SUMMARY

We investigated the kinematic rupture model of the 2018 M_w 6.8 Zakynthos, Ionian Sea (Greece), earthquake by using a non-linear joint inversion of strong motion data, high-rate GPS time-series and static coseismic GPS displacements. We also tested inversion results against tide-gauge recordings of the small tsunami generated in the Ionian Sea. In order to constrain the fault geometry, we performed several preliminary kinematic inversions by assuming the parameter values resulting from different published moment tensor solutions. The lowest cost function values were obtained by using the geometry derived from the United States Geological Survey (USGS) focal solution. Between the two conjugate USGS planes, the rupture model which better fits the data is the one with the N9°E-striking 39°ESE-dipping plane. The rupture history of this model is characterized by a bilateral propagation, featuring two asperities; a main slip patch extending between 14 and 28 km in depth, 9 km northeast from the nucleation and a slightly shallower small patch located 27 km southwest from the nucleation. The maximum energy release occurs between 8 and 12 s, when both patches are breaking simultaneously. The maximum slip is 1.8 m and the total seismic moment is 2.4 × 10¹⁹ Nm, corresponding to a M_w value of 6.8. The slip angle shows a dominant right-lateral strike-slip mechanism, with a minor reverse component that increases on the deeper region of the fault. This result, in addition to the observed possibility of similar mechanisms for previous earthquakes occurred in 1959 and 1997, suggests that the tectonic deformation between the Cephalonia Transform Fault Zone and the northern tip of the Hellenic Arc Subduction zone may be accommodated by prevailing right lateral low-dipping faults, occurring on re-activated structures previously experiencing (until Pliocene) compressional regime. Comparison of predicted and observed tsunami data suggests the need of a better characterization of local harbour response for this type of relatively short-wavelength events, which is important in the context of tsunami early warning. However, the suggested dominantly strike-slip character would in turn imply a reduced tsunami hazard as compared to a dominant thrust faulting regime from this source region.

中文翻译：

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2018年兆瓦6.8扎金索斯（希腊爱奥尼亚海）地震：地震源和当地海啸特征

概要

我们研究了2018 M _W的运动学破裂模型6.8爱奥尼亚海（希腊）扎金索斯地震，采用强运动数据的非线性联合反演，高速率GPS时间序列和静态同震GPS位移。我们还针对爱奥尼亚海中产生的小海啸的潮汐仪记录测试了反演结果。为了约束断层的几何形状，我们通过假设由不同的已公开矩张量解产生的参数值来执行几个初步的运动学反演。成本函数值最低的方法是使用从美国地质调查局（USGS）焦点解决方案得出的几何形状。在两个共轭USGS平面之间，最适合数据的破裂模型是使用N9°E撞击39°ESE浸渍平面的模型。该模型的破裂历史以双边传播为特征，具有两个粗糙点；一个主要的滑动斑块，其深度在14至28 km之间，从成核作用向东北方向延伸9 km，而一个稍浅的小斑块位于成核作用向西南27 km处。当两个贴片同时断裂时，最大的能量释放发生在8到12 s之间。最大滑差为1.8 m，总地震矩为2.4×10¹⁹ Nm，对应于M _w值6.8。滑移角显示出主要的右走向走滑机制，次要的逆向分量在断层的较深区域增加。这个结果，除了观察到的在1959年和1997年发生过类似地震的机制的可能性外，还表明，凯法利尼亚变换断层带与希腊弧俯冲带北端之间的构造变形可以通过占主导地位的右旋侧向低压来解决。 -浸渍断层，发生在先前经历（直到上新世）压缩状态的重新活化的结构上。比较预测的海啸数据和观察到的海啸数据表明，对于此类相对短波的事件，需要更好地表征当地港口的反应，这在海啸预警的背景下非常重要。然而，