[S-SS05] Crustal Deformation

[SSS05-P02] Application of a slow slip objective detection method to GNSS 6-hour coordinates

*Akio Kobayashi¹ (1.Meteorological Research Institute, Japan Meteorological Agency)

Keywords:slow slip event, Nankai Trough, GNSS

In the Nankai Trough, slow earthquakes such as short-term slow slip events (SSEs) and long-term SSEs have been observed. Kobayashi (2017) developed a method for objective detection of long-term SSEs and revealed their spatiotemporal distribution. Kobayashi (2021) applied the method to short-term SSEs and extracted the crustal deformations associated with short-term SSEs. Here we tried the same detection method using 6-hour GNSS coordinates.

From November 15 to December 5, 2017, deep low-frequency earthquakes and strain changes were observed from Nara Prefecture to near the Aichi-Nagano border. The short-term SSE objective detection method using GNSS daily coordinates showed a high correlation associated with this phenomenon. The correlation values with the ramp function with a 7-day slope at November 25 were 0.74 for the daily coordinates, 0.44 for the 6-hour coordinates, and 0.72 for the median of the past 24 hours for the 6-hour coordinates. The 6-hour coordinates had a low correlation value, probably due to its high variability, but the change in the median value over the past 24 hours was similar to the daily coordinates, and the correlation value was also similar to the daily coordinates. Monitoring by 6-hour coordinates may detect the phenomenon earlier than daily coordinates.