编辑-地球科学江南体育网页版堆栈交换江南电子竞技平台

你不是登录．您的编辑将被放置在队列中，直到完成同行评议．

我们欢迎编辑，使文章更容易理解和更有价值的读者。因为社区成员会审查编辑，所以请尽量让帖子比你发现它的时候更好，例如，通过修改语法或添加额外的资源和超链接。

原始地震数据、CMP叠加、NMO和机器学习之间的关系是什么

我最近加入了一个地球物理项目，协助他们的一些机器学习建模，但我正在努力收集参与所需的领域知识。

我不太理解的是common- middle - point stack, Normal MoveOut & raw data。我有这些segg -y文件，我可以用python绘制它们。对我来说，它们看起来很好，但我读了很多关于CMP堆叠，加权CMP堆叠和NMO的文章。分段y文件被认为是“原始地震数据”。CMP和NMO流程是否发生在我获取文件的阶段?我很困惑，因为这些似乎是标准的实践，但我无法在任何编程语言中找到任何一个实现。你有什么工具可以为机器学习建模准备地震数据吗?

回答

SEG-Y文件是一种通用的归档格式。所以他们可以是“任何东西”。2D地震，3D地震，原始的，加工的，未叠加的甚至衍生物(地震属性)。如何在SEG-Y文件中获取有关数据的信息:SEG-Y包含3种描述数据的头。[![SEG-Y结构。EBCDIC头是一个40 * 80字符的表，是穿孔卡片时代的遗迹[(我不是开玩笑)]。通常它包含有关地震状态的信息。处理工作流程，采集几何图形等。二进制报头包含关于数据集的更多固定数据。 The trace headers contrain every separate data set from the acquisition. Nice blog by Agile Scientific [here][3]. You can read about the details of seismic processing and conventions in the open access book "[Seismic Data Analysis][4]". It used to be several hundred dollars and has been cited in every seismic lecture I have ever attended. However, I'll give you some answers now. # Common Midpoints CMP stacking, weighted CMP and NMO are highly entangled. [![CMP Definition][5]][5] A seismic measurement, listens really close to the reflection from the subsurface. However, it's a little noisy. "Stacking" is recording the same place over and over, then adding it up to cancel out random noise and enhance coherent signal. However, just doing it in the same area would be very inefficient, therefore we change the acquisition over the point we illuminate, in the picture you see that we have a nice fan of ray geometries going to the same point in the middle, the Common MidPoint CMP. This leads some interesting behaviour. # Normal Moveout [![NMO equation][6]][6] this is the formulation to calculate how a record from a different angle can be shifted to be in line with another record for the aforementioned stacking. As you can imagine the records that have longer ray paths take longer, depending on the velocity of the rock they travel through. This shift down-ward is namen Normal MoveOut (NMO). The equation above is an approximation, but it's good enough for this explanation, check out the book for more info on this. # Post-Stack vs. Pre-Stack A seismic acquisition over a 2D area is named 3D seismic, because X-Y-T (recording time). The data, repeated over the same point in X-Y as mentioned above will have several record with the same T and a different "offset" between the source and the receiver. That means, 3D seismic data coming fresh out of the field will be four-dimensional. This is called pre-stack. Once we do a lot of data preconditioning and filtering and a smarter version of the CMP stacking above, we get 3D seismic that is actually three-dimensional. # Stacking versus Migration Stacked data will have all kinds of weird wave effects in it. Usually geologists will work on "migrated" data. A migration aims to find the "true" location of a reflector, reversing wave effects. I suspect you might get this one. # Time versus Dpeth You may have wondered from before about X-Y-T. T stands for time not depth, that is because our data is measured in recording time and most geophysicists will work in time. Most likely the migration even is done in time and you get a X-Y-T cube. However, depth-conversion does happen, but it depends on a accurate time-depth relationship. People tend not to trust these too much. Caveat: A depth migration does not have to result in a X-Y-Z cube that you get. # Practical Advice As a practical guide, you may want to start at the EBCDIC header. Was your data processed? Stacked? Migrated? Do you have a T-cube or Z-cube? Familiarize yourself with the binary header and a couple trace headers. What are the extents of your data? Etc. # Machine Learning Most machine learning is done in proprietary code. The only open source code I know of in seismic deep learning is [MalenoV][7]. However, loading a full 3D seismic into RAM will not always be possible. Loading it into the GPU RAM will seldomly be possible. This is the first place, where you are free to come up with a smart solution. # Bonus Here is a list of [Free Geophysics Software][8] and an [awesome list of open geoscience][9]. These aren't exhaustive, but a good start. [1]: https://i.stack.imgur.com/ivPgb.png [2]: http://the-geophysicist.com/ebcdic-how-punch-cards-helped-me-get-to-know-my-data [3]: https://agilescientific.com/blog/2014/3/26/what-is-seg-y.html [4]: https://wiki.seg.org/wiki/Seismic_Data_Analysis [5]: https://i.stack.imgur.com/BP4o7.png [6]: https://i.stack.imgur.com/VV62j.png [7]: https://github.com/bolgebrygg/MalenoV [8]: https://en.wikipedia.org/wiki/Comparison_of_free_geophysics_software [9]: https://github.com/softwareunderground/awesome-open-geoscience/

编辑总结

取消

添加评论 |

纠正小的拼写错误
阐明意思而不改变它
添加相关资源或链接
总是尊重作者的意图
不要用编辑回复作者

使用反撇号'或波浪号~创建代码围栏
' ' '
像这样
' ' '
添加语言标识符以突出显示代码
”“python
def函数(foo):
打印(foo)
' ' '
在段落之间放置返回
对于换行符，末尾加2个空格
_italic_或* *的* *
通过将>放在行开始来引用
要建立链接(尽可能使用HTTPS)
< https://example.com >
(例子)(https://example.com)
< a href = " https://example.com " > < / >示例
MathJax方程罪\ \ ^ 2θ美元

格式帮助:
回答帮助:

MathJax help»