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, 24).

************** 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：2025年 4月 24日 (木) 13:30~
場所：京都大学 防災研究所 本館E-232D

Date and Time：2025-04-24, 13:30~
Place：Uji Campus Main Building E232D

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Speaker 1（発表者）:　武田七海（Natsumi TAKEDA）

Title（題目）:
Enhancing Earthquake Forecasting: Incorporating Expanded SSE Data into ETAS Models

Abstract（要旨）:
The Hikurangi subduction zone in New Zealand frequently experiences Slow Slip Events (SSEs), which can influence earthquake occurrence. While the ETAS model does not account for these effects, a modified version by Nishikawa and Nishimura (2023) introduced an SSE-triggering function but included only three events.
This study expands the SSE dataset by automatically detecting events in GNSS data using the ΔAIC method from Nishimura et al. (2013). We identified 65 events from 2006 to 2024, including previously unstudied ones. Fault parameters and slip rates were estimated using DC3D (Okada, 1992). Duration was determined separately by stacking data from significant stations, fitting a double-hinged line, and conducting a grid search from 3 to 45 days.
While uncertainties remain due to broad parameter bounds and a simplified fault model, future work will refine these estimates, incorporate more realistic geometries, and assess SSE-earthquake relationships to further improve ETAS forecasting.

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Speaker 2（発表者）:　Ketzallina Flores Ibarra

Title（題目）:
Study of Scaled Energy at Mexico, Central America and South America

Abstract（要旨）:
Subduction zones are regions where one tectonic plate slides beneath another. This process generates various types of earthquakes, including interplate, tsunami, intraplate, and deep earthquakes. These different types of subduction zone earthquakes exhibit variations in the frequency content of the seismic energy they release (Venkataraman and Kanamori, 2004). For instance, tsunami earthquakes (Kanamori, 1972) occur in the shallow portions of subduction zones. An example of this type of event is the earthquake that occurred on April 18, 2002, in Guerrero, Mexico, which displayed characteristics typical of a tsunami earthquake despite its relatively small magnitude (Mw 6.7).
Tsunami earthquakes are deficient in high-frequency energy; however, they release significantly larger amounts of slip compared to ordinary subduction zone earthquakes. Despite their seismological similarities, there is currently no universally accepted model that explains the structural or morphological conditions around these faults that favor the generation of large tsunamis with minimal ground shaking (Sallares and Ranero, 2019).
The ratio of seismic energy to seismic moment, known as scaled energy, can be interpreted as the radiated energy per unit area and per unit slip on the fault plane (Izutani and Kanamori, 2001). Newman and Okal (1998) demonstrated that scaled energy, calculated from observed waveforms, is one of the most effective discriminants for identifying tsunami earthquakes. These events typically exhibit scaled energy values ranging from 7×10⁻⁷ to 3×10⁻⁶ (Venkataraman and Kanamori, 2004).
In this study, we estimate radiated seismic energy from teleseismic P-waves using the methodology proposed by Pérez-Campos et al. (2003). We calculate the scaled energy of events occurring near subduction zones in Mexico, Central America, and South America. We then compare the average values for each region with those reported by other authors. On the other hand, Bilek, Lay, and Ruff (2004) reported a weak correlation between scaled energy and depth in Chile, Peru, and Mexico—a relationship we also examine in this work.

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