Application of A10 Absolute Gravimeter for Monitoring Land Subsidence in Jakarta, Indonesia

To investigate the cause of land subsidence occurring in Jakarta, Indonesia, we have conducted absolute gravity measurements near or at the existing GPS points in 2008, 2009, 2010, 2011 and 2013, by using a portable absolute gravimeter Micro-G LaCoste A10 serial number 017 (MGL A10-017). The A10 measurements, particularly those conducted before 2010, were adversely affected by the influence of the high-temperature and high-humidity climate, which caused problems with the ion vacuum pump, laser controls and unstable behavior of the data processing personal computer. Moreover, some of the gravity points were lost mainly due to construction work. For these reasons, the number of reliable gravity data was restricted. Nevertheless, the observed gravity changes along the northern coastal area of Jakarta showed an increase in gravity, which was consistent with the GPS results. The analysis of the height changes versus the gravity changes suggested that the subsidence was caused by soil compaction and/or groundwater level changes, which are likely connected with excessive groundwater extraction.