We model long-term and interseismic deformation of elastic lithospheric blocks moving over a viscoelastic asthenosphere in eastern Taiwan. We invert geologic and geodetic data for block movements, fault slip rates, and distribution of interseismic creep using the model through a fully probabilistic inversion scheme. The data include GPS, InSAR, creepmeter measurements for interseismic deformation and Holocene marine terrace uplift rates. In our best model we include 4 blocks separated by three faults-Central Range fault, Longitudinal Valley fault and an offshore fault, which is a west-dipping thrust fault. We prescribed the geometry of the faults and a 30-km-thick crust. We assume the ratio of earthquake recurrence to asthenosphere relaxation time is less than 1 meaning that deformation between earthquakes is nearly steady deformation and timing of past earthquakes is not relevant. The model explains the essential features of interseismic and long-term measurement patterns. We find the OSF plays an important role in the model, in particular, for fitting marine terrace uplift rates. Its long-term slip rate is 35-55 mm/yr. Its high creep on northern segment may indicate the unmodeled effect of Ryukyu trench. The LVF has a long-term slip rate of 20-30 mm/yr with approximately equal magnitudes of reverse-slip and left-lateral strike-slip components for the upper segment above the intersection with the OSF. The southern segment of the LVF creeps at a rate of 10-30 mm/yr. The CRF has a uniform long-term slip of approximately 12 mm/yr with the northern segment largely creeping and the southern segment largely locked.