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Discussion papers
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 11 Jun 2019

Submitted as: research article | 11 Jun 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Natural Hazards and Earth System Sciences (NHESS).

Infrasound and seismoacoustic signatures of the September 28th 2018 Sulawesi super shear earthquake

Christoph Pilger1, Peter Gaebler1, Lars Ceranna1, Alexis Le Pichon2, Julien Vergoz2, Anna Perttu3, Dorianne Tailpied3, and Benoit Taisne3 Christoph Pilger et al.
  • 1BGR (Federal Institute for Geosciences and Natural Resources), Hannover, Germany
  • 2CEA, DAM, DIF (Commisariat à l’Energie Atomique et aux Energies Alternatives), Arpajon, France
  • 3EOS/NTU (Earth Observatory of Singapore / Nanyang Technological University), Singapore

Abstract. A magnitude 7.5 earthquake occurred on September 28th 2018 at 10:02:43 UTC near the city of Palu on the Indonesian island of Sulawesi. It was a shallow, strike-slip earthquake with fractures up to the surface and a rupture length of about 150 km. Moreover, this earthquake was identified as one of very few events having a super shear rupture speed.

Clear and long-lasting infrasound signatures related to this event were observed by four infrasound arrays of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization as well as one national infrasound station in Singapore. Although these infrasound stations SING (Singapore), I39PW (Palau), I07AU (Australia), I40PG (Papua New Guinea) and I30JP (Japan) are located in large distances between 1800 km and 4500 km from the earthquake’s epicentral region, the observed infrasound signals associated to this event were intense, including both seismic and acoustic arrivals. The seismic-to-acoustic coupling at nearby terrain features is supposed to generate distinct infrasonic signatures clearly recordable at remote infrasound arrays.

A detailed study of the event-related observations and the potential infrasound generation mechanisms is presented covering range- and time-dependent infrasound attenuation and propagation modeling, characterization of the atmospheric background conditions as well as identification of the regions of seismoacoustic activity by applying a backtracking method from the infrasound receivers to potential source regions. The back-projection of infrasonic arrivals allows to estimate that the main infrasound source region for the Sulawesi earthquake is related to the extended rupture zone and the nearby topography. This estimation and the comparison to other super shear as well as large regional earthquakes identifies no clear connection between the earthquake’s super shear nature and the strong infrasound emission.

Christoph Pilger et al.
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Christoph Pilger et al.
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Publications Copernicus
Short summary
This paper provides infrasound data analysis, modeling and interpretation of the source characteristics of the 28 September 2018 Magnitude 7.5 Sulawesi earthquake. Epicentral ground movement by the earthquake rupture as well as the secondary shaking of nearby mountaineous topography is responsible for the strong infrasound generated. Findings allow to improve the knowledge about infrasonic and seismoacoustic source processes and the monitoring capabilities of the infrasound arrays used.
This paper provides infrasound data analysis, modeling and interpretation of the source...