共中點道集

共中點道集（英語：Common midpoint gather）或共反射點道集（英語：Common reflection point gather）是是地震資料處理的最基本步驟之一，它是在地震資料採集完後，收集通過同一個地下反射點所有的地震道，而組構成的道集^[1] 。這些地震道都對同一地點從不同方向和角度的採樣，這種多次採樣的目的是降低隨機噪音，增加信噪比^[2]。

地震資料採集

在採集地震數據之前，需要規劃地震勘測設計^[3]，選取各種參數包括，例如震源類型、接收器類型、震源間距、接收器間距，陣列，通道數量、採樣率、記錄長度等^[4]。地震數據以地震道的形式記錄，也稱為震波曲線圖。它代表地震波由震源穿過地下，經由岩層的聲阻抗界面，反射回到接收器的信號^[1].

地震數據處理

地震數據處理主要包括三個過程：反褶積、疊加速度分析及地震偏移:

反褶積又稱反濾波（英語：inverse filter）,是通過壓縮基本子波來提高地震數據垂向分辨率的處理過程^[5]。反褶積不但能壓縮子波長度而且能衰減多次波。這種地震數據處理方法是假設地下地層結構是一個反射係數的時間函數^[6]。當地震震源子波與反射係數褶積後，形成的反射波就是檢波器所接受的信號。反褶積就是從信號中，導出反射係數的時間函數^[7]。
疊加速度分析是通過最佳擬合時距曲綫所得的地震波在介質傳播的速度值 ^[8]。疊加速度的推算必需依賴動校正。原理是設定一速度，根據雙曲線反射公式，對共中點（common midpoint )的道集，校正非法線反射到法線反射。若所設速度正確，在疊加這些道集後，反射波的振幅最大^[2].^[9].
地震偏移是把地震記錄上反射點回歸到其原來的真實位置。因爲反射面的傾斜，一個反射點的法綫,會被誤置在共中點的正下方，形成視傾角（見圖），故需要和把傾斜反射面歸位。偏移能消除繞射，尤其在地質複雜地區，偏移能對斷層，褶皺等構造的成像，增高精密度。

^[10] ^[11]. ^[12].

參考文獻

^ ^1.0 ^1.1 SCHLUMBERGER. "seismic trace - Schlumberger Oilfield Glossary". www.glossary.oilfield.slb.com.
^ ^2.0 ^2.1 Yilmaz, Öz (2001). Seismic data analysis. Society of Exploration Geophysicists. p. 274. ISBN 1-56080-094-1
^ Stone, Dale (1994).Designing surveys in two and three dimensions. Society of Exploration Geophysicists. ISBN 978-1560800736
^ Keary, Philip (2013). An Introduction to Geophysical Exploration (3., Auflage ed.). John Wiley & Sons. ISBN 9781118698938
^ O'Haver, T. "Intro to Signal Processing - Deconvolution". University of Maryland at College Park. Retrieved 2007-08-15.
^ Wiener, N. (1964). Extrapolation, Interpolation, and Smoothing of Stationary Time Series. Cambridge, Mass: MIT Press. ISBN 0-262-73005-7
^ 「Introduction to Deconvolution」https://www.olympus-lifescience.com/en/microscope-resource/primer/digitalimaging/deconvolution/dec^{[失效連結]}
^ AL-CHALABI, M. (1974), AN ANALYSIS OF STACKING, RMS, AVERAGE, AND INTERVAL VELOCITIES OVER A HORIZONTALLY LAYERED GROUND . Geophysical Prospecting, 22: 458-475. https://doi.org/10.1111/j.1365-2478.1974.tb00099.x
^ YILMAZ，ÖZDOǦAN （1989）VELOCITY‐STACK PROCESSING，Geophysical Prospecting, Volume 37, Issue 4, May 1989, p. 357 – 382。DOI: https://doi.org/10.1111/j.1365-2478.1989.tb02211.x
^ Chen, Yangkang; Yuan, Jiang; Zu, Shaohuan; Qu, Shan; Gan, Shuwei (2015). "Seismic imaging of simultaneous-source data using constrained least-squares reverse time migration". Journal of Applied Geophysics. 114: 32–35.Bibcode:2015JAG...114...32C. doi:10.1016/j.jappgeo.2015.01.004
^ Xue, Zhiguang; Chen, Yangkang; Fomel, Sergey; Sun, Junzhe (2016). "Seismic imaging of incomplete data and simultaneous-source data using least-squares reverse time migration with shaping regularization". Geophysics. 81 (1): S11–S20. Bibcode:2016Geop...81S..11X. doi:10.1190/geo2014-0524.1
^ Chen, Yangkang; Chen, Hanming; Xiang, Kui; Chen, Xiaohong (2017). "Preserving the discontinuities in least-squares reverse time migration of simultaneous-source data". Geophysics. 82 (3): S185–S196. Bibcode:2017Geop...82S.185C. doi:10.1190/geo2016-0456.1

