Kimia's+Chapter+5+Section+3+Notes


 * __Monitoring Earthquakes-Section 3__**

__ Key Terms __ Seismogram:the record of an earthquake's seismic waves produced by a seismogram. Friction:the force that opposes the motion of one surface.

The Seismograph A simple seismograph can consist of a heavy weight attached to a frame by a spring or wire.A pen connected to the weight rests its point on a drum that can rotate.As the drum rotates slowly,the pen draws a straight line on paper wrapped tightly around the drum.

Measuring Wave 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 during a quake.But the rest of the seismograph is anchored to the ground and vibrates when seismic waves arrive.

Reading a Seismograph You have probably seen a zigzag pattern of lines used to represent an earthquake.The pattern of lines is called a **seismogram.** Instruments that Monitor Faults Along a fault,scientists may detect a slight rise of fall in the elevation and tilt of the land.To monitor faults.geologists have developed instruments to measure changes in elevation,tilting of the land surface,and ground movements along the faults. Tiltmeters A tiltmeter measurestilting or raising of the ground.The tiltmeter used by a carpenter's level, you have used a type of tiltmeter.The tiltmeter used by geologists consist of two light bulbs that are filled with a liquid and connected by a hollow stem. Creep Meters A creep meter uses a wire stretched across a fault to measure horizontal movment of the ground.On one side of the fault,the wire is anchored to a post.On the other side,the wire is attached to a weight that can slide if the fault moves.Geologists determine how much the weight has moved a scale. Laser-Ranging Devices A laser-ranging device uses a laser beam to detect horizontal fault movements.The device times a laser beam as it travels to a reflector and back. GPS Satelites Scientists can monitor changes in elevation as well as horizontal along faults using a network of Earth-orbiting satelites called GPS.GPS (Global Positioning System) was developed to help ships and planes their route.Using GPS,scientists measure tiny movements of markers set up on the opposite sides of a fault.