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

Yuchen Wang; Mohammad Heidarzadeh; Kenji Satake; Gui Hu

doi:10.5194/nhess-22-1073-2022

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

Yuchen Wang, Mohammad Heidarzadeh, Kenji Satake, Gui Hu

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Abstract

On 4 March 2021, two tsunamigenic earthquakes (Mwg 7.4 and Mwg 8.1) occurred successively within 2g h in the Kermadec Islands, offshore New Zealand. We examined sea level records at tide gauges located at g 1/4100 to g 1/42000g km from the epicenters, conducted Fourier and wavelet analyses as well as numerical modeling of both tsunamis. Fourier analyses indicated that the energy of the first tsunami is mainly distributed over the period range of 5-17g min, whereas it is 8-32g min for the second tsunami. Wavelet plots showed that the oscillations of the first tsunami continued even after the arrival of the second tsunami. As the epicenters of two earthquakes are close to each other (g 1/455g 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, 16.0, and 9.8g min. The results are similar to those calculated using tsunami-To-background ratio method and are also consistent with the source models.

Original language	English
Pages (from-to)	1073-1082
Number of pages	10
Journal	Natural Hazards and Earth System Sciences
Volume	22
Issue number	3
DOIs	https://doi.org/10.5194/nhess-22-1073-2022
Publication status	Published - 1 Apr 2022

Bibliographical note

Funding Information:
Acknowledgements. We thank Takane Hori and Kentaro Imai from the Japan Agency for Marine-Earth Science Technology for their valuable suggestions. Mohammad Heidarzadeh is funded by the Royal Society (the United Kingdom), grant no. CHL\R1\180173. Yuchen Wang is funded by the Japan Society for the Promotion of Science, grant no. 19J20293.

Funding Information:
Financial support. This research has been supported by the Japan

Funding

Acknowledgements. We thank Takane Hori and Kentaro Imai from the Japan Agency for Marine-Earth Science Technology for their valuable suggestions. Mohammad Heidarzadeh is funded by the Royal Society (the United Kingdom), grant no. CHL\R1\180173. Yuchen Wang is funded by the Japan Society for the Promotion of Science, grant no. 19J20293. Financial support. This research has been supported by the Japan

ASJC Scopus subject areas

General Earth and Planetary Sciences

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title = "Characteristics of two tsunamis generated by successive Mwg 7.4 and Mwg 8.1 earthquakes in the Kermadec Islands on 4 March 2021",

abstract = "On 4 March 2021, two tsunamigenic earthquakes (Mwg 7.4 and Mwg 8.1) occurred successively within 2g h in the Kermadec Islands, offshore New Zealand. We examined sea level records at tide gauges located at g 1/4100 to g 1/42000g km from the epicenters, conducted Fourier and wavelet analyses as well as numerical modeling of both tsunamis. Fourier analyses indicated that the energy of the first tsunami is mainly distributed over the period range of 5-17g min, whereas it is 8-32g min for the second tsunami. Wavelet plots showed that the oscillations of the first tsunami continued even after the arrival of the second tsunami. As the epicenters of two earthquakes are close to each other (g 1/455g 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, 16.0, and 9.8g min. The results are similar to those calculated using tsunami-To-background ratio method and are also consistent with the source models. ",

author = "Yuchen Wang and Mohammad Heidarzadeh and Kenji Satake and Gui Hu",

note = "Funding Information: Acknowledgements. We thank Takane Hori and Kentaro Imai from the Japan Agency for Marine-Earth Science Technology for their valuable suggestions. Mohammad Heidarzadeh is funded by the Royal Society (the United Kingdom), grant no. CHL\R1\180173. Yuchen Wang is funded by the Japan Society for the Promotion of Science, grant no. 19J20293. Funding Information: Financial support. This research has been supported by the Japan ",

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N1 - Funding Information: Acknowledgements. We thank Takane Hori and Kentaro Imai from the Japan Agency for Marine-Earth Science Technology for their valuable suggestions. Mohammad Heidarzadeh is funded by the Royal Society (the United Kingdom), grant no. CHL\R1\180173. Yuchen Wang is funded by the Japan Society for the Promotion of Science, grant no. 19J20293. Funding Information: Financial support. This research has been supported by the Japan

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N2 - On 4 March 2021, two tsunamigenic earthquakes (Mwg 7.4 and Mwg 8.1) occurred successively within 2g h in the Kermadec Islands, offshore New Zealand. We examined sea level records at tide gauges located at g 1/4100 to g 1/42000g km from the epicenters, conducted Fourier and wavelet analyses as well as numerical modeling of both tsunamis. Fourier analyses indicated that the energy of the first tsunami is mainly distributed over the period range of 5-17g min, whereas it is 8-32g min for the second tsunami. Wavelet plots showed that the oscillations of the first tsunami continued even after the arrival of the second tsunami. As the epicenters of two earthquakes are close to each other (g 1/455g 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, 16.0, and 9.8g min. The results are similar to those calculated using tsunami-To-background ratio method and are also consistent with the source models.

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

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