Abstract
Nearby faults interact with each other through the exchange of stress. However, the extent of fault interaction is poorly understood. In particular, interactions may lead to slow-slip activity, resulting in episodes of transient surface motion. Our study concentrates on Northwest Sulawesi (Indonesia), which hosts two fault zones with potential for major earthquakes and tsunamis: the strike-slip Palu-Koro fault and the Minahassa subduction zone. Thanks to a 20-year-long effort in geodetic monitoring, we are able to identify multiple periods during which surface velocities deviate from their interseismic trend. We use a Bayesian methodology with forward predictions of slip on the two fault interfaces to match the observations following the 2018 Palu earthquake, and infer that both deep afterslip on the Palu-Koro fault and slow slip on the Minahassa subduction interface have caused the observed transient surface motion. This finding represents the first recording of a slow slip event on the Minahassa subduction interface. We also infer that the subduction interface and the strike-slip fault are likely interacting on a regular basis.
Data
Least squares parameterization of GPS data contains the station positions, jumps, transients and velocities shown in figure 2A and S1-13 in .txt format.
RINEX GPS data contains RINEX files of the campaign stations after the 2018 Palu earthquake
Model data contains model output files used to create the figures 4,6,7, S12-17 in .txt format and two supporting images in .png format.
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