Diverse rupture processes in the 2015 Peru deep earthquake doublet
Earthquakes in deeply subducted oceanic lithosphere can involve either brittle or dissipative ruptures. On 24 November 2015, two deep (606 and 622 km) magnitude 7.5 and 7.6 earthquakes occurred 316 s and 55 km apart. The first event (E1) was a brittle rupture with a sequence of comparable-size subevents extending unilaterally ~50 km southward with a rupture speed of ~4.5 km/s. This earthquake triggered several aftershocks to the north along with the other major event (E2), which had 40% larger seismic moment and the same duration (~20 s), but much smaller rupture area and lower rupture speed than E1, indicating a more dissipative rupture. A minor energy release ~12 s after E1 near the E2 hypocenter, possibly initiated by the S wave from E1, and a clear aftershock ~165 s after E1 also near the E2 hypocenter, suggest that E2 was likely dynamically triggered. Differences in deep earthquake rupture behavior are commonly attributed to variations in thermal state between subduction zones. However, the marked difference in rupture behavior of the nearby Peru doublet events suggests that local variations of stress state and material properties significantly contribute to diverse behavior of deep earthquakes.
© 2016 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 18 March 2016; Accepted 31 May 2016; Published 24 June 2016. The IRIS-DMC provided all of the seismic recordings. We thank three anonymous reviewers for their thoughtful comments. This work was supported in part by NSF grant EAR-1245717 (T.L.) and by the Initiative d'Excellence (IDEX) funding framework (Université de Strasbourg) and the CNRS international program for scientific cooperation (PICS) (Z.D.). Author contributions: L.Y. performed the teleseismic body-wave analysis. Z.D. performed the two-event W-phase analysis. L.Y., T.L., H.K., Z.Z., and Z.D. contributed to the interpretation and writing of the article. The authors declare that they have no competing interests. Data and materials availability: All of the raw waveform data are openly available from the Data Management System of IRIS. Other data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.
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