地球物理学进展 ›› 2019, Vol. 34 ›› Issue (1): 379-386.doi: 10.6038/pg2019BB0584

• 应用地球物理学Ⅱ(海洋、工程、环境、仪器等) • 上一篇    下一篇

大容量气枪震源广角地震数据的高频成分分析

王笋1,2,3,丘学林2,3,郭晓然1,赵明辉2,李普春1   

  1. 1. 福建省地震局厦门地震勘测研究中心,福建厦门 361021
    2. 中国科学院边缘海与大洋地质重点实验室(南海海洋研究所),广州 510301
    3. 中国科学院大学,北京 100049;
  • 收稿日期:2018-04-25 修回日期:2018-11-10 出版日期:2019-02-20 发布日期:2019-04-15
  • 作者简介:王笋,男,1984,在读博士,研究方向为地震勘探和重力勘探. (E-mail: atrax@scsio.ac.cn)
  • 基金资助:
    福建省地震局青年科技基金(Y201502);国家自然科学基金联合资助.(91428204);国家自然科学基金联合资助.(41730532)

Analysis of the high frequency components among wide-angle reflection/refraction data excited by large volume air-gun sources

WANG Sun1,2,3,QIU Xue-lin2,3,GUO Xiao-ran1,ZHAO Ming-hui2,LI Pu-chun1   

  1. 1. Xiamen Centre for Seismic Survey, Earthquake Administration of Fujian Province, Fujian Xiamen 361021, China
    2. CAS Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Guangzhou 510301, China
    3. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2018-04-25 Revised:2018-11-10 Online:2019-02-20 Published:2019-04-15

摘要:

大容量气枪震源由于能量集中在低频段、子波一致性好、绿色环保等优点,广泛应用于广角地震探测中,极大地推进了人们对地壳结构和地球动力学过程的认识.气枪信号的有效频带是地震数据质量评价和精细处理一个重要基础参数,以往研究由于数据源和研究方法的局限,认为最高有效频率在10 Hz以下.本文基于福建省地震局采集的大容量气枪源广角地震数据,根据地震道褶积模型分析了有效频带及其影响因素,对不同类型、不同台基条件的地震接收仪器记录的大容量气枪信号数据进行了分频扫描,结果显示台基条件较好的台站数据,在10~20 Hz频段仍有较高的信噪比,说明大容量气枪激发的地震波在经过深部地层衰减后,仍存在相当可观的高于10 Hz的成分.这些高频成分可以显著提升地震信号的倍频程,减少频带过窄带来的旁瓣效应等不利影响,是准确提取走时的必要条件.值得注意的是大容量气枪源数据中PmP震相的主频可达10~12 Hz,显著高于震源子波的主频,据此推断Moho面的广角反射系数有显著的蓝谱特征,因此10 Hz以上成分对准确提取走时、获取更为精细的地壳结构非常重要.本研究对大容量气枪源广角地震探测的野外采集和数据处理提供了关键质量指标,同时提出从构造反演向岩性反演推进是广角地震探测一个重要的研究方向.

关键词: 大容量气枪震源, 广角地震资料, 有效频带, 分频扫描, 反射系数频散

Abstract:

Large volume air-gun sources are widely used in wide-angle seismic exploration and have greatly promoted the understanding of crustal structure and geodynamic processes because they have many advantages such as dominantly low-frequency components, wavelet consistency, and environmental friendliness. The effective frequency-band is a very important parameter for the quality evaluation and fine processing of seismic data. Most of the previous research suggested that the highest reliable frequency was below 10 Hz due to the limit by data sources and processing methods. This paper studies effective frequency-band and effective parameters deduced by the convolution model of seismic traces on the basis of wide-angle seismic data excited by large volume air-gun sources. The data were tested using frequency scanning for different types of instruments and stations seismic basement, the results show that some stations’ data have still dominantly 10~20 Hz band with high signal-to-noise ratio. It indicates that the high frequency components (higher than 10 Hz) can be recorded and identified in the deep seismic data excited by large volume air-gun sources even their undergone deep strata attenuation. Those high frequency components can significantly improve the octave of seismic signals and reduce the side-lobe levels, is the key for the accurate extraction of travel time. More significantly, the dominant frequency of PmP phases produced by large volume air-gun sources is usually 10~12 Hz, which is obviously higher than the dominant frequency of source wavelet. So we deduce that the wide-angle reflection coefficients from Moho interface are of blue spectrum characteristic. So effective bandwidth and signal-to-noise ratio of high band should be used as the key indicators of the quantitative evaluation of deep seismic data produced by large volume air-gun sources. This study provides a critical quality criterion for seismic survey and data processing. Meanwhile, it proposes an important developing direction for wide angle seismic exploration from inversion of crustal structure to the interpretation of crustal lithology.

Key words: Large volume air-gun sources, Wide-angle seismic data, Seismic bandwidth, Frequency scanning, Reflectivity dispersion

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