New Insights into the Source of the Makran Tsunami of 27 November 1945 from Tsunami Waveforms and Coastal Deformation Data

Mohammad Heidarzadeh, Kenji Satake

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65 Citations (SciVal)

Abstract

We constrain the source of the 27 November 1945 tsunami in the Makran Subduction Zone (MSZ) using available tsunami waveforms recorded on tide gauges at Mumbai (India) and Karachi (Pakistan), and that inferred at Port Victoria (Seychelles), and coseismic deformation data along the Makran coast. Spectral analysis of the tsunami waveforms shows that the tsunami governing period was 40–50 min at Karachi whereas it was around 22 min at Mumbai. The inferred tsunami waveform at Port Victoria also indicated a period of around 21 min for the tsunami. Tsunami numerical simulations from the previously proposed source models failed in reproducing the observed tsunami waveforms and coseismic deformation data. Sensitivity analysis showed that the source fault needs to be extended offshore into deep water in order to reproduce the first 22-min signal at Mumbai. Based on the inversion of the observed tsunami waveforms, we propose a four-segment fault with varying slip amounts as the final source. This source includes a slip of 4.3 m onshore near Ormara (Pakistan) and a slip of 10 m offshore at water depth of around 3,000 m. The total fault length is 220 km, and the average slip is 6.1 m. This source, first, reproduces fairly well the observed tide gauge records at Mumbai and Karachi, second, produces ~1 m of uplift at Ormara and ~1 m of subsidence at Pasni, and third, gives a moment magnitude of 8.3 for the earthquake, which is in the acceptable range of seismic data. The computed 1 m uplift at Ormara is in the uplift range of 1–3 m reported in the literature. As the tide gauge stations were located in the far field, our proposed source explains mainly the tectonic source of the tsunami.

Original languageEnglish
Pages (from-to)621-640
Number of pages20
JournalPure and Applied Geophysics
Volume172
Issue number3-4
DOIs
Publication statusPublished - 31 Mar 2015

Bibliographical note

Funding Information:
oratory was supported by grants from the Austrian Science Fund (FWF, grants No. P11403-MED, P10416-MED, and P13049-MED), by Sankyo (Tokyo, Japan), Boehringer Mannheim/ LaRoche (Mannheim, Germany), and Johnson and Johnson (Raritan, NJ, USA). The authors are grateful to B. Brunmair, F. Gras, S. Neschen, M. Roden, P. Nowotny and many other staff colleagues who contributed to this research.

Publisher Copyright:
© 2014, Springer Basel.

Keywords

  • coseismic deformation
  • Fourier analysis
  • Makran earthquake of 27 November 1945
  • Makran Subduction Zone
  • spectral analysis
  • tsunami
  • tsunami waveform inversion
  • wavelet analysis

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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