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 23).

************** 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：2021年 12月 23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：2021-12-23, 14:00~
Place：Uji Campus Main Building E232D or Zoom (Hybrid)

====

Speaker 1 (発表者 1)：宮澤 理稔

Title (題名)：話題提供：今年の日本の地震を振り返る
　　　　　　Small talk: Earthquakes in Japan in 2021

Abstract (要旨)：
2021年も残すところあと僅か、今年も大中規模地震が日本で発生しました。そんな地震を地震学的視点から振り返ってみたいと思います。
Some moderate-to-large earthquakes were observed in Japan this year.
In this short talk, we (re)visit these earthquakes based on seismological insights.

............................................................................................................................................................
Presenter 2 (発表者 2)：MPUANG Admore

Title (題名)：Inversion for shallow dipping and anisotropic structures beneath Botswana: method development and application

Abstract (要旨)：
In receiver function analysis, velocity models developed under the assumption of horizontal isotropic interfaces suffer inaccuracies in the presence of dipping and anisotropic structures. In such cases, the receiver functions exhibit back-azimuthal variation of amplitude and delay time. Such features of receiver functions have been observed in records from stations located in the Okavango rift zone and Limpopo belt in Botswana. We consider the presence of dipping and anisotropic structures at shallow crustal depths in an attempt to redefine the seismic structure beneath the different tectonic regions in Botswana. We first apply a harmonic decomposition to 3Hz receiver functions to constrain the presence of dipping and anisotropic structures in the shallow crust. The harmonic stacks indicate the presence of shallow dipping interfaces or plunging anisotropy in the Limpopo belt. To differentiate between the two, we apply a genetic algorithm inversion technique developed in this study to quantify the crustal velocities, the magnitudes and orientations of dip and anisotropy in the shallow crust. The inversion technique uses a mass extinction concept and a new selection technique to avoid some drawbacks of the classic genetic algorithm inversion technique such as stagnation of the optimization process towards the end of a run. Preliminary inversion results suggest the presence of a steeply plunging anisotropic axis in metasedimentary layers overlying a SW dipping granite-greenstone basement beneath a station in the Limpopo belt.

====