Resolution analysis of the gravity survey network in the middle and south sections of Tan-Lu fault and recent changes in the gravity field

Abstract

In this paper, we computed the fractal dimension of three survey areas within the central and southern sections of the Tan-Lu fault zone using fractal analysis. Subsequently, simulations were conducted to analyze the gravity response under a forward model of equivalent density changes. Additionally, we thoroughly investigated the seismic monitoring capabilities of the gravity network in the central and southern regions of the Tan-Lu fault. Expanding on these analyses. Recent gravity field variations were examined in the mid-southern segment of the Tan-Lu fault zone and its surrounding areas from 2013 to 2023. The results indicate that the observation capabilities of the northern network in the study area outperform those of the southern gravity network, with the northern network demonstrating a more evenly distributed coverage. The optimal gravity anomaly recovery effect for the entire study area is achieved at a resolution of 0.5° × 0.5°. With an equivalent observable signal in the range of 30 × 10−8 m/s2 to 40 × 10−8 m/s2, the spatial resolution of the gravity network's field source is estimated to be approximately 55 km. From 2013 to 2023, a significant positive change has been observed in the gravity field within the study area. The Tan-Lu fault zone plays a crucial role in governing the crustal movement in this region, with the dextral strike-slip movement trend of the fault persisting. Small earthquakes occur more frequently in the southern section of the fault zone, while strong earthquakes are less common. The alignment of gravity field changes with the fault strike indicates ongoing activity in the fault zone without any signs of locking. In the central segment of the Tan-Lu fault zone in the Shandong region, there appears to be a weaker correlation between gravity field changes and fault trends. This discrepancy may suggest that the area is locked, resulting in the accumulation of stress and strain. It is imperative to monitor the continuous evolution of the gravity field in this region to gain insights into potential seismic risks.