Reflection seismic study of the post-glacial Burträsk fault: Cross-dip stack

In 2008, a 22 km long high resolution reflection seismic profile was acquired over the Burträsk fault in Northern Sweden. The Burträsk fault formed at the end of the last glacial, triggered by the rapid melting of the Scandinavian ice sheet and the following crustal rebound. The aim of the survey was to image the structure of the fault with depth. The profile followed existing roads resulting in a very crooked acquisition geometry. A list of the key acquisition parameters is given below.
The dataset was first processed and published in 2011. In 2018, the dataset was reprocessed using an additional cross-dip correction step to improve the imaging of reflection with a dip component in the cross-profile direction. The following data files are available for downloading:
1) raw shot gathers (decoded and quality controlled, with geometry information in the headers)
2) original stacked section from Juhlin and Lund (2011)
3) cross-dip corrected stacked section from Beckel and Juhlin (2019)
4) cross-dip corrected migrated section from Beckel and Juhlin (2019)
A short summary of the main processing steps for each dataset is given below. For a complete description, please refer to the above mentioned publications.

Key acquisition parameters:
Number of channels: 280
Near offset: 0 m
Geophone spacing: 20 m
Geophone type : 28 Hz single
Nominal source spacing : 20 m
Source type : VIBSIST
Hit interval between hammer blows : 100-200 ms
Sweeps per source point :3-4
Nominal fold : 140
Recording instrument : SERCEL 408L
Sample rate : 1ms
Field low cut : Out
Field high cut : 400 Hz
Record length : 23 s
Profile length : 22 km
Source points : 799
Dates acquired: 2008/08/05-2008/08/16

Short summary of the main processing steps:
1) BUR_shots_geom.sgy
The raw shot records are pre-processed with VIBSIST decoding, quality control. Information about the shot and receiver geometry has been added to the trace headers.
2) BUR_original_stack.sgy
The processing flow of the original data stack includes trace editing and balancing, spectral equalization, time-variant bandpass filtering, refraction and residual statics, horizontal median filtering, NMO correction, DMO correction, stacking and coherency filtering (for a complete description see Juhlin & Lund, 2011)
3) BUR_crossdip_stack.sgy
The main processing steps of the crossdip stack are very similar to those of the original stack, including trace editing and balancing, spectral equalization, time-variant bandpass filtering, refraction and residual statics, horizontal median filtering, NMO correction, DMO correction, stacking and coherency filtering. Before DMO correction, an additional cross-dip correction step has been added. For a complete description see Beckel & Juhlin, 2019.
4) BUR_crossdip_mig.sgy
The processing flow of the migrated section includes trace editing and balancing, spectral equalization, time-variant bandpass filtering, refraction and residual statics, horizontal median filtering, NMO correction, cross-dip correction, DMO correction, stacking, coherency filtering and migration (for a complete description see Beckel & Juhlin, 2019).

This dataset contains the cross-dip stack of the Burträsk profile (Beckel & Juhlin, 2019).
Processing steps for this data set:
1. Read decoded VIBSIST data
2. Bulk static shift to zero time
3. Apply geometry
4. Manual first-break picking
5. Trace balance: 0-3000 ms
6. Ground-roll and first-break muting in local time-
frequency domain: 25 % threshold
7. Spectral equalization: 30 Hz window,
25-40-120-150 Hz bandpass
8. Time-variant bandpass filtering:
0-200 ms: 35-60-120-180 Hz
250-500 ms: 30-50-120-180 Hz
600-900 ms: 25-40-110-165 Hz
1100-3000 ms: 20-35-100-150 Hz
9. Refraction statics: floating datum, replacement velocity
from model
10. Trace editing
11. Horizontal median filter: 11 traces, 5300 m s-1 and
3000 m s-1
12. Butterworth filter: 20-40-90-120 Hz
13. Spherical divergence correction: 0.8 tpower, 2.0 vpower
14. Velocity analysis
15. NMO correction: 40 % stretch mute
16. Residual statics
17. Cross-dip correction: 5400 m s-1 , 20 % taper;
Velocity analysis
18. DMO correction;
Velocity analysis
19. Stacking
20. FX deconvolution: 19 trace window
21. Trace balance

Processed seismic data stored as one file for the entire seismic profile, according to SEG technical standard SEG-Y revision 1 (SEG-Y_r1.0, 2002); https://seg.org/Publications/SEG-Technical-Standards

