Preprints
https://doi.org/10.5194/nhess-2020-387
https://doi.org/10.5194/nhess-2020-387

  18 Feb 2021

18 Feb 2021

Review status: this preprint is currently under review for the journal NHESS.

Modelling earthquake rates and associated uncertainties in the Marmara Region, Turkey

Thomas Chartier1,2,a, Oona Scotti2, Hélène Lyon-Caen1, Keith Richard-Dinger3, James H. Dieterich3, and Bruce E. Shaw4 Thomas Chartier et al.
  • 1Ecole Normale Supérieure, PSL University, CNRS, UMR 8538 - Laboratoire de Géologie, 24 rue Lhomond, 75005 Paris, France
  • 2Bureau d’Evaluation des Risques Sismiques pour la Sûreté des Installations, IRSN, Fontenay-aux-Roses, 92262, France
  • 3Department of Earth Sciences, University of California, Riverside, 92521, California, USA
  • 4Lamont Doherty Earth Observatory, Columbia University, Palisades, NY 10025, USA
  • anow at: GEM Hazard Team, GEM Foundation, via Ferrata, 1, 27100 Pavia, Italy

Abstract. Modelling the seismic potential of active faults and the associated epistemic uncertainty is a fundamental step of probabilistic seismic hazard assessment (PSHA). We use SHERIFS (Seismic Hazard and Earthquake Rate In Fault Systems), an open-source code allowing to build hazard models including earthquake ruptures involving several faults, to model the seismicity rates on the North Anatolian Fault (NAF) system in the Marmara region. Through an iterative approach, SHERIFS converts the slip-rate on the faults into earthquake rates that follow a Magnitude Frequency Distribution (MFD) defined at the fault system level, allowing to model complex multi-fault ruptures and off-fault seismicity while exploring the underlying epistemic uncertainties. In a logic tree, we explore uncertainties concerning the locking state of the NAF in the Marmara Sea, the maximum possible rupture in the system, the shape of the MFD and the ratio of off-fault seismicity. The branches of the logic tree are weighted according to the match between the modelled earthquake rate and the earthquake rates calculated from the local data, earthquake catalogue and paleoseismicity. In addition, we use the result of the physics-based earthquake simulator RSQSim to inform the logic tree and increase the weight on the hypotheses that are compatible with the result of the simulator. Using both the local data and the simulator to weight the logic tree branches, we are able to reduce the uncertainties affecting the earthquake rates in the Marmara region. The weighted logic tree of models built in this study is used in a companion article to calculate the probability of collapse of a building in Istanbul.

Thomas Chartier et al.

Status: open (until 01 Apr 2021)

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Thomas Chartier et al.

Thomas Chartier et al.

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Short summary
In order to evaluate the seismic risk, we first model the annual rate of occurrence of earthquakes on the faults near Istanbul. By using a novel modelling approach, we consider the fault system as a whole rather than each fault individually. We explore the hypotheses that are discussed in the scientific community concerning this fault system and compare the modelled results with local recorded data and a physics based model, gaining new insights in particular on the largest possible earthquake.
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