On the acceleration of land subsidence rate in Semarang City as detected from GPS surveys

Land subsidence is not a new phenomenon for Semarang the capital city of Central Java Province with recent population of about 1.5 million. Some report said the subsidence in Semarang probably is occurring for more than 100 years. Geodetic surveys such as GPS Surveys can detect land subsidence accurately. Land subsidence in Semarang exhibits spatial and temporal variations with the typical average rates of about 3 to 10 cm/year until recently it seem the acceleration existed in some region of the city. This acceleration will increase the risk of negative consequences from the land subsidence. This paper present and discuss the acceleration of land subsidence in Semarang as detected from GPS Surveys. The surveys have been conducted in 2008, 2009, 2010, 2012, 2016 and 2017. From 2008 to 2012 the subsidence generally follow linier rates while from 2012 to 2017 seem they are accelerating. The northern eastern region of Semarang along the coastal area still exhibits relatively higher rates of subsidence along with acceleration in rates compare to others region. Ground water exploitation is suspected to be the causes of that land subsidence phenomenon in Semarang cit