Crustal velocity structure and composition of Bayan Har block and surrounding areas

Abstract

The Bayan Har block, one of China's most seismically active regions, has experienced multiple major earthquakes (≥M 7.0) in recent years. It is a key area for investigating the interactions between the Qinghai-Xizang (Qingzang) Plateau and adjacent blocks, plateau uplift, and strong earthquake mechanisms. P-wave velocity and crustal composition provide key constraints on the properties of distinct tectonic units and their evolutionary modification processes. Based on the results of 8 Deep Seismic Sounding (DSS) profiles completed in the Bayan Har block and surrounding areas over the past 20 years, We constructed one-dimensional P-wave velocity models for the crust of Bayan Har block, Qilian fold belt, Qinling fold belt, Alxa block, Ordos block and Sichuan basin. Furthermore, crustal composition models for different tectonic units were established based on these results. The results reveal that the crustal thickness of the Bayan Har block gradually decreases towards the NNE, NE, and SE directions, while the average crustal velocity increases correspondingly. The felsic layer in the crust accounts for more than half of the total crustal thickness. The mafic content within the crust of different tectonic units exhibits notable variations, which may reflect that the Bayan Har block, Qilian fold belt, and Qinling fold belt have experienced more intensive lithospheric evolution processes compared to Ordos basin and Sichuan basin. The seismicity distribution in this region is significantly controlled by crustal velocity and composition heterogeneity across the Bayan Har block and adjacent areas, which demonstrates that earthquakes within and around the Bayan Har block exhibit both high frequency and larger magnitudes. These seismic characteristics primarily result from intense crustal stress accumulation and release during the outward expansion of the Qingzang Plateau.

Keywords

NE Qingzang plateau / Bayan Har / Crustal velocity structure / Crustal composition

CRediT authorship contribution statement

Jiyan Lin: Writing - original draft, Data curation. Tao Xu: Writing review & editing, Supervision. Zhenyu Fan: Writing - original draft, Investigation, Data curation. Yong Qiu: Writing - original draft, Software. Minjie Chen: Writing - original draft, Investigation. Yonghong Duan: Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The corresponding author Tao Xu is an editorial board member of Earthquake Research Advances and not involved by the peer review process.

Author agreement and acknowledgement

I would like to declare on behalf of my co-authors that the work described was original research that has not been published previouslyand is not under consideration for publication elsewhere, that has not been published previously, and is not under consideration for publication elsewhere, in whole or in part. All the authors listed have approved the manuscript that is enclosed.

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