Analyzing gravity anomaly variations before the 2016 Ms 6.4 earthquake in Menyuan, Qinghai with an interpolation/cutting potential field separation technique

摘要

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.