Crustal Deformation Monitoring in Beijing Using Radarsat-2

InSAR Time Series Analysis

L Y Hu

1,*

, Y S Li

, C Q Xing

, K R Dai

3,4

, R Yan

and X Guan

Beijing Earthquake Agency, China

Key Laboratory of Crustal Dynamics, Institute of Crustal Dynamics, CEA, China

College of Earth Sciences, Chengdu University of Technology, Chengdu, China.

State Key Laboratory of Geohazard Prevention and Geoenviroment Protection,

Chengdu University of Technology, China

The 29th research institute of CETC, China

Corresponding author and e-mail: L Y Hu, huleyin@bjseis.gov.cn

Abstract. The main aim of this study is to investigate the current vertical crustal movement

characteristics and evolution process in Beijing using InSAR technology. In this paper, the

InSAR time series analysis method was used to monitor the crustal deformation in Beijing

during the period from 2012 to 2015, and to quantitatively reveal the overall deformation

characteristics of different areas within the study area. Based on 33 Radarsat-2 wide-mode

SAR images covering Beijing, 68 interferograms were formed by optimizing the combination

of baselines. Using the FRAM-INSAR technique, the cumulative deformation time series and

images along the line-of-sight of the satellite in the 32-phase period were calculated, and the

annual average deformation velocity field in Beijing and neighbouring areas during 2012-

2015 was calculated. Based on the distribution of active structures in the study area and the

distribution of ground subsidence, the relationship between the deformation characteristics of

the entire crust and the tectonic activity and land subsidence in the study area was discussed,

which provided an effective criterion for accurately carrying out seismic risk assessment in

this area.

1. Introduction

As China’s political center, cultural center, international exchange center and scientific and

technological innovation center, Beijing has developed rapidly in recent years in economic, social

development and urban construction. However, with the rapid development of economy and urban

construction, land subsidence has gradually developed into one of the major geological hazards in

Beijing and even in the entire North China Plain. This has caused certain negative impacts on

Beijing’s urban development. Its potential harm has been increasingly concerned by the society and

the government [1,2]. Since 2002, the Beijing Municipal Government has increased its investment in

enhancing the monitoring capabilities on the urban land subsidence. With the completion of Beijing's

land subsidence early warning and forecasting system, a ground subsidence monitoring system

consisting of ground subsidence monitoring stations, ground level monitoring networks, GPS

monitoring networks and groundwater dynamic monitoring networks has been gradually formed [3].

710

Hu, L., Li, Y., Xing, C., Dai, K., Yan, R. and Guan, X.

Crustal Deformation Monitoring in Beijing Using Radarsat-2 InSAR Time Series Analysis.

In Proceedings of the International Workshop on Environmental Management, Science and Engineering (IWEMSE 2018), pages 710-717

ISBN: 978-989-758-344-5

At the same time, Beijing is also a region where the tectonic movement is more active. Since the

late Cenozoic era, there have been three active vertical tectonic zones (stripes) with strong

differential faults. They are the NE-trending North China Plain fault zone, the Shanxi fault

depression basin zone, and the Zhangjiakou-Bohai structural belt that is superimposed on the NW-

wise extension of the northern part of these two zones and the southern margin of the Yanshan

Mountains [4]. The seismic and geologic environment in the area is complex. The activities of the

new structure are intense and the active faults are developed. It is one of the regions with the most

severe earthquakes and the most serious earthquake disasters in the eastern part of China's mainland.

Historically, there have been many major earthquakes in the area, such as the magnitude 8.0

earthquake in Sanhe-Pinggu and many over magnitude 5.0 earthquake [5]. Strengthening the

monitoring and research on the features of crustal movement and fault activity in this area is of great

significance for the prevention and relief of disasters in the region.

