Pre-and Coseismic Analysis of the Mw7.6 Padang Earthquake 2009 from Geodetic Approach

On September 30, 2009, an Mw7.6 earthquake hit the west coast of Sumatra. This main shock caused the crustal deformation affecting a wide area in the western part of Sumatra. This paper presents the analysis of the deformation recorded by the Sumatran GPS Array (SuGAr) network. More than 40 GPS stations were installed to continuously monitor the deformation in Sumatra, among 12 of them is known to have been deformed by this earthquake. We processed whole data in 2009 to understand the dynamics of western part of Sumatra before, during and after the earthquake. Relative daily position data is obtained from postprocessing with GAMIT/GLOBK software, implementing the DGPS technique to estimate daily position from GPS RINEX data. GPS measurements shows that during the earthquake, most stations in Mentawai is deformed toward the southwest direction, varies from 8 – 50 mm, and the stations in mainland Sumatra is deformed toward various direction, varies from 5 – 28 mm. There is no anomaly and strange behaviour before the event as the precursor, and the deformation trend one day after the events seems to return to the preseismic pattern.