BACKGROUND
SEISMOMETER SITES
DATA and ANALYSIS
ABOUT US
Our Goals:
When we went to Denali National Park, our main goal was to record the number of earthquakes that occur in that area over the course of three days. We set up seismometers in three different locations and left them there. We also wanted to see where the earthquakes were coming from and the strength of each of the earthquakes that occurred.
What is an earthquake?
An earthquake occurs when tectonic plates bump into each other or fault lines in the Earth slip. When this happens, a large amount of energy is released in the form of waves. These waves travel through the Earth, shaking it. This shaking is what causes the destruction people generally associate with earthquakes.
What are P-waves and S-waves?
Earthquakes release two types of waves. The P-wave is the primary wave and is the first to arrive at the seismic station. The S-wave is a slower wave, and the second wave to arrive. The difference in arrival times between the P and S waves, measured in seconds, helps us determine the distance of the earthquake from the station. If you take the time difference between the P and S waves and multiply it by 10, you will get a rough estimate of the distance to the earthquake, in kilometers.
We chose to do our research on earthquakes in Denali because of all the faults in and around the park. The Alaska Range is right on the Denali Fault, and the mountains in that area are still growing today due to continuing collision and subduction of the Pacific Plate and the North American Plate. The earthquakes we record in this area are evidence that this area is still growing and changing today.
Left: Mt. McKinley, the tallest peak in North America.
Right: The Alaska Range
Why we used seismometers, and how they work:
We used seismometers because they are most accurate way to record earthquakes. Seismometers work by having a mass connected to a computer that records how much the mass moves. When an earthquake or any vibration occurs, it shakes the mass and the computer inside records the frequency and amplitude of the vibrations through a series of electrical impulses. There are three directional components in a seismometer; east, north and vertical. These three components give us more information on how to locate the earthquake. The recorded frequency and amplitude can be used to determine the location and calculate the magnitude of the earthquake. The seismometers give us a way to look at the continual movements of the faults in Denali, as well as the mountain building processes associated with Pacific Plate movement.
Left: a helicorder drum which records seismic data on heat sensitive paper.
Right: the seismometers we used in our experiment.
What is a seismogram?
A seismogram is a plot showing a record of information gathered by a seismic station. It shows the P and S waves for each individual seismic station. The seismogram may contain only one directional component, or it may contain all three (this one shows all three).
