Morioka-Shirakawa Line - Morioka-Shirakawa Line

Japanese: 盛岡‐白河線 - もりおかしらかわせん

A tectonic line running north-south through the Tohoku region, it was hypothesized by Tsuboi Chuji et al. (1956) as a zone of sudden change between the high (eastern) and low (western) Bouguer anomaly (gravity anomaly). It roughly coincides with the Quaternary volcanic front, and the area east of this line is an area of low activity (aseismic zone) of shallow earthquakes. In the tectonics of the island arc-trench system, it forms the boundary between the non-volcanic outer arc and the volcanic inner arc. Topographically, it forms lowlands such as the Kitakami and Abukuma River valleys, and is the central subsidence zone between the outer and inner arcs. It intersects obliquely with geological structures from before the Paleogene period, and was formed after the Neogene period, but it does not appear as a geological tectonic line (fault) on the surface, so its exact location cannot be determined.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

東北地方を南北に縦走する構造線で，ブーゲー異常(重力異常)の高(東側)低(西側)の間の急変帯の位置に，坪井忠二ほかによって想定された(1956)。第四紀の火山前線とほぼ一致し，またこの線より東側は浅発地震の低活動域(アサイスミック･ゾーン)である。島弧‐海溝系のテクトニクスでは，非火山性外弧と火山性内弧との境界をなす。地形的には北上･阿武隈河谷などの低地をなし，外弧と内弧の間の中央沈降帯にあたる。古第三紀以前の地質構造とは斜交しており，新第三紀以降に形成されたものであるが，地表部では地質学的な構造線(断層)として現れてはおらず，その正確な位置を示すことはできない。

出典　株式会社平凡社世界大百科事典第２版について　情報

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