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A total of 1314 very low frequency earthquakes (VLFEs) were identified along the Ryukyu trench from seismograms recorded at broadband networks in Japan (F‐net) and Taiwan (BATS) in 2007. The spectra of typical VLFEs have peak frequencies between 0.02 to 0.1 Hz. Among those, waveforms from 120 VLFEs were inverted to obtain their centoroid moment tensor (CMT) solutions and locations using an examination grid to minimize a residual between the observed and synthetic waveforms within an area of 11° × 14° in latitude and longitude and at depths of 0 to 60 km. Most of the VLFEs occur on shallow thrust faults that are distributed along the Ryukyu trench, which are similar to those earthquakes found in Honshu and Hokkaido, Japan. The locations and mechanisms of VLFEs may be indicative of coupled regions within the accretionary prism or at the plate interface; this study highlights the need for further investigation of the Ryukyu trench to identify coupled regions within it.

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We studied 38 slow slip events (SSEs) in 1997–2016 beneath the Iriomote Island, southwestern Ryukyu Arc, Japan, using continuous Global Navigation Satellite Systems data. These SSEs occur biannually on the same fault patch at a depth of ~30 km on the subducting Philippine Sea Plate slab with average moment magnitudes (Mw) of ~6.6. Here we show that the slip accumulation rate (cumulative slip/lapse time) of these SSEs fluctuated over a decadal time scale. The rate increased twice around 2002 and 2013 concurrently with earthquake swarms in the Okinawa Trough. This suggests that episodic activations of the back‐arc spreading at the Okinawa Trough caused extra southward movement of the block south of the trough and accelerated convergence at the Ryukyu Trench.