Present-day crustal deformation revealed active tectonics in Yogyakarta, Indonesia inferred from GPS observations

We investigated the active crustal structure in Yogyakarta, Indonesia, using new and denser Global Positioning System (GPS) data. Deformation rate estimated from five years (2013–2018) of observations on 22 campaign might record broad deformation after the 2006 Mw7.8 Java tsunami earthquake and postseismic transient due to the 2006 Mw6.3 Yogyakarta earthquake. We conducted a decomposition method to obtain a short wavelength feature by removing those postseismic deformations from the observation data. The short wavelength pattern revealed active tectonics indicating a combination of E–W dip-slip motion and N–S left-lateral structure. A large maximum shear strain rate (>0.1 microstrain/yr) was estimated along the Opak fault while a large dilatation rate (<-0.1 microstrain/yr) was estimated around the Bantul Graben. The analysis result indicates important implications for crustal dynamics and assessing future seismic hazards potential in the Yogyakarta region.