Issues

Front: Probabilistic forecasting of earthquake-producing fault ruptures informs all major decisions aimed at reducing seismic risk and improving earthquake resilience; the Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3) is the first model to provide self-consistent rupture probabilities over forecasting intervals from less than an hour to more than a century. Field et al. (this issue) provide an overview of UCERF3, illustrate the short-term probabilities with aftershock scenarios, and draw conclusions from the modeling results. Shown here are average earthquake nucleation rates following a magnitude 6.1 event near Parkfield, California (white line), as inferred from 200,000 simulations. Note that the new model (UCERF3-ETAS) exhibits triggering on faults, whereas previous models, such as the ETAS case shown at the upper right, have generally ignored faults. Back: Multiple earthquakes in the 2010–2011 Canterbury, New Zealand, sequence induced liquefaction, providing instruction for how to interpret paleoliquefaction features in the geologic record. The top photo shows a compound sand-silt fissure that formed 30 km southwest of Christchurch during the 22 February 2011 M 6.2 and 13 June 2011 M 6.0 Christchurch earthquakes. The bottom photo shows a sand blow that formed during the 22 February 2011 earthquake mainshock and aftershocks (photos by C. and R. Hardwick). These and other photos, as well as measurements of liquefaction features, can be found in the article and electronic supplement by Tuttle et al. (this issue), providing a unique dataset of liquefaction features formed during a modern earthquake sequence.