Three-dimensional S-wave attenuation structure in and around source area of the 2018 Hokkaido Eastern Iburi Earthquake, Japan

Abstract

We investigate S-wave attenuation (Qs) structure in and around Hokkaido, Japan, including the source area of the 2018 Hokkaido Eastern Iburi Earthquake (M 6.7) and its aftershocks. From the strong-motion seismograms recorded in the nationwide seismograph network in Japan, we compute spectrum amplitude at 1-10 Hz with every 1 Hz and then estimate Qs structure by adopting tomographic inversion technique. The obtained Qs structure suggests that lateral variations of Qs are remarkably formed in the study areas. The low-Qs anomalies distributing north to south are imaged in both sides of the Hidaka mountain range which is built in the central Hokkaido. These characteristics structures of Qs are extended from the ground surface to depths by about 50 km, indicating that heterogeneous structures resulted from the collision of the Kuril and northeastern Japan arcs develop at the depth ranges. Around the source area of the 2018 Hokkaido Eastern Iburi Earthquake, the abrupt changes of Qs values are identified. The 2018 Hokkaido Eastern Iburi Earthquake and its aftershocks seem to be arraigned on the high-Qs zones, whereas the low-Qs anomalies are also imaged next to the high-Qs zones. The boundary of the low-and high-Qs zones lies with near vertical, corresponding to aftershock distributions of the 2018 Hokkaido Eastern Iburi Earthquake. This agreement would propose that the heterogeneities formed due to the arc-arc collision would characterize faulting processes in the main shock of the Hokkaido Eastern Iburi Earthquake and the activities of its aftershocks.

Analysis of Changes in Land Use/Land Cover and Hydrological Processes Caused by Earthquakes in the Atsuma River Basin in Japan

“…Fujiwara et al [19] identified and analyzed the surface displacements associated with earthquakes. Nakamura et al [20] investigated the S-wave attenuation (Qs) structure in and around Hokkaido, Japan, including a consideration of the source area of the earthquake and its aftershocks. Fukuda et al [21] analyzed the sleep pattern data of junior high school students on the night of a blackout after an earthquake, comparing their sleep to a normal night.…”

Near-Source Waveform Modeling to Estimate Shallow Crustal Attenuation and Radiated Energy of Mw 2.0-4.5 Earthquakes

“…However, obtaining the depth profile of the 𝑄 −1 -structure is essential for adequately understanding this effect . Previous studies have estimated 𝑄-values that vary with depth (Hough & Anderson, 1988;Lin and Jordan, 2018;Wang et al, 2023), horizontally (Eulenfeld & Wegler, 2017 ;Prudencio et al, 2018 ), and in three dimensions (Eberhart-Phillips, 2005;Hauksson & Shearer, 2006;Nakajima & Matsuzawa, 2017;Nakamura & Shiina, 2019) , with various assumptions . However, few studies have examined the depth variation of the 𝑄 −1 -structure within the crust in detail given that most available data are far from the sources (>15 km).…”