Monitoring of Crustal Deformations from 2003 to 2009 in Marmara Region, Turkey: Preliminary Results from Absolute Gravity and GPS Observations

The aim of this study is to develop methods that clarified the systematic relations between vertical movements and mass changes by the help of absolute and relative gravity measurements as well as GPS observations. Using these relations, the anomalies about the vertical crustal deformation in the Marmara Region will be determined and obtained results will be used in connection with the earthquake hazards in this region. During summer 2009, the first time absolute gravity measurement with A10 absolute gravity meter was carried out at ten stations in the Marmara Region after 17 August 1999 Izmit earthquake, and along a calibration line stations which was established in the region for relative gravity meters. Also, a precise determination of vertical gravity gradients with two Scintrex CG-5 relative gravimeters were carried out at the all absolute stations for the reduction of measured gravity from the reference height of an instrument to the bench mark. Moreover, we have investigated the relationship between relative gravity changes and GPS motions since October 2003 in the Marmara Region and the joint analysis of GPS and relative gravity data help to constrain the 3D postseismic deformations. We present here the first results of this survey in order to understand the vertical component of the postseismic deformations of 1999 Izmit earthquakes between the 2003 and 2009 time interval and discuss their implications for future monitoring of gravity changes along the North Anatolian Fault.