Physics - seismic waves Flashcards
What are seismic wave?
Seismic waves are produce by earthquakes and can be monitored and tracked.
What are the 4 layers of the earth?
crust - relatively thin and rocky
mantle - has the properties of a solid, but can flow very slowly
outer core - made from liquid nickel and iron
inner core - made from solid nickel and iron
What is a P wave?
P waves are longitudinal waves, and their relative speed is faster than other waves. P waves can travel through solids and liquids.
What is an S wave?
S waves are transverse, and they are slower than P waves. They travel through solids only.
What is a surface wave?
Surface waves are also longitudinal waves, and they are the slowest. They travel along surfaces (hence the name).
How can the distance of the epicentre from the station be determined?
The time lag between the arrival of the P and S waves at a seismometer station can be used to determine the distance of the epicentre from the station. If we know the time lag between the arrival of P and S waves, we can calculate the distance of the earthquake from the station. This will give us the distance of the earthquake from the station, but not the direction.
How do P and S waves vary as they travel deeper into the earth?
The speed of P waves and S waves increases as they travel deeper into the Earth’s mantle. They travel through the Earth in curved paths, but they change direction suddenly when they pass through the boundary between substances in different states.
How do P waves act as they travel through the earth?
-Longitudinal
-Fast moving
-Travel through liquids and solids
-Go through all of the layers and only change direction when entering an exiting the inner core ( they bend in)
How do S waves act as they travel through the earth?
-Transverse
-Slower moving than P waves
-Travel through solids only
-Only go through the crust and mantle and do not go through the earths core.
What is the difference in properties of the three waves?
A surface wave travels along the surface of the Earth. It is the slowest of the three types of seismic wave. Surface waves usually have larger amplitude than the other waves and cause the most damage.
A P wave is a longitudinal wave and travels the fastest. It can travel through solids and liquids.
An S wave is a transverse wave and travels slower than a P wave, thus arriving after the P wave. S waves can only travel through solids, and as a result do not travel through the liquid core of the Earth.
What is the S wave shadow zone?
The S wave shadow zone is the area of the Earth’s surface where S waves are not detected following an earthquake. This shadow zone has led geologists to a model of the Earth with a solid mantle and a liquid core.
