青藏高原北部地区强震活动特征与地震大形势

THE STUDY ON THE SITUATION AND STRONGER EARTHQUAKE ACTIVITY FEATURES IN THE NORTH AREA OF THE QINGHAI—TIBET PLATEAU

本文研究了青藏高原北部地区强震活动的特征,结果是:地震活跃期为230—250年,平静期为130—150年;喜马拉雅南缘、青藏高原南部地区强震与本区强震明显相关,喜马拉雅南缘与缅甸北部地区发生强震后本区发震的概率分别为87.5%和66.7%;本区7级地震分带交替发生,最先发生的两个6级地震对预测未来7级地震发震地点有一定意义;中强震在8级地震前不活跃,而在7级地震前比较活跃,且青海北部与西部发生6级地震后,甘肃东南部或甘青川交界有5级地震活动。据此判断本区未来10年内存在发生7级强震的危险。

The features of seismicity in the north area of Qinghai—Tibet Plateau are obtained:(1) The active period of earthquake is about 230-250 years long, the tranquil period is about 130 to 150 years long,(2) The seismicity has a relation to the seismic activity in the south area and the south edge of the Himalayas. After stronger earthquakes occurred in the south area of the Himalayas and the north area of Burma, there would be stronger earthquakes to occur in these areas with probability 87.5% and 66.7%, respectively.(3) The earthquakes with M≥7 took place alternatively in several seismic zones. The first two earthquakes with M=6 would point out the furture location of next earthquake with M≥7.(4) The medium earthquakes were not in active before the earthquakes whth M≥8, but were active before the earthquakes with M≥7. Generally, the medium earthquakes happen in north and west parts of Qinghai and southeast part of Gansu or in the edge of Gansu and Sichuan before the earthquakes with magnitude about 7.According to above results, there may be an earthquake with M≥7 in the north area of Qinghai-Tibet Plateau in coming 10 years,