10:45 〜 12:15
[STT39-P03] Time-Dependent 2.5-D Surface Deformation of Semarang constrained by InSAR measurement
キーワード：InSAR, Surface Deformation, Time-Dependent , Semarang
Semarang City, one of Indonesia's largest cities, is composed of alluvial deposits, tertiary claystone, and quaternary volcanic material, as explained by Abidin et al. (2013). It makes Semarang susceptible to surface deformation that might have negative impacts on the economy, society, and environment. Factors causing surface deformation or subsidence can be natural such as soil compaction, earthquakes, or changes in the material structure of the soil due to changes in the aquifer layer. Other factors causing surface deformation are human-induced, such as gas and mineral extraction, over-abstraction of groundwater, and load construction. Semarang also has several faults and relatively trending in the east-west direction (Nurwidyanto et al. 2019). The most significant recent factor in Semarang subsidence is frequently associated with groundwater abstraction (Putranto et al. 2017). Based on this background, further studies are needed that can capture present-day temporal and spatial aspects of surface deformation monitoring.
This study exploited multi-geometry C-band SAR data from ESA in the period 2015-2022. We used more than a thousand interferograms from both ascending and descending geometry. It was processed using the new small baseline subset (NSBAS) technique by Lopez-Quiroz (2009), incorporating atmospheric corrections (Yu et al. 2018). We applied spatio-temporal filter to reduce residual noise for velocities and time series, respectively. The results obtained for spatial and temporal time series velocities are considerable deformation that is not affected by the season. It is relatively challenging to use the observed conventional line of sight (LOS) InSAR displacement to intuitively represent the surface deformation because it only measures from the satellite direction. We decomposed from time-dependent InSAR LOS results to obtain E-W and U-D components, respectively (Fujiwara et al. 2000). Significant vertical deformation occurred with no seasonal effects in the northeast of Semarang, exceeding 10 cm/yr. To evaluate the vertical results, we compared with another geodetic measurement from permanent GNSS data. The fastest subsidence occurs in highly populated areas suffer vulnerable to flooding and sea level rise impact. The correlation between the sinking city and groundwater use in urban areas will be driver of socio-economic disaster.
This study exploited multi-geometry C-band SAR data from ESA in the period 2015-2022. We used more than a thousand interferograms from both ascending and descending geometry. It was processed using the new small baseline subset (NSBAS) technique by Lopez-Quiroz (2009), incorporating atmospheric corrections (Yu et al. 2018). We applied spatio-temporal filter to reduce residual noise for velocities and time series, respectively. The results obtained for spatial and temporal time series velocities are considerable deformation that is not affected by the season. It is relatively challenging to use the observed conventional line of sight (LOS) InSAR displacement to intuitively represent the surface deformation because it only measures from the satellite direction. We decomposed from time-dependent InSAR LOS results to obtain E-W and U-D components, respectively (Fujiwara et al. 2000). Significant vertical deformation occurred with no seasonal effects in the northeast of Semarang, exceeding 10 cm/yr. To evaluate the vertical results, we compared with another geodetic measurement from permanent GNSS data. The fastest subsidence occurs in highly populated areas suffer vulnerable to flooding and sea level rise impact. The correlation between the sinking city and groundwater use in urban areas will be driver of socio-economic disaster.