Interplay Between Seismic and Aseismic Deformation on the Central Range Fault During the 2013 M_w 6.3 Ruisui Earthquake (Taiwan)

Abstract

The 2013 Ruisui earthquake represents the first unequivocal evidence of the activity of the Central Range fault in central Longitudinal Valley, Taiwan. Using a joint Bayesian finite‐fault source inversion of Global Navigation Satellite System and strain time series, we infer that coseismic rupture occurred between 4 to 19 km depth with maximum slip of 0.5 m located near the hypocenter. We then apply a variational Bayesian independent component analysis approach to displacement signals to infer a 3‐month long afterslip located in the near‐source region. This observation represents the first evidence of aseismic slip on the Central Range fault. Combining geodetic and seismological analysis with simulations based on rate‐and‐state friction mechanics, we analyze the interplay between seismic and aseismic deformation during the earthquake sequence. We observe that afterslip is the dominant postseismic deformation mechanism, with > 95% of the moment being released aseismically in the postseismic phase and also likely represents the driving force controlling aftershock productivity. Finally, we infer the presence of a shallow velocity strengthening zone ( ∼ 0‐4 km depth) associated with spatially heterogeneous slip during the postseismic phase with maximum slip of 0.18 m located above the zone of maximum coseismic deformation.