In recent years, more and more research teams have begun to pay attention to the phenomenon of

land subsidence in Beijing. A variety of crustal deformation observation methods, such as leveling,

GPS, and InSAR, are used for ground subsidence monitoring in the area. Among these observation

technologies, InSAR technology as a kind of surface deformation monitoring of the rapid

development of the technology, with its high monitoring precision, wide coverage, the application of

low cost, short repeated cycle of advantages, is widely used in the ground deformation monitoring [6].

Land subsidence due to over-extraction of groundwater in the Beijing region was investigated using

41 Envisat ASAR and 14 TSX images and the results reveal that the Beijing region has experienced

significant ground subsidence from 2003 to 2010 with a maximum accumulative displacement of 790

mm [7]. As the same method, Land subsidence from 2003 to 2014 due to groundwater extraction in

Beijing plain was detected based on 39 ENVISAT ASAR images and 27 RadarSat-2 images using

PS- InSAR, which showed that the land surface in Beijing plain area is settling at an accelerating rate,

and the accumulative displacement is up to 1426 mm along the LOS by the end of 2014 [8]. Based on

A multi-layer numerical groundwater flow model, an aquifer system of Beijing plain has been

developed to accurately describe the characteristics of the groundwater flow field [9]. A Wavelet

Based InSAR approach on two SAR image stacks was implemented to investigate the long-term

displacement in eastern Beijing Plain and found that the Land subsidence in Beijing Plain has

connection with hydraulic head level falling caused by over-exploitation of groundwater [10].

Based on the above research progress, there are still some problems as following:

1) Most studies focused on the relationship between land subsidence and groundwater

Overexploitation, without considering the context of the geological structure and the relationship

between fault activities.

2) Most of the studies focused only on the subsidence areas in the plain area and did not cover the

mountainous areas, which could not explain the overall movement characteristics of the whole area.

3) Due to the fact that there are few wide-range radar satellite data available during the period

2012-2015, most studies are based on high-resolution SAR images such as TerraSAR-X, which

limits the ability to acquire large-scale deformation signal.

In this paper, INSAR time series analysis method based on 33 Radarsat-2 wide SAR imagery

from 2012 to 2015 were used to obtain large-scale dynamic deformation time series and mean

deformation velocity field in Beijing. Based on these results, the information of the overall vertical

deformation in Beijing during this period was calculated, and the trend of land subsidence in the area

and its relationship with fault activity were analyzed.

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2. Study area and data

2.1. Study area

The research area of this study is in Beijing and its adjacent areas (115°E~118.2°E, 38.8°N~41°N),

which is located at the junction of the North China Plain and the Taihang Mountains and the Yanshan

Mountains. The southeastern part of this area is plain and belongs to the northwestern fringe of the

North China Plain; The western mountainous region is the northeastern part of the Taihang

Mountains; The northern and northeastern mountainous region is the western branch of the Yanshan

Mountains (Figure 1).

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Figure 1. Location of the study area and the coverage of SAR images.

Since 1950, a large area of land subsidence has continued to occur as a severe geological disaster.

By the end of 2005, the area of ground settlement greater than 50 mm reached 4114.12 km2, and the

area greater than 100 mm reached 2815.29 km2. Settlement amount reaches 1086mm, and the most

serious area is still sinking at a speed of 30~60mm/year. The maximum average settlement speed

reaches 66.3mm/year [11]. By the end of 2009, the maximum annual settling speed reached

137.51mm [12,13]. Land subsidence has brought major losses to Beijing's social economy. The

results of the study show that 34% of broken water supply pipelines in urban areas in Beijing were

caused by land subsidence [14].

2.2. Data

In this paper, we used 33 Radarsat-2 wide SAR images range from the year 2012 to 2015 covering

most of Beijing area to acquire the crustal deformation along the line of sight (LOS) direction. All the

SAR images were imaged in wide mode with the VV polarization mode. The coverage of the

Radarsat-2 SAR images is shown in figure 1.

