Constraint on the focal mechanism of the 2011 Tohoku earthquake from the radial modes
Constraint on the focal mechanism of the 2011 Tohoku earthquake from the radial modes
复制标题
DOI：
10.1016/j.geog.2023.04.002
复制
发表时间：
2023-06
影响因子：
2.4
通讯作者：
Weikun Chen;H. Ding
中科院分区：
文献类型：
--
作者：
Weikun Chen;H. Ding
与地球自由振动的其他简正模态依赖于质心矩张量的所有六个分量（Mrr、Mtt、Mpp、Mrt、Mrp和Mtp）不同，径向模态的振幅依赖于Mrr分量（例如，标量矩（M0）、倾角（δ）和滑动（λ））和震源深度，从而可以很容易地用来约束震源机制的这些参数。本文利用2011年日本东北大地震后超导重力仪（SG）记录，分析了0 S 0和1 S 0径向模。根据GCMT和USGS给出的聚焦机制解，我们可以得到这两种径向模的理论振幅。对比理论振幅和观测振幅发现，两者之间存在明显差异，说明GCMT和USGS的震源机制不能很好地代表2011年事件的真实的震源机制。以GCMT解为参考，改变深度和Mrr矩中的三个参数，标量矩（M0）和倾角（δ）的影响显著，而滑移量（λ）和深度的影响较小。通过比较，我们给出了2011年地震震源机制解的新约束条件（M0= 5.8 ± 0.09 × 1022 N·m，δ= 10.1 ± 0.08°，λ= 88°，深度= 20 km）。此外，我们还进一步确定了1 S 0模的中心频率（1.631567 ± 2.6e-6 mHz）和品质因数（2046.4± 50.1）。
Different from other normal modes of the Earth's free oscillation that depend on all the six components (Mrr,Mtt,Mpp,Mrt,Mrp, andMtp) of the centroid moment tensor, the amplitudes of the radial modes depend on theMrrcomponent (e.g., scalar moment (M0), dip (δ), and slip (λ)) and hypocenter depth of the focal mechanism, and hence can be easily used to constrain these parameters of the focal mechanism. In this study, we use the superconducting gravimeter (SG) records after the 2011 Tohoku earthquake to analyze the radial modes0S0and1S0. Based on the solutions of the focal mechanism provided by the GCMT and USGS, we can obtain the theoretical amplitudes of these two radial modes. Comparing the theoretical amplitudes with the observation amplitudes, it is found that there are obvious differences between the former and the latter, which means that the GCMT and USGS focal mechanisms cannot well represent the real focal mechanism of the 2011 event. Taking the GCMT solution as a reference and changing the depth and the three parameters of theMrrmoment, the scalar moment (M0) and the dip (δ) have significant influences, but the effects of the slip (λ) and the depth are minor. After comparisons, we provide a new constraint (M0= 5.8 ± 0.09 × 1022N·m,δ= 10.1 ± 0.08°,λ= 88°, and depth = 20 km) for the focal mechanism of the 2011 event. In addition, we further determine the center frequency (1.631567 ± 2.6e-6mHz) and quality factor (2046.4± 50.1) of the1S0mode.