Abstract
Over the past 20 years, analyzing the abundance of the isotope chlorine-36 (36Cl) has emerged as a popular tool for geologic dating. In particular, it has been observed that 36Cl measurements along a fault plane can be used to study the timings of past ground displacements during earthquakes, which in turn can be used to improve existing seismic hazard assessment. This approach requires accurate simulations of 36Cl accumulation for a set of fault-scarp rock samples, which are progressively exhumed during earthquakes, in order to infer displacement histories from 36Cl measurements. While the physical models underlying such simulations have continuously been improved, the inverse problem of recovering displacement histories from 36Cl measurements is still mostly solved on an ad hoc basis. The current work resolves this situation by providing a MATLAB implementation of a fast, automatic, and flexible Bayesian Markov-chain Monte Carlo algorithm for the inverse problem, and provides a validation of the 36Cl approach to inference of earthquakes from the demise of the Last Glacial Maximum until present. To demonstrate its performance, we apply our algorithm to a synthetic case to verify identifiability, and to the Fiamignano and Frattura faults in the Italian Apennines in order to infer their earthquake displacement histories and to provide seismic hazard assessments. The results suggest high variability in slip rates for both faults, and large displacements on the Fiamignano fault at times when the Colosseum and other ancient buildings in Rome were damaged.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 4383-4397 |
| Number of pages | 15 |
| Journal | Geoscientific Model Development |
| Volume | 11 |
| Issue number | 11 |
| DOIs | |
| State | Published - Nov 1 2018 |
Bibliographical note
KAUST Repository Item: Exported on 2020-10-01Acknowledged KAUST grant number(s): URF/1/2584-01-01
Acknowledgements: This work was supported by NERC directed grant NE/J017434/1 “Probability, Uncertainty and Risk in the Environment”, NERC standard grant NE/I024127/1 “Earthquake hazard from 36-Cl exposure dating of elapsed time and Coulomb stress transfer”, NERC standard grant NE/E016545/1, “Testing Theoretical Models for Earthquake Clustering using 36Cl Cosmogenic Exposure Dating of Active Normal Faults in Central Italy”, and the KAUST Office of Sponsored Research (OSR) under award no. URF/1/2584-01-01. We thank the many participants in these grants for discussions on earthquakes and 36Cl, although the views expressed in this paper are our own and any misconceptions are our sole responsibility. Francesco Iezzi kindly provided the field photograph in Fig. 1h. Eutizio Vittori kindly advised on interpretations of earthquake damage to buildings in Rome.