C5S3

 The Seismograph is a heavy weight attached to a frame by a spring or wire. A pen connected to the weight rests on its point on a drum that can rotate.

 Seismic waves cause the seismograph’s drum to vibrate. But the suspended weight with the pen attached moves very little. Therefore, the pen stays in place and records the drum’s vibrations.

 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.

 Look at C5S2 Notes for definition

 P waves travel fastest  S waves arrive shortly after P waves  Surface waves produce the largest disturbance on the seismogram.

 To monitor faults, geologists have developed instruments to measure changes in elevation, tilting of the land surface, and ground movement along faults.

 A tilt meter measures tilt or raising of the ground.  It consists of two bulbs that are filled with liquid and connected by a hollow stem. It works like a level.

 Uses a wire stretched across a fault to measure horizontal movement of the ground.  One side is anchored to a post and the other side is attached to a weight that can slide if the fault moves.

 Uses a laser beam to detect horizontal fault movement. The device times a laser beam as it travels to a reflector and back.

 Scientists can monitor changes in elevation as well as horizontal movements along faults using a network on Earth’s Orbiting Satellites GPS (global positioning System)

 Seismographs and fault-monitoring devices provide data used to map faults and detect changes along faults. Geologists are also trying to use data to develop a method of predicting earthquakes.

 Since most faults are hidden by a thick layer of rock and soil. Geologists had to figure a way to map faults. They discovered that when seismic waves hit a fault, the waves are reflected off the fault. Seismographs can detect these reflected seismic waves. Geologists use this information to map the fault.

 Geologists study the types of movement that occur along faults. Along parts of some faults, the rocks on both sides are smooth and slide by each other without much sticking.  Other faults have large amounts of sticking due to rough and jagged edges, this sticking creates friction.

 Is a force that opposes the motion of one surface as it moves across another surface. Friction exists because surfaces are not perfectly smooth.