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| Gravity change observed in a local gravity network and its implication to seasonal precipitation in Dali county, Yunnan province, China |
| Xin Zhou1, Wenke Sun1, Hui Li2, Shuhei Okubo3, Shaoan Sun2, Lelin Xing2, Dongzhi Liu2, Chongyang Shen2 |
1 Laboratory of Computational Geodynamics, University of Chinese Academy of Sciences, Beijing, China
2 Institute of Seismology, China Earthquake Administration, Wuhan, China
3 Earthquake Research Institute, The University of Tokyo, Tokyo, Japan |
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Abstract This study investigates data-processing methods and examines the precipitation effect on gravity measurements at the Dali gravity network, established in 2005. High-quality gravity data were collected during four measurement campaigns. To use the gravity data validly, some geophysical corrections must be considered carefully. We first discuss data-processing methods using weighted leastsquares adjustment with the constraint of the absolute gravity datum. Results indicate that the gravity precision can be improved if all absolute gravity data are used as constraints and if calibration functions of relative gravimeters are modeled within the observation function. Using this data-processing scheme, the mean point gravity precision is better than 12 μgal. After determining the best data-processing scheme, we then process the gravity data obtained in the four measurement campaigns, and obtain gravity changes in three time periods. Results show that the gravity has a remarkable change of more than 50 μgal in the first time period from Apr–May of 2005 to Aug–Sept of 2007. To interpret the large gravity change, a mean water mass change (0.6 m in height) is assumed in the ETOPO1 topographic model. Calculations of the precipitation effect on gravity show that it can reach the same order of the observed gravity change. It is regarded as a main source of the remarkable gravity change in the Dali gravity network, suggesting that the precipitation effect on gravity measurements must be considered carefully.
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Received: 21 August 2013
Published: 10 December 2013
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| Fund:the CAS/CAFEA International Partnership Program for creative research teams (No. KZZD-EW-TZ-19) and the National Natural Science Foundation of China (Nos. 41331066 and 41174063) |
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Corresponding Authors:
Wenke Sun
E-mail: sunw@ucas.ac.cn
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