Geometrics: Seismograph Records Alaskan Earthquake

On July 17, 2017 at approximately 4:30 pm San Jose, California time, a magnitude 7.7 earthquake struck the far western tip of the Aleutian Islands, near Nikol’skoye, Russia. The USGS estimates that the quake resulted from movement along a right-lateral transform fault on or near the Pacific and North American plate boundaries. Later analysis indicates that the focal point for this earthquake is approximately 11 km deep with a rupture plane on the order of 170 km long by approximately 20 km wide (as viewed in cross section).

At Geometrics in San Jose, approximately 5,300 kilometers away from the epicenter, Dr. Koichi Hayashi of OYOCorporation had a Geometrics Atom Wireless system with a 3-component 2 Hz geophone sitting on the floor of his office. The Atom was recording local ambient ground motion when it received the P, S, and surface waves from the earthquake. By the time ground motion from this quake reached San Jose, it was so weak that it was not noticeable except to the most sensitive instruments.

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