我国古代张衡在2世纪初,制造了世界上第一台地震仪。这台地震仪有8只口含铜球的龙,正对着下方有8只张着口的蟾蜍,哪个方向发生地震,哪边的铜球就落入下方的蟾蜍口中。地震是一个事件,它是否发生(也就是说地震信号有无)是我们所关心的;我们同时还关心,如果事件发生(也就是信号出现),它来自何方。张衡的地震仪应当是世界上最早的探测地震和地震勘探的SP设备。15世纪末,达 Zhang Heng in ancient China in the early 2000s, created the world’s first seismograph. The seismograph has eight dragons with copper spheres facing directly to the bottom of eight toads that stare at each other. In which direction the copper ball falls into the toad’s mouth below. An earthquake is an event and it is our concern whether it occurs (that is, whether a seismic signal is present or not); we also care about where the event came from (ie, the signal appeared). Zhang Heng’s seismograph should be the world’s earliest SP device for seismic and seismic exploration. Late 15th century