EARTHQUAKES AND PLATE TECTONICS CHAPTER 6 SECTION 1

ELASTIC REBOUND THEORY Rocks on each side of a fault are moving. Fault is locked, rocks stop moving. Rocks on each side of a fault are stressed. Rocks fracture and separate at weakest point. Rocks return to original shape.

Elastic Rebound Theory

AFTERSHOCKS Original earthquake releases energy in the form of vibrations called seismic waves. These vibrations may increase stress in other rocks along the fault. The increased stress on these rocks may cause them to fracture and spring back. The series of smaller tremors are called aftershocks.

FOCUS Area along a fault where the slippage first occurs Focus is beneath the earth’s surface The epicenter is directly above The depth of the focus varies

FOCUS DEPTH - 1975-95

FOCUS DEPTH OF EARTHQUAKES IN WASHINGTON 1977-1996

A point on the earth’s surface directly above the focus EPICENTER A point on the earth’s surface directly above the focus

MAJOR EARTHQUAKE ZONES Pacific Ring of Fire Mid-ocean ridges Eurasian-Melanesian Mountain Belt

MAJOR EARTHQUAKES AREAS

PUGET SOUND FAULT ZONES

Magnitude

STRUCTURAL DAMAGE Kobe Earthquake

LIQUEFACTION Kobe

RECORDING EARTHQUAKES CHAPTER 6, SECTION 2

TYPES OF SEISMIC WAVES P waves S waves L waves

P WAVES Fastest wave First recorded on seismograph Travel through solid and liquid Cause rock particles to move together and apart along the direction of the waves.

S WAVES Second wave to reach seismograph Travels through solids only Cause rock particles to move at right angles to the direction the wave is traveling

L WAVES Slowest moving of the three waves Also called surface or long waves Last to be recorded by the seismograph Travel over the earth’s surface similar to ocean waves Cause the greatest damage

SEISMOGRAPH A device used to measure seismic waves

LOCATING THE EPICENTER

EARTHQUAKE SCALES RICHTER MERCALLI

RICHTER SCALE Scale that ranges from 1-10 Each whole number increases the magnitude of the energy 31.7 times Largest recorded magnitude - 9.5 Above 7 - Major earthquake Between 6 and 7 - Moderate earthquake Between 2.5 and 6 - Minor earthquake Less than 2.5 - Microearthquake

MERCALLI SCALE Measures the intensity of the damaged caused by the earthquake Scale of I - XII (1-12)

I. Not felt except by a very few

II. Felt by a very few persons on the upper floors of buildings

III. Felt indoors

IV. Hanging objects swing

V. Felt outdoors

VI. Felt by all, many scared and run outdoors

VII. Difficult to stand

VIII. Damage slight in specially designed structures

IX. Damage considerable in specially designed structures

X. Ground cracked, rail bent

XI. Bridges destroyed, broad fissures in ground

XII. Damage total

Pacific Northwest Earthquake Information REQUEST FOR EARTHQUAKE INFORMATION

BEFORE - Be prepared DURING - Stay calm AFTER - Stay cautious EARTHQUAKE SAFETY BEFORE - Be prepared DURING - Stay calm AFTER - Stay cautious

ASSIGNMENT WORKSHEET 6.3 Page 111, #1-5