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.
Bayesian earthquake dating and seismic hazard assessment using chlorine-36 measurements (BED v1)