淺海震測氣泡震盪效應處理之研究

BUBBLE EFFECT IN SHALLOW WATER SHOOTING

許慶詳(C. H. Hsu) ； 陳俊逸(J. Y. Chen)

《鑛冶：中國鑛冶工程學會會刊》 29卷1期 (1985/03) Pp. 58-67

https://doi.org/10.30069/MM.198503_29(1).0007

摘要

淺海震波測勘，由於所使用的震源，很難有效的加以控制，常常造成嚴重的氣泡震盪效應。如單由傳統震測資料處理流程方式處理，所得的結果未能去除因氣泡震盪效應所引起的異常，通常會在淺層部分出現雜亂的信號，掩蓋了真正的地下地質，而整個剖面所含的資料除了震源爆炸後的瞬間反射之外，亦包含了氣泡震盪產生之反射信號，將令解釋者無法清楚的辨別何者為真正的地下地質反射，影響解釋甚大。本研究利用時間空間域傾斜濾波器以及多波道頻率域解廻旋，分別消除或衰減來自氣泡震盪效應的數串直達波及重複反射。由處理後所得的例子中，可以看出在淺層部分已可清楚的顯示出地下反射，而且複反射已大部分被衰減，由自對比資料可獲得印證，顯現本研究的結果，對淺海氣泡效應已有相當的成效。

並列摘要

To correlate onshore and offshore seismic data, a number of seismic profiles have been shot in shallow waters fringing the western coast of the island of Taiwan. The water depth varies from 0 to 30 meters. Dynamite was used as the energy source, despite of its adherence to the serious bubble effect. Because of the bubble effect there are two kinds of trouble for processing the shallow water records. First, direct waves generated by each collapse of bubble mix with the reflected energy that will otherwise be evident. Second, for each reflector, it will give rise to the events of the same reflector after each collapse of bubble. The aims of processing such data are to mute the direct waves generated by each collapse, keeping the reflections unaffected, and to attenuate the reflections due to the repeated bubble collapses. To remove the direct wave interference, a dip-filter is considered as an effective tool when geophone interval is small enough that there is no problem of spectrum aliasing. If the geophone interval is not sufficiently small, aliasing will affect the efficiency of the filtering process. Then EXP (iwt(x)) operator can be applied to the common shot section in (w, x) domain before Fourier transformation from x domain to k domain is made to avoid aliasing. The T-X domain dip-filter has been applied to the shallow water seismic records with great success. Since the bubble effect is associated with the shot itself, deconvolution of the common shot gathers was discussed. Sections processed by use of this techniques were compared with those of the convectionally processed. Apparent improvements indicate that this processing technique is viable and of practical value.