School of Information Engineering, Institute of Disaster Prevention, Beijing, China.
School of Electronic and Information Engineering, Liaoning University of Technology, Jinzhou, China.
PLoS One. 2021 Oct 1;16(10):e0257345. doi: 10.1371/journal.pone.0257345. eCollection 2021.
Infrasonic signals measured before an earthquake carry information about the size and development speed of the source fracture, the stress at the fracture site and the elastic properties of the geologic medium. The infrasonic signal has a stable time scale, and compared with other precursors, infrasound has a unique sensitivity to earthquake disasters. However, to date, there has been no relevant theoretical research on the mechanism of infrasonic anomalies, and information on the development of fracture sources cannot be obtained from these characteristics, which makes the application of this anomaly in earthquake prediction challenging. In this study, we obtained the characteristics of short-term and impending infrasonic anomalies based on the infrasound data of more than 100 strong earthquakes. With a range of elastic medium models with a large number of fractures, we completed the theoretical simulation of the formation process of infrasonic precursors during the formation of the main fractures, analyzed the physical evolution of acoustic signals when cracks are generated, and quantitatively described the stages of large fracture formation caused by the initiation and propagation of seismic cracks. Specifically, this study revealed the causes of various and complex forms of infrasonic precursors near the critical point and the causes of the time- and space-dependent characteristics of these precursors, such as a noticeable attenuation of the pulse number, a low frequency and a large amplitude, which verified the effectiveness of infrasonic anomalies as strong earthquake precursors.
在地震前测量到的次声信号携带着关于震源断裂的大小和扩展速度、断裂部位的应力以及地质介质弹性性质等信息。次声信号具有稳定的时间尺度，与其他前兆相比，次声对地震灾害具有独特的敏感性。然而，迄今为止，尚未有关于次声异常机制的相关理论研究，也无法从这些特征中获取关于断裂源发展的信息，这使得该异常在地震预测中的应用具有挑战性。在本研究中，我们基于超过 100 次强震的次声数据，获取了短期和临震次声异常的特征。通过大量带有裂缝的弹性介质模型，我们完成了主断裂形成过程中次声前兆形成过程的理论模拟，分析了裂缝产生时声波信号的物理演化，并对地震裂缝的起始和传播引起的大断裂形成阶段进行了定量描述。具体而言，本研究揭示了各种复杂形式的近临界点次声前兆的原因，以及这些前兆的时间和空间相关性的原因，例如脉冲数明显衰减、频率降低和幅度增大，从而验证了次声异常作为强震前兆的有效性。
