Seismic Response of Nenana Sedimentary Basin, Central Alaska
Seismic Response of Nenana Sedimentary Basin, Central Alaska
复制标题
DOI：
10.1785/0120220160
复制
发表时间：
2022-12
影响因子：
3
通讯作者：
Kyle Smith;C. Tape;V. Tsai
中科院分区：
文献类型：
--
作者：
Kyle Smith;C. Tape;V. Tsai
阿拉斯加中部的Nenana盆地是一个长（90公里），窄（12公里），深（7公里）的沉积盆地，与活动断裂带相对应，产生Mw≥6级地震。从2015年到2019年，该地区部署了13个宽带地震台站，作为地震活动断层定位和阿拉斯加构造项目的一部分。这些台站记录了大范围的地震，包括盆地正下方的3-4级地震以及几次6 - 6级的区域性地震。这43次局地和区域地震，加上5次远震事件和连续记录的环境噪声，提供了一个数据集，我们使用它来量化Nenana盆地对地震波场的响应。我们计算了48次地震中每个台站与基岩参考台站之间的频谱比。我们发现低频（0.1-0.5 Hz）的放大倍数为11-14 dB（放大比3.5-5.0），高频（0.5-4.0 Hz）的放大倍数为8-15 dB（放大比2.5-5.6）。在低频，地震波场的放大与地震噪声的放大非常吻合，两组数据在水平分量上的放大都比垂直分量大。此外，覆盖盆地较深部分的台站表现出更强的低频放大，而盆地边缘的台站表现出最小的低频放大。在较高的频率上，放大既发生在盆地较深的台站，也发生在盆地边缘台站。我们的研究为未来的理论和数值研究建立了一个不同事件的目录，可以利用Nenana盆地更好地了解沉积盆地对地震波场的复杂影响。
Nenana basin in central Alaska is a long (90 km), narrow (12 km), and deep (7 km) sedimentary basin aligned with an active fault zone producing Mw≥6 earthquakes. From 2015 to 2019, 13 broadband seismic stations were deployed in the region as part of the Fault Locations and Alaska Tectonics from Seismicity project. These stations recorded a wide range of earthquakes, including Mw 3–4 directly below the basin as well as several regional earthquakes Mw>6. These 43 local and regional earthquakes, in addition to five teleseismic events and continuously recorded ambient noise, provide a data set that we use to quantify the response of Nenana basin to the seismic wavefield. We calculate spectral ratios between each station and a bedrock reference station for 48 earthquakes. We find amplification of 11–14 dB (amplification ratio 3.5–5.0) for low frequencies (0.1–0.5 Hz), and 8–15 dB (amplification ratio 2.5–5.6) for high frequencies (0.5–4.0 Hz) on the vertical component. At low frequencies, amplification of the earthquake wavefield agrees well with amplification of seismic noise, with both data sets exhibiting stronger amplification on the horizontal components, in comparison with the vertical component. Furthermore, stations overlying the deeper part of the basin exhibit stronger amplification, whereas stations at the margin of the basin exhibit minimal low-frequency amplification. At higher frequencies, amplification occurs at both deeper basin stations and also marginal basin stations. Our study establishes a catalog of diverse events for future theoretical and numerical studies that can use Nenana basin to better understand the complex influence of sedimentary basins on the seismic wavefield.