Earthquakes Unit 12 2 Earthquake shaking of the

Earthquakes Unit 12. 2

Earthquake: shaking of the ground as a result of a ____________ sudden release of energy in Earth’s crust friction between moving tectonic plates that • often occurs as a result of _____ pressure builds-up ______ • about 80% of earthquakes occur in a ring bordering the ________ • the Juan de Fuca convergent plate boundary West of Vancouver Island has many earthquakes

Earthquake: shaking of the ground as a result of a ____________ sudden release of energy in Earth’s crust friction between moving tectonic plates that • often occurs as a result of _____ builds-up ______ pressure • about 80% of earthquakes occur in a ring bordering the ________ Pacific Ocean • the Juan de Fuca convergent plate boundary West of Vancouver Island has many earthquakes

Focus: _______ location where the pressure is finally released as an earthquake Epicenter: the point on the ______ surface ______ directly _____ above the focus Earthquakes occur at various depths, depending on the plates involved. more damage • earthquakes at the surface usually cause ________ Classification of Earthquakes Classification Depth of Focus Shallow Focus 0 to 70 km Intermediate Focus 70 to 300 km Deep Greater than 300 km

Seismic wave: ________ vibration energy released by earthquakes source of an earthquake (where an earthquake • can tell us the ______ happened) strength of an earthquake • can tell us the ______

primary wave Longitudinal wave (P wave) underground solids fastest 1 st same liquids gases

secondary wave Transverse wave (S wave) underground solids slower 2 nd perpendicular to

surface only surface wave (L wave) solids slowest last (3 rd) perpendicular to structural damage

composition and _____ size of Earth’s Seismic waves can tell us the ________ interior layers since they behave differently in different materials • some can travel underground • they travel _____ faster through solids than liquids

The velocity increases Since seismic waves travel faster through solids, this must mean that the outer core is liquid

L P mantle S P

Seismometer: a machine that measures and records seismic wave energy Seismograph: a graph that shows arrival time of seismic waves • ________ long • how _____ an earthquake lasted • an earthquake’s ________ magnitude (strength)

5 min 3000 km

The magnitude (size) of an earthquake is the size of the line on the seismograph The magnitude is measured by the Richter Scale 10 x stronger 1 in magnitude = _______ • an increase of ____ 10 102 103