At 8:29 a.m. this past Friday, November 30, a magnitude 7 earthquake sent Anchorage residents scurrying out of buildings and under desks. Six minutes later, GRCC’s seismometer picked up the primary waves that traveled from Alaska to Michigan at a speed of over 13,000 miles per hour. There are preliminary reports of damage in Alaska’s largest city and the surrounding communities. A Tsunami warning was issued and then canceled later in the day.
The image above shows GRMI’s seismic record of the magnitude 7 earthquake in Alaska on Friday morning, November 30, 2018. The two red arrows indicate arrival of the P-body wave and the surface waves.
Calkins Science Center at GRCC hosts a seismometer (GRMI) that is part of the MIQuakes network, a group of high schools, community colleges and universities in Michigan that host seismometers designed to record earthquake activity both locally and worldwide. The stations are sponsored by IRIS – Incorporated Research Institutes in Seismology and MESTA – the Michigan Earth Science Teachers Association.
If you are interested in or other earthquakes recorded by the GRCC seismometer, you can find them on the MIQuakes website.
The earthquakes keep rolling in to GRMI!
August continues to be a seismically busy month. GRMI picked up 3 notable earthquakes in the past week. You may not have heard about the magnitude 8.2 earthquake near Fiji on August 19th. That is because, at a depth of 563 km, this “deep-focus” earthquake was too distant to cause any damage on the surface of the Earth.
You may have heard of the widely felt magnitude 7.3 earthquake that shook Venezuela on August 21st. Large earthquakes are relatively rare in this region and this is the largest historic quake within 250 km of the surface in the last century. Fortunately, this earthquake was also relatively deep (123 km) and caused little damage.
Finally, on the morning of August 22nd, a magnitude 6.2 earthquake was generated on the seafloor off the Oregon coast. The earthquake appears to have been generated where the tiny Juan De Fuca tectonic plate (which is being subducted or shoved under the North American continent) is sliding past the huge Pacific plate. Despite being just 10 km below the sea floor, there was no tsunami generated.
If you are interested in earthquakes recorded by the GRCC seismometer, you can find them on the MIQuakes website.
GRMI seismogram of the M8.2 Fiji earthquake on August 19th (red arrow):
GRMI seismogram of the M7.3 earthquake in Venezuela (red arrow) and the M6.2 Oregon earthquake (blue arrow):
GRCC’s Calkins Science Center hosts a seismometer that’s part of the MIQuakes network, a group of Michigan high schools, community colleges and universities that host seismometers recording earthquake activity worldwide.
GRCC’s seismometer — GRMI — has picked up four earthquakes so far this month that were equal to or greater than magnitude 6:
On Aug. 5 at 11:46 a.m. Coordinated Universal Time, a magnitude 6.9 earthquake was generated near Pulau Lombok, Indonesia. Our seismometer recorded the earthquake 20 minutes later — the red arrow shows the arrival of the primary wave:
On Aug. 12, GRMI picked up two earthquakes — a magnitude 6.4 and 6 — both from northern Alaska. The primary waves from the Alaska earthquakes only took six minutes to arrive at the GRMI station.
Finally, on Aug. 15, a magnitude 6.6 earthquake shook the Tanaga Volcano in the Aleutian Islands and was picked up by GRMI 10 minutes later.