GRCC’s seismic station (GRMI) in Calkins picked up the magnitude 7.9 earthquake in Alaska on Tuesday morning. The earthquake was located at a depth of 25 km below the sea floor, southeast of Kodiak Island in the Gulf of Alaska. A tsunamic warning was initiated for much of the west coasts of the U. S. and Canada but was cancelled a few hours later. The fault that generated the earthquake was not of the type that usually triggers a damaging tsunami. More information about the earthquake can be found on the U. S. Geological Survey’s website. The figures below show the dramatic trace of the earthquake on the GRMI record. The second image is the pulled record of the earthquake and clearly exhibits the P wave (a seismic body wave that moves through the Earth) and the L wave (a high amplitude wave that travels on the surface of the Earth). The waves arrived at the GRCC station about 7 and 23 minutes, respectively, after the earthquake in Alaska, a testament to the speed of seismic waves!
Trace of M7.9 Alaska earthquake on GRMI
Pulled seismogram of M7.9 Alaska earthquake showing the relative arrival of the P and the L waves.
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