关键词: 地震矩张量, 地壳势能变化, 大陆岩石层地块

Abstract: Spatial distribution of the signs of the seismic moment tensor element M_rr is mapped by using the Harvard CMT catalogue and the catalogue of earthquake focal mechanisms in China. This distribution pattern corresponds to a simplified version of the change of crustal potential energy calculated by Tanimoto and Okamoto (2000), in which the sign of M_rr indicates the state of stress at the seismic source. When M_rr is positive, it represents a compressional state; when M_rr is negative, it represents a tensional state. We define the 'mixed state' for the case that positive and negative M_rr are mixed together, which corresponds to a complex stress state with a significant shear component. This simplification is taken because for many earthquakes the focal depths cannot be precisely determined so that the calculation of crustal potential energy cannot get reliable results; moreover, for most of the regional/local catalogues of focal mechanisms, their completeness cannot be ensured. Comparison between the spatial distribution of M_rr and the dynamic pattern of continental blocks in China shows that the stress state within each tectonic block has significant consistency, while the stress state at the boundary is different from that within the block, implying the existence of the blocks and their relative motions to each other.

Key words: seismic moment tensor, crustal potential energy, continental tectonic blocks