ON THE REALIZATION OF GEODETIC DEFORMATION MODEL FOR SEMIDYNAMIC DATUM IN INDONESIA

• Main Author: - NIM: 35112301 , SUSILO
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/31161
• Institution: Institut Teknologi Bandung

<p align="justify">Indonesia is an archipelago country with very complex and active tectonic and geological conditions. The interaction between the Australian plate, the Sunda block, the Philippine Sea plate, the Pacific plate and several micro block tectonic result in frequent occurrence of tectonic natural disasters, such as earthquakes, tsunamis, volcanoes, land subsidence etc. The tectonic natural disasters result in deformation on the earth's surface which can change the 3-dimensional geocentric coordinates of JKG (Geodesy Control Network) in Indonesia. The change of JKG coordinates due to deformation of the earth's surface associated with tectonic activity shall be taken into account in the use of geodetic datum for survey and mapping activites. <br /> <br /> <br /> Since October 11, 2013, Indonesia has been using a new geodetic datum called SRGI2013 (Indonesian Geospatial Reference System 2013). SRGI2013 is a semi dynamic datum with JKG coordinates defined at 1 January 2012 (2012.0) and tied to ITRF2008 (the International Terrestrial Reference Frame). The earth's surface deformation due to the activity of tectonic plates and earthquakes represents as a deformation model. The deformation model is used to transform the coordinates at the observation epoch to or from reference epoch of SRGI2013. <br /> <br /> <br /> This study uses cGPS (continuous Global Positioning System) and sGPS (survey Global Positioning System) data, earthquakes parameter and slip distribution, plate tectonic boundaries, bathymetry and topography to create and analyze the geodetic deformation model of SRGI2013. The method used are GPS data processing and analysis, linear velocity estimation, absolute deformation modeling, estimation and modeling of coseismic deformation, estimation and analysis of tectonic block rotation parameters, geodetic strain analysis, coordinate transformation, and updating model for coseismic deformation. The study result are an absolute deformation model, a coseismic deformation model, a rotation block deformation model, a model to update coseismic deformation. <br /> <br /> <br /> The analysis result shows that the JKG coordinates and linear velocities tied to ITRF2008 with the mean value rms about 0.002 ± 0.0006 m. The GPS velocities field describes different pattern of block tectonic motions in Indonesia. The rms value between GPS velocity and modeling velocity are 3.5 mm/yr and 3.4 mm/yr for EW (East West) and NS (North South) component, respectively. The rms value is strongly influenced by the lack of tightly distributed GPS stations, especially in eastern Indonesia. <br /> <br /> <br /> Analysis of the GPS and modeling of the coseismic deformation from several earthquakes between 2004 until 2012 with magnitude > 7 Mw indicates that most of Indonesia region influenced by coseismic deformation. The Sumatra-Andaman earthquake 2004, the Nias earthquake 2005, and the Wharton Basin earthquake 2012 are dominating coseismic deformation in Indonesia region. The residual rms between the GPS coseismic deformation and the modeling was 0.6 to 89.2 mm for the EW component and 1.6 to 76.0 mm for the NS component. <br /> <br /> <br /> Indonesia's geodetic strain pattern shows a very complex pattern with extensions and shortening. The Sunda Block is a stable block with a strain rate < 5 x 10-8 / yr. This is also shown from the magnitude of strain which represents the amount of strain in a region. The strain rates, dilatation, maximum shear strain and strain magnitude can be used to study surface deformation in local scale related to faults activity and to support tectonic block boundaries determination. <br /> <br /> <br /> Rotation block deformation is a linear deformation that can be represented in a block rotation parameter. Based on linear vector velocities distribution data of GPS stations and some previous studies, Indonesia is located in 19 tectonic blocks/plates (including the Australian plate, the Philippine Sea plate, and the Pacific plate) moving according to each block rotation parameters. The analysis of the rotation parameter of the blocks shows that there are still tectonic blocks estimated using only 2 or 3 linear velocity vectors of GPS stations, especially tectonic blocks in eastern Indonesia such as Banda and Papua. This happens because the distribution of GPS stations in the region is insufficient to meet to get more realistic results. <br /> <br /> <br /> The coordinate transformation to reference epoch of SRGI2013 used the absolute deformation model and the coseismic deformation model. The absolute deformation model is used for GPS stasions that not affected by coseismic deformation, while coseismic deformation used to corrected the coordinate of GPS stations that affected by coseismic deformation. The absolute deformation resulted rms residual of coordinates at reference epoch about 0.006 m, 0.007 m and 0.003 m for XYZ geocentric coordinate. The rms residual of 65 GPS stations which affected by coseismic deformation is about 0.048 m, 0.024 m, and 0.020 m for XYZ component without corrected by coseismic deformation model. By applying coseismic deformation model in the coordinates transformation, rms residual decreasing to 0.024 m, 0.021 m and 0.021 m in the XYZ. These result show that the coseismic deformation model is very important to corrected JKG coordinates in the coordinate transformation to SRGI2013, so updating coseismic deformation model is absolutely necessary when earthquake occurs. <br /> <br /> <br /> The coseismic deformation updating model was also performed in this study related to the 2016 Pidie Jaya earthquake (PiJay). The results and analysis show that the coseismic deformation in the GPS station does not affect the geospatial information data on the 1:1000 map scale because it is distorted with geometric accuracy about 20 cm. PiJay's coseismic deformation must remain corrected to the JKG coordinate value.<p align="justify">