Gravity increase before the 2015 Mw 7.8 Nepal earthquake

• Published in: Geophysical research letters Vol. 43; no. 1; pp. 111 - 117
• Main Authors: Chen, Shi, Liu, Mian, Xing, Lelin, Xu, Weimin, Wang, Wuxing, Zhu, Yiqing, Li, Hui
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.01.2016
• Subjects: Earthquakes; Energy; Fault zones; Gravimetry; Gravitation; Gravity; gravity change; Himalayan fault zone; India‐Eurasian collision; Mass; Methods; Monitoring; Monitoring methods; Nepal Mw7.8 earthquake; Plate tectonics; Plateaus; Regions; Secular variations; Seismic activity; Seismology; Wavelength; Tibetan Plateau; Nepal
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL066595

The 25 April 2015 Nepal earthquake (Mw 7.8) ruptured a segment of the Himalayan front fault zone. Four absolute gravimetric stations in southern Tibet, surveyed from 2010/2011 to 2013 and corrected for secular variations, recorded up to 22.40 ± 1.11 μGal/yr of gravity increase during this period. The gravity increase is distinct from the long‐wavelength secular trends of gravity decrease over the Tibetan Plateau and may be related to interseismic mass change around the locked plate interface under the Himalayan‐Tibetan Plateau. We modeled the source region as a disk of 580 km in diameter, which is consistent with the notion that much of the southern Tibetan crust is involved in storing strain energy that drives the Himalayan earthquakes. If validated in other regions, high‐precision ground measurements of absolute gravity may provide a useful method for monitoring mass changes in the source regions of potential large earthquakes. Key Points Absolute gravimetry in southern Tibet showed clear gravity increase before the 2015 Nepal earthquake The gravity increase may be related to strain or mass migration in a broad seismic source region High‐precision absolute gravimetry may become a useful method for monitoring seismicity