大型宇宙飞船的火箭噪声

大型多级火箭推进的宇宙飞船是进行载人空间探索的有力工具。这种大型火箭具有几百万磅的推力,火箭喷气可产生几千万瓦的声功率。火箭发射后,穿过大气层不断上升,这时宇宙飞行员和座舱中的仪器将处于火箭发动机的强声场和强振动中。飞船速度加大时,火箭的噪声级是从尾部到头部逐渐减少的。飞行速度超过声速后,座舱中的噪声甚至会完全消失,仅剩下了沿金属结构传输过来的火箭振动。但是,按照     

HIGH FREQUENCY GEOSOUND IN THE EPICENTRAL REGION

The geosound observation station has been set up in the epicentral region.High frequency geosoundsignals have been detected by means of anticlutter processing and the high frequency response characteristicof the geophone.Further analysis indicates that these signals are impulsive with weaker energy.The shortestduration of geosound impulse is only of the order of millisecond and the highest dominant frequency ishigher than 1kHz.The high frequency signal thus detected may represent the important feature of geosoundin the epicentral region.     

中强震的前兆地声

本文报道了滦县五级震前卢龙台站和昌黎台站的震前地声记录。从地声源的强度出发,作者对地声传播的可能距离作了初步分析。分析表明,地声一般不是来自震源,而是来自观测站附近的地下。从而说明彼此相距较远的观测站,其接收信号序列是不相关的。但由于震源体与震级成正比的关系,对于较大地震,我们仍可能在较大范围内和较早的时候收到前兆信息。     

震中区震前的高频地声

在近震区建立地声观测站,利用地听器的高频响应特征和对信号的抗干扰处理,结果发现了震前高频地声的存在。进一步分析表明,这些信号是一些能量较弱的脉冲型信息。其持续时间仅为ms的数量级,而最高的优势频率则超过1000Hz。该信息可能是震中附近地区地声的重要特征。     

PRECURSORY GEOSOUND OF MODERATELY STRONG EARTHQUAKES

The geosound recorded at Lulong and Changli stations prior to the Luanxian earthquake M=5is reported in this paper.Based on the strength of the geosound source,a preliminary analysis of itspossible propagation distance has been made.The analysis indicates that geosounds generally comefrom the underground near the observation stations instead of coming from the earthquake sources,so the signal sequences received at observation stations located far from each other are irrelevant.The precursory information before larger earthquakes may still be received within a large area at theearly stage so far as the earthquake source body is proportional to its magnitude.