Series of six figures showing recovered fault geometry and slip models, from early to late stages in the inversion procedure.
Snapshots of recovered fault geometry and slip models, from early to late stages in the inversion procedure, showing progressive convergence towards one of the most probable fault and slip solution well explaining surface data observations. Note the non-planar fault geometry. Credit: Dutta et al. [2021], Figure 8
Source: Journal of Geophysical Research: Solid Earth

The increasing density and accuracy of geodetic measurements of earthquake-related movements of the Earth’s surface can improve our understanding of the physics of earthquakes, a critical requirement to better assess seismic hazard in tectonically active regions.

Modeling of such surface observations allows to recover key parameters of the earthquake source, such as the geometry and spatial extent of the fault that broke during the earthquake as well as the amount of slip on this fault during rupture (the “coseismic slip”), all related to the energy released during the seismic event.

Although there has long been evidence of the geometric complexity of faults, most earthquake source models ignore this complexity, for the sake of simplicity and due to the lack of precise imaging of faults at depth. Planar fault geometries are generally assumed, which leads to biases in coseismic slip estimates.

Dutta et al. [2021] propose a method to simultaneously recover the fault geometry and the coseismic slip, allowing for non-planar faults and slip variability along fault (described by a limited set of parameters to be estimated). The method ultimately provides not a unique fault and slip model but an ensemble of plausible models, with uncertainties on all the estimated parameters, which is also essential for a proper interpretation of the results.

The approach is validated and its contribution discussed using synthetic cases of earthquakes, mimicking the main characteristics of real earthquakes in various tectonic contexts, to underline the importance of taking into account more realistic fault geometries in earthquake source modeling.

Citation: Dutta, R., Jónsson, S., & Vasyura-Bathke, H. [2021]. Simultaneous Bayesian estimation of non-planar fault geometry and spatially-variable slip. Journal of Geophysical Research: Solid Earth, 126, e2020JB020441.

 —Cécile Lasserre, Associate Editor, JGR: Solid Earth

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