黄土层地区环向水耦合爆破地震勘探技术的振动响应特征研究

Research on vibration response characteristics of circumferential water coupling blasting seismic exploration technology in loess layer areas

  • 摘要: 为解决传统爆炸震源在黄土层等特殊地形条件下获得的地震资料信噪比和结果准确性低的问题,采用环向水耦合爆破方法激发人工地震,开展现场试验。通过爆破测振仪监测地表振动响应,分析质点振动速度随爆心距变化规律,结合希尔伯特黄变换分析速度振动信号的时间‒频率‒能量特征;通过检波器获取环向水耦合单炮地震结果,采用双曲线时窗评价目的层连续性,结合能量、信噪比等指标评价地震资料可靠性。研究结果表明:环向水耦合爆破方法下的地表质点振动速度峰值大,传统爆破质点振动速度峰值为2.29 cm/s,多组水耦合爆破质点振动速度峰值的平均值为3.304 cm/s,提升幅度达44.3%;速度峰值随爆心距增大的衰减速度慢,能在一定程度上缓解地震波在黄土区域传播带来的能量耗散;EMD分解后得到的各阶IMF分量与原信号的相关性及频带能量均呈现正态分布特点,首尾模态低,中间模态高。传统爆破方式振动信号瞬时能量峰值可达3.13 (cm/s)2·Hz,环向水耦合爆破则为13.56 (cm/s)2·Hz,振动信号瞬时能量远远大于传统爆破方式;环向水耦合爆破在目的层双曲线时窗范围内的地震波主频、能量、信噪比3组指标均大于传统爆破方式,3指标分别提升了55.9%、33.3%和12.11%,水耦合爆破条件下的地震资料质量更高。环向水耦合爆破的质点振动速度峰值大、衰减慢、地震资料双曲线目的层连续性好。

     

    Abstract: To solve the problem of low signal-to-noise ratio and accuracy of seismic data obtained from traditional explosive sources in special terrains such as loess, field experiments were conducted using the circular water-coupled blasting method to artificially induce earthquakes. By monitoring the ground vibration response using blast seismographs, the variation of particle vibration velocity with distance from the explosion center was analyzed, and the time-frequency-energy characteristics of the velocity vibration signal were studied using the Hilbert-Huang transform. Seismic results for circular water-coupled blasting were obtained using detectors, and the reliability of the seismic data was evaluated by assessing the continuity of the target layer via hyperbolic time windows and considering indicators such as energy and signal-to-noise ratio. The research results showed that the peak particle velocity at the ground surface was higher with the Circular water coupled blasting method, with an average peak particle velocity of 3.304 cm/s compared to 2.29 cm/s with traditional blasting, representing a 44.3% increase. The decay rate of the peak velocity with increasing distance from the explosion center was slower, which helped alleviate energy loss and dissipation of seismic waves in loess regions. The correlation and frequency band energy of each intrinsic mode function component obtained through empirical mode decomposition (EMD) exhibited a normal distribution, with lower first and last modes and higher intermediate modes. The instantaneous energy peak of the vibration signal with traditional blasting reached 3.13 (cm/s)2·Hz, while it was 13.56 (cm/s)2·Hz with Circular water coupled blasting, indicating a significantly higher energy level with the latter method. The three indicators, main frequency, energy, and signal-to-noise ratio, within the hyperbolic time window range of Circular water coupled blasting were all higher than those of traditional blasting, with improvements of 55.9%, 33.3%, and 12.11%, respectively. Thus, seismic data obtained under water-coupled blasting conditions had higher quality. Circular water coupled blasting exhibited larger peak particle velocity, slower decay, and better continuity of seismic data within the hyperbolic target layer.

     

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