Seismic ambient noise imaging of Xinfengjiang reservoir and adjacent areas, Guangdong, China

The Xinfengjiang Water Reservoir (XWR) in the northwest of Heyuan city, Guangdong province, China, has hosted a large number of earthquakes since its impoundment. It is one of the reservoirs that have experienced earthquakes of magnitudes greater than 6, making it one of the most active seismic zones in Guangdong. After the significant increase in seismic activity since the reservoir water storage, many researchers have conducted a series of geophysical studies in the area. However, because of the station coverage restrictions, the detailed seismic structures within XWR have not been resolved, and the understanding of its seismic mechanism and future earthquake disaster risk are still unclear. In this study, we construct a high-resolution shear-wave velocity model in the whole crust at depths from the surface to ∼30 km based on both permanent and temporary stations deployed surrounding the XWR using ambient noise tomography. The permanent stations belong to the Guangdong Earthquake Early Warning Network, including stations equipped with broadband velocity instruments and stations equipped with acceleration strong motion instruments. The temporary stations belong to a short-period seismic array deployed surrounding the XWR in 2023, with a continuous recording duration of 30 days. The imaging results above 5 km show that, with the Heyuan-Shaowu Fault as the boundary, the XWR shows a high-speed anomaly and the Heyuan Basin shows a low-speed anomaly. We also found significant low wave velocity anomalies below the XWR at depths of 5-15 km. Although we have only obtained preliminary velocity models at the crustal scale in the area and made some discoveries, it can still promote a deeper understanding of the crustal structural characteristics and seismic mechanisms of the XWR and its adjacent areas.

References

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