Utilizing the Global Positioning System (GPS) Data from Sumatran GPS Array (SuGAr) to Measure Seismic Deformation Related to the Mw7.6 Padang Earthquake 2009

Abstract

AbstractThe Sumatran GPS Array (SuGAr), widely distributed in Sumatra, has provided the possibility to measure various mechanisms of plate deformations. This study analyzes deformation in the pre-seismic, co-seismic, and post-seismic phases related to the Mw7.6 Padang earthquake, September 30, 2009. GPS data were used to understand the deformation at several areas with various distances from the epicenter. Ten SuGAr data in RINEX format is processed using GAMIT/GLOBK software to obtain three-dimensional daily position data. The value of postfit nrms <0.25 for 96.98% data, Wide Lane >90%, and Narrow Lane >85% confirmed the reasonable processing procedures and the excellent ability to correct and eliminate errors due to ambiguity. This study demonstrated a stable rate of plate movement before the earthquake, followed by a sudden change at the co-seismic phase, where the GPS stations ABGS, BTHL, KTET, JMBI, LAIS, LNNG, MNNA, MSAI, NGNG, and PKRT showed significant deformations. GPS stations in the Mentawai Backthrust zone (BTHL, MSAI, NGNG, KTET, PKRT) showed the 2.62–47.13 mm southwestward movement at the co-seismic phase, the GPS stations in the west coast of Sumatra (ABGS, LNNG, LAIS, and MNNA) have been moved 2.26–25.13 mm to southeastward (ABGS), northwestward (LNNG), northeastward (LAIS), and southwestward (MNNA), and the GPS station in the north coast of Sumatra (JMBI) have been moved 3.26 mm to northwestward. The results also show that the further away from the epicenter, the smaller the deformation. The result also indicates that the plate movement returns to its pre-seismic stable rate immediately after the earthquake.KeywordsDeformationSuGARPre-seismicCo-seismicPost-seismicGAMIT/GLOBK