Mw 8.3 September 16, 2015 Illapel, Chile Earthquake
On September 16, 2015, a magnitude 8.3 earthquake occurred offshore of Illapel, Chile along the interface between the subducting Nazca and overriding South America plates. Here I’ve used seismic data recorded in North America to image the source distribution of high-frequency energy radiated during this event using a method called back-projection. The initial 60 seconds of the rupture propagates near the Chilean coast and is the likely source of strong ground shaking in the region. In contrast, the second half of the rupture that propagates near the Peru-Chile trench likely generated the tsunami waves observed following this event.
Movie Caption: Warm colors represent high energy release at a given time (upper left corner). The star is the epicenter of the event and the white dots are aftershocks on Sept. 16 and 17. The white line is the coastline of Chile and the black line with white sawteeth is the Peru-Chile trench.
Great post Eric! What causes the pulse-like behavior of the rupture?
Thanks Cin-Ty. For an earthquake of this magnitude, multiple asperities (regions of stress accumulation) rupture during the event. The pulses in these results are likely related to the failure of new asperities as the rupture propagates. In addition to producing high-amplitude seismic waves, these asperities can often be identified by observed changes in the rupture direction and speed.