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由于印度-欧亚板块碰撞,位于板块边界带的喜马拉雅地区大震频繁,但对其活动性的认识仍十分有限.2015年4月25日尼泊尔中东部地区时隔80年再次发生8级地震,为研究板缘地震提供了一次难得机遇.本文用西藏和尼泊尔的GPS连续观测数据和全球分布的远震地震波记录联合反演此次特大地震的破裂过程,结果显示此次地震发生在印度板块与青藏高原接触边界面——喜马拉雅主滑脱断层上.北倾11°、近东西(295°)走向的断层面破裂约100km长(博卡拉到加德满都),130km宽(从加德满都深入我国西藏吉隆县),破裂以逆冲滑动为主,平均幅度达到2.4m,释放的地震矩高达9.4×1020 N·m.反演结果还显示,震源体主要破裂分布深度范围为5~25km,应无地表破裂,属于一次盲地震.基于GPS资料推测的地壳现今运动速率及1833年地震的震源位置,我们推测地震在此次地震破裂区域复发的周期可能为150~200a,而极震区以南的深部滑脱断层仍保持闭锁,未来仍有导致灾害性大震的可能性.
As a result of the Indian-Eurasian plate collision, frequent earthquakes occurred in the Himalayas located in the boundary zone of the plateau, but their activities were still limitedly known. On April 25, 2015, another 8 earthquakes occurred in the eastern and central regions of Nepal after an interval of 80 years. Which provides a rare opportunity for the study of slab-edge earthquakes.This paper uses GPS continuous observation data from Tibet and Nepal and teleseismic seismic records distributed globally to jointly retrieve the rupture process of this epicenter earthquake. The results show that the earthquake occurred in the Indian Plate and the On the contact boundary between the Tibetan Plateau and the Himalayan main detachment fault, the fault ruptured about 11 ° northward and 295 ° east-west (about 100 km long) (Pokhara to Kathmandu) and 130 km wide (from Kathmandu to Tibet, China) , The rupture is mainly thrusting and sliding, the average amplitude reaches 2.4m, and the seismic moment released is as high as 9.4 × 1020 N · m. The inversion results also show that the main rupture distribution depth of focal body ranges from 5km to 25km and there should be no surface rupture, Belongs to a blind earthquake.According to the current crustal movement velocity and the location of the 1833 earthquakes based on GPS data, we speculate that the period of earthquake recurrence in this earthquake rupture zone may be 150 ~ 200a, while the deep detachment fault south of the extreme earthquake zone is still locked, so there is still a possibility of causing a catastrophic earthquake in the future.