今週のうなぎセミナーについてお知らせいたします。

Here is information of the Unagi-seminar(December, 8).

************** Seminar on Seismology IV B, D /地震学ゼミナールIV B, D (Unagi Seminar) **************

科目：地震学ゼミナールIV B, D / Seminar on Seismology IV B, D（修士・博士）
日時：2022年 12月 8日 (木) 14:00~
場所：京都大学 防災研究所 本館E-232D または オンライン(Zoom)

Date and Time：2022-12-8, 14:00~
Place：Uji Campus Main Building E232D or Zoom (Hybrid)

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Speaker: Admore Mpuang

Title: Azimuthal anisotropy in the crust and upper mantle of Botswana's seismogenic regions from analysis of ambient noise.

Abstract:
Botswana is thought to host the terminus of the southwesterly branch of the East African Rift System in the country's North and SE regions. Despite the observation of a low-velocity region connecting the two regions, the regional stress relationship between the two regions remains elusive, and efforts to reconcile the source(s) of the observed seismicity have been mostly inconclusive. In this study, we explore the relationship between the two regions by studying the azimuthal anisotropy induced on Rayleigh waves phase velocity measurements. Measurements at different periods are considered in order to analyze the depth variation of the anisotropy and enable a reconstruction of the regional stress state. Results from anisotropic eikonal tomographic inversion indicate fast directions parallel to the respective fault systems in the crust, suggesting crustal fabrics related to the stresses that cause the observed seismicity. The fast directions change direction with depth down into the upper-most mantle in a divergence-like mechanism, whose axis is a zone of lower velocity. We propose a geodynamic model to explain the observed anisotropy as well as rift initiation mechanism.

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