利用GPS与环境负荷形变数据研究台风引起的垂向地表位移

Analyzing typhoon-triggered vertical land motion from GPS and environmental load-induced deformation data

台风造成的强降雨、低气压、海面高度变化均会引起地表的形变.本文利用中国大陆构造环境监测网(陆态网)7个GPS台站每日的垂向位移和环境负荷形变模型分析2018年9月10—26日台风“山竹”期间不同负荷引起的区域垂向地表形变.结果表明,台风期间大气负荷和非潮汐海洋负荷垂向形变最大分别达到5.1 mm和-9.2 mm.模型能较好地反映河流区域地表水文负荷变化造成的垂向形变,但不同模型之间存在系统偏差.由于缺少地下水等信息,模型反映负荷长期形变效应的效果不佳,且形变的量级明显小于GPS观测的结果.迅速增加的水文负荷使北海GPS站从开始下沉到最低点(-15.6 mm)5天的下沉量达到25.7 mm;珠海、广州GPS站均观测到河流汇水作用造成地表的二次下沉,且珠海站一周后才抬升到正常位置;湛江和北海GPS站能较好地反映河流水位变化,相关系数分别为-0.66和-0.50.研究结果表明,相比于形变模型,GPS能更有效地监测台风短期水文负荷形变,可为台风洪水等灾害监测与预报提供有用的信息.

Typhoon can cause extremely heavy rainfall,low pressure and sea level change,and lead to ground deformations,which can be measured at millimeter-level precision with the Global Positioning System(GPS).Here daily GPS vertical position displacements at 7 stations from Crustal Movement Observation Network of China(CMONOC)were used to analyze regional vertical ground deformations induced by different loading changes of typhoon Mangkhut,along with environmental load-induced deformation data(including atmospheric,non-tidal oceanic and hydrological loading)during 10-26 September 2018.The model results showed that vertical ground deformations were caused by atmospheric and non-tidal oceanic loading one day before typhoon′s landfall,with the maximum deformation 5.1 mm and-9.2 mm,respectively.As typhoon rolled inland,the non-tidal oceanic load-induced deformation decreased quickly,while the atmospheric load-induced deformation was still significant.The model results can well reflect deformations caused by surface water loading in the area along the river,with a correlation of-0.62 between hydrological load-induced deformations and river water level changes.But systematic bias exists between different models.Due to lack of information on some hydrological variables like groundwater,the long-term hydrological loading effect cannot be simulated well in the model,and the variability of the modeled deformation was much smaller than that of GPS.The maximum subsidence of 25.7 mm was recorded at GXBH station in 5 days from the beginning of subsidence to the lowest position of-15.6 mm.Downward motions caused by a second time of water level increases were observed at GDZH and GUAN stations located at the downstream of the Pearl River basin.Additionally,it took one week for the GDZH station to uplift to normal.Relatively good correlations were found between the observed deformations at GDZJ and GXBH stations and river water level changes,with correlations of-0.66 and-0.50,respectively.This study shows that transient and long-term effects of hydrological loading induced by typhoon were well captured by GPS,which can provide useful information for monitoring and predicting disasters such as typhoon-induced flood events.