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通过反演震源机制数据,得到了东日本大地震前后日本东部内陆地区的应力场。地震前,在东北部(Tohoku),σ1轴呈EW方向,但在关东-东部(Kanto-Chubu)地区则呈NW-SE方向。地震后,在Tohoku北部和靠近磐城市(Iwaki City)的Tohoku东南部,应力场发生了变化,主应力取向大致等同于与地震相关的静应力变化取向。这说明地震前这些地区的差应力值小于1MPa。在Tohoku中部,虽然地震后加载的应力取向几乎逆转,但其应力场没有发生变化,说明那里的差应力值大大超过1MPa。在Kanto-Chubu,地震后加载了与背景应力方向近乎相同的应力,且应力场没有发生预期的变化。这可能就是Kanto-Chubu地区高地震活动水平的诱因。
Through the inversion of focal mechanism data, the stress fields in the inland areas of eastern Japan before and after the Great East Japan Earthquake were obtained. Before the earthquake, the To1 axis was in the EW direction in the Tohoku region, but NW-SE in the Kanto-Chubu region. After the earthquake, the stress field changed in the north of Tohoku and southeastern Tohoku, near Iwaki City. The principal stress orientation was roughly the same as that of the quake-related static stress. This shows that before the earthquake in these areas the difference between the value of less than 1MPa. In central Tohoku, the stress field did not change, although the orientation of the stress loaded after the earthquake almost reversed, indicating that the value of the differential stress there greatly exceeded 1 MPa. At Kanto-Chubu, nearly the same stress as the background stress was loaded after the earthquake and the stress field did not change as expected. This may be the reason for the high level of seismic activity in the Kanto-Chubu area.