The behaviour of tsunami waves at any location depends on the local morphology of the coasts, the encountered bathymetric features, and the characteristics of the source. However, the importance of accurately modelling the geometric properties of the causative fault for simulations of seismically-induced tsunamis is rarely addressed. In this work, we analyse the effects of using two different geometric models of the subduction interface of the Calabrian Arc (southern Italy, Ionian Sea) onto the simulated tsunamis: a detailed 3D subduction interface obtained from the interpretation of a dense network of seismic reflection profiles, and a planar interface that roughly approximates the 3D one. These models can be thought of as representing two end members of the level of knowledge of fault geometry. We define three hypothetical earthquake ruptures of different magnitudes (M_w 7.5, 8.0, 8.5) on each geometry. The resulting tsunami impact is evaluated at the 50-m isobath in front of coastlines of the central and eastern Mediterranean. Our results show that the source geometry imprint is evident on the tsunami waveforms, as recorded at various distances and positions relative to the source. The absolute differences in maximum and minimum wave amplitudes locally exceed one meter, and the relative differences remain systematically above 20 per cent with peaks over 40 per cent. We also observe that tsunami energy directivity and focusing due to bathymetric waveguides take different paths depending on which fault is used. Although the differences increase with increasing earthquake magnitude, there is no simple rule to anticipate the different effects produced by these end-member models of the earthquake source. Our findings suggest that oversimplified source models may hinder our fundamental understanding of the tsunami impact and great care should be adopted when making simplistic assumptions regarding the appropriateness of the planar fault approximation in tsunami studies. We also remark that the geological and geophysical 3D fault characterisation remains a crucial and unavoidable step in tsunami hazard analyses.

中文翻译：

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地震破裂几何形状对海啸建模的重要性：卡拉布里亚弧俯冲界面（意大利）案例研究

海啸波在任何位置的行为都取决于海岸的局部形态，所遇到的测深特征以及震源的特征。但是，很少涉及到准确模拟因果断层的几何特性以模拟地震引起的海啸的重要性。在这项工作中，我们分析了使用卡拉布里亚弧（意大利南部，爱奥尼亚海）俯冲界面的两种不同几何模型对模拟海啸的影响：详细的3D俯冲界面，通过解释密集的地震反射网络获得轮廓，以及大致接近3D的平面界面。可以将这些模型视为代表断层几何知识水平的两个末端成员。_w7.5、8.0、8.5）。由此产生的海啸影响在地中海中部和东部海岸线前50米的等压线进行了评估。我们的结果表明，如在相对于源的各种距离和位置处记录的那样，源的几何形状在海啸波形上很明显。最大和最小波幅的绝对差异局部超过一米，相对差异始终保持在20％以上，峰值超过40％。我们还观察到，由于测深波导管造成的海啸能量方向性和聚焦性取决于所使用的断层走的路径不同。尽管差异随着地震震级的增加而增加，但没有简单的规则可以预测这些震源最终成员模型产生的不同影响。我们的发现表明，过于简化的震源模型可能会阻碍我们对海啸影响的基本了解，在对海啸研究中的平面断层近似法的适用性进行简单假设时，应格外小心。我们还指出，在海啸危害分析中，地质和地球物理3D断层的表征仍然是至关重要且不可避免的步骤。