In general, there are three mechanisms causing crustal deformation: elastic, viscous, and plastic deformation. The separation of observed crustal deformation to each component has been a challenging problem. In this study, we succeed in separating plastic deformation as well as viscous deformation in the northern Niigata–Kobe Tectonic Zone (NKTZ), central Japan, using GNSS data before and after the 2011 Tohoku-oki earthquake, under the assumptions that elastic deformation is principally caused by the plate coupling along the Japan trench and that plastic deformation ceased after the Tohoku-oki earthquake due to the stress drop caused by the earthquake. The cessation of plastic deformation can be understood with the concept of stress shadow used in the field of seismic activity. The separated strain rates are about 30 nanostrain/year both for the plastic deformation in the preseismic period and for the viscous deformation in both the pre- and post-seismic periods, which means that the inelastic strain rate in the northern NKTZ is about 60 and 30 nanostrain/year in the pre- and post-seismic periods, respectively. This result requires the revision of the strain-rate paradox in Japan. The strain rate was exceptionally faster before the Tohoku-oki earthquake due to the effect of plastic strain, and the discrepancy between the geodetic and geologic strain rates is much smaller in usual time, when the plastic strain is off. In order to estimate the onset timing of plastic deformation, the information on stress history is essentially important.

中文翻译：

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使用 2011 年东北大地震震前和震后变形的 GNSS 数据检测塑性应变

一般来说，地壳变形有弹性、粘性和塑性变形三种机制。将观察到的地壳变形分离到每个组件一直是一个具有挑战性的问题。在这项研究中，我们使用 2011 年东北大地震前后的 GNSS 数据，假设弹性变形为主要是由沿日本海沟的板块耦合引起的，东北冲地震后由于地震引起的应力下降，塑性变形停止。塑性变形的停止可以用地震活动领域中使用的应力阴影的概念来理解。震前塑性变形和震前和震后粘滞变形的分离应变率均约为 30 纳应变/年，这意味着 NKTZ 北部的非弹性应变率约为 60 和在震前和震后时期分别为 30 纳应变/年。这个结果需要修正日本的应变率悖论。由于塑性应变的影响，东北冲地震前的应变率异常快，而在通常情况下，塑性应变关闭时，大地应变率和地质应变率之间的差异要小得多。为了估计塑性变形的开始时间，应力历史信息非常重要。