Notes Section 2-3 & Questions

• Zhang Heng, designed and build the earthquake detection device in China 2,000 years ago.
• Seismic waves cause the seismographs drum to vibrate. But the suspended weight with the pen attached moves very little. Therefore, the pen attached moves very little. Therefor the pen stays in place and records the drums vibration.
• The pattern of lines is called a seismograph.
• To monitor faults, geologists have developed instruments to measure changes in elevation, tilting of the land surface, and ground movement along the faults.
• Seismographs an fault-monitoring devices provide data used to map faults and detect changes also faults. Geologists are also trying to use these data to develop a method of predicting earthquakes.
• Friction
• Friction; is the force that opposes the motion of one surface as it moves across another surface.

Questions/Answers

1. What is a Seismograph?

A. A measuring instrument for detecting and measuring the intensity and direction and duration of movements of the ground (as an earthquake)

2. How does a Seismograph record seismic waves?

A. It is the Same when you write a sentence, the paper stays in one place while your hand moves the pen. But in a seismograph, it's the pen that remains stationary while the paper moves. Why is this? All seismographs make use of a basic principle of physics: Whether it is moving or at rest, every object resists any change to its motion. A seismograph's heavy weight resists motion during a quake. But the rest of the seismograph is anchored to the ground and vibrates when seismic waves arrive.

3. A seismograph records a strong earthquake and a week earthquake. How would the seismograph for the two earthquakes compare.

A. One of the lines recorded with be much smaller this will be the weaker earthquake.

4. What four instruments are used to monitor faults.

A. The creep meter, tilt meter, laser-ranging devices, and the satellite monitors.

5. What changes does each instrument measure

A. Tilt, then creep, and monitors.

6. A satellite that monitors a fault detects an increasing tilt in the land surface along the fault. What could this change in the land surface indicate

A. That there was an earthquake there.

7. What are three ways i which geologists use seismographs data?

A. They map faults, detect changes along faults, and develop a method of predicting earthquakes.

8. How do geologists use seismographic data to make map faults.

A. When seismic waves hit a fault, the waves are reflected off the fault.Seismograph can detect these refkected seismic waves.Geologists then use these data to map the fault's length and depth.

9. Why do geologists collect data on friction along the sides of faults.

A. So that geologist can predict how much force of pressure applied on the faults to predict how strong the earthquake.