The 2018 (Formula presented.) Palu earthquake is a remarkable strike-slip event due to its nature as a shallow supershear fault rupture across several segments and a destructive tsunami that followed coseismic deformation. GPS offsets in the wake of the 2018 earthquake display a transient in the surface motions of northwest Sulawesi. A Bayesian approach identifies (predominantly aseismic) deep afterslip on and below the coseismic rupture plane as the dominant physical mechanism causing the cumulative, postseismic, surface displacements whereas viscous relaxation of the lower crust and poro-elastic rebound contribute negligibly. We confirm a correlation between shallow supershear rupture and postseismic surface transients with afterslip activity in the zone below an interseismically locked fault plane where the slip rate tapers from zero to creeping.

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North Sulawesi Trench or Minahasa subduction area is a subduction zone between the oceanic crust of Sulawesi Sea and the North Sulawesi Arm located at the triple junction in Eastern Indonesia. This subduction activity causes the North Arm of Sulawesi as an earthquake-prone area. Tectonic activities in the region can be studied through geodetic monitoring using GNSS GPS observations and by physical modelling from the rate of geodetic geometric results. Yearly GNSS GPS campaign have been conducted in the region from 1997 to 2008 and continuously observed by BIG from 2008 to 2016 using permanent GNSS GPS stasion. The coordinates of monitoring stations realized in ITRF-2008 provide residual RMS values of 3.13 mm, 4.15 mm and 7.26 mm for the northern, eastern and vertical components, where this indicates a high degree of accuracy. A simple estimation profile using GNSS GPS data based on the Okada elastic equation for the subduction zone shows a subduction movement ranging from 4 to 5 cm/yr with a locking depth of about 50 km, a dip 300 and ending in the post-seismic phase due to the sequence of earthquakes occurring in Minahasa since January 1, 1996 Mw 7.9 to 16 June 2002 Mw 5.9.@en

One of methods that can be used to determine the tectonic deformation status is rate estimation from geometric rotation and strain using quantitative velocity data from GPS observations. Microplate Sulawesi region located in the zone of triple junction (Eurasia, Australia and Philippine Sea Plates) has very complex tectonic and seismic condition, which is why become very important to know its recent deformation status in order to study neotectonic and disaster mitigation. Deformation rate quantification is estimated in two parameters: rotation and geodetic strain rate of each GPS station Delaunay triangle in the study area. The analysis in this study is not done using the grids since there is no rheological information at location that can be used as the interpolation-extrapolation constraints. Our analysis reveals that Sulawesi is characterized by rapid rotation in several different domains and compression-strain pattern that varies depending on the type and boundary conditions of microplate. This information is useful for studying neo tectonic deformation status and earthquake disaster mitigation.@en

Sulawesi microplate Island is located at famous triple junction area of the Eurasian, India-Australian, and Philippine Sea plates. Under the influence of the northward moving Australian plate and the westward motion of the Philippine plate, the island at Eastern part of Indonesia is collide and with the Eurasian plate and Sunda Block. Those recent microplate tectonic motions can be quantitatively determine by GNSS-GPS measurement. We use combine GNSS-GPS observation types (campaign type and continuous type) from 1997 to 2015 to derive newly velocity field of the area. Several strategies are applied and tested to get the optimum result, and finally we choose regional strategy to reduce error propagation contribution from global multi baseline processing using GAMIT/GLOBK 10.5. Velocity field are analyzed in global reference frame ITRF 2008 and local reference frame by fixing with respect alternatively to Eurasian plate - Sunda block, India-Australian plate and Philippine Sea plates. Newly results show dense distribution of velocity field. This information is useful for tectonic deformation studying in geospatial era.@en