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巨大的2004年亚齐?苏门答腊地震是自1960年智利特大地震和1964年阿拉斯加特大地震以来记录的最大地震。地球自由振荡得到很强的激发,并被大量台站记录到,其信噪比极好,即便低频的振型也如此。这些特殊振型非常有意义,因为这些分隔良好的分裂自由振荡的相位携带了有关大地震(Mw>8)震源的运动学信息,尤其是有关长度、持续时间和平均破裂速度的信息。使用单峰剥离技术,我们研究了几个宽带永久台站[地球透镜、地震学联合研究协会(IRIS)和全球地球动力学计划(GGP)]记录的一些地球最低频自由振荡(0S2、0S3、0S4、1S2、0S0和1S0),以恢复各个单峰参数:相位、频率和品质因子。我们使用这些参数约束了2004年12月26日苏门答腊地震和2005年3月28日尼亚斯地震的震源时空展布。我们主要使用地震仪和超导重力仪的垂直分量数据,因为这些数据的噪声比水平地震数据低,但我们还需指出,对2004年地震也可使用水平分量(1S2)。根据本文给出的初始相位测量结果,我们得到2004年地震断层长度约为1250km,持续时间约为550s。对于2005年地震,我们测定所倾向的模型是,南段约40s之后破裂,但破裂的双向性质及其空间尺度使我们不能适当地约束其空间范围。
The huge 2004 Aceh-Sumatra earthquake was the largest one ever recorded since the great earthquake in Chile in 1960 and the Alaskan Grand Earth in 1964. Earth’s free oscillations are strongly motivated and recorded by a large number of stations with excellent signal-to-noise ratios, even at low frequencies. These special modes are of great interest as these well-separated phases of free-oscillation oscillate carry kinematic information about the focal point of a large earthquake (Mw> 8), especially information on length, duration and average rate of rupture. Using unimodal debonding, we studied some of the lowest earth-frequency free oscillations recorded by several broadband permanent stations [the Association of Earth’s Seismology, IRIS and GGP] (0S2, 0S3, 0S4, 1S2, 0S0 and 1S0) to recover individual unimodal parameters: phase, frequency and quality factor. We use these parameters to constrain the source spatiotemporal distribution of the Sumatra Earthquake on December 26, 2004 and the Nias Earthquake on March 28, 2005. We mainly use the vertical component data of seismometers and superconducting gravimeters because the noise of these data is lower than the horizontal seismic data. However, we also point out that the horizontal component (1S2) can also be used for the 2004 earthquake. According to the initial phase measurements given in this paper, we get the 2004 earthquake fault length of about 1250km, duration of about 550s. For the 2005 earthquake, the model we tended to determine was that the southern section ruptured after about 40 s, but the bi-directional nature of the rupture and its spatial scale prevented us from properly constraining its spatial extent.