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(April, 20).

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

科目：地震学ゼミナールIV A, C / Seminar on Seismology IV A, C（修士・博士）
日時：2023年 4月 20日 (木) 13:15~
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: 2023-04-20, 13:15~
Place: Uji Campus Main Building E232D or Zoom (Hybrid)

　　　　Please join the seminar on-site, especially students who need credit.

Speaker: Admore Mpuang

Title: Investigating crust and upper mantle structures beneath Botswana, southern Africa.

Abstract:
There has been debate on whether the terminus of the southwesterly branch of the East African Rift System lies in Botswana's north and SE regions. Recent improvements in seismic coverage provide a potential for new insights into the tectonic and geodynamic nature of this region. To this end, we carried out investigations into intra-crustal structures assuming an isotropic crust, shallow dipping and anisotropic crustal structures as well as azimuthal anisotropy in the crust and upper mantle. Our investigations used receiver functions and ambient noise analysis techniques. Intra-crustal structures reveal a region of low Vs at middle crustal depths where seismicity is observed, while results from shallow structure investigations show no evidence of rift related stresses in the shallow crust but are rather consistent with the observed geology. Azimuthal anisotropy fast directions parallel to the respective fault systems in the crust suggest the presence of crustal fabrics related to the stresses that cause the observed seismicity, but they change directions with depth into the upper mantle. Our results are consistent with a geodynamic model in which relative motion of crustal blocks has activated pre-existing weak zones in the crust, allowing fluid infiltration from uppermantle depths which promotes brittle deformation.