In the process of data processing, in order to maintain good interference coherence and to ensure

the reliability of the interference results, the Small Baseline Subset (SBAS) algorithm must be used

to select the time baseline and space baseline when combining the interference pairs. In this study,

the spatial baseline threshold was chosen to be ±200m and the time baseline threshold was ±300 days.

To ensure the stability of the mesh, some interference pairs with the baseline of the time was slightly

Crustal Deformation Monitoring in Beijing Using Radarsat-2 InSAR Time Series Analysis

713

longer than the baseline threshold and the vertical baseline was small. Finally, 47 interferograms with

high interference quality are obtained. The combined network diagram is shown in Figure 2.

Figure 2. Spatial and temporal baselines of Radarsat-2 SAR images used in this study.

In the data processing process, in order to remove the topographic phase in the interferometric

phase, the SRTM-DEM data SRTM3 (3 arc-seconds) jointly measured by the NASA and the

National Mapping Agency of the Ministry of National Defence (NIMA) was selected as the external

DEM data, which is at the version of V4.1 and was publicly released in 2003. The data range is 38°-

40° north latitude and 109°-111° east longitude. Figure 3 shows the image of the DEM we used in

this study.

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Figure 3. The DEM image we used in this study.

3. Data processing and results

Figure 4. The mean velocity field of crustal deformation along the line of sight (LOS)

direction from 2012-2015 derived from RADARSAT-2 WIDE mode SAR images.

Crustal Deformation Monitoring in Beijing Using Radarsat-2 InSAR Time Series Analysis

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Figure 5. The error distribution of the mean velocity field.

The InSAR time series analysis was carried out by using the software named Full RAnk Matrix –

Small BAseline Subset (FRAM-SBAS) which was developed by Yongsheng Li in Institute of Crustal

Dynamics, CEA, China and Newcastle University, UK.

FRAM-SBAS is a multi-function processing platform based on Linux that includes radar

interferometric processing, time series analysis, and geometric correction. Currently supports all

global commercial SAR satellite platform data. The software is simple and easy to use, supports

process processing, and can be applied to the domain of urban land subsidence, co-seismic and post-

earthquake deformation analysis, volcano monitoring, landslide debris flow monitoring. The FRAM-

SBAS software is one of the most effective processing tools to solve the small deformation

monitoring of the crustal plate. The continuous improvement and innovation of new methods and

innovations have continuously improved and supplemented the SBAS theoretical model in different

aspects [15].

Based on the FRAM-SBAS software, we got the mean velocity field of crustal deformation along

the line of sight (LOS) direction from 2012-2015 in Beijing area. Figure 4 shows the final result of

the mean velocity field and figure 5 shows the error distribution of the mean velocity, which show a

good result with reasonable accurate.

4. Conclusions

Based on 33 Radarsat-2 wide SAR images, in this paper, we obtained the crustal deformation field

information covering the entire Beijing area, including the annual mean deformation velocity field

and 32 periods of accumulated deformation sequence images from 2012 to 2015. From the

calculation results, the following conclusions can be drawn:

1) The overall performance of the Beijing area showed a trend of slow mountain uplift and rapid

settlement in the plain area, among which the mountain uplift speed is relatively slow,

averaging around 1 mm/year; the main urban area (within the third ring) is relatively stable;

the eastern part has more serious settlement, and the largest velocity reaches 130mm/year.

2) The subsidence areas in Beijing are mainly distributed in the plain area. There are three more

serious areas, namely The Haidian-Changping-Shunyi area, the Chaoyang-Tongzhou border

area, and the Langfang area bordering Beijing.

3) Judging from the cumulative deformation evolution image, During the period of 2012-2015 in

Beijing where the three settlements are more serious, the trend of settlement has continued to

increase.

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Acknowledgement

This research is funded by the project of the science for earthquake resilience (No. XH18001Y), the

Beijing financial project (No. DQXBSJ) and the Educational Commission of Sichuan Province of

China(15ZA0060)

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