Correlation between movement of tectonic blocks and earthquakes in groups

Abstract

The Chinese mainland is divided into some tectonic blocks by nearly NE- and EW-orientated faults. Meanwhile strong earthquakes in the Chinese mainland usually cluster in time and space. We call “earthquakes in groups”. Tectonic blocks separated by faults and earthquakes in groups are prominent features of the tectonics of the Chinese mainland. Correlation between movement of tectonic blocks and groups of earthquakes is discussed in this paper. The results show that earthquakes in groups often occurred at one or several block boundary faults. The released elastic strain energy is built up in the same periods and around blocks. It means that strong earthquakes in groups are mainly caused by movement of blocks. Four types of block movement are identified based on group earthquakes: movement along a single boundary of a block (or a combined blocks), movement of a single block, movement of multi-blocks, and movement in block interiors. If we consider distribution of all strong earthquakes occurred in the Chinese mainland, the movement along a single boundary of a block is more popular one inducing strong earthquakes. But if we only consider earthquakes in groups rather than single earthquakes the movement of a block dominates among four modes. Statistics with respect to group earthquakes show that the Taihangshan mountain and the North China block are much active in the eastern part of Chinese mainland, and in western part of Chinese mainland the active blocks are Sichuan-Yunnan and the Kunlun-Songpan ones.