全球大地震时空分布与动力学机制的初步研究

SPATIOTEMPORAL DISTRIBUTION OF GLOBAL GREAT EARTHQUAKES AND DYNAMIC MECHANISM

文中根据最新的全球大震资料划分了 10 0a来全球特大地震的时空演化过程 ,表现为环太平洋带与近纬向活动带两种强震分布图像 ,以 2 0a左右的时间段交替出现。逆冲和引张型地震释放了全球强震能量的主要部分。逆冲型地震主要发生在环太平洋地震带上 ,在喜马拉雅碰撞边界和巽他弧也有发生。引张型地震主要出现在洋脊和裂谷地区。而走滑型地震主要分布在东亚大陆内部、北美板块西边界和加勒比板块的周边、西南太平洋带、以及地中海 -喜马拉雅带部分区域 ,呈近纬向分布。地幔对流的垂直运动与水平运动分量的比率 ,决定了逆冲、引张与走滑型强震的能量释放份额。地幔运动在地表体现在逆冲、引张与走滑型强震空间分布的区域差异性。这种差异在时间上的演化形成了全球强震活动环太平带与近纬向分布图像的交替出现。

Spatiotemporal distribution of global great earthquakes in the past one hundred years represents two alternating periods:the circum-pacific period, and the almost-latitudinal period, which occurred by turns in the cycles of 10 to 20 years. Most of the seismic energy was released by the great thrust and normal earthquakes. The thrust earthquakes are mainly distributed on the circum-pacific seismic belt, the Himalaya collision boundary and the Sunda arc. The normal earthquakes occurred in the zones such as the ocean ridge and the continental rift valleys. The distribution of strike-slip earthquakes shows an almost-latitudinal belt including the interior of eastern Asian continent, west boundary of North American plate, around Caribbean plate, southwest Pacific belt and some segments of Mediterranean-Himalayas belt. The ratio of poloidal to toroidal component of mantle convection determined the proportion of seismic energy released in the thrust, normal, or strike-slip earthquakes. The heterogeneous mantle motion affected the spatial distribution among the thrust, the normal and the strike-slip earthquakes. The poloidal component was involved in the thrust and normal earthquakes, while the toroidal component was affected to the strike-slip earthquakes. The temporal evolution of poloidal and toroidal components induced the alternation of the circum-pacific period and the almost-latitudinal period.