Inter-event slow-slip process for the fore- to Main triggering of the 2016 Komamoto earthquake sequence

PKU Yue

Published August 14, 2019, SCEC Contribution #9645, 2019 SCEC Annual Meeting Poster #184

Cascade and preparation processes could interpret the triggering between fore- and mainshocks, which determine the possibility of using foreshocks for short term predictions. Discriminate between these processes are difficult due to rare near field observations of fore-main sequences. The nearfield observations of the 2016 Kumamoto earthquake. This sequence initiate as an Mw 6.4 foreshock and followed by an Mw 6.2 foreshock about 1 hour later. The mainshock occurs about 25 hours later after the Mw 6.2 foreshock. We obtained near-field GNSS stations which recorded the inter-event displacement time-series between the fore and the mainshock and resolved up to 1 cm of inter-event displacement. This displacement presents a logarithmic shape, which appears to be related to the after-slip process. We also observe a velocity direction change occurred 4 hours before the mainshock. By inverting the spatial slip pattern using a Principle Component Analysis method (PCA), we obtained a two-stage slow-slip process. The first stage locates at the shallow part of the mainshock fault plane and the second stage locates near the mainshock hypocenter. These two processes are also consistent with the foreshock activities in these areas. We propose the second stage of the inter-event process may be responsible for the fore-to-mainshock triggering of the 2016 Kumamoto sequence.

Key Words
Kumamoto earthquake, Foreshocks, slow-slips

Citation
Yue, P. (2019, 08). Inter-event slow-slip process for the fore- to Main triggering of the 2016 Komamoto earthquake sequence. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)