GPS观测得到的1998-2003年中国大陆地壳应变

Strain Accumulation in China′s Mainland during 1998 to 2003 Obtained by GPS Observations

利用1998年9月至2003年9月底中国地壳运动观测网络基准站与基本站GPS观测所获得的多期水平位移结果，计算了由观测站组成的各三角形的应变。鉴于量级不大的应变时空变化的复杂性，试图用统计的方法分析基本网观测得到的2001年11月14日昆仑山口西Ms8．1大地震前后的应变。此次地震前中国大陆，特别是中国大陆西部变形有加剧过程，且中国大陆西部最大剪应变方向总体上保持稳定。这表明，此次大地震前有明显的应变能积累；而在震中附近2000-2001年地震前应变速率很低，出现闭锁或成核现象。由最接近震中三角形计算得到的最大剪应变方向确定地震断层走向为N89．3°E。震后2002年的变形仍然较大，但2002～2003年中国大陆，特别是东部，变形最小。

Strain accumulation in the triangles formed by observation stations is calculated from results of horizontal displacements obtained from GPS observations of several epochs during September 1998 to the end of September 2003, at the basic stations and fiducial stations in The Crustal Movement Observation Network of China （CMONOC）. Because of the complicatedness of strain accumulation of small amount in time and space, strain accumulation in the basic network before and after the great Kunlun Mountain earthquake of Ms8.1 on Nov. 14, 2001 is analyzed on the basis of statistics. Before this event there was a process of intense crustal deformation in China＇s mainland, particularly in its western part, and in general, the directions of the maximum shear strain remained stable. These facts suggest that there was significant strain accumulation before this great event, in the area near the epicenter the rate of strain accumulation was rather low during 2000 to 2001 and there was lock of the faults or nucleation at the epicenter. The strike of the earthquake fault determined by the direction of maximum shear strain in a triangle which is the closest to the epicenter is N89.3°E. The deformation after the event was still large but the deformation in China＇s mainland, particularly in its eastern part the deformation became small during 2002 to 2003.