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ORIGINAL ARTICLE

Upper crustal velocity structure and geological significance of southwest Shandong Province, China: insights from double-difference seismic tomography Jinchao Shen & Minmin Xu & Huiyong Yin & Shicheng Li

Received: 3 April 2020 / Accepted: 28 August 2020 # Springer Nature B.V. 2020

Abstract As an important part of the North China Craton extension system, the southwest of Shandong Province comprises several uplift and fault depression structures. However, the tectonic activity there is controversial, and more studies are required for the upper crustal velocity structure. In the present study, the threedimensional upper crustal P wave velocity structure in Article Highlights • The southwest of Shandong Province comprises many vertical high-velocity structures, indicating that mantle-magma upwelling was strong there and formed the uplift structures. • The low-velocity anomaly 20 km below the eastern crust of the Taishan Mountain area shows that magma upwelling is concentrated mainly below 20 km. • The uplift of local regional crust due to vertical magma upwelling could drag the adjacent crust and form fault depression structures, and the fault depression and uplift structures are closely related in genesis. J. Shen (*) : H. Yin Shandong Key Laboratory of Depositional Mineralization & Sedimentary Mineral, College of Earth Science and Engineering, Shandong University of Science and Technology, 579 Qianwangang Road, Qingdao 266590, China e-mail: [email protected] J. Shen Jinan Earthquake Monitoring Center, Jinan 250000, China M. Xu Shandong Academy of Environmental Sciences Co., Ltd., Jinan 250000, China S. Li Department of Land Resource Management, School of Public Administration, China University of Geosciences, Wuhan 430074, China

southwestern Shandong Province was obtained using double-difference seismic tomography. The findings show that southwestern Shandong Province has many vertical high-velocity structures, indicating that mantlemagma upwelling was strong there and formed the uplift structures. It is reasoned that Taishan Mountain is still undergoing uplift caused by magma upwelling that is concentrated mainly below a depth of 20 km. The shallow–middle low-velocity structures in southwestern Shandong Province correspond strongly to the uplift depression structures. The tectonic activity in southwestern Shandong Province can be divided mainly into (i) brittle-ductile deformation of uplift depression structures at depths of 0–10 km and (ii) mantle-magma upwelling under the uplift structures. The formation of uplift structures promoted the formation of the fault depression structures, and the fault depression and uplift structures are closely related in genesis. Keywords Double-difference seismic tomography . Southwestern Shandong . Velocity structure

1 Introduction The North China Craton has experienced large-scale destruction and lithospheric thinning since the Mesozoic, and its tectonic environment has changed from a compressive one to an extensional one (Menzies et al. 1993; Zheng et al. 1998