open access

https://doi.org/10.14943/gbhu.88.33

https://hdl.handle.net/2115/94327

Investigation of seismic attenuation features in Akan-Kussharo region with MLTWA method

日本語

2025-03

北海道大学大学院理学研究院

Geophysical bulletin of Hokkaido University

88

33-52

The Akan-Kussharo region hosts post-caldera volcano groups which continue to experience active volcanism, as confirmed though GNSS observations. Over the past decades, seismic observations have contributed to understanding the subsurface structure, leading to studies on hypocenter distribution, velocity structure and attenuation structure. However, research on velocity and attenuation structures has been only primarily conducted as part of broader studies covering all of Hokkaido, Japan or studies in other regions, so that the relation between seismic attenuation characteristics and volcanic activity has not been fully elucidated yet. In this paper, we aim to uncover the features of seismic attenuation in Akan-Kussharo region through separated attenuation parameters, intrinsic and scattering attenuation, by using the MLTWA (Multiple Lapse Time Window Analysis) method with the data obtained by the Hi-net seismic network. Overall, this area shows as strong scattering and intrinsic attenuation as in other volcanic areas and seismically active regions such as Hawaii, Long Valley and southern Spain. Furthermore, temporal variations in attenuation parameters are presented over 2010-2023. However, these variations did not sufficiently clarify the relationship with the observed ground deformation. Instead, they might have been caused by differences in the hypocenter distribution and the mechanisms of the selected events, or by the inaccurate separation of scattering and intrinsic attenuation. In addition, we reveal approximate 30% of event waveforms stored in the seismic recording system in Hokkaido University are applicable to MLTWA in current seismic network. Although this study provides valuable insights into the attenuation characteristics in Akan-Kussharo region, we need further research to explore the association with temporal subsurface structural changes in more detail.

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Creative Commons Attribution-NonCommercial 4.0 International

0439-3503

AN0008976X