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首页> 外文期刊>Seismological research letters >The Sedimentary Record of the 2018 Anchorage Earthquake in Eklutna Lake, Alaska: Calibrating the Lacustrine Seismograph
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The Sedimentary Record of the 2018 Anchorage Earthquake in Eklutna Lake, Alaska: Calibrating the Lacustrine Seismograph

机译：2018年锚地地震的沉积记录在阿克拉斯湖，阿拉斯加州湖：校准湖泊地震仪

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摘要

The 30 November 2018 M-w 7.1 Anchorage earthquake caused modified Mercalli intensities of V1/4 to V1/2 at Eklutna Lake (south central Alaska). A few hours after the earth-quake, a "dirt streak" was observed on the lake surface, followed by a peak in sediment turbidity values (similar to 80 times normal) at a drinking water facility, which receives water from the lake through a pipe. These observations hint toward turbidity currents triggered by the earthquake in Eklutna Lake. Here, we study 32 short sediment cores retrieved from across Eklutna Lake and observe a millimeter-to-centimeter scale turbidite that can be confidently attributed to the 2018 earthquake in all coring locations. X-ray computed tomography, grain-size, and color-spectral analyses of the turbidite show that it shares physical characteristics with the turbidite generated by the 1964 M-w 9.2 Great Alaska earthquake, while it is considerably different from turbidites caused by historical floods. The 2018 turbidite reaches its largest thickness in the inflow-proximal basin, but when compared to the 1964 turbidite and thereby canceling out local site effects, it is relatively thick in the inflow-distal sub-basin. The latter was exposed to stronger shaking during the 2018 earthquake, and this relative thickness trend may therefore be attributed to shaking intensity and gives an indication of the location of the earthquake epicenter relative to the basin axis. Furthermore, in contrast to the 1964 turbidite, which was sourced from both deltas and hemipelagic slopes, the 2018 turbidite was sourced from deltas only, as evidenced by its distribution. These results confirm that while it is generally accepted that shaking intensities of >= VI are needed to trigger turbidity currents from hemipelagic slopes, intensities as low as V1/4 can be sufficient to trigger turbidity currents from deltaic slopes. Our results show that proglacial lakes can sensitively record differences in shaking intensity and that investigating deposits from recent earthquakes is crucial to calibrate the lacustrine seismograph.
机译：2018年11月30日M-W 7.1锚地地震导致Eklutna Lake（阿拉斯加南部南部）的V1 / 4至V1 / 2的修改梅卡利强度。在地震之后几个小时，在湖面上观察到“污垢条纹”，然后在饮用水设施的沉积物浊度值（类似于80倍正常）的峰值，然后通过A通过湖泊接收水管道。这些观察结果提示了Eklutna湖地震触发的浊度电流。在这里，我们研究了从eklutna湖跨越的32个短沉积物核心，并观察毫米至厘米的速度浊度，这可以自信地归因于所有核心位置的2018地震。 X射线计算断层扫描，晶粒尺寸和浊度分析，表明它与1964 M-W 9.2伟大的阿拉斯加地震产生的浊度分享了物理特性，同时它与由历史洪水引起的浊度不同。 2018年浊度在流入近端盆地中达到最大厚度，但与1964年浊度相比，从而取消局部场地效果，在流入 - 远端盆地中相对较厚。在2018次地震期间，后者暴露于较强的摇动，因此这种相对厚度趋势可能归因于颤抖强度，并赋予地震震中相对于盆轴的位置的指示。此外，与1964年的浊度相比，从谵妄和斜腹斜坡中源，2018年浊度仅由其分布所证明的。这些结果证实，虽然普遍认为> = vi的振荡强度来触发血管斜坡的浊度，但低至V1 / 4的强度可以足以引发来自Deltaic斜率的浊度电流。我们的研究结果表明，Proglacial Lakes可以敏感地记录振动强度的差异，并从最近的地震中调查沉积物对于校准Lapustline地震仪至关重要。

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