Recent Tectonic Uplift And Its Spatial Difference Analysis In Siming Mountain Area Of East Zhejiang Based On InSAR Technology

The Siming Mountain in eastern Zhejiang is a fault-blocking mountain formed by the east-west narrow and long-shaped distribution formed by the typical crustal deformation.This is a pleated mountain with an area of only 2,500 km2 and a maximum elevation of about 1010 m.Siming Mountain is bordered by Hangzhou Bay in the north,Chenzhou City and Fenghua City in the south,Cixi City in Ningbo,Zhenhai District and Yinzhou District in Ningbo,and Shangyu City in the west.In2006,a relatively well-preserved,paleo-planation surface was discovered in the Siming Mountain area by scholars.Later,paleo-planation surfacewas considered to be the widest low-altitude plane on the eastern coast of China,and it was named“Siming Mountain Plane”.The discovery of the plane has greatly attracted the attention of academic circles and the government.A large number of scholars have carried out research on Siming Mountain.The local government has also developed Siming Mountain into the Simingshan Provincial Geopark,which has become one of the major tourist attractions in the area.Siming Mountain is a typical area for the differential rise and fall of new structures in the middle and low mountains of eastern China.The pre-study's research on Simingshan mainly focuses on the investigation of ecological environment,the study of economic construction and the trace of history and culture,as well as the distribution and genesis of the Siming Mountain plane.The current research on the new tectonic activities in the Siming Mountain area and the recent surface deformation and uplift Rate studies are still in the initial exploration phase.The conventional surface deformation monitoring method not only has a large workload,a small monitoring period,and high cost,but also is affected by human factors and random errors,resulting in low precision and certain limitations.InSAR(the Synthetic Aperture Radar Interferometry)is a space-to-earth observation technology that developed in recent years.This technology has an obviousadvantage of large-area measurement.In general,the spatial coverage of a scene interferogram eaches 100 times 100 square kilometers.Besides,it also has the advantages of high resolution,all weather,and all-day time,which provide a new way for the monitoring of surface deformation.Therefore,this paper attempts to use this technology to make a preliminary analysis of the spatial difference of the recent uplift,in order to obtain a better understanding of the recent status of tectonic uplift and the possible spatial differences in surface deformation in the study area.Relatongship between the surface deformation and the distribution of the paleo-planation surface is discussed.This paper adopts a total of 22 Sentinel-1A radar satellite image data with a good current situation and a six-day revisit period.The images are from May 15 th,2016 to April 23,2018.The image was taken from the Sentinel Scientific Data Hub.It is supplemented by Google Earth HD image data and ASTER GDEM data,using D-InSAR technology and improved small baseline set technology(SBAS-InSAR)technology for data processing and analysis.The differential interferograms in the study area and the deformation values in the time series are obtained and their spatial distribution patterns are discussed.The differences between the surface deformation results of the Siming Mountain obtained by D-InSAR technology and SBAS-InSAR technology are further compared.The influence of different precision thresholds on the processing results under SBAS-InSAR geocoding is analyzed.It is found that the processing results caused by setting different precision thresholds have obvious differences.Usually,the higher the precision threshold is set,the less the results are obtained.In this paper,four regions with obvious deformation are selected in the map of the surface deformation rate of Siming Mountain.The deformation time series curves of the pixel points in the region are analyzed.The results show that the overall fluctuation of the deformation time series curve is large and undulating.There is acertain correlation between the deformation variable and the seasonal variation.The spatial distribution of surface deformation in the distribution area of the Simingshanplanation surface is obtained,and the spatial distribution patterns of surface deformation are selected from seven typical flat planes: The uplift is mainly concentrated in the vicinity of Baiyuping-Simingshan Town in the middle of Siming Mountain and near Nanxun Town.The average uplift rate is about 10mm/a;the Dayangshan,Datun and Luochengshan areas show a slight uplift,and the uplift rate is about 2-4mm/a;the upper Wanggang area is characterized by surface subsidence,and the sedimentation rate is about 5mm/a.Based on natural factors(geological structure,fault zone,lithology and climate)and human activities factors,the spatial distribution of surface deformation in Siming Mountain is discussed.It is believed that the uplifting area of Siming Mountain may be more affected by natural factors.In particular,the impact of geological tectonic fault zones,and the area where subsidence occurs is mainly related to human activity factors,and further analysis and verification are needed.