The Cimandiri fault is one of the great fault in West Java. Running in the direction from Pelabuhan Ratu, passing Sukabumi, Cianjur and Padalarang makes Cimandiri fault to become the longest fault in West Java and also the closest fault to Java subduction zone. Due to this location, Cimandiri fault is the best fault for knowing the influence of Java subduction zone to the Java island. In addition, it is necessary to do research on the velocities and strain rates around the Cimandiri fault.
In this research, both of parameters, velocities and strain rates, are derived from GPS observation data including the continues GPS stations or CORS which are maintained by Indonesia Geospatial Agency (BIG) in 2008 to 2013 and the campaign/periodic GPS stations which the observation were conducted by Research Group of Geodesy and Geomatics Engineering Study Program, ITB in 2008 to 2011. To derived the velocities from GPS observation data, the first processing data use GPS Analyze at Massachusetts Institute of Technology (GAMIT) software to produce daily solutions. The coordinates in each daily solutions from GAMIT is refer to ITRF2008. These coordinates should be transform into ITRF2000 to get the daily coordinates as same as Sundaland Block velocity reference frame. This steps is used to eliminate the effect of Sundaland Block motion in every GPS stations. The second steps are calculating the velocities and strain rates from using the Least Square method.
Based on the results of GPS data processing The GPS sites in the west part have velocity direction to the south east while the GPS sites in the north east part have velocity to north west direction. The magnitude of velocity at GPS sites around Cimandiri fault is also varying from 1 mm/year to 19 mm/year. Based on the pattern of strain, that the near coastal area part, both of south and north part of fault zone move together while the accumulation of strain in the near coastal area located in the middle part of fault zone. In the middle part of of fault line, the strain component which dominate the part is same so it can be said that part is active fault while in the end of fault line, the dominated strain is different between south and north part of fault. It is seen as inactive fault.This shows the activity of the Java subduction zone around Cimandiri fault area.