earthquake measurement science chapter 7, section 2 notes science chapter 7, section 2 notes

18
Earthquake Measurement Science Chapter 7, Section 2 Notes

Upload: alvin-sherman

Post on 18-Jan-2018

234 views

Category:

Documents


0 download

DESCRIPTION

I. Studying Earthquakes 1. Scientists use earthquake-sensing instruments called seismometers, or seismographs. 2. Record the vibrations of P waves, S waves, and surface waves. 3. Also record the time waves take to arrive at seismometer station. 1. Scientists use earthquake-sensing instruments called seismometers, or seismographs. 2. Record the vibrations of P waves, S waves, and surface waves. 3. Also record the time waves take to arrive at seismometer station.

TRANSCRIPT

Page 1: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

Earthquake Measurement

ScienceChapter 7, Section

2 Notes

Page 2: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

Section Vocabulary• epicenter: the point on Earth’s surface directly

above an earthquake’s starting point, or focus. The prefix epi- means upon

• focus: the location within Earth along a fault at which the first motion of an earthquake occurs. (inside Earth)

• magnitude: a measure of the strength of an earthquake

• intenstiy:in Earth science, the amount of damage caused by an earthquake

Page 3: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

I. Studying Earthquakes

1. Scientists use earthquake-sensing instruments called seismometers, or seismographs.

2. Record the vibrations of P waves, S waves, and surface waves.

3. Also record the time waves take to arrive at seismometer station.

Page 4: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

I. Studying Earthquakes

A. Determining Locationa. Use data to determine earthquake’s

epicenter.b. Epicenter is directly above earthquake’s

starting point.c. Focus is point inside the Earth where the

earthquake began.

Page 5: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

I. Studying Earthquakes

B. Triangulationa. The time between the arrival of the P waves and

the S waves is called lag time.b. Epicenter is located by drawing a circle around

three seismometer stations and radius of each circle is equal to the distance from the station to the epicenter.

c. The point at which all three circles intersect is the epicenter.

Page 6: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

QuickTime™ and a decompressor

are needed to see this picture.

Page 7: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

II. Earthquake Magnitude

1. Size of the waves on a seismogram indicates amount of ground motion.

2. The amount of ground motion is used to calculate magnitude.

3. Magnitude measures earthquake’s strength.

Page 8: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

II. Earthquake Magnitude

A. The Richter Scalea.Mainly used in the past to measure

magnitude.b.Measures the ground motion from

earthquake and adjusts for distance.c.Each increase of a number (ex: 1 to 2)

represents a 10-fold increase.d.Values generally range from 0 to 9.

Page 9: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

II. Earthquake Magnitude

B. The Moment Magnitude Scalea. Mainly used today to measure instead of

Richter scale.– More accurate measurement of earthquakes.– Represents the size of the area of the fault that

moves, the average distance that the fault blocks move, and the rigidity of the rocks in the fault zone.

– Related to the physical effects that take place.

Page 10: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

QuickTime™ and a decompressor

are needed to see this picture.

The second map shows the locations of California earthquakes of magnitude 4.5 or greater during a 40-year period.

Page 11: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

III. Earthquake Intensity

1. The effects of the earthquake and how it is felt is the intensity of the earthquake.

A. The Modified Mercalli Scalea. Used to describe intensity of an earthquake.b. Scale ranges from I (1) to XII (12).c. Level I (1) are barely noticeable.d. Level XII (12) cause total destruction.

Page 12: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

QuickTime™ and a decompressor

are needed to see this picture.

Page 13: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

III. Earthquake Intensity

B. Mapping Earthquake Intensitya. Show the level of ground shaking expected to occur in different areas that experienced same earthquake.b. Uses data obtained from previous

earthquakes.c. Data is used to model differences in amount of ground shaking that may occur in future earthquakes.

Page 14: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

IV. The Effects of Earthquakes

A.Distance from the Epicentera. As seismic waves move away from an

epicenter they grow larger like circles in a pond when a pebble is dropped.

b. The total energy in a seismic wave stays constant as the wave travels.

c. The amount of energy at a point on the wave decreases as the wave grows larger. This is because the same amount of energy is involved in a larger area (circle).

Page 15: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

IV. The Effects of Earthquakes

A. Local Geologya. The amount of damage depends on the

material the waves travel through.b. Solid rock will not increase the

intensity or time that the ground shakes. c. Seismic waves are dangerous when

they travel through loose soils and sediments with large amounts of water

Page 16: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

IV. The Effects of Earthquakes

d. When water-saturated soil or sediment is shaken by seismic waves, the grains that make up the sediment lose contact with one another and are surrounded by water. This is called liquefaction.

e. Liquefaction can intensify ground shaking and also cause the ground to settle.

f. Settling can cause structures to tilt or even collapse.

Page 17: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

IV. The Effects of Earthquakes

A. Earthquake-Resistant Constructiona. Structures made of brick or concrete are

not flexible.b. They are easily damaged by earthquakes.c. Wood and steel are more flexible.d. Flexible structures are more likely to

survive in strong earthquakes.

Page 18: Earthquake Measurement Science Chapter 7, Section 2 Notes Science Chapter 7, Section 2 Notes

IV. The Effects of Earthquakes

e. Taller buildings are more susceptible to damage than shorter ones.

f. Structures that have solid foundations are firmly anchored to the ground are most likely to be left standing in an earthquake.