地震前低频事件的实验研究

介绍了几种强震前超低频事件的观测证据,并通过实验,研究了产生和传播机理。初步结果表明,微破裂的集结和断层的破裂起始会出现超低频脉冲,并透射到空气中形成次声波。塑性体的冲击或超临界流体的膨胀比脆性破裂更容易激发（超）低频波,且不伴随明显高频辐射成分。这样可以较为合理地解释震前“平衡”背景下的（超）低频事件。对实验中破坏前的低频脉冲给出了断裂力学解释。断裂力学的实验和膨胀－－扩容理论证明了震前会产生断层的张裂隙,从而为超临界流体提供了运移空间。流体在运移过程中突然涨缩会激发（超）低频辐射波。讨论了改进（超）低频事件的观测条件问题。

Experimental investigation of precursory low-frequency events before strong earthquakes

In this paper, some evidence from observation of precursory low-frequency events before strong earthquakes are presented, and the mechanism of producing and propagation is investigated experimentally. The primary results show that the ultra low-frequency pulses may produce in the process of nucleation of micro-cracks and faults, and transmit to the air as infrasonic sound. The plastic impact or the dilatancy of ultra-critical liquid can excite ultra low frequency easier without obvious high-frequency radiation. The phenomenon of low frequency pulses before failure of the sample is interpreted by using the theory of fracture mechanics. Theses results may interpret the low-frequency events under the "quiet" background before strong earthquakes more rationally. The experiments of fracture mechanics and the D-D theory prove that tensile cracks may be brought before earthquakes, and so as to offer the space of liquid transmission. In the process of transmission, the liquid may dilate and contract and excite(ultra) low frequency radiate wave. Besides, the improving of observation condition of low-frequency events is discussed.