地震雷达

Seismic Radar

利用绿色、环保的人工震源,主动向地下发射地震波,构建地震雷达,实现大范围的地下探测,是地球科学的一个前沿课题.最早,探测地球内部利用的是天然地震产生的地震波,这是因为天然地震释放的能量大,一次天然地震释放的能量相当于万吨级炸药.几千公里远处仍可以接收到信噪比大于1的地震波信号,但天然地震发生频度低和震源位置定位精度低限制了利用天然地震进行地下探测的精度;后来,利用人工源的地震勘探得到迅速的发展,探测精度明显提高,但受到人工源能量的限制,探测的空间尺度有限;今天,以小当量激发实现大尺度探测是发展地震雷达的一个关键问题,是将地震波理论和现代信息科学相结合的一个新的领域.发展人工震源的编码和接收信号的解码等理论和技术,可以从电磁波雷达在过去半个世纪所经过的道路得到许多借鉴和启发.可以预期,地震雷达的发展将会对观测地震学带来全面的影响.

It is the frontal research of Earth Science that green artificial source which generates seismic waves propagating underground is used to construct seismic radar. Such method can be used to investigate the structure of the interior of the Earth in large scale. On the early stage of seismology, only seismic waves of natural earthquakes are used to detect the physical properties of the Earth＇ s interior because an earthquake may release huge amount of energy. The energy released by an earthquake can be equivalent to tens of thousands tons of explosive. The ratio of the seismic signal detected thousands of kilometers away over background noise is greater than 1. However, due to of the limited occurring frequency of natural earthquakes and the uncertainty of hypocenter location, the resolution of its investigation is restricted. Thereafter, seismic exploration survey using artificial sources develops quickly, and the surveying resolution is greatly improved. Because the energy of artificial sources is comparably small, the generated signals can only be detected in very limited scale. Nowadays, study on using small source to get distant information in large scale plays an important role in developing seismic radar. This is a new field of intercrossing integration between seismology and information science. The technique of encoding and decoding artificial seismic waves may be derived from the developing process of electromagnetic radar in the past half a century. It is sure that seismic radar will greatly promote the development of seismology and its observation.