An improved approach for subsurface three-dimensional density structure imaging: Application in Wudalianchi Volcano Field, Northeast China

In the study of volcanism, other than seismic and magnetotelluric surveys, gravity survey is also an effective way to study the subsurface geological structures and materials composition. Gravity anomalies can imply the anomalous bodies with unique densities, like mineral deposits, magmas, faults, etc. Based on terrestrial gravimetry, density structure can be imaged by means of three-dimensional gravity inversion technique. To reduce the skin effects, we proposed an improved approach that combining spatial trend decomposition and direct gravity inversion. By numerical tests, the better performance is confirmed in complex study areas.Wudalianchi is one of the well-known Cenozoic volcanos in Northeastern China.Recent terrestrial gravity survey was taken in Wudalianchi Volcano Field (WVF). Using these high-quality data, we imaged the full-field density structure beneath WVF up to 20 km depth for the first time, and tried explaining the mechanism of WVF eruption. Several anomalous bodies lower than 2.5g/cm^3 were found under some monogenetic volcano cones, and also channel-like bodies. From density results, we speculated that the upwelling melts gathering at the southwestlower crust, flow northeast through channels and erupted out of cones over the past millions years. Our hypothesis is also supported by isotopic dating studies. Specifically, Weishan cone, to the northeast of Huoshaoshan cone erupted ~300 years ago, may be under active status. We suggest more attention and continuous geophysical monitoring at Weishan volcano cone. 

The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)