Seismic Data from MSM21/4 to Knipovich Ridge on the western Svalbard margin

The seismic data were acquired north of the Knipovich Ridge on the western Svalbard margin during cruise MSM21/4. They were recorded using a Geometrics GeoEel streamer of either 120 channels (profiles p100-p208) or 88 channels (profiles p300-p805) with a group spacing of 1.56 m and a sampling rate of 2 kHz. A GI-Gun (2×1.7 l) with a main frequency of ~150 Hz was used as a source and operated at a shot interval of 6-8 s.
Processing of profiles p100-p208 and p600-p805: Positions for each channel were calculated by backtracking along the profiles from the GI-Gun GPS positions. The shot gathers were analyzed for abnormal amplitudes below the seafloor reflection by comparing neighboring traces in different frequency bands within sliding time windows. To suppress surface-generated water noise, a tau-p filter was applied in the shot gather domain. Common mid-point (CMP) profiles were then generated through crooked-line binning with a CMP spacing of 1.5625 m. A zero-phase band-pass filter with corner frequencies of 60 Hz and 360 Hz was applied to the data. Based on regional velocity information from MCS data [Sarkar, 2012], an interpolated and extrapolated 3D interval velocity model was created below the digitized seafloor reflection of the high-resolution streamer data. This velocity model was used to apply a CMP stack and an amplitude-preserving Kirchhoff post-stack time migration.
Processing of profiles p400-p500: Data were sampled at 0.5 ms and sorted into common midpoint (CMP) domain with a bin spacing of 5 m. Normal move out correction was carried out with a velocity of 1500 m s-1 and an Ormsby bandpass filter with corner frequencies at 40, 80, 600 and 1000 Hz was applied. The data were time migrated using the water velocity.

本套地震数据采集于斯瓦尔巴（Svalbard）西部陆缘克尼波维奇海岭（Knipovich Ridge）以北海域，采集航次为MSM21/4。数据采用Geometrics公司GeoEel型拖缆（Streamer）进行记录：其中p100-p208测线采用120道配置，p300-p805测线采用88道配置，道间距为1.56 m，采样率为2 kHz。本次采集使用容积为2×1.7 L的GI枪（GI-Gun）作为震源，其主频约为150 Hz，激发间隔设置为6~8 s。

针对p100-p208与p600-p805测线的处理工作如下：首先，根据GI枪的GPS定位信息，沿测线反向追踪计算各道的位置；随后，在滑动时间窗内的不同频带中对比相邻道记录，对海底反射界面下方的异常振幅进行分析；为压制水面次生水层噪声，在炮集（Shot Gather）域应用tau-p滤波（tau-p filter）。之后通过弯曲线分箱（Crooked-line Binning）生成共中心点（Common Mid-Point, CMP）剖面，CMP间距为1.5625 m；随后对数据施加拐角频率为60 Hz与360 Hz的零相位带通滤波器（Zero-phase Band-pass Filter）。基于多道地震（Multichannel Seismic, MCS）数据的区域速度场信息[Sarkar, 2012]，在高分辨率拖缆数据的数字化海底反射界面下方，构建了经插值与外推得到的三维层速度模型（Interval Velocity Model）。利用该速度模型完成共中心点叠加（CMP Stack）与保振幅基尔霍夫（Kirchhoff）叠后时间偏移（Amplitude-preserving Kirchhoff Post-stack Time Migration）。

针对p400-p500测线的处理工作如下：数据采样间隔为0.5 ms，将其整理至共中心点域，分箱间距为5 m；采用1500 m·s⁻¹的速度进行正常时差校正（Normal Move Out, NMO），并施加拐角频率分别为40 Hz、80 Hz、600 Hz与1000 Hz的Ormsby带通滤波器（Ormsby Band-pass Filter）；最后采用水体速度完成时间偏移处理。