Science Spotlight

Station WHIT


Researcher: Andria Bilich
National Geodetic Survey


Station WHIT is operated by Natural Resources Canada (NRCan). The station is located above the Yukon River Valley just outside of Whitehorse.


Name: WhiteHorse
State: Canada
Country: Canada
Elevation: 1427.4 m
Lat/Long:  60.7505 / -135.2221

Denali Fault Earthquake

On November 3, 2002, the magnitude 7.9 Denali Fault earthquake generated large, permanent surface displacements in Alaska and large-amplitude seismic waves throughout western North America. All broadband seismometers within thousands of kilometers of the rupture front saturated (Figure 1) and for this reason could not record the correct ground motions. GPS stations recording data at 1 sample per second in Alaska and western Canada provided the first test of GPS seismology. GPS receivers—including this one in Whitehorse, Canada—detected seismic waves 750 to 3800 km from the epicenter. Using "high-rate GPS"—or GPS seismology—to study the rupture of earthquakes is now commonplace.

Figure 1. Left: Broadband seismometers operating at the time of the 2002 Denali fault Earthquake. Most of the seismometers near the rupture front clipped because of the earthquake's very large size and shallow epicenter. Right: GPS sites operating at 1-Hz (shown in blue) were able to record these very large ground displacements.

 

Figure 2. Position changes for WHIT in a North America fixed reference frame. The GPS data are sampled once per second. GPS data from WHIT are distributed through the IGS.

Spotlight Questions

  • Why is the vertical component of the seismic waves so much smaller than the horizontal components?
  • In many Earth Science classes you learn about P-waves, S-waves, and surface waves. What kind of waves do you think are shown in Figure 2?

Last modified: 2019-12-26  16:24:49  America/Denver  

 

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