27 Apr 2022
27 Apr 2022
Status: a revised version of this preprint is currently under review for the journal NHESS.

Characteristics of consecutive tsunamis and resulting tsunami behaviors in southern Taiwan induced by the doublet earthquakes on 26 December 2006

An-Chi Cheng1,2, Anawat Suppasri2,3, Kwanchai Pakoksung3, and Fumihiko Imamura2,3 An-Chi Cheng et al.
  • 1Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, 6-6-06 Aoba, Aramaki-Aza, Aoba, Sendai 980-0845, Japan
  • 2WISE Program for sustainability in the Dynamic Earth, Tohoku University, 6-3 Aoba, Aramaki Aza, Aoba, Sendai 980-8578, Japan
  • 3International Research Institute of Disaster Science, Tohoku University, 468-1 Aoba, Aramaki-Aza, Aoba, Sendai 980-0845, Japan

Abstract. Consecutive Mw 7.0 and Mw 6.9 submarine earthquakes occurred offshore Hengchun Peninsula, Taiwan on 26 December 2006. A small tsunami was generated, and recorded at tide gauge stations for the first time. This important event attracted public interest as it was generated by doublet sources and demonstrated tsunami risk in Taiwan. This study analyzed tide gauge tsunami waveforms and numerical simulations to understand the source characteristics and resulting tsunami behaviors. The maximum wave heights at three stations were 0.08 m (Kaohsiung), 0.12 m (Dongkung), and 0.3 m (Houbihu), and only Houbihu recorded the first wave crest as the largest. The tsunami durations were 3.9 h at Dongkung, and more than 6 h at Kaohsiung and Houbihu. Spectral analyses detected dominant periodic components of spectral peaks on tsunami waveforms. The period band from 15.5–26.6 min was identified as the tsunami source spectrum, and the approximate source area for the consecutive tsunamis was constrained to be 800 km2. Comparing the simulated tsunami waveforms to observed tsunami waveforms showed that the GCMT focal mechanisms explained the observations at all three stations better than the USGS solutions. Numerical simulations based on real and hypothetical bathymetry examined its influence on the transmission of tsunami waves. The results revealed that wave trapping was connected to wave refraction caused by bathymetry. Trapped waves interfered with incident waves at shelf edges amplified tsunami waves and prolonged oscillations, which explained unusual observations recorded by the tide gauges. These elucidate the generation of the consecutive 2006 tsunamis, and consequent tsunami behaviors in southern Taiwan, contributing essential knowledge for tsunami warning and coastal emergency response in Taiwan to reduce disaster risk.

An-Chi Cheng et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on nhess-2022-126', Anonymous Referee #1, 15 May 2022
    • AC1: 'Reply on RC1', An chi Cheng, 20 Jul 2022
    • AC3: 'Reply on RC1', An chi Cheng, 21 Jul 2022
  • RC2: 'Comment on nhess-2022-126', Anonymous Referee #2, 26 May 2022
    • AC2: 'Reply on RC2', An chi Cheng, 20 Jul 2022

An-Chi Cheng et al.

An-Chi Cheng et al.


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Short summary
Consecutive earthquakes occurred offshore southern Taiwan on the 26 December 2006. This event revealed unusual tsunami generation, propagation, as well as unexpected consequences at the coast (i.e., amplified waves and prolonged durations). This study aims to elucidate the tsunami source characteristics, and the important behaviors responsible for tsunami hazards in insular countries of Taiwan such as wave trapping, edge waves, and shelf resonance.