Three-dimensional seismic body wave attenuation tomography of the North China Craton : implications for craton destruction and transformation

The North China Craton (NCC) was formed from the Archean to the Paleoproterozoic and is one of the oldest cratons in the world, which can be divided into three parts: the Western Block, the Eastern Block, and the Central Orogenic Belt. Since the Mesozoic, the NCC has experienced significant destruction and transformation, and has developed a large number of extensional structures, accompanied by intense magmatic activity, metal minerals and oil and gas resources. Many seismic velocity tomography studies have been conducted in NCC, however, there are very few seismic attenuation tomography studies in the region. For this reason, this study collects P- and S-wave seismograms from ~6,000 earthquakes recorded by 477 permanent and 111 temporary stations in North China from 2013 to 2017, and uses body wave attenuation tomography to determine its three-dimensional attenuation structure of the crust and uppermost mantle.

We first use the seismic amplitude spectrum to determine about 60,000 P-wave t* and 57,000 S-wave t* data, and use the spectrum ratio method of Guo and Thurber (2021) to construct event-pair differential t* data. By using both absolute and differential t* data, we determined 3D Qp and Qs models of the NCC lithosphere with grid intervals of 0.5°×0.5° in the horizontal directions and 10 km in the depth. Overall. the Q features in the crust correspond well to the regional geological structures. In the shallow depths, thicker sedimentary zones are associated with low Q values, such as the Bohai Bay Basin and the western part of the Central Orogenic Belt (COB). Relatively low Q values are also associated with fault zones, such as the Tanlu fault zone and the Zhangbo fault zone. In addition, the Hetao rift and the Weihe rift zones  also have relatively low Q values. Beneath the Datong volcanic field, evident low Q values extend from the crust to the upper mantle, suggesting the existence of partial melting.

In comparison, the Yanshan orogenic belt has significantly higher Q values. In the uppermost mantle, both Qp and Qs models have high values in the eastern part of the NCC, and the COB and western part have lower Q values. Across the North-South Gravity Lineament, there is a sharp change of Q values with lower to the west and higher to the east. We will combine Qp and Qs models with the available velocity models to further understand the destruction and dynamic processes of the NCC.