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一、引言地震时和地震前,能够听到地声,这已为许多的资料所证实。在群众性的测防工作中,出现了不少探测地声的装置,为此做了不少的工作。本文企图从理论上阐明在地震发生时或发生前的小震、岩石破裂所发出的10~2赫以下的音频声波,在距震中一定的范围内是可以接收到的。在考虑到土层的内摩擦对声波的吸收情况下,给出了声强级与频率和距离的关系式。本文暂先讨论半无界空间均匀介质内纵波的传播情况,暂不考虑横波、表面波的影响,也不考虑表面、岩层、断层、介质不均匀性等对声波的影响。
I. INTRODUCTION Earthquakes can be heard during an earthquake and before an earthquake. This has been confirmed by many sources. In the mass-measurement work, there have been many devices for detecting sounds of the ground and a lot of work has been done for this purpose. This article attempts to theoretically clarify that sound waves below 10-2 Hz emitted by small earthquakes and rock breaks before or during an earthquake are receivable within a certain range from the epicenter. Taking into account the absorption of acoustic waves by the internal friction of the soil layer, the formula of the relationship between sound intensity level and frequency and distance is given. This paper first discusses the propagation of longitudinal waves in a homogenous medium with semi-unbounded space. The effects of shear waves and surface waves are not considered for the moment, and the effects of surface, rock layers, faults, and medium inhomogeneities on acoustic waves are not considered.