Ishii Miaki, Shearer Peter M, Houston Heidi, Vidale John E
Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, IGPP 0225, University of California San Diego, La Jolla, California 92093, USA.
Nature. 2005 Jun 16;435(7044):933-6. doi: 10.1038/nature03675.
The disastrous Sumatra-Andaman earthquake of 26 December 2004 was one of the largest ever recorded. The damage potential of such earthquakes depends on the extent and magnitude of fault slip. The first reliable moment magnitude estimate of 9.0 was obtained several hours after the Sumatra-Andaman earthquake, but more recent, longer-period, normal-mode analyses have indicated that it had a moment magnitude of 9.3, about 2.5 times larger. Here we introduce a method for directly imaging earthquake rupture that uses the first-arriving compressional wave and is potentially able to produce detailed images within 30 min of rupture initiation. We used the Hi-Net seismic array in Japan as an antenna to map the progression of slip by monitoring the direction of high-frequency radiation. We find that the rupture spread over the entire 1,300-km-long aftershock zone by propagating northward at roughly 2.8 km s(-1) for approximately 8 minutes. Comparisons with the aftershock areas of other great earthquakes indicate that the Sumatra-Andaman earthquake did indeed have a moment magnitude of approximately 9.3. Its rupture, in both duration and extent, is the longest ever recorded.
2004年12月26日发生的苏门答腊-安达曼灾难性地震是有史以来震级最大的地震之一。此类地震的破坏潜力取决于断层滑动的范围和震级。苏门答腊-安达曼地震发生数小时后，首次得到可靠的矩震级估计为9.0，但最近进行的、周期更长的正常模式分析表明，其矩震级为9.3，约为前者的2.5倍。在此，我们介绍一种直接成像地震破裂的方法，该方法利用初至压缩波，有可能在破裂开始后30分钟内生成详细图像。我们利用日本的Hi-Net地震阵列作为天线，通过监测高频辐射方向来绘制滑动过程。我们发现，破裂以大约2.8千米/秒的速度向北传播约8分钟，覆盖了整个长达1300千米的余震区。与其他特大地震的余震区域相比，表明苏门答腊-安达曼地震的矩震级确实约为9.3。其破裂的持续时间和范围都是有记录以来最长的。
