What does a seismogram show about P waves?
Seismograms contain a lot of information about an earthquake: its strength, length, and distance. Wave height is used to determine the magnitude of the earthquake. The seismogram shows the different arrival times of the seismic waves (Figure below). The first waves are P-waves since they are the fastest.
Do P waves travel up and down?
They are called primary waves because they are the first type of wave to arrive at seismic recording stations. P waves can travel through solids, liquids, and even gases. These are the shake waves that move the ground up and down or from side to side.
What pattern do P waves travel in?
P waves, also called compressional or longitudinal waves, give the transmitting medium—whether liquid, solid, or gas—a back-and-forth motion in the direction of the path of propagation, thus stretching or compressing the medium as the wave passes any one point in a manner similar to that of sound waves in air.
Why do P waves travel?
In P or compressional waves, the vibration of the rock is in the direction of propagation. P waves travel fastest and are the first to arrive from the earthquake. The direct P wave arrives first because its path is through the higher speed, dense rocks deeper in the earth. …
What does a seismogram look like?
When you look at a seismogram, there will be wiggly lines all across it. These are all the seismic waves that the seismograph has recorded. Most of these waves were so small that nobody felt them. Because P waves are the fastest seismic waves, they will usually be the first ones that your seismograph records.
How are P waves measured?
First, the amplitude of the surface wave is measured on a seismogram produced by a Wood-Anderson seismometer (a specfic type of seismometer) and then it is compared with distance from the earthquake or the S-P time (which is the amount of time between the P-wave and S-wave arrival) to yield a magnitude.
Where do P waves travel the fastest?
Because the earth’s mantle becomes more rigid and compressible as the depth below the asthenosphere increases, P-waves travel faster as they go deeper in the mantle. The density of the mantle also increases with depth below the asthenosphere. The higher density reduces the speed of seismic waves.
What happens when P waves move?
Seismic P waves are also called compressional or longitudinal waves, they compress and expand (oscillate) the ground back and forth in the direction of travel, like sound waves that move back and forth as the waves travel from source to receiver.
Why do P waves arrive first in the seismograph stations?
Because P waves are the fastest seismic waves, they will usually be the first ones that your seismograph records. Surface waves travel a little slower than S waves (which, in turn, are slower than P waves) so they tend to arrive at the seismograph just after the S waves.
How do you read seismogram?
The seismogram is “read” like a book, from left to right and top to bottom (this is the direction that time increases). As with a book, the right end of any horizontal line “connects” with the left end of the line below it. Each line represents 15 minutes of data; four lines per hour.
What is meant by seismogram?
A seismogram is the recording of the ground shaking at the specific location of the instrument. On a seismogram, the HORIZONTAL axis = time (measured in seconds) and the VERTICAL axis= ground displacement (usually measured in millimeters).