The Trembling Earth

now at blogs.agu.org/tremblingearth

Japan’s 8.9 quake and the Pacific tsunami

Everyone–scientists and public alike–has been inundated with information and media about yesterday’s gargantuan earthquake in the subduction zone off the coast of Japan. Its occurrence at midday in one of the most technologically advanced countries in the world has offered some unprecedented views of the phenomena accompanying Great earthquakes.

The tsunami generated by the Magnitude 8.9 earthquake pours ashore along the Iwanuma coast in Japan on March 11. Image courtesy http://www.nola.com

There is an innumerable multitude of videos of the quake happening, which YouTube has already begun compiling on its CitizenTube channel. No doubt this collection will grow and grow in the coming hours and days. Here are some highlights:

A grocery store rocks relentlessly as workers scramble to hold up jostling goods:

Two high-rise buildings sway threateningly toward each other while officeworkers across the street look on

There’s also a noisy video of the city shaking filmed from outside on the street:

In this immediately post-quake video you hear the eerie wail of civil defense sirens warning of the imminent tsunami:

A video I find particularly fascinating is this footage from inside a laboratory of some fancy seismic safety equipment doing what it’s supposed to: buffering the countertop equipment from the shaking of the room around it

Everyone has no doubt seen the truly horrific footage of the tsunami surging inland on the hard-hit northern coast of Japan, compiled here by the BBC.

This was the 5th largest earthquake humans have ever recorded with instruments, surpassed by a 1957 9.0 on the Kamchatka peninsula, the 2004 9.1 in Sumatra, the 1964 9.2 in Alaksa, and Chile’s 9.5 in 1960. The energy released by this earthquake was tremendous, and is still ringing the globe. People may be surprised to hear the relatively low casualty count of such a sizable temblor (tsunami aside), but this tends to be the M.O. of subduction zone megathrust quakes. Although they represent the unzipping of a vast swath of Earth’s crust, the ruptures are buried deep and emerge far offshore, meaning that despite ground shaking that lasts for hundreds of seconds, only modest accelerations are experienced on land, nothing strong enough to bring down buildings.

As is common, the New York Times has some excellent graphics illustrating what went on.

Unfortunately, I must get on with the day’s actual research, so I’ll update this post a bit later. Feel free to add links to info, images, etc. that you find. Callen Bentley at Mountain Beltway blog has a good summary post and links to blogs a-plenty covering this event. I’ll be back once today’s to-do list is all checked off!

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