Romano F, Trasatti E, Lorito S, Piromallo C, Piatanesi A, Ito Y, Zhao D, Hirata K, Lanucara P, Cocco M
Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy.
Disaster Prevention Research Institute, Kyoto University, Japan.
Sci Rep. 2014 Jul 9;4:5631. doi: 10.1038/srep05631.
The 2011 Tohoku earthquake (Mw = 9.1) highlighted previously unobserved features for megathrust events, such as the large slip in a relatively limited area and the shallow rupture propagation. We use a Finite Element Model (FEM), taking into account the 3D geometrical and structural complexities up to the trench zone, and perform a joint inversion of tsunami and geodetic data to retrieve the earthquake slip distribution. We obtain a close spatial correlation between the main deep slip patch and the local seismic velocity anomalies, and large shallow slip extending also to the North coherently with a seismically observed low-frequency radiation. These observations suggest that the friction controlled the rupture, initially confining the deeper rupture and then driving its propagation up to the trench, where it spreads laterally. These findings are relevant to earthquake and tsunami hazard assessment because they may help to detect regions likely prone to rupture along the megathrust, and to constrain the probability of high slip near the trench. Our estimate of ~40 m slip value around the JFAST (Japan Trench Fast Drilling Project) drilling zone contributes to constrain the dynamic shear stress and friction coefficient of the fault obtained by temperature measurements to ~0.68 MPa and ~0.10, respectively.
2011年东北地震（Mw = 9.1）凸显了逆冲型地震事件一些以前未被观测到的特征，比如在相对有限区域内的大滑动以及浅部破裂扩展。我们使用有限元模型（FEM），考虑了直至海沟区域的三维几何和结构复杂性，并对海啸和大地测量数据进行联合反演以获取地震滑动分布。我们发现主深部滑动区与局部地震速度异常之间存在紧密的空间相关性，并且大的浅部滑动向北连贯延伸，与地震观测到的低频辐射一致。这些观测结果表明，摩擦力控制了破裂，最初限制了深部破裂，然后促使其向海沟方向扩展，并在海沟处横向传播。这些发现与地震和海啸灾害评估相关，因为它们可能有助于探测沿逆冲断层可能易于发生破裂的区域，并限制海沟附近发生高滑动的概率。我们对日本海沟快速钻探项目（JFAST）钻探区域周围约40米滑动值的估计，有助于将通过温度测量得到的断层动态剪应力和摩擦系数分别限制在约0.68兆帕和约0.10。
