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

Abstract

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.

Holocene seismic activity of the Priene–Sazlı Fault revealed by cosmogenic 36Cl,Western Anatolia, Turkey

“…Fault scarp dating with cosmogenic 36 Cl was first introduced by Zreda and Noller (1998), with reconstruction of six prehistoric seismic activity ages in the Hebgen Lake fault scarp, Montana, USA. Afterwards, the time-slip histories of limestone fault scarps were modeled in several locations in the Eastern Mediterranean and the Middle East (Mitchell et al, 2001;Benedetti et al, 2002Benedetti et al, , 2003Benedetti et al, , 2013Palumbo et al, 2004;Schlagenhauf et al, 2010Schlagenhauf et al, , 2011Akçar et al, 2012;Mouslopoulou et al 2014;Tikhomirov, 2014;Tesson et al, 2016;Cowie et al, 2017;Beck et al, 2018;Mechernich et al, 2018). In addition, 10 Be, 14 C, and 26 Al cosmogenic nuclides were tested for dating of fault scarps (Harrington et al, 2000;Kong et al, 2010).…”

“…explored at least six seismic events on the Pisia Fault, Greece, during the last 7.3 ka following Schlagenhauf et al (2010). Beck et al (2018) proposed a Bayesian MATLAB code, an improved version of that of Schlagenhauf et al (2010) and Cowie et al (2017), to determine displacement on the Fiamignano and Frattura faults, Italy. Fault scarp dating analyzes the cosmogenic 36 Cl concentration along the fault scarp surface, namely in the uppermost few centimeters.…”

Temporal and spatial earthquake clustering revealed through comparison of millennial strain-rates from 36Cl cosmogenic exposure dating and decadal GPS strain-rate

“…We collected multiple discontinuous samples (spacing between samples 23–31 cm, wider on higher and weathered sectors of fault planes) from each fault in the orientation of the fault slip vector. We modelled the slip histories using the Beck et al 28 code, which is specifically designed to recover slip-rate variations on faults from discontinuous sampling.…”

“…Beck et al 28 code models fault slip histories from the 36 Cl concentrations using a Bayesian MCMC code 28 (details of the modelling inputs and priors are given in Supplement S2 a,b). This code iterates the slip history several million times, forward modelling expected 36 Cl concentrations each time, and attempting to minimize misfit to measured 36 Cl concentrations.…”

Uncertainty in strain-rate from field measurements of the geometry, rates and kinematics of active normal faults: Implications for seismic hazard assessment

“…Analysis and dating of tephras showed that the scarps are covered by a superficial layer of Holocene deposits (Giraudi, 1995), deposited during and after the demise of the glaciation (Giraudi and Frezzotti, 1997). Moreover, the age of the scarps has been assessed through in situ cosmogenic 36 Cl exposure dating (Palumbo et al, 2004;Schlagenhauf et al, 2010Schlagenhauf et al, , 2011Cowie et al, 2017;Tesson et al, 2016;Beck et al, 2018;Tesson and Benedetti, 2019) and palaeoseismological studies (e.g. Michetti et al, 1996;Pantosti et al, 1996).…”