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2022年9月18日 台湾台東地方の地震 (ML6.8)
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この地震は台湾東部・台東県池上で発生し、最大震度6(台湾の震度階）の強い地震動が観測されました。 被害にあわれました皆様にお見舞い申し上げます。

我々は、台湾気象局および台湾中央研究院の強震記録を分析しました。日本の気象庁の震度に換算すると、震源近傍では最大震度6弱の強い揺れが観測されていました。また、最大速度は3成分合成で100kineを超え、周期が5秒程度のパルス状の揺れが観測されました。

日本の緊急地震速報で利用されているIPF法を適用して、地震の早期検知の可能性をシミュレーションしました。この観測網のデータを利用した場合、地震発生の5秒後には震源を精度よく推定することが出来ました。

我々は、2018年の花蓮地震でも台湾中央気象局と緊急地震速報の共同研究を行っており、その成果は論文としてまとめられています。(参考論文)

This earthquake occurred in Chishang, Taitung County, eastern Taiwan, and strong seismic shakings with a maximum intensity of 6 (in Taiwan's seismic intensity scale) were observed.

We have analyzed the strong-motion records of the Taiwan Central Weather Bureau and the Academia Sinica. The maximum intensity of the quake was 6-lower on the JMA seismic intensity scale. In addition, a pulse-like ground motion with a maximum velocity exceeding 100 kine and a period of about 5 seconds were observed.

We applied the IPF method used in Japan's earthquake early warning system to simulate the possibility of early detection of this earthquake. Using data from this observation network, we were able to accurately estimate the epicenter 5 seconds after the earthquake.

We also collaborated with the Central Weather Bureau of Taiwan for the 2018 Hualien earthquake on the Earthquake Early Warning system, the results of which are summarized in a paper. (reference)

1.地震について (Earthquake Information)

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   2022/09/18 06:44:15 23.14 121.2 7.0 6.8
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Table1. Earthquake information. Origin time (UTC), Epicentral latitude, longitude, depth, and local magnitude from the left.(ref. CWB catalog)


Fig.1. Event location.



2.観測点分布 (Station Distribution)


Fig.2. Station Distribution.



3.緊急地震速報発信状況 (Earthquake Early Warning Report)

台湾中央気象局による地震の内容

4.観測記録 (Observed Records)


Fig.3. Peak Ground Acceleration (left) and Peak Ground Velocity (right).


Fig.4. JMA shaking intensity.


Fig.5. Example of the velocity waveforms at the EYUL station (cm/s). The epicenter distance is about 20 km.

5.解析結果 (Analytical Result)


Fig.6. Time history of the estimates for source parameters by the IPFx method. The horizontal axis shows the time of processing.
- upper left: error of epicenter against the final estimation
- upper right: JMA magnitude (black) and maximum estimated shaking intensity (red)
- lower left: epicenter depth
- lower right: automatic picking time (black) and theoretical arrival time (red)


Fig.7. Simulation of the IPFx method. The triangles show seismic stations, and colored triangles are triggered stations. The star shows the estimated location of an earthquake. The color of the samples is proportional to the likelihood of the hypocenter location.
Fig.8. The waveforms aligned from the epicenter estimated by the IPFx method.

References:
  • Chung-Che Chou, Chiun-Lin Wu, Juin-Fu Chai, George C. Yao (2022). Reconnaissance Report on Seismic Damage Caused by Guanshan Earthquake and Chihshang Earthquake, Taiwan, 2022 (third edition, v3.0), NCREE, Taiwan. Website
  • 台灣地震科學中心 教育推廣委員會 (2022). 2022-09-17 ML 6.4 關山地震 與2022-09-18 ML 6.8 池上地震 Website
  • Yamada, M., K. Tamaribuchi, and S. Wu (2021). IPFx: Extended integrated particle filter method for achieving high-performance earthquake early warning system. Bulletin of the Seismological Society of America, 111(3), pp.1263-1272, https://doi.org/10.1785/0120210008, 2021.05. journal
  • Yamada, M. and J. Mori (2021). P-wave picking for earthquake early warning: Refinement of a Tpd method, Geophysical Journal International, ggab349, https://doi.org/10.1093/gji/ggab349, 2021.08. journal
  • Yamada, M. and D.-Y. Chen (2022). Automatic Hypocenter Determination with the IPFx method for the 2018 Hualien earthquake sequence. Terrestrial, Atmospheric and Oceanic Sciences, 33:18. https://doi.org/10.1007/s44195-022-00018-y 2022.06. journal


    • Acknowledgements:
    台湾中央気象局の地震情報、波形記録 (https://gdmsn.cwb.gov.tw/dataDownload.php)、Palertの波形記録(https://palert.earth.sinica.edu.tw/index_e.php)を利用しました。

    緊急地震速報を発表した地震の解析結果
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