2008年，在瑞典北部的布尔特拉斯克断层（Burträsk fault）上采集了一条长22公里的高分辨率反射地震剖面（seismic profile）。布尔特拉斯克断层形成于末次冰期末期，由斯堪的纳维亚冰盖的快速融化及随后的地壳回弹触发。本次调查的目的是对断层的深部结构进行成像。该剖面沿现有道路布设，导致采集几何形态极不规则。以下列出关键采集参数。
数据集于2011年首次处理并发表；2018年，通过增加交叉倾角校正（cross-dip correction）步骤对其进行重新处理，以改善剖面横向具有倾角分量的反射成像效果。
以下数据文件可供下载：
1) 原始炮集（shot gathers，已解码且经过质量控制，头文件中包含几何信息）
2) Juhlin和Lund（2011）的原始叠加剖面
3) Beckel和Juhlin（2019）的交叉倾角校正叠加剖面
4) Beckel和Juhlin（2019）的交叉倾角校正偏移剖面
以下给出各数据集主要处理步骤的简要概述。完整描述请参考上述文献。

关键采集参数：
通道数：280
近偏移距：0米
检波器间距：20米
检波器类型：28 Hz单分量
名义震源间距：20米
震源类型：VIBSIST
锤击间隔：100-200毫秒
每震源点扫描次数：3-4
名义覆盖次数：140
记录仪器：SERCEL 408L
采样率：1毫秒
野外低切：关闭
野外高切：400 Hz
记录长度：23秒
剖面长度：22公里
震源点数：799
采集日期：2008/08/05-2008/08/16

主要处理步骤简要概述：
1) BUR_shots_geom.sgy
原始炮集记录经过VIBSIST解码、质量控制预处理，震源与接收点几何信息已添加至道头文件。
2) BUR_original_stack.sgy
原始数据叠加的处理流程包括道编辑与均衡、谱均衡、时变带通滤波、折射静校正与剩余静校正、水平中值滤波、动校正（Normal Moveout, NMO）、倾角时差校正（Dip Moveout, DMO）、叠加及相干滤波（完整描述见Juhlin & Lund,2011）。
3) BUR_crossdip_stack.sgy
交叉倾角校正叠加的主要处理步骤与原始叠加极为相似，包括道编辑与均衡、谱均衡、时变带通滤波、折射静校正与剩余静校正、水平中值滤波、动校正、倾角时差校正、叠加及相干滤波。在倾角时差校正前增加了交叉倾角校正步骤。完整描述见Beckel & Juhlin,2019。
4) BUR_crossdip_mig.sgy
偏移剖面的处理流程包括道编辑与均衡、谱均衡、时变带通滤波、折射静校正与剩余静校正、水平中值滤波、动校正、交叉倾角校正、倾角时差校正、叠加、相干滤波及偏移（完整描述见Beckel & Juhlin,2019）。

本数据集包含布尔特拉斯克剖面的交叉倾角校正叠加结果（Beckel & Juhlin,2019）。

本数据集处理步骤：
1.读取已解码的VIBSIST数据
2.批量静校正至零时刻
3.应用几何信息
4.手动初至拾取
5.道均衡：0-3000毫秒
6.局部时频域内地滚波与初至切除：阈值25%
7.谱均衡：30 Hz窗口，25-40-120-150 Hz带通
8.时变带通滤波：
0-200毫秒：35-60-120-180 Hz
250-500毫秒：30-50-120-180 Hz
600-900毫秒：25-40-110-165 Hz
1100-3000毫秒：20-35-100-150 Hz
9.折射静校正：浮动基准面，模型提供的替换速度
10.道编辑
11.水平中值滤波：11道，5300 m/s与3000 m/s
12.巴特沃斯滤波器：20-40-90-120 Hz
13.球面扩散校正：时间幂0.8，速度幂2.0
14.速度分析
15.动校正：40%拉伸切除
16.剩余静校正
17.交叉倾角校正：5400 m/s，20%锥形过渡；速度分析
18.倾角时差校正；速度分析
19.叠加
20.FX反褶积：19道窗口
21.道均衡

处理后的地震数据按照勘探地球物理学家学会（Society of Exploration Geophysicists, SEG）技术标准SEG-Y修订版1（SEG-Y_r1.0,2002）存储为整个地震剖面的单个文件；网址：https://seg.org/Publications/SEG-Technical-Standards