A study of time-lapse or 4D microgravity has been conducted to detect subsidence zones and the rate of subsidence between 2014 and 2018 in Jakarta. Jakarta city is mostly covered by a quaternary alluvium fan. Subsidence happened by several factors including excessive water exploitation, loss of recharge area, surface load, and the natural sinking properties of unconsolidated alluvium. By combining the complete Bouguer Anomaly (CBA) equation and gravity gradiometry methods, the Bouguer density of 2.33 g/cm3 can be obtained. Since subsidence occurred in the near-surface, the regional gravity anomaly has been separated from CBA by using combined spectrum analysis and moving average methods after implementing a Fourier Transform. The result shows that subsidence occurred all over the coastal area of Jakarta. In northern Jakarta, the average subsidence rate is more than 10 cm/year, and the highest rate happened in Tambora district with 15.9 cm/year. There is also a negative 4D microgravity anomaly in the southern part of Jakarta that seems to be related to ground level uplift and declining groundwater level.
- Moving Average