2000—2018年全国形变台站周边环境时空变化特征及对垂直摆观测影响分析

Spatio-temporal Variation Characteristics of Surrounding Environment and Associated Impact on Vertical Pendulum Observation of Deformation Stations in China from 2000 to 2018

摘要:

利用中国自主研制的全球首套30 m分辨率GlobeLand30地表覆盖产品调查全国定点形变台站周边5 km范围内的土地覆盖类型分布。应用地类面积/变化率、类型转入转出率等指标分析研究区各类型的转移规律，并辅以MODIS土地覆盖年数据集从全国和分区角度揭示2001—2018年间各土地类型时空变化格局，最后以垂直摆倾斜观测为例，探索台站周边土地覆盖变化总量与仪器观测背景噪声的关系。结果表明：（1）中国定点形变台站周边5 km范围内主要以耕地、森林为主。2000—2010年间，人造地表占比从11.8%升高至14.5%，而耕地和草地面积分别减少了2.2%和1.6%。研究区内耕地转为人造地表的面积最大，共计525 km²。（2）中国大陆各地震区内台站周边土地覆盖变化格局不同，华北地震区的耕地降低和人造地表增长最为剧烈；新疆地震区以草地类型的降低和裸地类型的升高为主；东北地震区草地类型增长而人造地表稍有下降。（3）2001—2018年间，研究区森林面积在波动中缓慢升高；耕地面积则持续减少，尤其在2005—2016年间，减少幅度增大；人造地表类型则是逐年持续、稳定的增加。（4）2016年全国垂直摆倾斜仪观测背景噪声与台站周边全年的土地覆盖变化总量有一定的相关性，但华南地震区内台站由于受到海洋运动的影响，其仪器的噪声水平与周边环境变化不成正相关。

Abstract:

This paper investigated the temporal and spatial change of land cover type within 5 km around the deformation stations in China by using the GlobeLand30 product and MODIS-MCD12Q1 land cover dataset from 2000 to 2018. Then taking the vertical pendulum observation as an example, the relationship between the total land cover changes around deformation stations and the background noise of instrument observation was explored. The results showed that: (1) Cultivated land and forest are the main land types within 5 km around the fixed deformation stations in China. From 2000 to 2010, the proportion of artificial surface increased from 11.8% to 14.5%, while the area of cultivated land and grassland decreased by 2.2% and 1.6%, respectively. The area of cultivated land converted to man-made surface is the largest in the study area, with a total value of 525 km². (2) The decrease of cultivated land and the increase of man-made surface are the most severe in North China seismic region; the decrease of grassland type and the increase of bare land type are the main types in Xinjiang seismic region; the increase of grassland type and the decrease of man-made land surface are slightly in Northeast China seismic region.The change of land cover around stations in different seismic regions of mainland China is different. The area of cultivated land decreased while the artificial surface increased acutely in North China; Xinjiang seismic zone was mainly decreased in grassland and increased in bare land; the grassland in Northeast seismic zone increased while the artificial surface decreased slightly. (3) During 2001-2018, the forest area in the study area increased slowly and the cultivated land continued to decrease, especially in 2005-2016; the artificial surface continued to increase steadily year by year. (4) In 2016, the background noise observed by the vertical pendulum tiltmeter had a certain correlation with the total annual land cover change around the station. However, due to the influence of ocean motion, the noise level of the instruments in South China seismic zone was not positively related to the change of surrounding environment.