FRI MAR 11, 2011 2:46 PM JST. SENDAI, MIYAGI PREF. Latent energy has been accumulating in the Japan Trench east of Sendai since 1933, in geologic time a scant 78 years. This latent energy is suddenly released as the North American plate, to the west, snaps upward along a 300-kilometer long underwater fault line, allowing the adjacent Pacific plate, to the east, to slip below its crust. Tectonic movement is first detected by seismometers at 14:45 JST, triggering an early warning system that alerts citizens to an impending earthquake. Approximately one minute later, Japan’s largest and most populous island of Honshu begins shaking.
During the next several minutes, the torn fissure at the epicenter cascades into a series of ruptures rippling north and south along its fault line, situated under the Pacific Ocean, 130 kilometers east of the city of Sendai. The earth’s mantle grinds laterally over itself, east and west, as much as twenty meters, along the zone of subduction; vertical thrust is estimated to be as much as 30-40 meters.
A ten-centimeter drop in ocean-wave height is instantaneously measured at the nearest coastal station in Kamaishi. Two minutes later a ten-centimeter rise in ocean wave height is measured at Ishinomaki, one hundred kilometers to the south. Like a bathtub that is disturbed by a fallen object, these instantaneous changes in surface elevation, measured far away along the rim, are only a precursor to what is set in motion, ripples on sea skin, a faint clue to the massive sub-surface displacement that has begun its journey. The Japan Meteorological Agency, detecting the jolt, with the aid of a computer model, determines that a major tsunami of up to three meters in Iwate and Fukushima prefectures, and of up to six meters in Miyagi prefecture, is likely to occur as a result of the upheaval. It broadcasts an official tsunami warning to residents along the Tōhoku Coast.
FRI MAR 11, 2:46 PM. TOKYO. Seismic monitors detect the impending earthquake, triggering an automatic shutdown of Japan Railway’s bullet trains. The railway’s 27 high-speed trains quickly brake to a safe stop about fifteen seconds before the earthquake begins. Hundreds of regional and local trains and subways are notified by other means that an earthquake is happening and engineers stop all trains in their tracks. All platform departures are suspended.
Eleven nuclear reactors at Onagawa, Fukushima and Tokai begin automatic shutdown, as part of their standard operating protocol, in response to the onset of the earthquake.
Television and radio broadcasts are interrupted by the emergency public broadcast system, which announces the presently occurring earthquake’s intensity and geographic distribution. Drivers are instructed to use caution, while building occupants are advised to seek safety immediately.
An orderly first response in an orderly country.