Do Now – In Notebooks

1. What is an earthquake?

2. What kind of stress acts on a normal fault? Does the crust lengthen or shorten?

3. What is the difference between the focus and epicenter of an earthquake?

Measuring Earthquakes

How are earthquakes measured?

Seismology

The study of earthquake waves is called Seismology

Earthquake waves can be detected at great distances by Seismometers

A seismometer’s record is known as a Seismogram

Time-Travel Curves

Years of data collection has led to time-travel curves

The curves tell the time an S- and P-wave takes to reach a certain distance

P-waves arrive first The difference between waves on a

seismogram determines the distance from the epicenter

Time-Travel Curves

Locating Earthquakes

Epicenters are located by the separation between S- and P-waves on a seismogram

Cannot use one location to map epicenter

Need to use three or more seismic stations

Time can be measured in same way

Magnitude and Intensity

The amount of energy released during an earthquake is known as its magnitude

The amount of damage done by an earthquake is known as intensity

Three scales measuring intensity/magnitude Richter Scale Moment Magnitude Scale Modified Mercalli Scale

Do Now – In Notebooks

What is the difference between an earthquake’s magnitude and intensity?

What is the amplitude of a curve?

You will need: Notebooks Southern California Earthquake Packet Pencil Calculator (See me if you need one)

MAGNITUDE AND INTENSITY

How are earthquakes measured?

Richter Scale - Magnitude

The Richter Scale is based on the largest waves generated by the quake

Each number on the scale is an increase of 10 Ex: 8 is 10x larger

than 7, 100x larger than 6

Moment Magnitude Scale

The Moment Magnitude Scale includes: Size of fault rupture Amount of movement

along fault Rocks’ stiffness

Uses more data than Richter Scale – More accurate

Modified Mercalli Scale - Intensity

The Modified Mercalli Scale assesses damage from a quake

Factors affecting Intensity

Depth of Focus

Distance from Epicenter