yuminzhao91/Modelscarp_Inversion

Constraining the past seismic activity and the slip-rates of faults over several millennials is crucial for seismic hazard assessment. Chlorine 36 (36Cl) in situ produced cosmogenic nuclide is increasingly used to retrieve past earthquakes histories on seismically exhumed limestone normal fault-scarps. Following Schlagenhauf et al., [2010] modelling approach, we present a new methodology to retrieve the exhumation history based on a Bayesian transdimensional inversion of the 36Cl data. This procedure uses the reversible jump Markov chains Monte-Carlo algorithm (RJ-MCMC, Green [1995]) which enables 1-exploring the parameter space (number of events, age and slip of the events), 2-finding the more probable scenarios, and 3-precisely quantifying the associated uncertainties. Through a series of synthetic tests, the algorithm revealed a great capacity to constrain event slips and ages in a short computational time (several days) with a precision that can reach 0.1 ky and 0.5 m for the age and slip of exhumation event, respectively. In addition, our study show that the amount of 36Cl accumulated when the sampled fault-plane was still buried under the colluvial wedge, prior its exhumation, might represents up to 35 % of the total 36Cl. This contribution can be accurately determined with a depth profile, reducing uncertainty on the exhumation scenario.

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