随州-信阳M_L4.2地震前定点形变异常特征

STUDY ON CHARACTERS OF FIXED DEFORMATION ANOMALIES BEFORE THE SUIZHOU-XINYANG M_L4.2 EARTHQUAKE

分析了 2 0 0 0年 1月 2 8日随州和信阳交界处发生的ML4 .2地震前 ,信阳地震台 (Δ =35km)定点形变中短期及临震异常特征 .分析研究表明 :该次地震前信阳台目视水管倾斜仪EW向测值从 1 999年 6月开始出现反向变化 ,NS向测值从 1 999年3月开始出现加速变化 ;水平摆倾斜仪EW向和NS向测值分别从 1 999年 2月和1 999年 6月开始出现反向变化 .这些异常于 2 0 0 0年下半年结束 .震前 3天水管倾斜仪EW向测值出现加速变化 ;震前 5～ 8天NS向测值除了出现加速变化外 ,还出现突跳 .震前约 2 0天 ,水平摆倾斜仪 2个方向测值均出现了准周期性波动变化 .另外 。

An earthquake (M L=4.2) occurred in the boundary area between Xinyang, Henan and Suizhou, Hubei on January 28,2000. Xinyang seismic station is located on northeast of the epicenter with a distance of 35 km and in the same fault with the source.Several kinds of medium short term and impending earthquake anomalies of the fixed crust deformation are recorded in the station before the event.The study results indicate that variations of the observation values before the event are larger.The observation values of EW by water tube tiltmeter changed in reverse from June,1999 and changed acceleratively three days before the event.The values of NS by the meter changed acceleratively from March,1999 and jumped suddenly 5～8 days before the event.The values of EW and NS by horizontal pendulum tiltmeter changed in reverse respectively from February and June,1999 and fluctuated quasi periodically about 20 days before the event.Moreover,the obvious anomalies of the deformation tide factor from the station arised too before the event.