2.2

What type of data do geologists use to locate an earthquakes epicenter?

1. Determine the difference in arrival times between P&S wavesfrom the seismograph 2. convert the difference in arrival time between P&S waves into distance using a data sorce(usually a graph) 3. draw a circle using the distance as the radius 4. plot this info from 3 or more seismic stations on a map 5. the point at which 3 overlap is the epicenter

What are three commonly used methods of measuring earthquakes?

1. The Mercalli scale- rate earthquakes according to the level of damage at a given place 2. The Richter scale- a rating of an earthquakes magnitude based on the size of the earthquakes seismic waves. Provides accurate measurements for small, nearby earthquakes but it does not work well for large, or distant earthquakes. 3. Moment Magnitude Scale- A rating system that estimates the total energy released by an earthquake can be used to rate earthquakes of all sizes near or far.

What is an earthquakes magnitude?

An earthquakes magnitude is a number that geologists assign to an earthquake based on the earthquakes size.

How does energy from an earthquake reach Earth's surface?

During an earthquake seismic waves race out from the focus in all directions (like a pebble thrown in a pond, an earthquake produces vibrations called waves). Seismic waves carry energy from an earthquake away from the focus, through Earth's interior, and across the surface.

How is magnitude measured using the Richter scale?

Geologists determine magnitude by measuring the seismic waves and fault movement that occur during the earthquake. The Richter scale is a rating of an earthquake's magnitude based on the size of the earthquake's seismic waves using an instrument called a seismograph.

What evidence do geologists use to rate an earthquake on the moment magnitude scale?

Geologists study data from seismographs. The data shows what kind of seismic waves the earthquake produced, how strong they were, and they helped geologists infer how much movement occurred along the fault and the strength of the rocks that broke when the fault slipped.

What kind of movement is produced by each three types of seismic waves?

P waves- compress and expand the ground like an accordian. Travel through both solids and liquids. S waves- vibrate from side to side as well as up and down. They shake the ground back and forth and when they reach the surface they shake structures violently. Only move through solids. Surface waves- when S and P waves reach the surface they become surface waves. Surface waves move slower than P and S waves but they can produce severe ground movements. Some surface waves make the ground roll like ocean waves. Other surface wave sake buildings from side to side.

When do P waves arrive at the surface in relation to S waves and surface waves?

The P waves arrive first followed by S waves and then surface waves.

What are the advantages of using the moment magnitude scale to measure an earthquake?

This rating scale looks at many variables (kinds of seismic wave, strength of seismic waves, amount of movement long the fault, strength of the rock when the fault slipped) which enable them to rate earthquakes of all sizes near, or far.

seismograph

a device that records ground movements caused by seismic waves as they move through Earth

Richter scale

a scale that rates an earthquake's magnitude based on the size of its seismic waves

Mercalli scale

a scale that rates earthquakes according to their intensity and how much damage they cause at a particular place

moment magnitude scale

a scale that rates earthquakes by estimating the total energy released by an earthquake

P wave

a type of seismic wave that compresses and expands the ground

surface wave

a type of seismic wave that forms when P waves and S waves reach Earth's surface

S wave

a type of seismic wave that moves the ground up and down or side to side

Which type of seismic wave causes the ground to roll like ocean waves?

surface waves

magnitude

the measurement of an earthquake's strength based on seismic waves and movement along faults

focus

the point beneath Earth's surface where rock breaks under stress and causes an earthquake

epicenter

the point on Earth's surface directly above an earthquakes focus

earthquake

the shaking that results from the movement of rock beneath Earth's surface