These disparate movements cause stresses that build up during non-earthquake and relax when suddenly the earthquake occurs. An outburst of energy that causes a rupture of the crust.
March 11, 2011, the Japan Meteorological Agency provided an estimate of the earthquake magnitude of 7.9 within 3 minutes after the earthquake. The agency at the same time issued a tsunami warning for waves with a height of 6 meters along the coast of Miyagi Prefecture and 3 meters for Iwate and Fukushima. The warning system worked well, says Hiroo Kanamori, a seismologist at Caltech (California Institute of Technnology, United Kingdom), but the calculations have underestimated the wave height.
In Iwate Prefecture, where protective walls 10 meters were built, residents have thought beyond the reach of the tsunami.
To improve the estimates and alerts, you must base calculations on a larger volume of data, Hiroo Kanamori believes. In this case, the Japanese agency had information from seismometers “short period” which should have been added seismometers “long period”, the two recording seismic waves of different nature. The technology exists, it is better to use it, concludes the researcher.