Preprints
https://doi.org/10.5194/nhess-2021-369
https://doi.org/10.5194/nhess-2021-369

  02 Dec 2021

02 Dec 2021

Review status: this preprint is currently under review for the journal NHESS.

Characteristics of two tsunamis generated by successive Mw 7.4 and Mw 8.1 earthquakes in Kermadec Islands on March 4, 2021

Yuchen Wang1,a, Mohammad Heidarzadeh2, Kenji Satake1, and Gui Hu3 Yuchen Wang et al.
  • 1Earthquake Research Institute, The University of Tokyo, Tokyo, 113-0032, Japan
  • 2Department of Civil and Environmental Engineering, Brunel University London, Uxbridge, UB8 3PH, UK
  • 3Guangdong Provincial Key Laboratory of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-Sen University, Guangzhou, 510275, China
  • anow at: Japan Agency for Marine–Earth Science and Technology, Kanazawa, Yokohama, 236-0001, Japan

Abstract. On March 4, 2021, two tsunamigenic earthquakes (Mw 7.4 and Mw 8.1) occurred successively within 2 h in Kermadec Islands. We examined sea level records at tide gauges located at ~100 km to ~2,000 km from the epicenters, conducted Fourier and Wavelet analyses as well as numerical modelling of both tsunamis. Fourier analyses indicated that the energy of the first tsunami is mainly distributed in the period range of 5–17 min, whereas it is 8–28 min for the second tsunami. Wavelet plots showed that the oscillation of the first tsunami continued even after the arrival of the second tsunami. As the epicenters of two earthquakes are close (~ 55 km), we reconstructed the source spectrum of the second tsunami by using the first tsunami as the empirical Green’s function. The main spectral peaks are 25.6 min, 16.0 min, and 9.8 min. The results are similar to those calculated using tsunami/background ratio method and also consistent with source models.

Yuchen Wang et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2021-369', Alexander Rabinovich, 20 Dec 2021 reply
    • AC1: 'Reply on RC1', Yuchen Wang, 07 Jan 2022 reply
    • AC2: 'Reply on RC1', Yuchen Wang, 07 Jan 2022 reply
  • RC2: 'Comment on nhess-2021-369', Anonymous Referee #2, 27 Dec 2021 reply
    • AC3: 'Reply on RC2', Yuchen Wang, 07 Jan 2022 reply

Yuchen Wang et al.

Yuchen Wang et al.

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Short summary
Tsunami waveforms contain the features of its source, propagation path, and local topography. On March 4, 2021, two tsunamis were generated by earthquakes in Kermadec Islands, New Zealand within two hours. This rare case gives us a valuable opportunity to study the characteristics of two tsunamis. We analyzed the records of two tsunamis at tide gauges by spectral analysis tools. It is found that two tsunamis superpose during the few hours after the arrival of the second tsunami.
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