Roaming Earthquakes in North China and Central-Eastern US: How and Why?

Abstract:

Large earthquakes in mid-continents often occur in unexpected places. In North China, large earthquakes roamed between distant fault systems in the past 2000 years such that no large events ruptured the same fault segment twice during this period. In the central-eastern US, although historic earthquake records only go back a few hundred years, increasing paleoseismic evidence reveals large events in places of little seismicity today. Such spatiotemporal patterns of mid-continental earthquakes differ significantly from those at plate boundary zones, where relative plate motion loads the plate boundary faults steadily at relatively high rates, leading to localized seismicity with some arguable quasi-periodicity. In mid-continents, tectonic loading is slow and accommodated collectively by a complex system of interacting faults, each of which can be active for a short period after long dormancy. The mechanics of fault interaction in mid-continents remain to be fully understood. Besides the well studied Coulomb stress perturbations due to dislocation on the fault planes, property changes of fault zones by a large rupture may cause redistribution of regional stress and strain fields in mid-continents. Further studies of fault interaction and the resulting spatiotemporal occurrence of large earthquakes in mid-continents are imperative for improving earthquake hazard assessment in North China, central-eastern US, and other highly populated and earthquake-prone mid-continents.