Group A, Poster #131, Fault and Rupture Mechanics (FARM)

Islands of chaos in a sea of periodic earthquakes: Constraining the allowable friction parameter space for large-magnitude earthquakes using recurrence patterns from the Alpine fault Hokuri Creek paleoseismic record, New Zealand

Judith Gauriau, Sylvain D. Barbot, & James F. Dolan
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Poster Presentation

2022 SCEC Annual Meeting, Poster #131, SCEC Contribution #11959 VIEW PDF
Earthquake recurrence patterns on some faults derive from paleoseismic records that challenge time- and slip-predictable models. Such records are often categorized as clustered, random, or quasi-periodic according to the coefficient of variation (COV) of the recurrence time intervals obtained for the whole record. Quasi-periodicity is thus inferred for any record whose COV is less than 1. While this is the case for the thus-far longest paleoseismic record obtained on a major fault: the 7,900-year-long, 24-event Hokuri Creek record on the Alpine fault (Berryman et al., 2012), we show here that this record is best explained by a chaotic recurrence model. We explore three non-dimensional parame...ters over hundreds of 20,000-year-long simulations and refine the frictional parameter space that can generate a record that resembles the Hokuri Creek record. Among a sea of periodic earthquake recurrence patterns, incompatible with the geological observations, we find a few “islands of chaos”, i.e., chaotic models that reproduce the Hokuri Creek recurrence intervals with up to 11 consecutive events. Our results reveal that the Alpine fault is considerably longer than the characteristic nucleation size and that its friction behavior is Byerlee-like, and that slip- and time-predictable models cannot explain the observed behavior. The compatibility of quasi-periodicity of seismic cycles with a fundamentally chaotic underlying mechanical system renders any attempt of earthquake prediction on a specific fault functionally impossible.