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Examining the impact of the Great Barrier Reef on tsunami propagation using numerical simulations
Natural Hazards ( IF 3.7 ) Pub Date : 2021-03-25 , DOI: 10.1007/s11069-021-04686-w
Mandi C. Thran , Sascha Brune , Jody M. Webster , Dale Dominey-Howes , Daniel Harris

Coral reefs may provide a beneficial first line of defence against tsunami hazards, though this is currently debated. Using a fully nonlinear, Boussinesq propagation model, we examine the buffering capacity of the Great Barrier Reef against tsunamis triggered by several hypothetical sources: a series of far-field, Solomon Islands earthquake sources of various magnitudes (Mw 8.0, Mw 8.5, and Mw 9.0), a submarine landslide source that has previously been documented in the offshore geological record (the “Gloria Knolls Slide”), and a potential future landslide source (the “Noggin Block”). We show that overall, the Great Barrier Reef acts as a large-scale regional buffer due to the roughness of coral cover and the complex bathymetric features (i.e. platforms, shoals, terraces, etc.) that corals construct over thousands of years. However, the buffering effect of coral cover is much stronger for tsunamis that are higher in amplitude. When coral cover is removed, the largest earthquake scenario (Mw 9.0) exhibits up to a 31% increase in offshore wave amplitude and estimated run-up. These metrics increase even more for the higher-amplitude landslide scenarios, where they tend to double. These discrepancies can be explained by the higher bed particle velocities incited by higher-amplitude waves, which leads to greater frictional dissipation at a seabed covered by coral. At a site-specific level, shoreline orientation relative to the reef platforms also determines the degree of protectiveness against both types of tsunamis, where areas situated behind broad, shallow, coral-covered platforms benefit the most. Additionally, we find that the platforms, rather than gaps in the offshore reef structure, tend to amplify wave trains through wave focussing when coral cover is removed from simulations. Our findings have implications for future tsunami hazards along the northeastern Australian coastline, particularly as the physiological stressors imposed by anthropogenic climate change further exacerbate coral die-off and reductions in ecosystem complexity. Therefore, areas that experience a protective benefit by the Great Barrier Reef’s platforms could be disproportionately more vulnerable in the future.



中文翻译:

使用数值模拟研究大堡礁对海啸传播的影响

珊瑚礁可能提供抵御海啸危害的有益的第一道防线,尽管目前对此进行了辩论。使用完全非线性的Boussinesq传播模型,我们研究了大堡礁对海啸的缓冲能力,海啸的缓冲源是由以下几种假设来源触发的:一系列不同强度的所罗门群岛远场地震源(兆瓦级8.0,兆瓦级8.5,和M w9.0),海底滑坡源(先前已记录在海上地质记录中)(“ Gloria Knolls Slide”)和潜在的未来滑坡源(“ Noggin Block”)。我们表明,总体而言,大堡礁由于珊瑚覆盖的粗糙度和数千年来珊瑚构造的复杂的测深特征(即平台,浅滩,阶地等)而充当了大规模的区域性缓冲区。但是,对于振幅较高的海啸,珊瑚覆盖的缓冲作用要强得多。去除珊瑚覆盖后,最大的地震场景(兆瓦9.0)的海上波幅和估计的上升幅度最多可增加31%。对于高振幅滑坡方案,这些度量标准甚至会增加更多,而在这种情况下,它们往往会增加一倍。这些差异可以通过较高振幅的波引起的较高的床层速度来解释,这会导致在被珊瑚覆盖的海床处产生更大的摩擦耗散。在特定地点的水平上,相对于礁石平台的海岸线方位也决定了对两种类型海啸的防护程度,海啸位于宽阔,浅层,被珊瑚覆盖的平台后面的区域受益最大。此外,我们发现,当从模拟中移除珊瑚覆盖层时,平台而不是海上礁石结构中的缝隙会通过波聚焦来放大波列。我们的发现对澳大利亚东北部沿海地区未来的海啸危害具有重要意义,特别是由于人为气候变化带来的生理压力进一步加剧了珊瑚的死亡和生态系统复杂性的降低。因此,将来通过大堡礁平台获得保护利益的地区可能会变得更加脆弱。

更新日期:2021-03-25
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