On 28 September 2018, Indonesia was struck by an MW 7.5 strike‐slip earthquake. An unexpected tsunami followed, inundating nearby coastlines leading to extensive damage. Given the traditionally non‐tsunamigenic mechanism, it is important to ascertain if the source of the tsunami is indeed from coseismic deformation, or something else, such as shaking induced landsliding. Here we determine the leading cause of the tsunami is a complex combination of both. We constrain the coseismic slip from the earthquake using static offsets from geodetic observations and validate the resultant “coseismic‐only” tsunami to observations from tide gauge and survey data. This model alone, although fitting some localized run‐up measurements, overall fails to reproduce both the timing and scale of the tsunami. We also model coastal collapses identified through rapidly acquired satellite imagery and video footage as well as explore the possibility of submarine landsliding using tsunami raytracing. The tsunami model results from the landslide sources, in conjunction with the coseismic‐generated tsunami, show a greatly improved fit to both tide gauge and field survey data. Our results highlight a case of a damaging tsunami the source of which is a complex mix of coseismic deformation and landsliding. Tsunamis of this nature are difficult to provide warning for and are underrepresented in regional tsunami hazard analysis.

中文翻译：

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2018帕卢海啸：中世纪滑坡和震源

2018年9月28日，印度尼西亚发生7.5兆瓦级走滑地震。随后发生了意外海啸，淹没了附近的海岸线，造成了严重破坏。考虑到传统上的非海啸致灾机制，重要的是要确定海啸的根源是否确实是由于同震变形或其他原因，例如晃动引起的滑坡。在这里，我们确定海啸的主要原因是两者的复杂结合。我们使用大地观测的静态偏移量来限制地震引起的同震滑移，并验证由此产生的“仅发生地震”的海啸对潮汐仪和调查数据的观测结果。单独使用此模型，尽管可以拟合一些局部的启动测量结果，但总体上无法重现海啸的时机和规模。我们还对通过快速获取的卫星图像和视频片段识别出的沿海崩塌进行建模，并探索使用海啸射线追踪海底滑坡的可能性。来自滑坡源的海啸模型以及同震产生的海啸显示出对潮汐仪和野外测量数据的拟合度大大提高。我们的研究结果突出了一个破坏性海啸的案例，其根源是同震变形和滑坡的复杂结合。这种海啸难以提供警告，在区域海啸危害分析中代表性不足。表明潮汐仪和野外测量数据的拟合度大大提高。我们的研究结果突出了一个破坏性海啸的案例，其源头是同震变形和滑坡的复杂结合。这种海啸难以提供警告，在区域海啸危害分析中代表性不足。表明潮汐仪和野外测量数据的拟合度大大提高。我们的研究结果突出了一个破坏性海啸的案例，其根源是同震变形和滑坡的复杂结合。这种海啸很难提供预警，在区域海啸灾害分析中代表性不足。