Brittleness ductility transition depth of new fracture in the Baodi Miaozhuang Uplift
Li He, Dong Yi-Bing2*, Wang Yi-Xi, Gao Wu-Ping, Yan Cheng-Guo, Cai Ling-Ling, Wu Bo-Yang, Peng Zhao
1. Tianjin Earthquake Agency, Tianjin 300201,China
2. School of Information Technology,Hebei University of Economics and Business, Shijiazhuang 050061,China.
3. State Key Laboratory of Geodesy and Earth’s Dynamics, Innovation Academy for Precision Measurement Science and Technology, CAS, Wuhan 430077,China
4. Hebei Earthquake Agency, Shijiazhuang 050021, China
Abstract Today’s earthquakes are the most direct manifestation of the latest tectonic activity and are the most powerful tool to understand the characteristics of nonrigid deformation within a continent. Particularly, the newly formed faults that have been active since the Late Pleistocene are characterized to have low development maturity, poor connectivity in geometric structure, and obvious difference in strike/depth dip in different sections. Therefore, earthquakes can reveal their three-dimensional space changes, especially the characteristics of brittle–ductile transition depth. Earthquakes can also promote the understanding of the preparation and earthquake generation process of newly formed active faults. The newly formed strike-slip active faults in the Bohai Bay Basin have experienced many strong earthquakes, including the Tangshan MS7.8 and the three Ninghe MS≥ 6.2 earthquakes. The crustal brittle–ductile transition depth revealed by these earthquakes has an important practical significance to understanding the seismogenic mechanism and activity of the region. In this paper, the new fault in the Baodi Miaozhuang uplift in the Bohai Bay Basin is taken as the target fault. In addition, the 2012 Baodi MS4.0 and MS3.5 earthquakes in the Baodi uplift and the 1976 Ninghe MS6.2 and MS6.9 and the 1977 Ninghe MS6.2 earthquakes in the Miaozhuang uplift are taken as the research objects. Finally, the CAP method is used to study the source mechanism solution and the source depth of the Baodi MS4.0 and MS3.5 earthquakes based on the waveform data from the Capital Circle Digital Seismic Network. The double difference method is used to locate the source positions of two earthquake sequences by employing the Sp converted wave of near earthquakes to accurately determine the source depth. Moreover, combined with other data, the seismogenic mechanism of earthquakes in this area and the brittle–ductile transition depth of new fractures are discussed. The following results were found. (1) The source properties of the Baodi MS4.0 and MS3.5 earthquakes are not completely consistent with the known faults on the exposed surface of the Baodi Miaozhuang uplift. Combining the research results of the source parameters of the three Ninghe earthquakes having an MS ≥ 6.2, it is inferred that they all occurred in the Baodi–Ninghe deep fault. (2) Based on the models of electrical structure and rheological structure in the focal area, the five significant earthquakes in Baodi Miaozhuang uplift reveal that the brittle–ductile transition depth of the Baodi–Ninghe deep fault is about 15 km. (3) Based on the dynamic evolution process of the Bohai Bay Basin and relevant deep geophysical exploration data, it is hypothesized that the seismic activity in this area is mainly the result of the Baodi–Ninghe deep fault and deep fluid actions.
Fund: the Internal Medicine Research Program of Tianjin Seismological Bureau (Zd202108 and Zd202204), the Seismological Science and Technology Spark Program (XH20003Y), the Three Combination Program of Monitoring, Forecasting and Scientific Research of China Seismological Bureau (3JH-202201040), the Scientific Research and Development Program of Hebei University of Economics and Trade (2021ZD06), the Higher Education Teaching Reform Research and Practice Program of Hebei Province (2021GJJG175) and the Teaching Research Program of Hebei University of Economics and Trade (2021JYQ05)
About author: Li He, senior engineer of Tianjin Seismological Bureau, graduated from the Institute of Disaster Prevention Science and Technology with a bachelor’s degree in exploration technology and engineering in 2011. Mainly engaged in seismology and application research of digital seismic data. E-mail:lihe200888@sina.com.
Cite this article:
. Brittleness ductility transition depth of new fracture in the Baodi Miaozhuang Uplift[J]. APPLIED GEOPHYSICS, 2024, 21(1): 188-202.
2024, Vol. 21 
