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2001年11月14日青藏可可西里地震(Mw7．8)造成青藏北部的西昆仑断层破裂约400 km。我们对全球地震台网记录的P和SH波采用两种反演方法复原时空破裂过程。观测到的地表破裂由两个走滑段组成,其间有张性阶跃带,范围约长45 km, 宽10 km以上。虽然在阶跃带中的地堑系内几乎没有观测到地表破裂,但我们的结果表明破裂并没有跳过这个大的空挡,而是连续地穿过地堑。地震以小的走滑子事件开始,推测其沿着两个断层段的最西部发展。5 s之后,发生一个约相同大小、具有较大正断层分量的斜断层破裂子事件,其位置可能就在地堑内。倾斜滑动事件可能使破裂转移到主昆仑断层上。主要的矩释放在破裂起始约18 s、沿昆仑断层向东传播350 km之后发生。在这个断层段上滑动非常不均匀,在初始的200 km平均约2 m,在随后的 50 km内突然增加,达到最大值7．5 m,然后又很快下降。沿主段的平均破裂速度较高 (-3．6 km·s-1),可能超过了该区的剪切波速度。Mw7．8级可可西里地震与2002年 11月Mw7．9级迪纳利断层(阿拉斯加)地震相比,具有较长的地表破裂,较快的平均破裂速度及释放了较多的能量,并且可能具有较低的平均破裂能量。证据表明,破裂前缘速度过了最大滑动点后明显下降,这意味着断层两端的摩擦强度有很大不同。
On November 14, 2001, the Hoh Xil earthquake in the Qinghai-Tibet region (Mw7.8) resulted in a fault of about 400 km in the western Kunlun fault in northern Tibet. We use two inversion methods to recover the spatiotemporal rupture of P and SH waves recorded by the global seismograph network. The observed surface rupture consists of two strike-slip segments with a tension step between them, covering a length of about 45 km and a width of 10 km or more. Although there was almost no surface rupture observed in the graben system in the step zone, our results show that the rupture did not skip this large neutral, but continuously traversed the graben. The earthquake started with a small strike-slip event, presumably along the westernmost part of both fault segments. After 5 s, a ramp fault rupture event about the same size with a larger normal faulting component may occur within the graben. Tilting slip events may cause ruptures to migrate to the main Kunlun fault. The main moments of release occurred about 18 s after the rupture began and 350 km eastward along the Kunlun fault. The slip on this fault segment is very inhomogeneous with an average of about 2 m at the initial 200 km, a sudden increase within the next 50 km, reaching a maximum of 7.5 m, and then declining rapidly again. The higher average rupture velocity along the main section (-3.6 km · s-1) may exceed the shear wave velocity in this area. The Mw 7.8 earthquake in Hoh Xil has longer surface ruptures, faster average velocity of rupture and more energy released than the Mw 7.9 Napier earthquake of magnitude 7.9 in November 2002 and may have Lower average burst energy. The evidence shows that the ruptured frontal velocity drops significantly after passing the maximum slip point, which means that the frictional strengths at both ends of the fault are quite different.