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摘要
Western Junggar is the most remote area from coastal zones in the mainland China. This article analyzed the source of ambient noise in the western Junggar area by using frequency domain beamforming (f-k analysis). We deployed two three-component arrays of different sizes there and acquired two groups of records (one is 61-day-long, and the other is 31-day-long). By calculating their array response functions, we identified the optimal frequency ranges for this analysis, which are 0.04 similar to 0.1 Hz and 0.5 similar to 3 Hz. For the lower-frequency ambient noise (recorded by Western Junggar Large-scale Array, or WJLA), it mainly refers to the primary microseism. WJLA is able to receive ambient noise that is generated from the surrounding coastal zones of Eurasia. Especially, signals from the west coastal zone of the North Pacific and east coastal zone of the North Atlantic are strongest. By analyzing ambient noises from two extra-tropical cyclones, we proved that their influence districts are different, and found that the ocean will stay active for a long period (about 20 days) after the cyclones died down. For higher-frequency data, the result indicates that there is a persistent and stable noise source within 1 similar to 2. 5 Hz in the western Junggar area. It comes from 60 degrees east of north (NEE), which is produced by various kinds of human activities in and near Karamay city. Besides, a source with relatively stronger energy and faster propagation speed occurs in the orientation of 80 degrees west of north (NWW) sometimes, possibly being the result of mining activities. This research manifested that the ambient noise is strong enough even in Northwest China. As there exists strong azimuthal anisotropy of noise sources, the orientation feature should be taken into consideration when applying ambient noise methods to image the Earth's interior in this region.
- 出版日期2017-4
- 单位浙江大学; 中国地质大学（北京）
