Abstract We evaluated 2011–2015 mobile relative gravity data from the Hexi monitoring network that covers the epicenter of the 2016 Menyuan Ms6.4 earthquake, Qinghai Province, China and examined the spatiotemporal characteristics of the gravity field at the focal depth. In addition, we assessed the regional gravity field and its variation the half-year before the earthquake. We use first different interpolation algorithms to build a grid for the gravity data and then introduce potential field interpolation–cutting separation techniques and adaptive noise filtering. The results suggest that the gravity filed at the focal depth of 11.12 km separated from the total gravity field at about −400~150 × 10−8 m/s2 in the second half of 2015, which is larger than that in the same period in 2011 to 2014 (±30 × 10−8 m/s2). Moreover, at the same time, the gravity field changed fast from September 2014 to May 2015 and May 2015 to September 2015, reflecting to some extent material migration deep in the crust before the Menyuan earthquake.
This work was supported by the Science for Earthquake Resilience (No. XH17058Y), Science and Technology Innovation Fund of the First Crust Monitoring and Application Center, CEA (No. FMC2016004) and Special Program for Basic Work of the Ministry of Science and Technology, China (No.2015FY210403).
Cite this article:
. Analyzing gravity anomaly variations before the 2016 Ms 6.4 earthquake in Menyuan, Qinghai with an interpolation/cutting potential field separation technique[J]. APPLIED GEOPHYSICS, 2018, 15(1): 137-146.
Aja-Fernández, S., Vegas-Sánchez-Ferrero, G., Martín- Fernández, M., et al., 2009, Automatic noise estimation in images using local statistics. Additive and multiplication cases: Image and Vision Computing, 27, 756-770.
Al-Zoubi, A., Eppelbaum, L, Abueladas, A, et al., 2013, Removing Regional Trends in Microgravity in Complex Environments: Testing on 3D Model and Field Investigations in the Eastern Dead Sea Coast (Jordan). International Journal of Geophysics, 1-13.
Beltrao, J. F., Silva, J. B. C., and Costa J. C., 1991, Robust polynomial fitting method for regional gravity estimation. Geophysics, 56(1): 80-89.
Cheng, F. D., Liu, D J, Yao, R X. 1987, A study on the indentification of regional and local gravity field:. Computing Techniques for Geophysical and Geochemical Exploration (in Chinese), 9(1),1-9.
Chen, S., Liu, M., Xing, L. L., et al., 2016, Gravity increase before the 2015 Mw 7.8 Nepal earthquake: Geophysical Research Letters, 43(1), 111-117.
Guo, S. S., Zhu, Y. Q., and Zhao, Y. F., 2016, Characteristics of gravity variation and dynamic mechanism analysis in Hexi area before Qinghai Menyuan M6.4 Earthquake: Journal of Geodesy and Geodynamics, 4(36), 294-297.
Guspi, F., and Introcaso, B., 2000, A sparse spectrum technique for gridding and separating potential field anomalies: Geophysics, 65,1154-1161.
Hammer, S., 1963. Deep gravity interpretation by stripping: Geophysics, 28, 369-378.
Hou, Z. Z., Yang, W. C., Yu C. Q., 2014, Three-Dimensional Density Structure of North China's Craton Crust and Its Geological Implications: Chinese J. Geophys. (in Chinese), 57(7), 2334-2343.
Hu, C. Z., Yang, P. X., Li, Z. M., et al., 2016, Seimogenic mechanism of the 21 January 2016 Menyuan, Qinghai Ms6.4 earthquake: Chinese J. Geophys. (in Chinese), 59(5), 1637-1646.
Liu, J. Z., Liu, L. T., Liang, X. H., et al., 2015, 3D density inversion of gravity gradient data using the extrapolated Tikhonov regularization: Applied Geophysics, 12(2), 137-146.
Li, Y. G., Douglas W. 1998, Oldenbrug. 3-D inversion of gravity data: Geophysics. 63(1), 109-119.
Mad, J.M., Henrik, O., Ploug,C., et al., 2007, Gravity field separation and mapping of buried quaternary valleys in Lolland Denmark using old geophysical data: Journal of Geodynamics, 43(2), 330-337.
Martínez-Moreno, F. J., Galindo-Zaldívar, J., Pedrera, A., et al. 2015, Regional and residual anomaly separation in microgravity maps for cave detection: the case study of Gruta de las Maravillas (SW Spain): Journal of Applied Geophysics, 114, 1-11.
Spector, A., and F. S. Grant, 1970, Statistical models for interpreting aeromagnetic data: Geophysics, 35(2), 293-302.
Wang, B. Z., Xu, S. Z., and Liu, B. H., 1997, An example of aeromagnetic anomaly separation using multi-interpolation division. Oil Geophysical Prospecting, 32(3), 431-438.
Wen, B.H., and Cheng, F.D., 1990, A new interpolating cut method for identifying regional and local fields of magnetic anomaly: J. Cent. South Inst. Min. 21(3), 229-235.
Xu, S. Z., Yu, H. L., Li, F. D., et al., 2009a, The inversion of apparent density based on the separation and continuation of potential field: Chinese J. Geophys.(in Chinese), 52(6):1592-1598.
Xu, Y., Hao, T., Li, Z., et al. 2009b, Regional gravity anomaly separation using wavelet transform and spectrum analysis. Journal of Geophysics and Engineering, 6(3), 279-287.
Xu, S. Z., Zhang, Y, Wen, B. H., et al. 2006, The application of cutting method to interpretation of magnetic anomaly in region of Ludong: Geophysical Prospecting for Petroleum, 45(3), 316-318.
Zhu, Y. Q., Li, T.M., Hao, M., et al. 2016. Gravity changes before the Menyuan, Qinghai Ms6.4 earthquake of 2016: Chinese J. Geophys. (in Chinese), 59(10), 3744-3752.
Zhu, Y, Zhan, F. B, Zhou, J, et al. 2010, Gravity measurements and their variations before the 2008 Wenchuan earthquake. Bulletin of the Seismological Society of America, 100(5B), 2815-2824.