AP Photo/Kyodo News)

The fifth largest earthquake in recorded history struck Japan on Friday afternoon. The magnitude 8.9 event occurred at a shallow depth of 24km, 400 km off the east coast of Japan, releasing a devastating amount of energy to the surrounding area. The earthquake was a result of thrust faulting near the subduction zone plate boundry between the westward moving Pacific Plate and the North America Plate (aprox rate of movement is 83 mm/year). The sea-floor displacement caused a tsunami which was up to 30ft high and extended inland about 10 km in the Miyagi Prefecture on Japan’s east coast. The death toll is still being tallied as search and rescue workers and officials attempt to locate the tens of thousands missing. The Tsunami reached the US Pacific coast earlier this morning where little damage was reported. Damage reports from Japan include extensive fires, including an oil refinery and a petrochemical plant in Sendai, train derailments, a burst dam, and the threats associated with nuclear power plant shut down. There were several fore-shocks which happened earlier in the week. Aftershocks continue to pour in and dominate seismic records in the region.

Currently, the most complete source of scientific information available is from the USGS at:


For other damage figures, try the Red Cross:


The AISN was shaken by this event which occurred ~9,000 km away (from Phoenix, 80.66 degrees). The seismogram below is a paper record from a short period sensor at the Flagstaff station on the NAU campus. Shaking here started on our instruments at 11.58pm local time and continued for hours as additional energy reached us from aftershocks.

Seismic waves captured on the paper record from NAU station FLAG

Digital records from short period (CCAZ) and broadband stations (Y14A) both clip at high wave amplitudes even at such a great distance from the hypocenter. Phase picks from stations U15A, X18A, 319A and 113A of the Arizona Integrated Seismic Network were used in the preliminary USGS data for this event.

March 11, 2011 Lisa Linville

AISN station CCAZ, 44 milesNE of Flagstaff, AZ

AISN station Y14A near Wintersburg, AZ