Earthquakes

I. Earthquakes are vibrations caused by the sudden movement of the surface rocks

A. Seismic Waves – the large amounts of energy released when these rocks move

1. 80% of all earthquakes occur in the Pacific ring

2. They are common along ocean ridges

II. Three basic types of Earth’s forces

A. Tension – stretching or pulling apart

B. Compression – a system of forces that eventually causes the object to be squeezed into folds

C. Shearing – forces that push from different sides and causes twisting and tearing

III. Types of Earthquakes

A. Shallow focus earthquakes occur when the outer edges of trenches where the plate is bent downward and scrape

B. Deep focus earthquakes occur when the plate is subducted deeper into the mantle

IV. Measurement of Earthquakes comes in several forms

A. Mercalli Scale measure the damage a quake caused

B. Richter Scale is the measure of the intensity of the quake

1. Focus is the internal origin of the earthquake

2. Epicenter is the surface origin of the earthquake

V. Measurement of Earthquakes

A. Seismologist are scientist who study earthquakes

B. Seismographs record tremors that travel through the earth

C. Seismogram is the lines made by the seismograph on the recording tape

1. Bodywaves are waves traveling outward from the focus in all directions through the Earth’s interior