福建及沿海地区地震活动力源探讨

Discussion of force source of seismic activity in Fujian and its coastal area

综合地震震源机制解和地壳形变观测资料的研究,求得福建及其沿海地区现代震源应力场,认为这与台湾地区、台湾海峡应力场相互衔接,主压应力轴优势方位为NW-SE向,力轴仰角较小,应力场近于水平挤压,形变场反映近期福建沿海亦受北西方向,接近与海岸垂直的挤压力。进一步分析该区域内的断裂构造特征和地震活动强度由东至西逐渐减弱的规律,认为菲律宾海板块与欧亚板块的相互作用力不仅是台湾强震力源所在,而且其影响向西扩展,福建及其沿海地区地震活动主要力源仍然是来自这两大板块的相互作用力。

Through synthetical analysis of solutions of focal mechanism and the study of crustal deformation observation data, the recent stress field of hypocenters in Fujian and its coastal area has been obtained, which is considered to links up the stress field in Taiwan and Taiwan Strait, and the dominant direction of axis of principal compressive stress is NW-SE. The elevation angle of stress axis is small, so the stress field is almost squeezing in horizon. The deformation field also implies that the direction of force of squeezing which is near perpendicular to the seashore is west-northern in Fujian coastal area in recent period. Further analysis of regional characteristics of fracture structure and the regularity of gradual decrease of the intensity of seismic activity from east to west imply that the mutually acting force between Philippine Plate and Eurasia plate is not only the force source of strong earthquakes of Taiwan but also the main force source of the seismic activity in Fujian and its coastal area when the force derived from the interaction of the two plates extends to west.