Explaining land subsidence variation along the north coast of Java for Semarang and Pekalongan, Indonesia

This study investigates the significant land subsidence in the cities of Semarang and Pekalongan on the north coast of Java. High land subsidence rates of several cm up to dm per year have being reported, directly contributing to relative sea-level rise. This research uses PS-InSAR data to analyze the spatial and temporal variations in subsidence and identify its causes, which are expected to be both natural and human-induced. Subsidence in both the Semarang and Pekalongan study areas show a clear relation with geology, with high rates (>10 cm/yr) occurring in unconsolidated coastal geological units. In Pekalongan, subsidence rates and patterns strongly correlate to increased anthropogenic activities and population density. In Semarang-Demak, this correlation is less strong, presumably due to the profound geological division between subsidence prone geological units overprinting the InSAR signal. However, the high rates of subsidence and their spatial occurrence clearly indicate also human-induced subsidence in the Semarang-Demak study area. The goal is to improve understanding of these processes, increase awareness of land subsidence, and aid in developing effective mitigation measures.