Abstract: The M_S7.9 Mani earthquake happened at the north border of the Qiangtang basin of Tibet, near the NEE trending Maergaichaka-Ruolacuo fault, on November 8, 1997. The region of Qiangtang with cold weather and thin air means harsh field conditions. There is no deformation observation station around in several hundreds kilometers scale. All these realistic situations put limits on learning the surface deformation field of the earthquake region and deformation of active faults. Fortunately, D-InSAR technology is available which is not affected by all these factors and has preponderant advantages in acquiring information of spatial deformation field evolution.This research collected 12 scenes ERS-1/2 Radar Satellite data of ESA from January 1995 to December 2000. ERS-1 SAR data are included, i.e. 2889/19960415, 2907 /19960415. And there are 10 ERS-2 SAR data: 2889/19960416, 2907/19960416, 2889/19970121, 2907/19970121, 2889/19970610, 2907/19970610, 2889/19970819, and 2907/19970819. These SAR data were handled using three-pass of four-pass Differential Interferomertric modes.Three dynamic images of pre-seismic Interferometric Deformation Field of the 1997 M_S7.9 Mani earthquake were acquired by using D-InSAR technology. The result shows that 10 months prior to the Mani event, a left-lateral shear trend appeared in the seismic area, which was in accordance with the earthquake fault in nature. The quantity of local deformation on the northern wall was slightly larger than that on the southern wall, and the deformation distribution area of the northern wall was relatively large. With the event being impending, the deformation of the southern wall varied increasingly, and the deformation center shifted eastward. Two and half months before the event, the western side of the fault was still locked while the eastern side began to slide, implying that the whole fault would rupture any moment. The most remarkable deformation zones appeared in northern and southern walls, which were parallel to and apart from the fault about 40km, with accumulated local displacements of 344mm on the northern wall and 251mm on the southern wall, respectively. The southern wall was the active one with larger displacements.

Key words: D-InSAR, Mani Earthquake, preseismic surface deformation field, dynamic evolution, earthquake forecast

摘要： 采用D-InSAR技术获取了1997年11月8日西藏玛尼地震前3期地表干涉形变场时空演化图像。通过对干涉形变场图像进行分析,得到了震前积累形变场时空演化特征与震源破裂面闭锁之间的对应关系。结果表明:玛尼地震前10个月孕震区地表形变场就开始出现了与发震断层性质一致的变化趋势———左旋扭动,且随着发震时间的临近,南盘形变加剧,形变中心向E进一步扩展。南盘变形量明显大于北盘,南盘为主动盘。到震前2个半月,断层两盘的闭锁进一步加剧,有随时破裂的可能。从震前1996年4月16日到震前2个半月之间,南盘局部累计扭曲变形量达344mm。

关键词: D-InSAR, 玛尼地震, 震前地表形变场, 动态演化, 地震预测