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封面故事：2019年四川长宁MS6.0级地震震区龙头镇NW向构造节理。通过对震区双河NW向大背斜的调查, 发现背斜核部和翼部普遍发育两组NW向节理, 地震序列呈明显NW向条带, 破裂型式以逆冲为主兼具左旋走滑分量。长宁地震可能是双河背斜赋存超压环境叠加NE向古构造应力场和旋转应力场作用, 导致区域性NW向节理发生构造强化、贯通, 并进一步破裂的结果。本文成果有助于深入认识构造相对稳定区的孕震机理与发震机制, 也丰富了对不同构造背景下强震成因的认识。这项由云南省地震局常祖峰研究团队取得的相关成果, 详见本期469-480页。(图片提供：常祖峰)
Cover Story：Longtouzhen NW-trending structure of the 2019 Changning MS6.0 Earthquake area in Sichuan. According to the investigation of Shuanghe anticline, two groups of NW-trending joints are generally developed in the core and wing of the anticline, the seismic sequence shows obvious NW-trending features, and the fracturing process is mainly controlled by thrusting with some left lateral strike slip component. The Changning earthquake may be the result of structural strengthening, transfixion and further fracturing of regional NW-trending longitudinal joints caused by overpressure environment in Shuanghe anticline with the superposition of NE-trending paleotectonic stress field and rotation stress field. The results are helpful to in-depth understanding of the mechanism of earthquake preparation and seismogenesis in the relatively stable area of the structure, and also enrich the understanding of the causes of strong earthquakes in different structural backgrounds. The research achievement was obtained by research group led by Professor CHANG Zu-feng, Yunnan Earthquake Agency. For details, see pp. 469-480 of this issue. (Photo by CHANG Zu-feng)
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