# Earthquakes and Seismic Waves

Pages: 5 (915 words) Published: August 19, 2013
Earthquakes and Seismic Waves

Earthquake-is violent shaking of Earth's crust

Focus-exact point within the crust where the fist movement occurs

Epicenter-point on Earth's crust directly above the focus

Types of Seismic Waves

P Wave
Primary-1st
Fastest
Accordion-in and out

S Wave
Secondary
Snake-like
Can't travel through liquid

Surface Wave-roll through the top of the crust creating the most damage

Measuring Earthquakes

Mercalli scale
-measures damage

The Richter Scale
-magnitude
-seismograph-needle and paper

The Moment Magnitude Scale
-measures energy

Comparing Magnitudes
-1 point = 32x energy

Locating the Epicenter

-time the difference between P and S waves

-plot time on graph to determine distance

-use compass to encircle station

-repeat with 2 other stations
-epicenter is where all 3 meet

The Richter scale measures an earthquake based on the size of the seismic waves that it produces.

The focus is the point beneath Earth’s surface where rock that is under stress breaks, triggering an earthquake. The epicenter is the point on the surface directly above the earthquake’s focus.

P waves compress and expand the ground they travel through, whereas S waves thrust the ground from side to side and up and down. S waves are not as fast as P waves, and they cannot travel through liquids as P waves can.

A tiltmeter measures vertical movement along a fault. Tiltmeters work much like a carpenter’s level. They consist of two bulb containing liquid. A scale allows scientists to determine any changes in to volume of liquid in either bulb. The Global Positioning System, or GPS, consists of a network of satellites that can be used to locate points on Earth’s surface with great precision. This satellite network allows scientists to measure tiny movements of receivers placed on the ground on opposite sides of a fault. GPS satellites can be used to detect horizontal movements along a fault as well as vertical movements, like changes in elevation or tilting.

The seismogram from the stronger earthquake will have more jagged traces that have greater amplitude than those produced by the weaker earthquake.

False-The pen on a seismograph swings freely.

A device that uses wire stretched across a fault to measure horizontal movement of the ground is called a creep meter

GPS-Which of the following monitors both vertical and horizontal movements along a fault The energy from an earthquake is carried to the surface in the form of seismic waves.

The epicenter of this earthquake is located in southern Illinois.

The moment magnitude scale is a rating system that is used to estimate the total energy released by an earthquake. Geologists rate earthquakes on the scale based on seismic wave data recorded by modern electronic seismographs. The higher the magnitude of an earthquake on the scale, the more energy is released by the earthquake and the greater is the destruction produced.

Tiltmeter-Which type of fault-monitoring device is most like a carpenter’s level?

By measuring friction along faults, scientists can tell where rocks are moving along easily and where they are locked. They hope to use this information to predict where major earthquakes might occur.

A seismograph has a heavy weight that is attached to the machine by a spring or wire.A pen connected to the weight runs along a paper on a rotating drum. When seismic waves cause the machine to vibrate, the weight and pen remain steady. This causes the trace of the pen on the rotating drum to produce zigzagging lines.

A laser-ranging device is used to measure horizontal movement at a fault. A laser is located on one side of a fault and a reflector is placed on the other side. A laser-ranging device measures movement by determining the time it takes for the laser to be reflected back across the fault.

Geologists use a(n) tiltmeter to measure the tilting of the ground along a fault....