【摘要】 发生在孕震区周边地块上的临震预滑和震颤现象,对破坏性地震预测有一定前兆意义,是值得地震学界关注的问题。选取2008年5月12日汶川M_W 7.9地震发生前,临夏和湟源地震台分量应变仪记录与临夏、恩施和西安地震台数字地震仪记录以及临夏和周至地震台深井水位仪记录,分析发现,在临震前数天至数小时,上述各地震台不同学科观测仪器均记录到一些"跃变"和"震颤"震相。文中试图以颗粒物理原理,来认识不同距离、不同台站、不同学科的观测仪器在临震前相近时间段内记录的低频和高频震相,可能是不同地块在临震前发生预滑错动后激发的预滑震相Xp和地下气体在裂隙内流动激发的震颤震相Tp。观测结果表明:2008年5月8日03时至主震发生,各地震台所处地块在相近时段内逐次发生次数不等的预滑错动,其中1—2次较大错动可在噪声背景中被识别;各地震台预滑错动方向指向或背向主震震中。据此认为:汶川M_W7.9地震前,上述各地震台所处地块在不同大小、不同方向的力链驱动下,发生指向或背向主震震中的临震预滑现象。更多还原

【Abstract】 The premonitory slip and the tremor phenomenon of imminent earthquake, occurred at around the seismogenic area, have certain precursor significance for the destructive earthquake prediction. It is worth the seismological community concern. After the M_W 7.9 earthquake occurred at Wenchuan, China, on 12 May 2008. We find some "jumping" and "tremor" phase during the period of several hours to several days before the main earthquake, on the recordings of four-gauge borehole strainmeters(FGBS) of Linxia station and Huangyuan station; on the recordings of broadband digital seismograph of Linxia station, Enshi station and Xi’an station;on the recording of deep borehole water level of Linxia station and Zhouzhi station, China. First we discuss the reliability of these seismic data, then according the granular physics principle, we tries to explain the recordings of low frequency and high frequency seismic phase at the different distances, different stations and different discipline observation instruments at similar period immediate the main earthquake. It may be the pre-slip seismic phase Xp which may be excited by pre-slip dislocation process. It may be the tremor seismic phase Tp which may be excited by the underground gas which flowing through fracture. These pre-slip dislocation process may be occurred at the different block immediate the main earthquake. The results showed that, since 3 o’clock, 8 May, there are many times pre-slip dislocation between the block of different station at similar period immediate the main earthquake. There is 1 to 2 time larger pre-slip dislocation,which can be recognized from the background noise. The most direction of pre-slip dislocation points to the main earthquake epicenter or back to the main earthquake epicenter. According to this result, we think the immediate pre-slip dislocation phenomena that tectonic blocks under stations moved to toward or away from main epicenter of Wenchuan M_W 7.9 earthquake had happened.These blocks are driven by force chains of different sizes and different directions.更多还原