Deep Panuke whale sightings 2003

Original provider:
Encana Corporation

Dataset credits:
Marielle Thillet, Deep Panuke Project, Encana Corporation

Abstract:
We present marine mammal observation statistics, high-frequency seismic source characteristics, and example denoising of marine mammal acoustical recordings using data collected during the mitigation and monitoring program for a 3-D seismic survey by Encana Corporation, Calgary, Alberta, Canada, in the northwest Atlantic during 2003. Marine mammals were observed both visually and acoustically. No marine mammal incidents or adverse reactions were observed during the survey.

Acoustical observations were made by the Seamap Passive
Acoustic Cetacean Monitoring System (SPACMS), consisting of
two hydrophones placed 50 m apart, towed ahead of and to one
side of the seismic source. Visual and acoustical detections were uncorrelated, indicating the complementary nature of the two observational techniques. Visual detections were more common per hour of effort than acoustical detections. Acoustical detection rates showed no significant day–night difference.

Marine mammals appeared to have avoided very close ranges (100 m) from the seismic array during seismic acquisition, but the overall number of marine mammals in the observable radius (1–2 km) did not change significantly when the seismic source was “on” compared to “off.” Marine mammals were observed in larger groups and appeared to have become less vocal when the seismic source was active. It should be noted however, that the results from this data gathering effort may be affected by potential sources of bias (such as the combination of data from toothed and baleen whales).

Signal processing of seismic source signatures indicated some
high-frequency energy content consistent with expectations from
earlier work. This analysis confirmed that most of the seismic
energy was concentrated at lower frequencies (500 Hz). No
low-frequency comparisons with near-field data could be made
due to the geometry of the SPACMS recording hydrophones
and seismic source, which resulted in the Lloyd’s mirror effect
obliterating low-frequency components in the SPACMS records.
A wavelet-based denoising method was applied to improve the visibility of marine mammal vocalizations on a spectrogram display.

原始提供方：恩卡纳公司（Encana Corporation）
数据集贡献者：Marielle Thillet、加拿大阿尔伯塔省卡尔加里恩卡纳公司Deep Panuke项目团队

摘要：本数据集基于加拿大阿尔伯塔省卡尔加里的恩卡纳公司（Encana Corporation）于2003年在西北大西洋开展的三维地震勘探项目的缓解与监测程序所收集的数据，涵盖海洋哺乳动物观测统计、高频震源特征，以及针对海洋哺乳动物声学记录的示例去噪处理结果。本次勘探期间，研究人员通过视觉与声学两种手段对海洋哺乳动物进行观测，未发现任何海洋哺乳动物受影响事件或不良反应。

声学观测采用海洋哺乳动物被动声学鲸类监测系统（Seamap Passive Acoustic Cetacean Monitoring System，SPACMS）完成，该系统由两个间距50米的水听器组成，拖曳于震源前方及一侧。视觉观测与声学观测的结果并无相关性，这表明两种观测技术具备互补性。单位观测时长内的视觉检出频次高于声学检出频次，且声学检出率未表现出显著的昼夜差异。

观测结果显示，海洋哺乳动物似乎会避开地震采集期间震源阵列100米以内的极近区域，但当震源开启与关闭时，可观测半径（1至2公里）内的海洋哺乳动物总数量并未出现显著变化。当震源处于工作状态时，观测到的海洋哺乳动物群体规模更大，且其发声活跃度有所降低。但需注意，本次数据采集工作的结果可能受到潜在偏倚因素的影响，例如将齿鲸与须鲸的数据合并分析。

对震源信号的分析表明，其包含的部分高频能量与此前相关研究的预期相符。本次分析证实，大部分地震能量集中于低频段（500赫兹）。由于SPACMS的记录水听器与震源的几何布局产生了劳埃德镜（Lloyd’s mirror）效应，掩盖了SPACMS记录中的低频分量，因此无法与近场数据开展低频对比。研究人员采用基于小波的去噪方法，提升了频谱图显示中海洋哺乳动物发声的可见度。