[”SCHLUMBERGER”-1] 1.0 ^1.1 SCHLUMBERGER. "seismic trace - Schlumberger Oilfield Glossary". www.glossary.oilfield.slb.com.

[”Yilmaz”-2] 2.0 ^2.1 Yilmaz, Öz (2001). Seismic data analysis. Society of Exploration Geophysicists. p. 274. ISBN 1-56080-094-1

[”Stone”-3] Stone, Dale (1994).Designing surveys in two and three dimensions. Society of Exploration Geophysicists. ISBN 978-1560800736

[”Keary”-4] Keary, Philip (2013). An Introduction to Geophysical Exploration (3., Auflage ed.). John Wiley & Sons. ISBN 9781118698938

[O'Haver”-5] O'Haver, T. "Intro to Signal Processing - Deconvolution". University of Maryland at College Park. Retrieved 2007-08-15.

[”Wiener,”-6] Wiener, N. (1964). Extrapolation, Interpolation, and Smoothing of Stationary Time Series. Cambridge, Mass: MIT Press. ISBN 0-262-73005-7

[”Introduction”-7] 「Introduction to Deconvolution」https://www.olympus-lifescience.com/en/microscope-resource/primer/digitalimaging/deconvolution/dec^{[失效連結]}

[”-8] AL-CHALABI, M. (1974), AN ANALYSIS OF STACKING, RMS, AVERAGE, AND INTERVAL VELOCITIES OVER A HORIZONTALLY LAYERED GROUND . Geophysical Prospecting, 22: 458-475. https://doi.org/10.1111/j.1365-2478.1974.tb00099.x

[”Yilmaz1”-9] YILMAZ，ÖZDOǦAN （1989）VELOCITY‐STACK PROCESSING，Geophysical Prospecting, Volume 37, Issue 4, May 1989, p. 357 – 382。DOI: https://doi.org/10.1111/j.1365-2478.1989.tb02211.x

[”Chen”-10] Chen, Yangkang; Yuan, Jiang; Zu, Shaohuan; Qu, Shan; Gan, Shuwei (2015). "Seismic imaging of simultaneous-source data using constrained least-squares reverse time migration". Journal of Applied Geophysics. 114: 32–35.Bibcode:2015JAG...114...32C. doi:10.1016/j.jappgeo.2015.01.004

[”Xue”-11] Xue, Zhiguang; Chen, Yangkang; Fomel, Sergey; Sun, Junzhe (2016). "Seismic imaging of incomplete data and simultaneous-source data using least-squares reverse time migration with shaping regularization". Geophysics. 81 (1): S11–S20. Bibcode:2016Geop...81S..11X. doi:10.1190/geo2014-0524.1

[”Chen1”-12] Chen, Yangkang; Chen, Hanming; Xiang, Kui; Chen, Xiaohong (2017). "Preserving the discontinuities in least-squares reverse time migration of simultaneous-source data". Geophysics. 82 (3): S185–S196. Bibcode:2017Geop...82S.185C. doi:10.1190/geo2016-0456.1

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]