Chile 2014
A seismotectonic analysis by Gordon Lister and Nick Stubbs
The April 2014 earthquake off Chile had a moment magnitude of 8.1 which makes it one of the destructive earthquakes termed "Great Earthquakes" because of the enormous amount of energy released. It occurred on a megathrust, where the South American plate is pushing over the subducting Nazca Plate. The earthquake took place on a fault rupture that dipped about 18° to the east, over a distance of at least 170-200 km.
In the next few days, the pattern of aftershocks will tell us whether the rupture broke more or less symmetrically, or whether the initial break (i.e. the hypocentre) was at the north end of a much larger rupture.
Does this rupture correspond with the 1877 Great Earthquake?
The figure below shows earthquakes above Mw 7 in the past 40 years in this region. The hypocentre is where the rupture begins to radiate seismic energy, with the epicentre the location at the surface (as plottted).
The figure below again shows all earthquakes above Mw 4 in the past 40 years in this region. Note how they are clustered. These clusters show how the megathrust is segmented, noting that each cluster may represent the aftershocks associated with a single large earthquake. The inferred rupture for the April 2014 event may well coincide with the segment broken by the 1877 earthquake. A long recurrence interval (in this case 137 years) reflects the rate of stress build up on locked segments of the megathrust.
References
Historical rupture extents extracted from 26 MAY 2006 VOL 312 SCIENCE www.sciencemag.org
D. P. Robinson,* S. Das, A. B. Watts, 2006. Earthquake rupture stalled by a subducting fracture zone.
Updated: 29 June 2020/ Responsible Officer: Structure Tectonics Team Leader/ Page Contact: WebAdmin
