The 2010 Mw 8.8 Chile earthquake: Triggering on multiple segments and frequency-dependent rupture behavior

Multi-frequency back-projection results of the February 27, 2010, Mw 8.8 Chile earthquake reveal that this earthquake consists of distinct subevents with different slip characteristics. The subevent south of the epicenter releases its energy at low frequencies (0.05-0.1 Hz), implying slow slip, and has a rupture speed around 0.8 km/s. Two subevents north of the epicenter are characterized by high-frequency energy (1-5 Hz) release. The first of these subevents appears to trigger slip on the second segment to the north, which has higher amplitude energy release and a fast propagation speed of about 2.9 km/s. In addition to these rupture details, high-frequency energy release is observed at the rupture front followed by lower-frequency energy release. This observation suggests that the rupture of large earthquakes involves dynamic weakening of faults and hence their rupture properties may not be related easily to those of small earthquakes. These distinct slip behaviors point out the need to consider data from a wide range of frequencies to fully assess the rupture process and associated hazards of giant earthquakes.