P-waves (P stands for primary) arrive at the detector first. They are longitudinal waves which mean the vibrations are along the same direction of travel. Other Examples of longitudinal waves include sound waves and waves in a stretched spring.
S-waves (S stands for secondary) arrive at the detector of a seismometer second. They are transverse waves which means the vibrations are at right angles to the direction of travel. Other examples of transverse waves include light waves and water waves. I used this picture to show an example and difference of P- waves and S-waves. P-waves uses compression and Dilation, but S-waves uses Amplitude and Wavelength.
Both types of seismic wave can be detected near the earthquake centre but only P-waves can be detected on the other side of the Earth. This is because P-waves can travel through solids and liquids whereas S-waves can only travel through solids. This means the liquid part of the core blocks the passage of S-waves.
S-waves (S stands for secondary) arrive at the detector of a seismometer second. They are transverse waves which means the vibrations are at right angles to the direction of travel. Other examples of transverse waves include light waves and water waves. I used this picture to show an example and difference of P- waves and S-waves. P-waves uses compression and Dilation, but S-waves uses Amplitude and Wavelength.
Both types of seismic wave can be detected near the earthquake centre but only P-waves can be detected on the other side of the Earth. This is because P-waves can travel through solids and liquids whereas S-waves can only travel through solids. This means the liquid part of the core blocks the passage of S-waves.
- Measure the time that elapses between the arrival of the P (primary) wave and the arrival of the S (secondary) wave to the seismic stations.
- Using the S-P time, determine the epicentral distance of each station to the earthquake using a travel time curve.
- Use a map and graphical compass to draw arcs of radii equal to the epicentral distances around each station. Where these arcs overlap, you may approximate your epicenter.
Richter Scale - a scale, ranging from 1 to 10, for indicating the intensity of an earthquake. The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes.
A straight line is drawn from the distance measurement to the amplitude measurement of the three seismographs. The three lines should all meet at a single point on the magnitude scale in the middle, giving a magnitude reading for the earthquake. This is an example of the Richter Scale. You find the Distance and the Amplitude for three seismographs in order to find the magnitude of the earthquake.
A straight line is drawn from the distance measurement to the amplitude measurement of the three seismographs. The three lines should all meet at a single point on the magnitude scale in the middle, giving a magnitude reading for the earthquake. This is an example of the Richter Scale. You find the Distance and the Amplitude for three seismographs in order to find the magnitude of the earthquake.