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(January, 19).

************** 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：2023年 1月 19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：2023-01-19, 14:00~
Place：Uji Campus Main Building E232D or Zoom (Hybrid)

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Speaker 1：Yanhan Chen

Title（題目）：P wave polarization of CDSN and time correction to teleseismic P wave tomography in Central Asian Orogenic Belt

Abstract（要旨）：
I will introduce my work during my master study and my research plan during my PhD study.
I mainly do some work about the P wave polarization and anisotropy of China Digtial Seismic Network. I test those seismic stations and conclude LSA’s and KMI station’s polarization and anisotropy. I used the principal component analysis method. For the three component seismic waveforms, I calculate the characteristics values by make the co-variance matrix. After concluding the characteristics values, the anisotropy in the station can be calculated by the harmonic method. The function includes the estimate of the misorientation, lateral heterogeneity and anisotropy. Limited by the back azimuth coverage, the results is not precisely, but it can reflect the anisotropy in some degree. Then I give the examples of this process. The two stations in LSA and KMI shows that a northeast direction and the Qinghai-Tibet Plateau pushed northeastward. It is speculated that the explanation is mainly lithospheric deformation. Then I take the time corrections to teleseismic P wave tomography derived from SKS in Central Asian Orogenic Belt, the SKS had been investigated, so I use other person’s result to correct the anisotropy in the isotropy tomography. By comparing the result in isotropy tomography and tomography with anisotropy corrected, I conclude the direction of isotropy in the Central Asian orogenic belt supports the NE-SW compression of the lithosphere and the dynamic model of asthenospheric flow in the region, which is speculated to be affected by the north-east far-field effect of the Tibetan Plateau.
For my PhD study work, I mainly focus on the low frequency earthquakes in Guerrero Gap. The close relationship between LFEs and tremors has been suspected with tectonic tremors suggested to be made up of a swarm of LFEs. To evaluate this relationship in Guerrero, I start from the group member’s work in detection and location tremors, by inspecting all the waveform and spectrogram, I search for the low frequency earthquakes as the family template, after that, I could get the low frequency earthquakes template, then I could detect and locate the LFEs by the envelope correlation method or other method.

Speaker 2：Ketzallina Flores

Title（題目）：Study of source of earthquakes near the Mexican subduction zone

Abstract (要旨）：
In my master thesis, I characterized the source process of the tsunami earthquake that occurred on April 18th, 2002 (Mw 6.7). It was located about 55 km off the coast of Guerrero, near to the Mesoamerican Trench. The hypocenter location (Pacheco & Singh, 2010) was just inside the Guerrero Gap, in which no large (M>7) earthquake in at least 100 years has been observed (Singh et al., 1981).
It is important to describe characteristics of earthquakes near the Mexican subduction zone toward earthquake and tsunami disaster mitigation in Mexico. To achieve this objective, I propose creating a catalog of tsunami earthquakes in the area of Mexican subduction. I plan that the catalog has parameters of source.
The catalog can help to understand the plate interface geometry and explain a mechanism of generation tsunami earthquakes in the Mexican subduction zone.

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