Sensitivity of tidal marshes as recorders of major megathrust earthquakes: constraints from the 25 December 2016 M w 7.6 Chiloé earthquake, Chile
Sensitivity of tidal marshes as recorders of major megathrust earthquakes: constraints from the 25 December 2016 M w 7.6 Chiloé earthquake, Chile
复制标题
潮汐沼泽作为大型逆冲地震记录器的敏感性：2016 年 12 月 25 日智利 M w 7.6 Chiloé 地震的限制
DOI：
10.1002/jqs.3323
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发表时间：
2021
影响因子：
2.3
通讯作者：
Brader M
中科院分区：
文献类型：
--
作者：
Brader M
我们提出了2016年Mw7.6 Chiloé地震导致的陆地水平变化的证据，这些证据来自智利Isla de Chiloé南部海岸线沿着的潮汐湿地，以测试低水平（<0.1 m）同震陆地水平变化的检测标准。为了记录潮汐湿地沉积物中的同震陆面变化，必须超过创造和保存阈值。对两个潮汐沼泽地沉积物块的高分辨率硅藻分析显示，2016年地震超过了地震的发生阈值，记录了硅藻组合的统计学显著变化。相比之下，保存阈值没有被超过，同震地面运动的记录在任何访问的位置都没有被保存下来。九个月后，地震间和同震的变化在统计上是无法区分的。潮汐湿地最敏感的部分在研究地点之间并不一致，这可能是地震后沉积物变化的结果。我们将阿拉斯加大地震的变化记录与奇洛埃地震的记录进行比较，以探索检测极限。我们建议，沿海古地震记录很可能低估了主要（Mw 7 -8）地震的频率，具有重要意义的复发间隔和评估未来的地震灾害。
We present evidence of land‐level change resulting from the 2016 Mw7.6 Chiloé earthquake from tidal wetlands along the southern coastline of Isla de Chiloé, Chile, to test criteria for the detection of low‐level, <0.1 m, coseismic land‐level change. In order to record coseismic land‐level change in tidal wetland sediments, both the creation and preservation thresholds must be exceeded. High‐resolution diatom analyses of sediment blocks at two tidal marshes reveal that the 2016 earthquake exceeded the creation threshold and a statistically significant change in diatom assemblage is recorded. In contrast, the preservation threshold was not exceeded and the record of coseismic land‐level motion is not preserved at any location visited. After nine months, interseismic and coseismic changes are statistically indistinguishable. The most sensitive part of the tidal wetland is not consistent between research locations, possibly as a result of changes in sedimentation after the earthquake. We compare records of change from great earthquakes in Alaska with the record from the Chiloé earthquake to explore the detection limit. We propose that coastal palaeoseismological records are highly likely to underestimate the frequency of major (Mw7–8) earthquakes, with important implications for recurrence intervals and assessment of future seismic hazards.