Thursday, March 10, 2011

8.9 Earthquake in Japan

We are learning more about a massive quake in Japan, with an estimated magnitude of 8.9 offshore of Sendai, Honshu. A major tsunami has been generated and the cable news shows are showing aerial shots of an extraordinary wave spreading across agricultural fields, overwhelming roads and villages. From the maps, it appears that the quake was generated in the subduction zone on the Pacific side. There is a good chance that a tsunami could be spreading through the Pacific, but I have not heard any confirmation. I would only say that if the authorities issue a warning, take it seriously and get to a safe place.

The most stunning aspect so far has been the aerial perspective of the tsunami spreading across the landscape. The 2004 tsunami in Indonesia was documented better than any previous event, but I don't recall seeing any aerial shots like this. Tsunamis are not really waves, they are surges of water that rush inland at speeds sometimes approaching 100 mph. The surge picks up debris and uses it as a battering ram. It is terrifying to see.

The TV commentators are starting to get up to speed, but for the best information from seismologists, check out the U.S. Geological Survey here. They have links to the current tsunami conditions in the Pacific basin.

My night class watched the 7.2 quake on Tuesday on our teaching seismograph, and I assume it was a foreshock to this event. Ironically, the subject of the day in my physical geology class was the types of damage caused by quakes. We mentioned tsunamis...

I pray for those in the path of the devastation.

UPDATE #1: A tsunami watch has been issued for the Hawaiian Islands. If a wave has been generated, it will arrive about 3 am Hawaii time.

UPDATE #2: The tsunami watch has been upgraded to a tsunami warning in Hawaii. Please take it seriously. The waves, if any, will reach the coast of California and Oregon around 7-7:30 am local time. At that distance, I don't expect much, but things can change overnight.

UPDATE #3: If 8.9 magnitude becomes official, this is the 5th largest quake in the world since 1900. Chile 1960, 9.5; Alaska 1964, 9.2; Sumatra 2004, 9.1; Kamchatka, Russia, 1952, 9.0. I finally hear an MSNBC commentator get the energy numbers right: the difference in energy between this and the Haiti quake at 7.0 is closer to 1,000 times, not 100 times. The equivalent of 1,000 Haiti quakes just hit offshore of Japan.

UPDATE #4: A tsunami watch has been announced for the coast of California. Take it seriously if you live in coastal areas. If it comes, it will arrive around 7:30-7:45 am in the morning. Listen for official warnings and obey them! Don't do the California thing and wander down to the beach to look for it.

UPDATE #5: The Pacific Coast is now under a tsunami warning, with expected wave heights of 3 feet or so, arriving around 8 in the morning depending on location. Take it seriously; if you are on the beach, you could easily be swept away by such waves. Follow official warnings; emergency personnel know what they are doing!

UPDATE #6: Some damage is now being reported in California as surges of water hit Crescent City and other coastal towns. Damage is "significant", not major, mostly along the lines of boats being jostled and ripped from moorings. I'm hearing of waves 5-6 feet high along parts of the California coast, and of 8 foot waves in Hawaii. 11 people were killed at Crescent City in 1964 from a tsunami of 12 feet, in part because they didn't realize the waves come in groups, and the first wave is not necessarily the largest. It is a cautionary tale for all the people rushing out to the beach to "see the tsunami". It might not be a good idea to become, literally, part of the story. Stay out of coastal areas until an "all clear" signal is given.

UPDATE #7: Silver Fox at Looking for Detachment has a list of the geoblogosphere's response to the Japan earthquake here.

UPDATE #8: Both the USGS and Japanese geologists have upgraded the magnitude of the quake to 9.0, making it the 4th largest ever recorded.
Post a Comment