10.3 and 10.4 Vocab and Review

Seismometer

A machine that measures seismic waves and other ground motions.

Seismograph

An older type of seismometer in which a suspended, weighted pen wrote on a drum that moved with the ground.

For an earthquake prediction to be really useful, what would need to be predicted?

Both place/location and approximate timing of the earthquake.

Liquefaction

Clay, sand, and sand saturated with water become like quicksand, lose their strength, and behave more like a liquid that a solid.

On a seismogram, which waves arrive first, second, and third?

First waves are Primary waves, then secondary waves, and finally Rayleigh and love waves.

Why do you need at least three seismographs to locate an earthquakes epicenter?

If you only had two, there would be two possible points where the epicenter could have occurred. When you have three circles they only overlap at one point.

If a seismogram records P-waves and surface waves but not S-waves where was the earthquake epicenter located relative to the seismograph and why?

It would determine that the earthquake was on the other side of earth, because the S-waves cannot travel through the outer liquid core.

What is liquefaction and how does it cause damage in an earthquake?

Liquefaction is clay, silt, and sand, saturated with water to become like quicksand. This causes damage by the buildings slowly sinking to the ground.

How do seismologists use earthquake foreshocks to predict future earthquakes?

Seismologists use foreshocks to predict earthquakes in the sense of where they will be, although foreshocks aren't very helpful when it comes to the timeline of how soon an earthquake will occur.

What usually kills or injures people in an earthquake?

Structures collapsing, and fires caused by broken pipelines.

What were the problems of the Mercalli scale measuring earthquake magnitudes? Why did Richter and moment magnitude need to be developed?

The Mercalli scale was developed based on the structural damage of buildings, and how much people could feel it. This cause the data to be skewed. The Richter/moment magnitude scales needed to be developed because they measured by the same standards no matter what the location.

In two earthquakes of the same magnitude, what could produce more damage- a location in the epicenter, or further away?

The amount of damage produced by an earthquake would largely depend on the population, but if the city was further away from the epicenter, then the surface waves would have time to grow or time to die down depending on the magnitude of the earthquake.

Using what you know about elastic strength, will a building better withstand an earthquake if it is build absolutely solid or is able to sway?

The building will be more solid if it is able to sway. If it was completely solid, the building would crumble when it was moved, but if allowed to sway, the wave motion wouldn't do as much damage.

Why is the moment magnitude scale more accurate than the Richter scale scale for measuring earthquake magnitudes?

The moment magnitude scale is more accurate than the Richter scale because the Richter scale has an upper limit, and was proved unreliable at distances over 350 miles. The magnitude in the moment magnitude scale is based off of the average amount of slip on the fault and the size of the area that slipped, which is more accurate.

Seismogram

The printed record of seismic activity produced by a seismometer.

How can a seismograph measure ground shaking if all parts of it must be attached to the ground?

They use a large mass combined with levers and electronicsro magnify the signal, making very small signals detectable. A large mechanical seismograph may have 1000 lbs. or more, and this helps the pen write a more accurate seismograph of the earthquake.

What can an architect do to make an earthquake safe?

Use flexible materials, anchor structure to bedrock, use lighter materials, buildings can even be put on rollers to prevent earthquakes damage.

What information is needed to calculate the distance from a seismic station to an earthquakes epicenter?

You can calculate the distance from a seismic station to the epicenter by determining how far it was away from the station, and then drawing a circle with the distance away as the radius. Then repeat this process with two other stations and where all three circles touch is the location of the epicenter.