甘肃地区地震活动的某些特征及其意义

SOME CHARACTERISTICS OF SEISMICITY IN GANSU REGION AND ITS SIGNIFICANCE

摘要:

研究了甘肃地区地震活动的特征.结果表明:甘肃地区3级以上地震活动表现出明显的近32个月的准周期性.甘肃及附近地区的6级以上大震均发生在3级地震年频次曲线的谷段附近.1980年以来青藏块体北缘地震活跃期内的中强地震活动的时空图象呈现多组地震自西向东有规律且稳定地迁移.各组地震迁移情况表明本活跃期地震活动已转向低潮,2002年前后可进入平静期.青藏块体北缘西端5级以上地震的发生是甘肃地区中强以上地震活动过程开始的信号.

Abstract:

About 32 months quasi-periodicity was clearly shown in activity of M_S≥3.0 earthquakes in Gansu region.The great shocks with M_S≥6.0 in and near the region occurred near the valley of annual frequency curve of M_S≥3.0 earthquakes. Since 1980,moderate shocks in Gansu region migrated regularly and steadily in groups from west to east along the northern edge of Qinghai-Xizang block.The migrations show clearly that seismicity in current period has been at a low ebb now,and may enter on a quiet phase in about the year 2002.There will be a seismic activity of M_S≥5.5 at about the end of the year 1998 in the Gansu region and its vicinity. That the moderate events of M_S≥5.0 occurred at the west end of northern edge of Qinghai-Xizang block is a signal of the beginning of active process of strong moderate earthquakes in Gansu region.