16:00 〜 16:15
[SGD01-08] 最近の消失から拘束されるチャンドラーウォブルの低いQ：地球物理学的な意味合い
キーワード：チャンドラーウォブル、Q、非弾性、下部マントル、減衰
Yamaguchi and Furuya (2024, EPS) pointed out that the Chandler Wobble (CW) has not been excited since 2015 and further suggested that the quality factor (Q) of the CW was not as high as 100; there have been a couple of times differences even in the recently estimated Q, e.g., from 49 by Furuya and Chao (1996), 97 by Seitz et al (2012), and 127 by Nastula and Gross (2015). As long as the CW has been excited and present, we should employ the excitation data to reliably estimate the period (P) and Q of the CW (e.g., Furuya and Chao 1996). Yamaguchi and Furuya (2024), however, took advantage of the recent absence of CW to reliably constrain the upper bound of Q without using any geophysical excitation data. This was first made possible because the CW became unexcited for the first time in the observation history.
Smith and Dahlen (1981) theoretically and "quantitatively" interpreted the previous estimates of the P and Q with an emphasis on the role of lower mantle anelasticity; their preferred Q was 100. We discuss the lower Q than previously thought will suggest a need to revise/update the theory and have an implication for the lower-mantle rheology.
In terms of the excitation processes, the lower Q is also significant because its value controls the power level of the excitation sources of CW. We may consider two end members for the excitation process model. One is a Gaussian random noise, and the other is a near-resonant process with its period close to the P. The former excitation will prefer higher Q, whereas the latter does lower Q.
Smith and Dahlen (1981) theoretically and "quantitatively" interpreted the previous estimates of the P and Q with an emphasis on the role of lower mantle anelasticity; their preferred Q was 100. We discuss the lower Q than previously thought will suggest a need to revise/update the theory and have an implication for the lower-mantle rheology.
In terms of the excitation processes, the lower Q is also significant because its value controls the power level of the excitation sources of CW. We may consider two end members for the excitation process model. One is a Gaussian random noise, and the other is a near-resonant process with its period close to the P. The former excitation will prefer higher Q, whereas the latter does lower Q.