Spatiotemporal subsidence feature decomposition and hotspot identification

Subsidence occurs from excessive groundwater drawdown, but varies in response to underlying hydrogeologic conditions, land use factors, and variations of pumping rates. For subsidence feature decomposition, the empirical orthogonal function (EOF) is used to identify to extract the main components of the land subsidence data, such as continuous trend of subsidence and seasonal subsidence from various regions. Result shows that the major subsidence feature components contain the long-term, periodic (seasonal), and intra-seasonal ones which are related to human activities and hydrogeology from the inland, distal-fan area and coastal area in west-central Taiwan. The subsidence trend and seasonal variation at the observations can be separated from empirical mode decomposition (EMD) for validation. Moreover, subsidence and groundwater monitoring data are used to generate the stress–strain relations at the major EOFs locations. The outcome implies a strongly elastic nature, yet reveals a diverse correlation between stress and strain within the subsidence region. The decomposition and identification of subsidence features offer valuable applications for the effective management of land subsidence and groundwater resources.