EGU21-924, updated on 22 Dec 2023
https://doi.org/10.5194/egusphere-egu21-924
EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Multiple pulses in lacustrine turbidites reveal earthquake doublets

Katleen Wils1, Maxim Deprez2, Catherine Kissel3, Morgan Vervoort1, Maarten Van Daele1, Mudrik R. Daryono4, Veerle Cnudde2,5, Danny H. Natawidjaja4, and Marc De Batist1
Katleen Wils et al.
  • 1Ghent University, Renard Centre of Marine Geology, Department of Geology, Gent, Belgium (katleen.wils@ugent.be)
  • 2PProGRess/UGCT, Department of Geology, Ghent University, Belgium
  • 3Laboratoire des Sciences du Climat et de l’Environnement, Université Paris-Saclay, France
  • 4Research Center for Geotechnology, Indonesian Institute of Sciences (LIPI), Indonesia
  • 5Environmental Hydrogeology, Department of Earth Sciences, Utrecht University, Princetonlaan 8a, 3584 CB Utrecht, The Netherlands

Earthquake doublets form a particular challenge for seismic hazard assessment and can provide insights into potentially characteristic fault behaviour. However, knowledge on this type of earthquake sequences is limited to information provided by historical archives as their identification in paleoseismic records is ambiguous. The continuous sedimentation records provided by lacustrine settings might be able to resolve closely-timed earthquakes, but confident identification of earthquake doublets has, up to now, not been made. To reveal the potential of these high-resolution records, we perform a detailed analysis of a multi-pulsed turbidite that has been identified in the sedimentary infill of Lake Singkarak and that was generated by the March 2007 West Sumatra earthquake doublet (i.e. two Mw>6 shocks on adjacent fault segments at 2 hours apart). In order to distinguish non-synchronously generated pulses in this turbidite (different earthquake, same turbidite source area) from those that are potentially synchronously-generated (same earthquake, different turbidite source areas), we develop a new methodology that allows analysing paleoflow directions by using grain-size analysis, natural remanent magnetization measurements and high-resolution X-ray computed tomography. Combining these techniques allows us to reveal the absolute geographical orientation of elongated grains, which are considered to be deposited aligned to the dominant paleoflow direction. Application to the 2007 turbidite in Lake Singkarak allows identifying the presence of non-synchronously generated pulses, thus confirming that each earthquake in the 2007 West Sumatra doublet triggered separate turbidity currents in the lake. Our study thus underscores the invaluable sensitivity of lacustrine paleoseismic records and outlines a promising methodology to analyse previously-described multi-pulsed lacustrine turbidites to reveal the occurrence of, up to now, unknown earthquake doublets.

How to cite: Wils, K., Deprez, M., Kissel, C., Vervoort, M., Van Daele, M., Daryono, M. R., Cnudde, V., Natawidjaja, D. H., and De Batist, M.: Multiple pulses in lacustrine turbidites reveal earthquake doublets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-924, https://doi.org/10.5194/egusphere-egu21-924, 2021.

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