Abstract
Abstract. We have delineated ten years of urban subsidence derived from continuous GPS stations operated by the Crustal Movement Observational Network of China (CMONOC) within and adjacent to the municipality of Tianjin. A method for obtaining accurate site velocities with respect to a stable regional reference frame is described. CMONOC stations in Jizhou (JIXN) and Baodi (TJBD) districts recorded minor subsidence of approximately 1 to 2 mm yr−1 during the period from 2010 to 2019. One station in Wuqing (TJWQ) district and one station in Binhai (TJBH) district recorded steady subsidence of approximately 5 and 2 cm yr−1 from 2010 to 2019, respectively. One station in Cangzhou (HECX) of Hebei Province, adjacent to Tianjin, recorded steady subsidence of approximately 2.4 cm yr−1 during 2010–2014 and more rapid subsidence of 4 cm yr−1 since 2015. TJWQ recorded the most rapid land subsidence and the most significant seasonal ground oscillations (uplift and subsidence) among these five stations. This study indicates that subsidence rates in Tianjin vary significantly in space and time. Particular attention should be paid, therefore, to extrapolate or infer a rate of subsidence for an area on the basis of a subsidence rate obtained from previous GPS observations or proximal GPS sites. The subsidence time series presented in this study provide reliable “ground truth” and constraints for calibrating or validating subsidence estimations from numerical modeling and repeated surveys using other remote sensing techniques, such as Interferometric Synthetic Aperture Radar (InSAR).
Highlights
Tianjin, the largest port city in north China and the center of the industrial and economic area around Bohai Bay, has experienced severe subsidence problems since the 1950s (Hu et al, 2004)
Large Continuously Operating Reference GPS Stations (CORS) networks have been established in many countries for land surveying and crustal monitoring purposes, which recorded important land subsidence information, as a by-product
This study investigated Crustal Movement Observational Network of China (CMONOC) stations within and adjacent to the municipality of Tianjin
Summary
The largest port city in north China and the center of the industrial and economic area around Bohai Bay, has experienced severe subsidence problems since the 1950s (Hu et al, 2004). During the past two decades, Global Positioning System (GPS) technologies have been gradually applied to urban subsidence studies, both as a compliment and an alternative to conventional surveying methods. A great number of Continuously Operating Reference GPS Stations (CORS) have been installed in China during the past two decades. The Crustal Movement Observational Network of China (CMONOC), the largest CORS network in China, operates over 260 continuous permanent GPS stations across the China mainland (Fig. 1). R. Zhao et al.: Rapid Land Subsidence in Tianjin
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