Synchronous earthquakes on multiple fault segments or on imbricate reverse faults have larger magnitudes than isolated ruptures.
Determining where those fault segment boundaries are, and how often they are breached in earthquakes, is less clear. Using field mapping, GPS and Total Station surveying, GPR, trenching, Quaternary geochronologic techniques, and structural/stress modelling, I try to figure out the typical and maximum magnitudes that can be expected from a fault system. I use Monte Carlo simulations to produce realistic probability distributions of Mw.
This work is important in light of the most complex surface-rupturing earthquake ever documented, the 2016 Mw 7.8 Kaikoura Earthquake in New Zealand. Work is on-going to determine how all of these faults ‘communicated’ in this event.
Above: Sharon Hornblow (Otago Regional Council) cleaning a trench wall of the Fox Peak fault, Canterbury, New Zealand