause rocks to move at right angles in relation to the direction of the wave

Surface Waves: move in two directions (up and down), what it actually felt on the surface

Measuring Earthquakes

Seismometer: device used to measure the strength of earthquakes. A hanging device records vibrations

Seismogram: the record produced by a seismometer

Measuring Earthquakes

Magnitude: the amount of energy released by an earthquake

Richter Scale: earthquake rating based on the size of the seismic waves released by the earthquake

Locating Earthquakes

Earthquake Damage

Structures: buildings fall as ground shakes

Fires: disturbed soil destroys gas and power lines, leading to fires

Land/Soil: landslides are a common result of earthquakes

Earthquake Damage

Tsunami: a large ocean wave generated by vertical motions of the seafloor during an earthquake

Predicting Earthquakes

Earthquake prediction is based largely on probability. Factors used for these predictions are: Earthquake history: many hot spots have

earthquake recurrences Seismic Gaps: active faults that have not

experienced an earthquake recently Strain accumulation : the build up of strain in

one location